Patent Publication Number: US-RE46728-E

Title: Digital broadcasting system and data processing method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Reissue application of U.S. Pat. No. 8,374,252, issued on Feb. 12, 2013 from U.S. patent application Ser. No. 12/976,963, filed on Dec. 22, 2010, which is a continuation of U.S. patent application Ser. No. 12/146,938, filed on Jun. 26, 2008, now U.S. Pat. No. 7,953,157, which claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2008-0060491, filed on Jun. 25, 2008, and also claims the benefit of U.S. Provisional Application Ser. Nos. 60/946,143, filed on Jun. 26, 2007, 60/957,714, filed on Aug. 24, 2007, 60/974,084, filed on Sep. 21, 2007, and 60/977,379, filed on Oct. 4, 2007, the contents of which are all hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a digital broadcasting system, and more particularly, to a digital broadcasting system and a data processing method. 
     2. Discussion of the Related Art 
     The Vestigial Sideband (VSB) transmission mode, which is adopted as the standard for digital broadcasting in North America and the Republic of Korea, is a system using a single carrier method. Therefore, the receiving performance of the digital broadcast receiving system may be deteriorated in a poor channel environment. Particularly, since resistance to changes in channels and noise is more highly required when using portable and/or mobile broadcast receivers, the receiving performance may be even more deteriorated when transmitting mobile service data by the VSB transmission mode. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a digital broadcasting system and a data processing method that substantially obviate one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a digital broadcasting system and a data processing method that are highly resistant to channel changes and noise. 
     Another object of the present invention is to provide a digital broadcasting system and a data processing method that can enhance the receiving performance of the receiving system by performing additional encoding on mobile service data and by transmitting the processed data to the receiving system. 
     A further object of the present invention is to provide a digital broadcasting system and a data processing method that can also enhance the receiving performance of the receiving system by inserting known data already known in accordance with a pre-agreement between the receiving system and the transmitting system in a predetermined region within a data region. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a digital broadcast transmitting system may include a service multiplexer and a transmitter. The service multiplexer may multiplex mobile service data and main service data at a predetermined coding rate and may transmit the multiplexed data to the transmitter. The transmitter may perform additional encoding on the mobile service data being transmitted from the service multiplexer. The transmitter may also group a plurality of additionally encoded mobile service data packets so as to form a data group. The transmitter may multiplex mobile service data packets including mobile service data and main service data packets including main service data in packet units and may transmit the multiplexed data packets to a digital broadcast receiving system. 
     Herein, the data group may be divided into a plurality of regions depending upon a degree of interference of the main service data. Also, a long known data sequence may be periodically inserted in regions without interference of the main service data. Also, a digital broadcast receiving system according to an embodiment of the present invention may be used for modulating and channel equalizing the known data sequence. 
     In another aspect of the present invention, a receiving system may include a signal receiving unit, a demodulating unit, a demultiplexer, and IP data processor. The signal receiving unit receives a broadcasting signal including RS frame and main service data, the RS frame consisting of a plurality of MPH service data packets, each of which includes MPH header of M bytes including identification information and payload of N-M bytes. The demodulating unit demodulates data of the RS frame of the broadcasting signal received in the signal receiving unit. The demultiplexer identifies an MPH service data packet including IP datagram of mobile service data with reference to MPH header within each MPH service data packet within the RS frame demodulated by the demodulating unit, and outputs IP datagram of the mobile service data from payload within the identified MPH service data packet. The IP data processor outputs audio/video data for audio/video decoding if the IP datagram of the mobile service data output from the demultiplexer is the audio/video data. 
     In another aspect of the present invention, a method of processing data in a receiving system may include receiving a broadcasting signal including RS frame and main service data, the RS frame consisting of a plurality of MPH service data packets, each of which includes MPH header of M bytes including identification information and payload of N-M bytes, demodulating data of the RS frame of the received broadcasting signal, identifying an MPH service data packet including IP datagram of mobile service data with reference to MPH header within each MPH service data packet within the demodulated RS frame, and extracting IP datagram of the mobile service data from payload within the identified MPH service data packet, and outputting audio/video data for audio/video decoding if the extracted IP datagram of the mobile service data is the audio/video data. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  illustrates a structure of a MPH frame for transmitting and receiving mobile service data according to the present invention; 
         FIG. 2  illustrates an exemplary structure of a VSB frame; 
         FIG. 3  illustrates a mapping example of the positions to which the first 4 slots of a sub-frame are assigned with respect to a VSB frame in a space region; 
         FIG. 4  illustrates a mapping example of the positions to which the first 4 slots of a sub-frame are assigned with respect to a VSB frame in a time region; 
         FIG. 5  illustrates an alignment of data after being data interleaved and identified; 
         FIG. 6  illustrates an enlarged portion of the data group shown in  FIG. 5  for a better understanding of the present invention; 
         FIG. 7  illustrates an alignment of data before being data interleaved and identified; 
         FIG. 8  illustrates an enlarged portion of the data group shown in  FIG. 7  for a better understanding of the present invention; 
         FIG. 9  illustrates an exemplary assignment order of data groups being assigned to one of 5 sub-frames according to the present invention; 
         FIG. 10  illustrates an example of multiple data groups of a single parade being assigned (or allocated) to an MPH frame; 
         FIG. 11  illustrates an example of transmitting 3 parades to an MPH frame according to the present invention; 
         FIG. 12  illustrates an example of expanding the assignment process of 3 parades to 5 sub-frames within an MPH frame; 
         FIG. 13  illustrates a block diagram showing a general structure of a digital broadcast transmitting system according to an embodiment of the present invention; 
         FIG. 14  illustrates a block diagram showing an example of a service multiplexer; 
         FIG. 15  illustrates a block diagram showing an example of a transmitter according to an embodiment of the present invention; 
         FIG. 16  illustrates a block diagram showing an example of a pre-processor according to the present invention; 
         FIG. 17  illustrates a conceptual block diagram of the MPH frame encoder according to an embodiment of the present invention; 
         FIG. 18  illustrates a detailed block diagram of an RS frame encoder among a plurality of RS frame encoders within an MPH frame encoder; 
         FIG. 19(a)  and  FIG. 19(b)  illustrate a process of one or two RS frame being divided into several portions, based upon an RS frame mode value, and a process of each portion being assigned to a corresponding region within the respective data group; 
         FIG. 20(a)  to  FIG. 20(c)  illustrate error correction encoding and error detection encoding processes according to an embodiment of the present invention; 
         FIG. 21  illustrates an example of performing a row permutation (or interleaving) process in super frame units according to the present invention; 
         FIG. 22(a)  and  FIG. 22(b)  illustrate an example of creating an RS frame by grouping data, thereby performing error correction encoding and error detection encoding; 
         FIG. 23(a)  and  FIG. 23(b)  illustrate an exemplary process of dividing an RS frame for configuring a data group according to the present invention; 
         FIG. 24  illustrates a block diagram of a block processor according to an embodiment of the present invention; 
         FIG. 25  illustrates a detailed block diagram of a convolution encoder of the block processor of  FIG. 24 ; 
         FIG. 26  illustrates a symbol interleaver of the block processor of  FIG. 24 ; 
         FIG. 27  illustrates a block diagram of a group formatter according to an embodiment of the present invention; 
         FIG. 28  illustrates a detailed diagram of one of 12 trellis encoders included in the trellis encoding module of  FIG. 15 ; 
         FIG. 29  illustrates an example of assigning signaling information area according to an embodiment of the present invention; 
         FIG. 30  illustrates a detailed block diagram of a signaling encoder according to the present invention; 
         FIG. 31  illustrates an example of a syntax structure of TPC data according to the present invention; 
         FIG. 32  illustrates an example of power saving of in a receiver when transmitting 3 parades to an MPH frame level according to the present invention; 
         FIG. 33  illustrates an example of a transmission scenario of the TPC data and the FIC data level according to the present invention; 
         FIG. 34  illustrates an example of a training sequence at the byte level according to the present invention; 
         FIG. 35  illustrates an example of a training sequence at the symbol according to the present invention; 
         FIG. 36  illustrates a block diagram of a demodulating unit in a receiving system according to the present invention; 
         FIG. 37  illustrates a data structure showing an example of known data being periodically inserted in valid data according to the present invention; 
         FIG. 38  illustrates a block diagram showing a structure of a demodulator of the demodulating unit shown in  FIG. 36 ; 
         FIG. 39  illustrates a detailed block diagram of the demodulator shown in  FIG. 38 ; 
         FIG. 40  illustrates a block diagram of a frequency offset estimator according to an embodiment of the present invention; 
         FIG. 41  illustrates a block diagram of a known data detector and initial frequency offset estimator according to the present invention; 
         FIG. 42  illustrates a block diagram of a partial correlator shown in  FIG. 41 ; 
         FIG. 43  illustrates a second example of the timing recovery unit according to the present invention; 
         FIG. 44(a)  and  FIG. 44(b)  illustrate examples of detecting timing error in a time domain; 
         FIG. 45(a)  and  FIG. 45(b)  illustrate other examples of detecting timing error in a time domain; 
         FIG. 46  illustrates an example of detecting timing error using correlation values of  FIG. 44  and  FIG. 45 ; 
         FIG. 47  illustrates an example of a timing error detector according to the present invention; 
         FIG. 48  illustrates an example of detecting timing error in a frequency domain according to an embodiment of the present invention; 
         FIG. 49  illustrates another example of a timing error detector according to the present invention; 
         FIG. 50  illustrates a block diagram of a DC remover according to an embodiment of the present invention; 
         FIG. 51  illustrates an example of shifting sample data inputted to a DC estimator shown in  FIG. 50 ; 
         FIG. 52  illustrates a block diagram of a DC remover according to another embodiment of the present invention; 
         FIG. 53  illustrates a block diagram of another example of a channel equalizer according to the present invention; 
         FIG. 54  illustrates a detailed block diagram of an example of a remaining carrier phase error estimator according to the present invention; 
         FIG. 55  illustrates a block diagram of a phase error detector obtaining a remaining carrier phase error and phase noise according to the present invention; 
         FIG. 56  illustrates a phase compensator according to an embodiment of the present invention; 
         FIG. 57  illustrates a block diagram of another example of a channel equalizer according to the present invention; 
         FIG. 58  illustrates a block diagram of another example of a channel equalizer according to the present invention; 
         FIG. 59  illustrates a block diagram of another example of a channel equalizer according to the present invention; 
         FIG. 60  illustrates a block diagram of an example of a CIR estimator according to the present invention; 
         FIG. 61  illustrates a block diagram of an example of a block decoder according to the present invention; 
         FIG. 62  illustrates a block diagram of an example of a feedback deformatter according to the present invention; 
         FIG. 63  to  FIG. 65  illustrate process steps of error correction decoding according to an embodiment of the present invention; 
         FIG. 66  illustrates a block diagram of a receiving system according to an embodiment of the present invention; 
         FIG. 67  illustrates a bit stream syntax for a VCT according to the present invention; 
         FIG. 68  illustrates a service_type field according to an embodiment of the present invention; 
         FIG. 69  illustrates a service location descriptor according to an embodiment of the present invention; 
         FIG. 70  illustrates examples that may be assigned to the stream_type field according to the present invention; 
         FIG. 71  illustrates a bit stream syntax for an EIT according to the present invention; and 
         FIG. 72  illustrates a block diagram of a receiving system according to another embodiment of the present invention; 
         FIG. 73  illustrates an example of a protocol stack for a main service according to the embodiment of the present invention; 
         FIG. 74  illustrates an example of a protocol stack for a mobile service according to the embodiment of the present invention; 
         FIG. 75  illustrates an example of an IP datagram generated by  FIG. 74 ; 
         FIG. 76  illustrates another example of a protocol stack for a mobile service according to the embodiment of the present invention; 
         FIG. 77  illustrates an example of an IP datagram generated by  FIG. 76 ; 
         FIG. 78  illustrates another example of an RS frame according to the embodiment of the present invention; 
         FIG. 79  illustrates an example of an MPH header structure within an MPH service data packet according to the embodiment of the present invention; 
         FIG. 80(a)  and  FIG. 80(b)  illustrate another examples of an RS frame according to the embodiment of the present invention; 
         FIG. 81(a)  to  FIG. 81(f)  illustrate extension examples of an MPH service data packet according to the embodiment of the present invention; 
         FIG. 82  illustrates an example of a temporary header structure added during extension of  FIG. 81 ; 
         FIG. 83  illustrates another example of a service multiplexer according to the embodiment of the present invention; 
         FIG. 84  illustrates another example of packet multiplexing according to the embodiment of the present invention; 
         FIG. 85  illustrates an example of a protocol stack for a parade structure of  FIG. 84 ; 
         FIG. 86  is a block diagram illustrating another example of a receiving system according to the embodiment of the present invention; 
         FIG. 87  is a flow chart illustrating an operation example of a demultiplexer of  FIG. 86 ; 
         FIG. 88  is a flow chart illustrating an example of a procedure of demultiplexing IP datagram in a demultiplexer of  FIG. 86 ; 
         FIG. 89  is a flow chart illustrating an example of a procedure of demultiplexing PSI/PSIP data in a demultiplexer of  FIG. 86 ; 
         FIG. 90  is a flow chart illustrating an example of a procedure of demultiplexing IP datagram in a demultiplexer of  FIG. 86 ; and 
         FIG. 91  is a flow chart illustrating an example of a procedure of demultiplexing PSI/PSIP data in a demultiplexer of  FIG. 86 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In addition, although the terms used in the present invention are selected from generally known and used terms, some of the terms mentioned in the description of the present invention have been selected by the applicant at his or her discretion, the detailed meanings of which are described in relevant parts of the description herein. Furthermore, it is required that the present invention is understood, not simply by the actual terms used but by the meaning of each term lying within. 
     Among the terms used in the description of the present invention, main service data correspond to data that can be received by a fixed receiving system and may include audio/video (A/V) data. More specifically, the main service data may include A/V data of high definition (HD) or standard definition (SD) levels and may also include diverse data types required for data broadcasting. Also, the known data correspond to data pre-known in accordance with a pre-arranged agreement between the receiving system and the transmitting system. Additionally, among the terms used in the present invention, “MPH” corresponds to the initials of “mobile”, “pedestrian”, and “handheld” and represents the opposite concept of a fixed-type system. Furthermore, the MPH service data may include at least one of mobile service data, pedestrian service data, and handheld service data, and will also be referred to as “mobile service data” for simplicity. Herein, the mobile service data not only correspond to MPH service data but may also include any type of service data with mobile or portable characteristics. Therefore, the mobile service data according to the present invention are not limited only to the MPH service data. 
     The above-described mobile service data may correspond to data having information, such as program execution files, stock information, and so on, and may also correspond to A/V data. Most particularly, the mobile service data may correspond to A/V data having lower resolution and lower data rate as compared to the main service data. For example, if an A/V codec that is used for a conventional main service corresponds to a MPEG-2 codec, a MPEG-4 advanced video coding (AVC) or scalable video coding (SVC) having better image compression efficiency may be used as the A/V codec for the mobile service. Furthermore, any type of data may be transmitted as the mobile service data. For example, transport protocol expert group (TPEG) data for broadcasting real-time transportation information may be transmitted as the main service data. 
     Also, a data service using the mobile service data may include weather forecast services, traffic information services, stock information services, viewer participation quiz programs, real-time polls and surveys, interactive education broadcast programs, gaming services, services providing information on synopsis, character, background music, and filming sites of soap operas or series, services providing information on past match scores and player profiles and achievements, and services providing information on product information and programs classified by service, medium, time, and theme enabling purchase orders to be processed. Herein, the present invention is not limited only to the services mentioned above. In the present invention, the transmitting system provides backward compatibility in the main service data so as to be received by the conventional receiving system. Herein, the main service data and the mobile service data are multiplexed to the same physical channel and then transmitted. 
     Furthermore, the digital broadcast transmitting system according to the present invention performs additional encoding on the mobile service data and inserts the data already known by the receiving system and transmitting system (e.g., known data), thereby transmitting the processed data. Therefore, when using the transmitting system according to the present invention, the receiving system may receive the mobile service data during a mobile state and may also receive the mobile service data with stability despite various distortion and noise occurring within the channel. 
     MPH Frame Structure 
     In the embodiment of the present invention, the mobile service data are first multiplexed with main service data in MPH frame units and, then, modulated in a VSB mode and transmitted to the receiving system. At this point, one MPH frame consists of K 1  number of sub-frames, wherein one sub-frame includes K 2  number of slots. Also, each slot may be configured of K 3  number of data packets. In the embodiment of the present invention, K 1  will be set to 5, K 2  will be set to 16, and K 3  will be set to 156 (i.e., K 1 =5, K 2 =16, and K 3 =156). The values for K 1 , K 2 , and K 3  presented in this embodiment either correspond to values according to a preferred embodiment or are merely exemplary. Therefore, the above-mentioned values will not limit the scope of the present invention. 
       FIG. 1  illustrates a structure of a MPH frame for transmitting and receiving mobile service data according to the present invention. In the example shown in  FIG. 1 , one MPH frame consists of 5 sub-frames, wherein each sub-frame includes 16 slots. In this case, the MPH frame according to the present invention includes 5 sub-frames and 80 slots. Also, in a packet level, one slot is configured of 156 data packets (i.e., transport stream packets), and in a symbol level, one slot is configured of 156 data segments. Herein, the size of one slot corresponds to one half (½) of a VSB field. More specifically, since one 207-byte data packet has the same amount of data as a data segment, a data packet prior to being interleaved may also be used as a data segment. At this point, two VSB fields are grouped to form a VSB frame. 
       FIG. 2  illustrates an exemplary structure of a VSB frame, wherein one VSB frame consists of 2 VSB fields (i.e., an odd field and an even field). Herein, each VSB field includes a field synchronization segment and 312 data segments. The slot corresponds to a basic time period for multiplexing the mobile service data and the main service data. Herein, one slot may either include the mobile service data or be configured only of the main service data. If one MPH frame is transmitted during one slot, the first 118 data packets within the slot correspond to a data group. And, the remaining 38 data packets become the main service data packets. In another example, when no data group exists in a slot, the corresponding slot is configured of 156 main service data packets. Meanwhile, when the slots are assigned to a VSB frame, an off-set exists for each assigned position. 
       FIG. 3  illustrates a mapping example of the positions to which the first 4 slots of a sub-frame are assigned with respect to a VSB frame in a space region. And,  FIG. 4  illustrates a mapping example of the positions to which the first 4 slots of a sub-frame are assigned with respect to a VSB frame in a time region. Referring to  FIG. 3  and  FIG. 4 , a 38 th  data packet (TS packet # 37 ) of a 1 st  slot (Slot # 0 ) is mapped to the 1 st  data packet of an odd VSB field. A 38 th  data packet (TS packet # 37 ) of a 2 nd  slot (Slot # 1 ) is mapped to the 157 th  data packet of an odd VSB field. Also, a 38 th  data packet (TS packet # 37 ) of a 3 rd  slot (Slot # 2 ) is mapped to the 1 st  data packet of an even VSB field. And, a 38 th  data packet (TS packet # 37 ) of a 4 th  slot (Slot # 3 ) is mapped to the 157 th  data packet of an even VSB field. Similarly, the remaining 12 slots within the corresponding sub-frame are mapped in the subsequent VSB frames using the same method. 
     Meanwhile, one data group may be divided into at least one or more hierarchical regions. And, depending upon the characteristics of each hierarchical region, the type of mobile service data being inserted in each region may vary. For example, the data group within each region may be divided (or categorized) based upon the receiving performance. In an example given in the present invention, a data group is divided into regions A, B, C, and D in a data configuration prior to data deinterleaving. 
       FIG. 5  illustrates an alignment of data after being data interleaved and identified.  FIG. 6  illustrates an enlarged portion of the data group shown in  FIG. 5  for a better understanding of the present invention.  FIG. 7  illustrates an alignment of data before being data interleaved and identified. And,  FIG. 8  illustrates an enlarged portion of the data group shown in  FIG. 7  for a better understanding of the present invention. More specifically, a data structure identical to that shown in  FIG. 5  is transmitted to a receiving system. In other words, one data packet is data-interleaved so as to be scattered to a plurality of data segments, thereby being transmitted to the receiving system.  FIG. 5  illustrates an example of one data group being scattered to 170 data segments. At this point, since one 207-byte packet has the same amount of data as one data segment, the packet that is not yet processed with data-interleaving may be used as the data segment. 
       FIG. 5  shows an example of dividing a data group prior to being data-interleaved into 10 MPH blocks (i.e., MPH block  1  (B 1 ) to MPH block  10  (B 10 )). In this example, each MPH block has the length of 16 segments. Referring to  FIG. 5 , only the RS parity data are allocated to portions of the first 5 segments of the MPH block  1  (B 1 ) and the last 5 segments of the MPH block  10  (B 10 ). The RS parity data are excluded in regions A to D of the data group. More specifically, when it is assumed that one data group is divided into regions A, B, C, and D, each MPH block may be included in any one of region A to region D depending upon the characteristic of each MPH block within the data group. 
     Herein, the data group is divided into a plurality of regions to be used for different purposes. More specifically, a region of the main service data having no interference or a very low interference level may be considered to have a more resistant (or stronger) receiving performance as compared to regions having higher interference levels. Additionally, when using a system inserting and transmitting known data in the data group, wherein the known data are known based upon an agreement between the transmitting system and the receiving system, and when consecutively long known data are to be periodically inserted in the mobile service data, the known data having a predetermined length may be periodically inserted in the region having no interference from the main service data (i.e., a region wherein the main service data are not mixed). However, due to interference from the main service data, it is difficult to periodically insert known data and also to insert consecutively long known data to a region having interference from the main service data. 
     Referring to  FIG. 5 , MPH block  4  (B 4 ) to MPH block  7  (B 7 ) correspond to regions without interference of the main service data. MPH block  4  (B 4 ) to MPH block  7  (B 7 ) within the data group shown in  FIG. 5  correspond to a region where no interference from the main service data occurs. In this example, a long known data sequence is inserted at both the beginning and end of each MPH block. In the description of the present invention, the region including MPH block  4  (B 4 ) to MPH block  7  (B 7 ) will be referred to as “region A (=B 4 +B 5 +B 6 +B 7 )”. As described above, when the data group includes region A having a long known data sequence inserted at both the beginning and end of each MPH block, the receiving system is capable of performing equalization by using the channel information that can be obtained from the known data. Therefore, the strongest equalizing performance may be yielded (or obtained) from one of region A to region D. 
     In the example of the data group shown in  FIG. 5 , MPH block  3  (B 3 ) and MPH block  8  (B 8 ) correspond to a region having little interference from the main service data. Herein, a long known data sequence is inserted in only one side of each MPH block B 3  and B 8 . More specifically, due to the interference from the main service data, a long known data sequence is inserted at the end of MPH block  3  (B 3 ), and another long known data sequence is inserted at the beginning of MPH block  8  (B 8 ). In the present invention, the region including MPH block  3  (B 3 ) and MPH block  8  (B 8 ) will be referred to as “region B(=B 3 +B 8 )”. As described above, when the data group includes region B having a long known data sequence inserted at only one side (beginning or end) of each MPH block, the receiving system is capable of performing equalization by using the channel information that can be obtained from the known data. Therefore, a stronger equalizing performance as compared to region C/D may be yielded (or obtained). 
     Referring to  FIG. 5 , MPH block  2  (B 2 ) and MPH block  9  (B 9 ) correspond to a region having more interference from the main service data as compared to region B. A long known data sequence cannot be inserted in any side of MPH block  2  (B 2 ) and MPH block  9  (B 9 ). Herein, the region including MPH block  2  (B 2 ) and MPH block  9  (B 9 ) will be referred to as “region C(=B 2 +B 9 )”. Finally, in the example shown in  FIG. 5 , MPH block  1  (B 1 ) and MPH block  10  (B 10 ) correspond to a region having more interference from the main service data as compared to region C. Similarly, a long known data sequence cannot be inserted in any side of MPH block  1  (B 1 ) and MPH block  10  (B 10 ). Herein, the region including MPH block  1  (B 1 ) and MPH block  10  (B 10 ) will be referred to as “region D (=B 1 +B 10 )”. Since region C/D is spaced further apart from the known data sequence, when the channel environment undergoes frequent and abrupt changes, the receiving performance of region C/D may be deteriorated. 
       FIG. 7  illustrates a data structure prior to data interleaving. More specifically,  FIG. 7  illustrates an example of 118 data packets being allocated to a data group.  FIG. 7  shows an example of a data group consisting of 118 data packets, wherein, based upon a reference packet (e.g., a 1 st  packet (or data segment) or 157 th  packet (or data segment) after a field synchronization signal), when allocating data packets to a VSB frame, 37 packets are included before the reference packet and 81 packets (including the reference packet) are included afterwards. In other words, with reference to  FIG. 5 , a field synchronization signal is placed (or assigned) between MPH block  2  (B 2 ) and MPH block  3  (B 3 ). Accordingly, this indicates that the slot has an off-set of 37 data packets with respect to the corresponding VSB field. The size of the data groups, number of hierarchical regions within the data group, the size of each region, the number of MPH blocks included in each region, the size of each MPH block, and so on described above are merely exemplary. Therefore, the present invention will not be limited to the examples described above. 
       FIG. 9  illustrates an exemplary assignment order of data groups being assigned to one of 5 sub-frames, wherein the 5 sub-frames configure an MPH frame. For example, the method of assigning data groups may be identically applied to all MPH frames or differently applied to each MPH frame. Furthermore, the method of assigning data groups may be identically applied to all sub-frames or differently applied to each sub-frame. At this point, when it is assumed that the data groups are assigned using the same method in all sub-frames of the corresponding MPH frame, the total number of data groups being assigned to an MPH frame is equal to a multiple of ‘5’. According to the embodiment of the present invention, a plurality of consecutive data groups is assigned to be spaced as far apart from one another as possible within the MPH frame. Thus, the system can be capable of responding promptly and effectively to any burst error that may occur within a sub-frame. 
     For example, when it is assumed that 3 data groups are assigned to a sub-frame, the data groups are assigned to a 1 st  slot (Slot # 0 ), a 5 th  slot (Slot # 4 ), and a 9 th  slot (Slot # 8 ) in the sub-frame, respectively.  FIG. 9  illustrates an example of assigning 16 data groups in one sub-frame using the above-described pattern (or rule). In other words, each data group is serially assigned to 16 slots corresponding to the following numbers: 0, 8, 4, 12, 1, 9, 5, 13, 2, 10, 6, 14, 3, 11, 7, and 15. Equation 1 below shows the above-described rule (or pattern) for assigning data groups in a sub-frame.
 
j=(4i+0)mod 16   Equation 1
         0=0 if i&lt;4,   0=2 else if i&lt;8,   Herein,   0=1 else if i&lt;12,   0=3 else.   Herein, j indicates the slot number within a sub-frame. The value of j may range from 0 to 15 (i.e., 0≦j≦15). Also, variable i indicates the data group number. The value of i may range from 0 to 15 (i.e., 0≦i≦15).       

     In the present invention, a collection of data groups included in a MPH frame will be referred to as a “parade”. Based upon the RS frame mode, the parade transmits data of at least one specific RS frame. The mobile service data within one RS frame may be assigned either to all of regions A/B/C/D within the corresponding data group, or to at least one of regions A/B/C/D. In the embodiment of the present invention, the mobile service data within one RS frame may be assigned either to all of regions A/B/C/D, or to at least one of regions A/B and regions C/D. If the mobile service data are assigned to the latter case (i.e., one of regions A/B and regions C/D), the RS frame being assigned to regions A/B and the RS frame being assigned to regions C/D within the corresponding data group are different from one another. 
     In the description of the present invention, the RS frame being assigned to regions A/B within the corresponding data group will be referred to as a “primary RS frame”, and the RS frame being assigned to regions C/D within the corresponding data group will be referred to as a “secondary RS frame”, for simplicity. Also, the primary RS frame and the secondary RS frame form (or configure) one parade. More specifically, when the mobile service data within one RS frame are assigned either to all of regions A/B/C/D within the corresponding data group, one parade transmits one RS frame. Conversely, when the mobile service data within one RS frame are assigned either to at least one of regions A/B and regions C/D, one parade may transmit up to 2 RS frames. More specifically, the RS frame mode indicates whether a parade transmits one RS frame, or whether the parade transmits two RS frames. Table 1 below shows an example of the RS frame mode. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 RS frame mode 
                   
               
               
                 (2 bits) 
                 Description 
               
               
                   
               
             
            
               
                 00 
                 There is only one primary RS frame for all group 
               
               
                   
                 regions 
               
               
                 01 
                 There are two separate RS frames. 
               
               
                   
                 Primary RS frame for group regions A and B 
               
               
                   
                 Secondary RS frame for group regions C and D 
               
               
                 10 
                 Reserved 
               
               
                 11 
                 Reserved 
               
               
                   
               
            
           
         
       
     
     Table 1 illustrates an example of allocating 2 bits in order to indicate the RS frame mode. For example, referring to Table 1, when the RS frame mode value is equal to ‘00’, this indicates that one parade transmits one RS frame. And, when the RS frame mode value is equal to ‘01’, this indicates that one parade transmits two RS frames, i.e., the primary RS frame and the secondary RS frame. More specifically, when the RS frame mode value is equal to ‘01’, data of the primary RS frame for regions A/B are assigned and transmitted to regions A/B of the corresponding data group. Similarly, data of the secondary RS frame for regions C/D are assigned and transmitted to regions C/D of the corresponding data group. 
     Additionally, one RS frame transmits one ensemble. Herein, the ensemble is a collection of services requiring the same quality of service (QOS) and being encoded with the same FEC codes. More specifically, when one parade is configured of one RS frame, then one parade transmits one ensemble. Conversely, when one parade is configured of two RS frames, i.e., when one parade is configured of a primary RS frame and a secondary RS frame, then one parade transmits two ensembles (i.e., a primary ensemble and a secondary ensemble). More specifically, the primary ensemble is transmitted through a primary RS frame of a parade, and the secondary ensemble is transmitted through a secondary RS frame of a parade. The RS frame is a 2-dimensional data frame through which an ensemble is RS-CRC encoded. 
     As described in the assignment of data groups, the parades are also assigned to be spaced as far apart from one another as possible within the sub-frame. Thus, the system can be capable of responding promptly and effectively to any burst error that may occur within a sub-frame. Furthermore, the method of assigning parades may be identically applied to all sub-frames or differently applied to each sub-frame. According to the embodiment of the present invention, the parades may be assigned differently for each MPH frame and identically for all sub-frames within an MPH frame. More specifically, the MPH frame structure may vary by MPH frame units. Thus, an ensemble rate may be adjusted on a more frequent and flexible basis. 
       FIG. 10  illustrates an example of multiple data groups of a single parade being assigned (or allocated) to an MPH frame. More specifically,  FIG. 10  illustrates an example of a plurality of data groups included in a single parade, wherein the number of data groups included in a sub-frame is equal to ‘3’, being allocated to an MPH frame. Referring to  FIG. 10 , 3 data groups are sequentially assigned to a sub-frame at a cycle period of 4 slots. Accordingly, when this process is equally performed in the 5 sub-frames included in the corresponding MPH frame, 15 data groups are assigned to a single MPH frame. Herein, the 15 data groups correspond to data groups included in a parade. Therefore, since one sub-frame is configured of 4 VSB frame, and since 3 data groups are included in a sub-frame, the data group of the corresponding parade is not assigned to one of the 4 VSB frames within a sub-frame. 
     For example, when it is assumed that one parade transmits one RS frame, and that a RS frame encoder located in a later block performs RS-encoding on the corresponding RS frame, thereby adding 24 bytes of parity data to the corresponding RS frame and transmitting the processed RS frame, the parity data occupy approximately 11.37% (=24/(187+24)×100) of the total code word length. Meanwhile, when one sub-frame includes 3 data groups, and when the data groups included in the parade are assigned, as shown in  FIG. 10 , a total of 15 data groups form an RS frame. Accordingly, even when an error occurs in an entire data group due to a burst noise within a channel, the percentile is merely 6.67% (= 1/15×100). Therefore, the receiving system may correct all errors by performing an erasure RS decoding process. More specifically, when the erasure RS decoding is performed, a number of channel errors corresponding to the number of RS parity bytes may be corrected. By doing so, the receiving system may correct the error of at least one data group within one parade. Thus, the minimum burst noise length correctable by a RS frame is over 1 VSB frame. 
     Meanwhile, when data groups of a parade are assigned as described above, either main service data may be assigned between each data group, or data groups corresponding to different parades may be assigned between each data group. More specifically, data groups corresponding to multiple parades may be assigned to one MPH frame. Basically, the method of assigning data groups corresponding to multiple parades is very similar to the method of assigning data groups corresponding to a single parade. In other words, data groups included in other parades that are to be assigned to an MPH frame are also respectively assigned according to a cycle period of 4 slots. At this point, data groups of a different parade may be sequentially assigned to the respective slots in a circular method. Herein, the data groups are assigned to slots starting from the ones to which data groups of the previous parade have not yet been assigned. For example, when it is assumed that data groups corresponding to a parade are assigned as shown in  FIG. 10 , data groups corresponding to the next parade may be assigned to a sub-frame starting either from the 12 th  slot of a sub-frame. However, this is merely exemplary. In another example, the data groups of the next parade may also be sequentially assigned to a different slot within a sub-frame at a cycle period of 4 slots starting from the 3 rd  slot. 
       FIG. 11  illustrates an example of transmitting 3 parades (Parade # 0 , Parade # 1 , and Parade # 2 ) to an MPH frame. More specifically,  FIG. 11  illustrates an example of transmitting parades included in one of 5 sub-frames, wherein the 5 sub-frames configure one MPH frame. When the 1 st  parade (Parade # 0 ) includes 3 data groups for each sub-frame, the positions of each data groups within the sub-frames may be obtained by substituting values ‘0’ to ‘2’ for i in Equation 1. More specifically, the data groups of the 1 st  parade (Parade # 0 ) are sequentially assigned to the 1 st , 5 th , and 9 th  slots (Slot # 0 , Slot # 4 , and Slot # 8 ) within the sub-frame. Also, when the 2 nd  parade includes 2 data groups for each sub-frame, the positions of each data groups within the sub-frames may be obtained by substituting values ‘3’ and ‘4’ for i in Equation 1. More specifically, the data groups of the 2 nd  parade (Parade # 1 ) are sequentially assigned to the 2 nd  and 12 th  slots (Slot # 3  and Slot # 11 ) within the sub-frame. Finally, when the 3 rd  parade includes 2 data groups for each sub-frame, the positions of each data groups within the sub-frames may be obtained by substituting values ‘5’ and ‘6’ for i in Equation 1. More specifically, the data groups of the 3 rd  parade (Parade # 2 ) are sequentially assigned to the 7 th  and 11 th  slots (Slot # 6  and Slot # 10 ) within the sub-frame. 
     As described above, data groups of multiple parades may be assigned to a single MPH frame, and, in each sub-frame, the data groups are serially allocated to a group space having 4 slots from left to right. Therefore, a number of groups of one parade per sub-frame (NOG) may correspond to any one integer from ‘1’ to ‘8’. Herein, since one MPH frame includes 5 sub-frames, the total number of data groups within a parade that can be allocated to an MPH frame may correspond to any one multiple of ‘5’ ranging from ‘5’ to ‘40’. 
       FIG. 12  illustrates an example of expanding the assignment process of 3 parades, shown in  FIGS. 11 , to 5 sub-frames within an MPH frame. 
     General Description of the Transmitting System 
       FIG. 13  illustrates a block diagram showing a general structure of a digital broadcast transmitting system according to an embodiment of the present invention. 
     Herein, the digital broadcast transmitting includes a service multiplexer  100  and a transmitter  200 . Herein, the service multiplexer  100  is located in the studio of each broadcast station, and the transmitter  200  is located in a site placed at a predetermined distance from the studio. The transmitter  200  may be located in a plurality of different locations. Also, for example, the plurality of transmitters may share the same frequency. And, in this case, the plurality of transmitters receives the same signal. Accordingly, in the receiving system, a channel equalizer may compensate signal distortion, which is caused by a reflected wave, so as to recover the original signal. In another example, the plurality of transmitters may have different frequencies with respect to the same channel. 
     A variety of methods may be used for data communication each of the transmitters, which are located in remote positions, and the service multiplexer. For example, an interface standard such as a synchronous serial interface for transport of MPEG-2 data (SMPTE-310M). In the SMPTE-310M interface standard, a constant data rate is decided as an output data rate of the service multiplexer. For example, in case of the 8VSB mode, the output data rate is 19.39 Mbps, and, in case of the 16VSB mode, the output data rate is 38.78 Mbps. Furthermore, in the conventional 8VSB mode transmitting system, a transport stream (TS) packet having a data rate of approximately 19.39 Mbps may be transmitted through a single physical channel. Also, in the transmitting system according to the present invention provided with backward compatibility with the conventional transmitting system, additional encoding is performed on the mobile service data. Thereafter, the additionally encoded mobile service data are multiplexed with the main service data to a TS packet form, which is then transmitted. At this point, the data rate of the multiplexed TS packet is approximately 19.39 Mbps. 
     At this point, the service multiplexer  100  receives at least one type of mobile service data and program specific information/program and system information protocol (PSI/PSIP) table data for each mobile service so as to encapsulate the received data to each TS packet. Also, the service multiplexer  100  receives at least one type of main service data and PSI/PSIP table data for each main service and encapsulates the received data to a transport stream (TS) packet. Subsequently, the TS packets are multiplexed according to a predetermined multiplexing rule and outputs the multiplexed packets to the transmitter  200 . 
     Service Multiplexer 
       FIG. 14  illustrates a block diagram showing an example of the service multiplexer. The service multiplexer includes a controller  110  for controlling the overall operations of the service multiplexer, a PSI/PSIP generator  120  for the main service, a PSI/PSIP generator  130  for the mobile service, a null packet generator  140 , a mobile service multiplexer  150 , and a transport multiplexer  160 . 
     The transport multiplexer  160  may include a main service multiplexer  161  and a transport stream (TS) packet multiplexer  162 . 
     Referring to  FIG. 14 , at least one type of compression encoded main service data and the PSI/PSIP table data generated from the PSI/PSIP generator  120  for the main service are inputted to the main service multiplexer  161  of the transport multiplexer  160 . The main service multiplexer  161  encapsulates each of the inputted main service data and PSI/PSIP table data to MPEG-2 TS packet forms. Then, the MPEG-2 TS packets are multiplexed and outputted to the TS packet multiplexer  162 . Herein, the data packet being outputted from the main service multiplexer  161  will be referred to as a main service data packet for simplicity. 
     Thereafter, at least one type of the compression encoded mobile service data and the PSI/PSIP table data generated from the PSI/PSIP generator  130  for the mobile service are inputted to the mobile service multiplexer  150 . 
     The mobile service multiplexer  150  encapsulates each of the inputted mobile service data and PSI/PSIP table data to MPEG-2 TS packet forms. Then, the MPEG-2 TS packets are multiplexed and outputted to the TS packet multiplexer  162 . Herein, the data packet being outputted from the mobile service multiplexer  150  will be referred to as a mobile service data packet for simplicity. 
     At this point, the transmitter  200  requires identification information in order to identify and process the main service data packet and the mobile service data packet. Herein, the identification information may use values pre-decided in accordance with an agreement between the transmitting system and the receiving system, or may be configured of a separate set of data, or may modify predetermined location value with in the corresponding data packet. 
     As an example of the present invention, a different packet identifier (PID) may be assigned to identify each of the main service data packet and the mobile service data packet. 
     In another example, by modifying a synchronization data byte within a header of the mobile service data, the service data packet may be identified by using the synchronization data byte value of the corresponding service data packet. For example, the synchronization byte of the main service data packet directly outputs the value decided by the ISO/IEC13818-1 standard (i.e., 0x47) without any modification. The synchronization byte of the mobile service data packet modifies and outputs the value, thereby identifying the main service data packet and the mobile service data packet. Conversely, the synchronization byte of the main service data packet is modified and outputted, whereas the synchronization byte of the mobile service data packet is directly outputted without being modified, thereby enabling the main service data packet and the mobile service data packet to be identified. 
     A plurality of methods may be applied in the method of modifying the synchronization byte. For example, each bit of the synchronization byte may be inversed, or only a portion of the synchronization byte may be inversed. 
     As described above, any type of identification information may be used to identify the main service data packet and the mobile service data packet. Therefore, the scope of the present invention is not limited only to the example set forth in the description of the present invention. 
     Meanwhile, a transport multiplexer used in the conventional digital broadcasting system may be used as the transport multiplexer  160  according to the present invention. More specifically, in order to multiplex the mobile service data and the main service data and to transmit the multiplexed data, the data rate of the main service is limited to a data rate of (19.39-K) Mbps. Then, K Mbps, which corresponds to the remaining data rate, is assigned as the data rate of the mobile service. Thus, the transport multiplexer which is already being used may be used as it is without any modification. 
     Herein, the transport multiplexer  160  multiplexes the main service data packet being outputted from the main service multiplexer  161  and the mobile service data packet being outputted from the mobile service multiplexer  150 . Thereafter, the transport multiplexer  160  transmits the multiplexed data packets to the transmitter  200 . 
     However, in some cases, the output data rate of the mobile service multiplexer  150  may not be equal to K Mbps. In this case, the mobile service multiplexer  150  multiplexes and outputs null data packets generated from the null packet generator  140  so that the output data rate can reach K Mbps. More specifically, in order to match the output data rate of the mobile service multiplexer  150  to a constant data rate, the null packet generator  140  generates null data packets, which are then outputted to the mobile service multiplexer  150 . 
     For example, when the service multiplexer  100  assigns K Mbps of the 19.39 Mbps to the mobile service data, and when the remaining (19.39-K) Mbps is, therefore, assigned to the main service data, the data rate of the mobile service data that are multiplexed by the service multiplexer  100  actually becomes lower than K Mbps. This is because, in case of the mobile service data, the pre-processor of the transmitting system performs additional encoding, thereby increasing the amount of data. Eventually, the data rate of the mobile service data, which may be transmitted from the service multiplexer  100 , becomes smaller than K Mbps. 
     For example, since the pre-processor of the transmitter performs an encoding process on the mobile service data at a coding rate of at least 1/2, the amount of the data outputted from the pre-processor is increased to more than twice the amount of the data initially inputted to the pre-processor. Therefore, the sum of the data rate of the main service data and the data rate of the mobile service data, both being multiplexed by the service multiplexer  100 , becomes either equal to or smaller than 19.39 Mbps. 
     Therefore, in order to match the data rate of the data that are finally outputted from the service multiplexer  100  to a constant data rate (e.g., 19.39 Mbps), an amount of null data packets corresponding to the amount of lacking data rate is generated from the null packet generator  140  and outputted to the mobile service multiplexer  150 . 
     Accordingly, the mobile service multiplexer  150  encapsulates each of the mobile service data and the PSI/PSIP table data that are being inputted to a MPEG-2 TS packet form. Then, the above-described TS packets are multiplexed with the null data packets and, then, outputted to the TS packet multiplexer  162 . 
     Thereafter, the TS packet multiplexer  162  multiplexes the main service data packet being outputted from the main service multiplexer  161  and the mobile service data packet being outputted from the mobile service multiplexer  150  and transmits the multiplexed data packets to the transmitter  200  at a data rate of 19.39 Mbps. 
     According to an embodiment of the present invention, the mobile service multiplexer  150  receives the null data packets. However, this is merely exemplary and does not limit the scope of the present invention. In other words, according to another embodiment of the present invention, the TS packet multiplexer  162  may receive the null data packets, so as to match the data rate of the finally outputted data to a constant data rate. Herein, the output path and multiplexing rule of the null data packet is controlled by the controller  110 . The controller  110  controls the multiplexing processed performed by the mobile service multiplexer  150 , the main service multiplexer  161  of the transport multiplexer  160 , and the TS packet multiplexer  162 , and also controls the null data packet generation of the null packet generator  140 . At this point, the transmitter  200  discards the null data packets transmitted from the service multiplexer  100  instead of transmitting the null data packets. 
     Further, in order to allow the transmitter  200  to discard the null data packets transmitted from the service multiplexer  100  instead of transmitting them, identification information for identifying the null data packet is required. Herein, the identification information may use values pre-decided in accordance with an agreement between the transmitting system and the receiving system. For example, the value of the synchronization byte within the header of the null data packet may be modified so as to be used as the identification information. Alternatively, a transport_error_indicator flag may also be used as the identification information. 
     In the description of the present invention, an example of using the transport_error_indicator flag as the identification information will be given to describe an embodiment of the present invention. In this case, the transport_error_indicator flag of the null data packet is set to ‘1’, and the transport_error_indicator flag of the remaining data packets are reset to ‘0’, so as to identify the null data packet. More specifically, when the null packet generator  140  generates the null data packets, if the transport_error_indicator flag from the header field of the null data packet is set to ‘1’ and then transmitted, the null data packet may be identified and, therefore, be discarded. In the present invention, any type of identification information for identifying the null data packets may be used. Therefore, the scope of the present invention is not limited only to the examples set forth in the description of the present invention. 
     According to another embodiment of the present invention, a transmission parameter may be included in at least a portion of the null data packet, or at least one table or an operations and maintenance (OM) packet (or OMP) of the PSI/PSIP table for the mobile service. In this case, the transmitter  200  extracts the transmission parameter and outputs the extracted transmission parameter to the corresponding block and also transmits the extracted parameter to the receiving system if required. More specifically, a packet referred to as an OMP is defined for the purpose of operating and managing the transmitting system. For example, the OMP is configured in accordance with the MPEG-2 TS packet format, and the corresponding PID is given the value of 0x1FFA. The OMP is configured of a 4-byte header and a 184-byte payload. Herein, among the 184 bytes, the first byte corresponds to an OM_type field, which indicates the type of the OM packet. 
     In the present invention, the transmission parameter may be transmitted in the form of an OMP. And, in this case, among the values of the reserved fields within the OM_type field, a pre-arranged value is used, thereby indicating that the transmission parameter is being transmitted to the transmitter  200  in the form of an OMP. More specifically, the transmitter  200  may find (or identify) the OMP by referring to the PID. Also, by parsing the OM_type field within the OMP, the transmitter  200  can verify whether a transmission parameter is included after the OM_type field of the corresponding packet. The transmission parameter corresponds to supplemental data required for processing mobile service data from the transmitting system and the receiving system. 
     The transmission parameter corresponds to supplemental data required for processing mobile service data from the transmitting system and the receiving system. Herein, the transmission parameter may include data group information, region information within the data group, block information, RS frame information, super frame information, MPH frame information, parade information, ensemble information, information associated with serial concatenated convolution code (SCCC), and RS code information. The significance of some information within the transmission parameters has already been described in detail. Descriptions of other information that have not yet been described will be in detail in a later process. 
     The transmission parameter may also include information on how signals of a symbol domain are encoded in order to transmit the mobile service data, and multiplexing information on how the main service data and the mobile service data or various types of mobile service data are multiplexed. 
     The information included in the transmission parameter are merely exemplary to facilitate the understanding of the present invention. And, the adding and deleting of the information included in the transmission parameter may be easily modified and changed by anyone skilled in the art. Therefore, the present invention is not limited to the examples proposed in the description set forth herein. 
     Furthermore, the transmission parameters may be provided from the service multiplexer  100  to the transmitter  200 . Alternatively, the transmission parameters may also be set up by an internal controller (not shown) within the transmitter  200  or received from an external source. 
     Transmitter 
       FIG. 15  illustrates a block diagram showing an example of the transmitter  200  according to an embodiment of the present invention. Herein, the transmitter  200  includes a controller  200 , a demultiplexer  210 , a packet jitter mitigator  220 , a pre-processor  230 , a packet multiplexer  240 , a post-processor  250 , a synchronization (sync) multiplexer  260 , and a transmission unit  270 . Herein, when a data packet is received from the service multiplexer  100 , the demultiplexer  210  should identify whether the received data packet corresponds to a main service data packet, a mobile service data packet, or a null data packet. For example, the demultiplexer  210  uses the PID within the received data packet so as to identify the main service data packet and the mobile service data packet. Then, the demultiplexer  210  uses a transport_error_indicator field to identify the null data packet. The main service data packet identified by the demultiplexer  210  is outputted to the packet jitter mitigator  220 , the mobile service data packet is outputted to the pre-processor  230 , and the null data packet is discarded. If a transmission parameter is included in the null data packet, then the transmission parameter is first extracted and outputted to the corresponding block. Thereafter, the null data packet is discarded. 
     The pre-processor  230  performs an additional encoding process of the mobile service data included in the service data packet, which is demultiplexed and outputted from the demultiplexer  210 . The pre-processor  230  also performs a process of configuring a data group so that the data group may be positioned at a specific place in accordance with the purpose of the data, which are to be transmitted on a transmission frame. This is to enable the mobile service data to respond swiftly and strongly against noise and channel changes. The pre-processor  230  may also refer to the transmission parameter when performing the additional encoding process. Also, the pre-processor  230  groups a plurality of mobile service data packets to configure a data group. Thereafter, known data, mobile service data, RS parity data, and MPEG header are allocated to pre-determined regions within the data group. 
     Pre-processor within Transmitter 
       FIG. 16  illustrates a block diagram showing the structure of a pre-processor  230  according to the present invention. Herein, the pre-processor  230  includes an MPH frame encoder  301 , a block processor  302 , a group formatter  303 , a signaling encoder  304 , and a packet formatter  305 . The MPH frame encoder  301 , which is included in the pre-processor  230  having the above-described structure, data-randomizes the mobile service data that are inputted to the demultiplexer  210 , thereby creating a RS frame. Then, the MPH frame encoder  301  performs an encoding process for error correction in RS frame units. The MPH frame encoder  301  may include at least one RS frame encoder. More specifically, RS frame encoders may be provided in parallel, wherein the number of RS frame encoders is equal to the number of parades within the MPH frame. As described above, the MPH frame is a basic time cycle period for transmitting at least one parade. Also, each parade consists of one or two RS frames. 
       FIG. 17  illustrates a conceptual block diagram of the MPH frame encoder  301  according to an embodiment of the present invention. The MPH frame encoder  301  includes an input demultiplexer (DEMUX)  309 , M number of RS frame encoders  310  to  31 M−1, and an output multiplexer (MUX)  320 . Herein, M represent the number of parades included in one MPH frame. The input demultiplexer (DEMUX)  309  splits input ensembles. Then, the split input ensembles decide the RS frame to which the ensembles are to be inputted. Thereafter, the inputted ensembles are outputted to the respective RS frame. At this point, an ensemble may be mapped to each RS frame encoder or parade. For example, when one parade configures one RS frame, the ensembles, RS frames, and parades may each be mapped to be in a one-to-one (1:1) correspondence with one another. More specifically, the data in one ensemble configure a RS frame. And, a RS frame is divided into a plurality of data groups. Based upon the RS frame mode of Table 1, the data within one RS frame may be assigned either to all of regions A/B/C/D within multiple data groups, or to at least one of regions A/B and regions C/D within multiple data groups. 
     When the RS frame mode value is equal to ‘01’, i.e., when the data of the primary RS frame are assigned to regions A/B of the corresponding data group and data of the secondary RS frame are assigned to regions C/D of the corresponding data group, each RS frame encoder creates a primary RS frame and a secondary RS frame for each parade. Conversely, when the RS frame mode value is equal to ‘00’, when the data of the primary RS frame are assigned to all of regions A/B/C/D, each RS frame encoder creates a RS frame (i.e., a primary RS frame) for each parade. Also, each RS frame encoder divides each RS frame into several portions. Each portion of the RS frame is equivalent to a data amount that can be transmitted by a data group. 
     The output multiplexer (MUX)  320  multiplexes portions within M number of RS frame encoders  310  to  310 M−1 are multiplexed and then outputted to the block processor  302 . For example, if one parade transmits two RS frames, portions of primary RS frames within M number of RS frame encoders  310  to  310 M−1 are multiplexed and outputted. Thereafter, portions of secondary RS frames within M number of RS frame encoders  310  to  310 M−1 are multiplexed and transmitted. The input demultiplexer (DEMUX)  309  and the output multiplexer (MUX)  320  operate based upon the control of the control unit  200 . The control unit  200  may provide necessary (or required) FEC modes to each RS frame encoder. The FEC mode includes the RS code mode, which will be described in detail in a later process. 
       FIG. 18  illustrates a detailed block diagram of an RS frame encoder among a plurality of RS frame encoders within an MPH frame encoder. One RS frame encoder may include a primary encoder  410  and a secondary encoder  420 . Herein, the secondary encoder  420  may or may not operate based upon the RS frame mode. For example, when the RS frame mode value is equal to ‘00’, as shown in Table 1, the secondary encoder  420  does not operate. The primary encoder  410  may include a data randomizer  411 , a Reed-Solomon-cyclic redundancy check (RS-CRC) encoder ( 412 ), and a RS frame divider  413 . And, the secondary encoder  420  may also include a data randomizer  421 , a RS-CRC encoder ( 422 ), and a RS frame divider  423 . 
     More specifically, the data randomizer  411  of the primary encoder  410  receives mobile service data of a primary ensemble outputted from the output demultiplexer (DEMUX)  309 . Then, after randomizing the received mobile service data, the data randomizer  411  outputs the randomized data to the RS-CRC encoder  412 . At this point, since the data randomizer  411  performs the randomizing process on the mobile service data, the randomizing process that is to be performed by the data randomizer  251  of the post-processor  250  on the mobile service data may be omitted. The data randomizer  411  may also discard the synchronization byte within the mobile service data packet and perform the randomizing process. This is an option that may be chosen by the system designer. In the example given in the present invention, the randomizing process is performed without discarding the synchronization byte within the corresponding mobile service data packet. 
     The RS-CRC encoder  412  uses at least one of a Reed-Solomon (RS) code and a cyclic redundancy check (CRC) code, so as to perform forward error collection (FEC) encoding on the randomized primary ensemble, thereby forming a primary RS frame. Therefore, the RS-CRC encoder  412  outputs the newly formed primary RS frame to the RS frame divider  413 . The RS-CRC encoder  412  groups a plurality of mobile service data packets that is randomized and inputted, so as to create a RS frame. Then, the RS-CRC encoder  412  performs at least one of an error correction encoding process and an error detection encoding process in RS frame units. Accordingly, robustness may be provided to the mobile service data, thereby scattering group error that may occur during changes in a frequency environment, thereby enabling the mobile service data to respond to the frequency environment, which is extremely vulnerable and liable to frequent changes. Also, the RS-CRC encoder  412  groups a plurality of RS frame so as to create a super frame, thereby performing a row permutation process in super frame units. The row permutation process may also be referred to as a “row interleaving process”. Hereinafter, the process will be referred to as “row permutation” for simplicity. 
     More specifically, when the RS-CRC encoder  412  performs the process of permuting each row of the super frame in accordance with a pre-determined rule, the position of the rows within the super frame before and after the row permutation process is changed. If the row permutation process is performed by super frame units, and even though the section having a plurality of errors occurring therein becomes very long, and even though the number of errors included in the RS frame, which is to be decoded, exceeds the extent of being able to be corrected, the errors become dispersed within the entire super frame. Thus, the decoding ability is even more enhanced as compared to a single RS frame. 
     At this point, as an example of the present invention, RS-encoding is applied for the error correction encoding process, and a cyclic redundancy check (CRC) encoding is applied for the error detection process in the RS-CRC encoder  412 . When performing the RS-encoding, parity data that are used for the error correction are generated. And, when performing the CRC encoding, CRC data that are used for the error detection are generated. The CRC data generated by CRC encoding may be used for indicating whether or not the mobile service data have been damaged by the errors while being transmitted through the channel. In the present invention, a variety of error detection coding methods other than the CRC encoding method may be used, or the error correction coding method may be used to enhance the overall error correction ability of the receiving system. Herein, the RS-CRC encoder  412  refers to a pre-determined transmission parameter provided by the control unit  200  and/or a transmission parameter provided from the service multiplexer  100  so as to perform operations including RS frame configuration, RS encoding, CRC encoding, super frame configuration, and row permutation in super frame units. 
       FIG. 19  illustrates a process of one or two RS frame being divided into several portions, based upon an RS frame mode value, and a process of each portion being assigned to a corresponding region within the respective data group. More specifically,  FIG. 19(a)  shows an example of the RS frame mode value being equal to ‘00’. Herein, only the primary encoder  410  of  FIG. 18  operates, thereby forming one RS frame for one parade. Then, the RS frame is divided into several portions, and the data of each portion are assigned to regions A/B/C/D within the respective data group.  FIG. 19(b)  shows an example of the RS frame mode value being equal to ‘01’. Herein, both the primary encoder  410  and the secondary encoder  420  of  FIG. 18  operate, thereby forming two RS frames for one parade, i.e., one primary RS frame and one secondary RS frame. Then, the primary RS frame is divided into several portions, and the secondary RS frame is divided into several portions. At this point, the data of each portion of the primary RS frame are assigned to regions A/B within the respective data group. And, the data of each portion of the secondary RS frame are assigned to regions C/D within the respective data group. 
     Detailed Description of the RS Frame 
       FIG. 20(a)  illustrates an example of an RS frame being generated from the RS-CRC encoder  412  according to the present invention. According to this embodiment, in the RS frame, the length of a column (i.e., number of rows) is set to 187 bytes, and the length of a row (i.e., number of column) is set to N bytes. At this point, the value of N, which corresponds to the number of columns within an RS frame, can be decided according to Equation 2. 
     
       
         
           
             
               
                 
                   N 
                   = 
                   
                     
                       ⌊ 
                       
                         
                           5 
                           × 
                           NoG 
                           × 
                           PL 
                         
                         
                           187 
                           + 
                           P 
                         
                       
                       ⌋ 
                     
                     - 
                     2 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
               
             
           
         
       
         
         
           
             Herein, NoG indicates the number of data groups assigned to a sub-frame. PL represents the number of SCCC payload data bytes assigned to a data group. And, P signifies the number of RS parity data bytes added to each column of the RS frame. Finally, └X┘ is the greatest integer that is equal to or smaller than X. 
           
         
       
    
     More specifically, in Equation 2, PL corresponds to the length of an RS frame portion. The value of PL is equivalent to the number of SCCC payload data bytes that are assigned to the corresponding data group. Herein, the value of PL may vary depending upon the RS frame mode, SCCC block mode, and SCCC outer code mode. Table 2 to Table 5 below respectively show examples of PL values, which vary in accordance with the RS frame mode, SCCC block mode, and SCCC outer code mode. The SCCC block mode and the SCCC outer code mode will be described in detail in a later process. 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 SCCC outer code mode 
                   
               
            
           
           
               
               
               
               
               
            
               
                 for Region A 
                 for Region B 
                 for Region C 
                 for Region D 
                 PL 
               
               
                   
               
               
                 00 
                 00 
                 00 
                 00 
                 9624 
               
               
                 00 
                 00 
                 00 
                 01 
                 9372 
               
               
                 00 
                 00 
                 01 
                 00 
                 8886 
               
               
                 00 
                 00 
                 01 
                 01 
                 8634 
               
               
                 00 
                 01 
                 00 
                 00 
                 8403 
               
               
                 00 
                 01 
                 00 
                 01 
                 8151 
               
               
                 00 
                 01 
                 01 
                 00 
                 7665 
               
               
                 00 
                 01 
                 01 
                 01 
                 7413 
               
               
                 01 
                 00 
                 00 
                 00 
                 7023 
               
               
                 01 
                 00 
                 00 
                 01 
                 6771 
               
               
                 01 
                 00 
                 01 
                 00 
                 6285 
               
               
                 01 
                 00 
                 01 
                 01 
                 6033 
               
               
                 01 
                 01 
                 00 
                 00 
                 5802 
               
               
                 01 
                 01 
                 00 
                 01 
                 5550 
               
               
                 01 
                 01 
                 01 
                 00 
                 5064 
               
               
                 01 
                 01 
                 01 
                 01 
                 4812 
               
            
           
           
               
               
            
               
                 Others 
                 Reserved 
               
               
                   
               
            
           
         
       
     
     Table 2 shows an example of the PL values for each data group within an RS frame, wherein each PL value varies depending upon the SCCC outer code mode, when the RS frame mode value is equal to ‘00’, and when the SCCC block mode value is equal to ‘00’. For example, when it is assumed that each SCCC outer code mode value of regions A/B/C/D within the data group is equal to ‘00’ (i.e., the block processor  302  of a later block performs encoding at a coding rate of 1/2), the PL value within each data group of the corresponding RS frame may be equal to 9624 bytes. More specifically, 9624 bytes of mobile service data within one RS frame may be assigned to regions A/B/C/D of the corresponding data group. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 SCCC outer code mode 
                 PL 
               
               
                   
                   
               
             
            
               
                   
                 00 
                 9624 
               
               
                   
                 01 
                 4812 
               
               
                   
                 Others 
                 Reserved 
               
               
                   
                   
               
            
           
         
       
     
     Table 3 shows an example of the PL values for each data group within an RS frame, wherein each PL value varies depending upon the SCCC outer code mode, when the RS frame mode value is equal to ‘00’, and when the SCCC block mode value is equal to ‘01’. 
     
       
         
           
               
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 SCCC outer code mode 
                   
               
            
           
           
               
               
               
            
               
                 for Region A 
                 for Region B 
                 PL 
               
               
                   
               
               
                 00 
                 00 
                 7644 
               
               
                 00 
                 01 
                 6423 
               
               
                 01 
                 00 
                 5043 
               
               
                 01 
                 01 
                 3822 
               
            
           
           
               
               
            
               
                 Others 
                 Reserved 
               
               
                   
               
            
           
         
       
     
     Table 4 shows an example of the PL values for each data group within a primary RS frame, wherein each PL value varies depending upon the SCCC outer code mode, when the RS frame mode value is equal to ‘01’, and when the SCCC block mode value is equal to ‘00’. For example, when each SCCC outer code mode value of regions A/B is equal to ‘00’, 7644 bytes of mobile service data within a primary RS frame may be assigned to regions A/B of the corresponding data group. 
     
       
         
           
               
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 SCCC outer code mode 
                   
               
            
           
           
               
               
               
            
               
                 for Region C 
                 for Region D 
                 PL 
               
               
                   
               
            
           
           
               
               
               
            
               
                 00 
                 00 
                 1980 
               
               
                 00 
                 01 
                 1728 
               
               
                 01 
                 00 
                 1242 
               
               
                 01 
                 01 
                 990 
               
            
           
           
               
               
            
               
                 Others 
                 Reserved 
               
               
                   
               
            
           
         
       
     
     Table 5 shows an example of the PL values for each data group within a secondary RS frame, wherein each PL value varies depending upon the SCCC outer code mode, when the RS frame mode value is equal to ‘01’, and when the SCCC block mode value is equal to ‘00’. For example, when each SCCC outer code mode value of regions C/D is equal to ‘00’, 1980 bytes of mobile service data within a secondary RS frame may be assigned to regions C/D of the corresponding data group. 
     According to the embodiment of the present invention, the value of N is equal to or greater than 187 (i.e., N≧187). More specifically, the RS frame of  FIG. 20(a)  has the size of N(row)×187(column) bytes. More specifically, the RS-CRC encoder  412  first divides the inputted mobile service data bytes to units of a predetermined length. The predetermined length is decided by the system designer. And, in the example of the present invention, the predetermined length is equal to 187 bytes, and, therefore, the 187-byte unit will be referred to as a “packet” for simplicity. For example, the inputted mobile service data may correspond either to an MPEG transport stream (TS) packet configured of 188-byte units or to an IP datagram. Alternatively, the IP datagram may be encapsulated to a TS packet of 188-byte units and, then, inputted. 
     When the mobile service data that are being inputted correspond to a MPEG transport packet stream configured of 188-byte units, the first synchronization byte is removed so as to configure a 187-byte unit. Then, N number of packets are grouped to form an RS frame. Herein, the synchronization byte is removed because each mobile service data packet has the same value. Meanwhile, when the input mobile service data of the RS frame do not correspond to the MPEG TS packet format, the mobile service data are inputted N number of times in 187-byte units without being processed with the removing of the MPEG synchronization byte, thereby creating a RS frame. 
     In addition, when the input data format of the RS frame supports both the input data corresponding to the MPEG TS packet and the input data not corresponding to the MPEG TS packet, such information may be included in a transmission parameter transmitted from the service multiplexer  100 , thereby being sent to the transmitter  200 . Accordingly, the RS-CRC encoder  412  of the transmitter  200  receives this information to be able to control whether or not to perform the process of removing the MPEG synchronization byte. Also, the transmitter provides such information to the receiving system so as to control the process of inserting the MPEG synchronization byte that is to be performed by the RS frame decoder of the receiving system. Herein, the process of removing the synchronization byte may be performed during a randomizing process of the data randomizer  411  in an earlier process. In this case, the process of the removing the synchronization byte by the RS-CRC encoder  412  may be omitted. 
     Moreover, when adding synchronization bytes from the receiving system, the process may be performed by the data derandomizer instead of the RS frame decoder. Therefore, if a removable fixed byte (e.g., synchronization byte) does not exist within the mobile service data packet that is being inputted to the RS-CRC encoder  412 , or if the mobile service data that are being inputted are not configured in a packet format, the mobile service data that are being inputted are divided into 187-byte units, thereby configuring a packet for each 187-byte unit. 
     Subsequently, N number of packets configured of 187 bytes is grouped to configure a RS frame. At this point, the RS frame is configured as a RS frame having the size of N(row)×187(column) bytes, in which 187-byte packets are sequentially inputted in a row direction. More specifically, each of the N number of columns included in the RS frame includes 187 bytes. When the RS frame is created, as shown in  FIG. 20(a) , the RS-CRC encoder  412  performs a (Nc,Kc)-RS encoding process on each column, so as to generate Nc−Kc(=P) number of parity bytes. Then, the RS-CRC encoder  412  adds the newly generated P number of parity bytes after the very last byte of the corresponding column, thereby creating a column of (187+P) bytes. Herein, as shown in  FIG. 20(a) , Kc is equal to 187 (i.e., Kc=187), and Nc is equal to 187+P (i.e., Nc=187+P). Herein, the value of P may vary depending upon the RS code mode. Table 6 below shows an example of an RS code mode, as one of the RS encoding information. 
     
       
         
           
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 RS code mode 
                 RS code 
                 Number of Parity Bytes (P) 
               
               
                   
               
             
            
               
                 00 
                 (211, 187) 
                 24 
               
               
                 01 
                 (223, 187) 
                 36 
               
               
                 10 
                 (235, 187) 
                 48 
               
               
                 11 
                 Reserved 
                 Reserved 
               
               
                   
               
            
           
         
       
     
     Table 6 shows an example of 2 bits being assigned in order to indicate the RS code mode. The RS code mode represents the number of parity bytes corresponding to the RS frame. For example, when the RS code mode value is equal to ‘10’, (235,187)-RS-encoding is performed on the RS frame of  FIG. 20(a) , so as to generate 48 parity data bytes. Thereafter, the 48 parity bytes are added after the last data byte of the corresponding column, thereby creating a column of 235 data bytes. When the RS frame mode value is equal to ‘00’ in Table 1 (i.e., when the RS frame mode indicates a single RS frame), only the RS code mode of the corresponding RS frame is indicated. However, when the RS frame mode value is equal to ‘01’ in Table 1 (i.e., when the RS frame mode indicates multiple RS frames), the RS code mode corresponding to a primary RS frame and a secondary RS frame. More specifically, it is preferable that the RS code mode is independently applied to the primary RS frame and the secondary RS frame. 
     When such RS encoding process is performed on all N number of columns, a RS frame having the size of N(row)×(187+P)(column) bytes may be created, as shown in  FIG. 20(b) . Each row of the RS frame is configured of N bytes. However, depending upon channel conditions between the transmitting system and the receiving system, error may be included in the RS frame. When errors occur as described above, CRC data (or CRC code or CRC checksum) may be used on each row unit in order to verify whether error exists in each row unit. The RS-CRC encoder  412  may perform CRC encoding on the mobile service data being RS encoded so as to create (or generate) the CRC data. The CRC data being generated by CRC encoding may be used to indicate whether the mobile service data have been damaged while being transmitted through the channel. 
     The present invention may also use different error detection encoding methods other than the CRC encoding method. Alternatively, the present invention may use the error correction encoding method to enhance the overall error correction ability of the receiving system.  FIG. 20(c)  illustrates an example of using a 2-byte (i.e., 16-bit) CRC checksum as the CRC data. Herein, a 2-byte CRC checksum is generated for N number of bytes of each row, thereby adding the 2-byte CRC checksum at the end of the N number of bytes. Thus, each row is expanded to (N+2) number of bytes. Equation 3 below corresponds to an exemplary equation for generating a 2-byte CRC checksum for each row being configured of N number of bytes.
 
g(x)=x 16 +x 12 +x 5 +1   Equation 3
 
     The process of adding a 2-byte checksum in each row is only exemplary. Therefore, the present invention is not limited only to the example proposed in the description set forth herein. As described above, when the process of RS encoding and CRC encoding are completed, the (N×187)-byte RS frame is expanded to a (N+2)×(187+P)-byte RS frame. Based upon an error correction scenario of a RS frame expanded as described above, the data bytes within the RS frame are transmitted through a channel in a row direction. At this point, when a large number of errors occur during a limited period of transmission time, errors also occur in a row direction within the RS frame being processed with a decoding process in the receiving system. However, in the perspective of RS encoding performed in a column direction, the errors are shown as being scattered. Therefore, error correction may be performed more effectively. At this point, a method of increasing the number of parity data bytes (P) may be used in order to perform a more intense error correction process. However, using this method may lead to a decrease in transmission efficiency. Therefore, a mutually advantageous method is required. Furthermore, when performing the decoding process, an erasure decoding process may be used to enhance the error correction performance. 
     Additionally, the RS-CRC encoder  412  according to the present invention also performs a row permutation (or interleaving) process in super frame units in order to further enhance the error correction performance when error correction the RS frame.  FIG. 21(a)  to  FIG. 21(d)  illustrates an example of performing a row permutation process in super frame units according to the present invention. More specifically, G number of RS frames RS-CRC-encoded is grouped to form a super frame, as shown in  FIG. 21(a) . At this point, since each RS frame is formed of (N+2)×(187+P) number of bytes, one super frame is configured to have the size of (N+2)×(187+P)×G bytes. 
     When a row permutation process permuting each row of the super frame configured as described above is performed based upon a pre-determined permutation rule, the positions of the rows prior to and after being permuted (or interleaved) within the super frame may be altered. More specifically, the i th  row of the super frame prior to the interleaving process, as shown in  FIG. 21(b) , is positioned in the j th  row of the same super frame after the row permutation process, as shown in  FIG. 21(c) . The above-described relation between i and j can be easily understood with reference to a permutation rule as shown in Equation 4 below.
 
j=G(imod(187+P))+└i/(187+P)┘
 
i=(187+P)(jmod G)+└j/G┘
 
where 0≦i, j≦(187+P)G−1; or
 
where 0≦i, j&lt;(187+P)G   Equation 4
         Herein, each row of the super frame is configured of (N+2) number of data bytes even after being row-permuted in super frame units.       

     When all row permutation processes in super frame units are completed, the super frame is once again divided into G number of row-permuted RS frames, as shown in  FIG. 21(d) , and then provided to the RS frame divider  413 . Herein, the number of RS parity bytes and the number of columns should be equally provided in each of the RS frames, which configure a super frame. As described in the error correction scenario of a RS frame, in case of the super frame, a section having a large number of error occurring therein is so long that, even when one RS frame that is to be decoded includes an excessive number of errors (i.e., to an extent that the errors cannot be corrected), such errors are scattered throughout the entire super frame. Therefore, in comparison with a single RS frame, the decoding performance of the super frame is more enhanced. 
     The above description of the present invention corresponds to the processes of forming (or creating) and encoding an RS frame, when a data group is divided into regions A/B/C/D, and when data of an RS frame are assigned to all of regions A/B/C/D within the corresponding data group. More specifically, the above description corresponds to an embodiment of the present invention, wherein one RS frame is transmitted using one parade. In this embodiment, the secondary encoder  420  does not operate (or is not active). 
     Meanwhile, 2 RS frames are transmitting using one parade, the data of the primary RS frame may be assigned to regions A/B within the data group and be transmitted, and the data of the secondary RS frame may be assigned to regions C/D within the data group and be transmitted. At this point, the primary encoder  410  receives the mobile service data that are to be assigned to regions A/B within the data group, so as to form the primary RS frame, thereby performing RS-encoding and CRC-encoding. Similarly, the secondary encoder  420  receives the mobile service data that are to be assigned to regions C/D within the data group, so as to form the secondary RS frame, thereby performing RS-encoding and CRC-encoding. More specifically, the primary RS frame and the secondary RS frame are created independently. 
       FIG. 22  illustrates examples of receiving the mobile service data that are to be assigned to regions A/B within the data group, so as to form the primary RS frame, and receives the mobile service data that are to be assigned to regions C/D within the data group, so as to form the secondary RS frame, thereby performing error correction encoding and error detection encoding on each of the first and secondary RS frames. More specifically,  FIG. 22(a)  illustrates an example of the RS-CRC encoder  412  of the primary encoder  410  receiving mobile service data of the primary ensemble that are to be assigned to regions A/B within the corresponding data group, so as to create an RS frame having the size of N 1 (row)×187(column). Then, in this example, the primary encoder  410  performs RS-encoding on each column of the RS frame created as described above, thereby adding P 1  number of parity data bytes in each column. Finally, the primary encoder  410  performs CRC-encoding on each row, thereby adding a 2-byte checksum in each row. 
       FIG. 22(b)  illustrates an example of the RS-CRC encoder  422  of the secondary encoder  420  receiving mobile service data of the secondary ensemble that are to be assigned to regions C/D within the corresponding data group, so as to create an RS frame having the size of N 2 (row)×187(column). Then, in this example, the secondary encoder  420  performs RS-encoding on each column of the RS frame created as described above, thereby adding P 2  number of parity data bytes in each column. Finally, the secondary encoder  420  performs CRC-encoding on each row, thereby adding a 2-byte checksum in each row. At this point, each of the RS-CRC encoders  412  and  422  may refer to a pre-determined transmission parameter provided by the control unit  200  and/or a transmission parameter provided from the service multiplexer  100 , the RS-CRC encoders  412  and  422  may be informed of RS frame information (including RS frame mode), RS encoding information (including RS code mode), SCCC information (including SCCC block information and SCCC outer code mode), data group information, and region information within a data group. The RS-CRC encoders  412  and  422  may refer to the transmission parameters for the purpose of RS frame configuration, error correction encoding, error detection encoding. Furthermore, the transmission parameters should also be transmitted to the receiving system so that the receiving system can perform a normal decoding process. 
     The data of the primary RS frame, which is encoded by RS frame units and row-permuted by super frame units from the RS-CRC encoder  412  of the primary encoder  410 , are outputted to the RS frame divider  413 . If the secondary encoder  420  also operates in the embodiment of the present invention, the data of the secondary RS frame, which is encoded by RS frame units and row-permuted by super frame units from the RS-CRC encoder  422  of the secondary encoder  420 , are outputted to the RS frame divider  423 . The RS frame divider  413  of the primary encoder  410  divides the primary RS frame into several portions, which are then outputted to the output multiplexer (MUX)  320 . Each portion of the primary RS frame is equivalent to a data amount that can be transmitted by one data group. Similarly, the RS frame divider  423  of the secondary encoder  420  divides the secondary RS frame into several portions, which are then outputted to the output multiplexer (MUX)  320 . 
     Hereinafter, the RS frame divider  413  of the primary RS encoder  410  will now be described in detail. Also, in order to simplify the description of the present invention, it is assumed that an RS frame having the size of N(row)×187(column), as shown in  FIG. 20(a)  to  FIG. 20(c) , that P number of parity data bytes are added to each column by RS-encoding the RS frame, and that a 2-byte checksum is added to each row by CRC-encoding the RS frame. Accordingly, the RS frame divider  413  divides (or partitions) the encoded RS frame having the size of (N+2)(row)×187(column) into several portions, each having the size of PL (wherein PL corresponds to the length of the RS frame portion). 
     At this point, as shown in Table 2 to Table 5, the value of PL may vary depending upon the RS frame mode, SCCC block mode, and SCCC outer coder mode. Also, the total number of data bytes of the RS-encoded and CRC-encoded RS frame is equal to or smaller than 5×NoG×PL. In this case, the RS frame is divided (or partitioned) into ((5×NoG)−1) number of portions each having the size of PL and one portion having a size equal to smaller than PL. More specifically, with the exception of the last portion of the RS frame, each of the remaining portions of the RS frame has an equal size of PL. If the size of the last portion is smaller than PL, a stuffing byte (or dummy byte) may be inserted in order to fill (or replace) the lacking number of data bytes, thereby enabling the last portion of the RS frame to also be equal to PL. Each portion of an RS frame corresponds to the amount of data that are to be SCCC-encoded and mapped into a single data group of a parade. 
       FIG. 23(a)  and  FIG. 23(b)  respectively illustrate examples of adding S number of stuffing bytes, when an RS frame having the size of (N+2)(row)×(187+P)(column) is divided into 5×NoG number of portions, each having the size of PL. More specifically, the RS-encoded and CRC-encoded RS frame, shown in  FIG. 23(a) , is divided into several portions, as shown in  FIG. 23(b) . The number of divided portions at the RS frame is equal to (5×NoG). Particularly, the first ((5×NoG)−1) number of portions each has the size of PL, and the last portion of the RS frame may be equal to or smaller than PL. If the size of the last portion is smaller than PL, a stuffing byte (or dummy byte) may be inserted in order to fill (or replace) the lacking number of data bytes, as shown in Equation 5 below, thereby enabling the last portion of the RS frame to also be equal to PL.
 
S=(5×NoG×PL)−((N+2)×(187+P))   Equation 5
         Herein, each portion including data having the size of PL passes through the output multiplexer  320  of the MPH frame encoder  301 , which is then outputted to the block processor  302 .       

     At this point, the mapping order of the RS frame portions to a parade of data groups in not identical with the group assignment order defined in Equation 1. When given the group positions of a parade in an MPH frame, the SCCC-encoded RS frame portions will be mapped in a time order (i.e., in a left-to-right direction). For example, as shown in  FIG. 11 , data groups of the 2 nd  parade (Parade # 1 ) are first assigned (or allocated) to the 13 th  slot (Slot # 12 ) and then assigned to the 3 rd  slot (Slot # 2 ). However, when the data are actually placed in the assigned slots, the data are placed in a time sequence (or time order, i.e., in a left-to-right direction). More specifically, the 1 st  data group of Parade # 1  is placed in Slot # 2 , and the 2 nd  data group of Parade # 1  is placed in Slot # 12 . 
     Block Processor 
     Meanwhile, the block processor  302  performs an SCCC outer encoding process on the output of the MPH frame encoder  301 . More specifically, the block processor  302  receives the data of each error correction encoded portion. Then, the block processor  302  encodes the data once again at a coding rate of 1/H (wherein H is an integer equal to or greater than 2 (i.e., H≧2)), thereby outputting the 1/H-rate encoded data to the group formatter  303 . According to the embodiment of the present invention, the input data are encoded either at a coding rate of 1/2 (also referred to as “1/2-rate encoding”) or at a coding rate of 1/4 (also referred to as “1/4-rate encoding”). The data of each portion outputted from the MPH frame encoder  301  may include at least one of pure mobile service data, RS parity data, CRC data, and stuffing data. However, in a broader meaning, the data included in each portion may correspond to data for mobile services. Therefore, the data included in each portion will all be considered as mobile service data and described accordingly. 
     The group formatter  303  inserts the mobile service data SCCC-outer-encoded and outputted from the block processor  302  in the corresponding region within the data group, which is formed in accordance with a pre-defined rule. Also, in association with the data deinterleaving process, the group formatter  303  inserts various place holders (or known data place holders) in the corresponding region within the data group. Thereafter, the group formatter  303  deinterleaves the data within the data group and the place holders. 
     According to the present invention, with reference to data after being data-interleaved, as shown in  FIG. 5 , a data groups is configured of 10 MPH blocks (B 1  to B 10 ) and divided into 4 regions (A, B, C, and D). Also, as shown in  FIG. 5 , when it is assumed that the data group is divided into a plurality of hierarchical regions, as described above, the block processor  302  may encode the mobile service data, which are to be inserted to each region based upon the characteristic of each hierarchical region, at different coding rates. For example, the block processor  302  may encode the mobile service data, which are to be inserted in region A/B within the corresponding data group, at a coding rate of 1/2. Then, the group formatter  303  may insert the 1/2-rate encoded mobile service data to region A/B. Also, the block processor  302  may encode the mobile service data, which are to be inserted in region C/D within the corresponding data group, at a coding rate of 1/4 having higher (or stronger) error correction ability than the 1/2-coding rate. Thereafter, the group formatter  303  may insert the 1/2-rate encoded mobile service data to region C/D. In another example, the block processor  302  may encode the mobile service data, which are to be inserted in region C/D, at a coding rate having higher error correction ability than the 1/4-coding rate. Then, the group formatter  303  may either insert the encoded mobile service data to region C/D, as described above, or leave the data in a reserved region for future usage. 
     According to another embodiment of the present invention, the block processor  302  may perform a 1/H-rate encoding process in SCCC block units. Herein, the SCCC block includes at least one MPH block. At this point, when 1/H-rate encoding is performed in MPH block units, the MPH blocks (B 1  to B 10 ) and the SCCC block (SCB 1  to SCB 10 ) become identical to one another (i.e., SCB 1 =B 1 , SCB 2 =B 2 , SCB 3 =B 3 , SCB 4 =B 4 , SCB 5 =B 5 , SCB 6 =B 6 , SCB 7 =B 7 , SCB 8 =B 8 , SCB 9 =B 9 , and SCB 10 =B 10 ). For example, the MPH block  1  (B 1 ) may be encoded at the coding rate of 1/2, the MPH block  2  (B 2 ) may be encoded at the coding rate of 1/4, and the MPH block  3  (B 3 ) may be encoded at the coding rate of 1/2. The coding rates are applied respectively to the remaining MPH blocks. 
     Alternatively, a plurality of MPH blocks within regions A, B, C, and D may be grouped into one SCCC block, thereby being encoded at a coding rate of 1/H in SCCC block units. Accordingly, the receiving performance of region C/D may be enhanced. For example, MPH block  1  (B 1 ) to MPH block  5  (B 5 ) may be grouped into one SCCC block and then encoded at a coding rate of 1/2. Thereafter, the group formatter  303  may insert the 1/2-rate encoded mobile service data to a section starting from MPH block  1  (B 1 ) to MPH block  5  (B 5 ). Furthermore, MPH block  6  (B 6 ) to MPH block  10  (B 10 ) may be grouped into one SCCC block and then encoded at a coding rate of 1/4. Thereafter, the group formatter  303  may insert the 1/4-rate encoded mobile service data to another section starting from MPH block  6  (B 6 ) to MPH block  10  (B 10 ). In this case, one data group may consist of two SCCC blocks. 
     According to another embodiment of the present invention, one SCCC block may be formed by grouping two MPH blocks. For example, MPH block  1  (B 1 ) and MPH block  6  (B 6 ) may be grouped into one SCCC block (SCB 1 ). Similarly, MPH block  2  (B 2 ) and MPH block  7  (B 7 ) may be grouped into another SCCC block (SCB 2 ). Also, MPH block  3  (B 3 ) and MPH block  8  (B 8 ) may be grouped into another SCCC block (SCB 3 ). And, MPH block  4  (B 4 ) and MPH block  9  (B 9 ) may be grouped into another SCCC block (SCB 4 ). Furthermore, MPH block  5  (B 5 ) and MPH block  10  (B 10 ) may be grouped into another SCCC block (SCB 5 ). In the above-described example, the data group may consist of 10 MPH blocks and 5 SCCC blocks. Accordingly, in a data (or signal) receiving environment undergoing frequent and severe channel changes, the receiving performance of regions C and D, which is relatively more deteriorated than the receiving performance of region A, may be reinforced. Furthermore, since the number of mobile service data symbols increases more and more from region A to region D, the error correction encoding performance becomes more and more deteriorated. Therefore, when grouping a plurality of MPH block to form one SCCC block, such deterioration in the error correction encoding performance may be reduced. 
     As described-above, when the block processor  302  performs encoding at a 1/H-coding rate, information associated with SCCC should be transmitted to the receiving system in order to accurately recover the mobile service data. Table 7 below shows an example of a SCCC block mode, which indicating the relation between an MPH block and an SCCC block, among diverse SCCC block information. 
     
       
         
           
               
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                   
                 SCCC Block Mode 
               
            
           
           
               
               
               
               
               
            
               
                   
                 00 
                 01 
                 10 
                 11 
               
            
           
           
               
               
            
               
                   
                 Description 
               
            
           
           
               
               
               
               
               
            
               
                   
                 One MPH Block 
                 Two MPH Blocks 
                   
                   
               
               
                   
                 per SCCC Block 
                 per SCCC Block 
                 Reserved 
                 Reserved 
               
            
           
           
               
               
            
               
                   
                 SCB 
               
            
           
           
               
               
               
               
               
            
               
                   
                 SCB input, 
                 SCB input, 
                   
                   
               
               
                   
                 MPH Block 
                 MPH Blocks 
               
               
                   
               
               
                 SCB1 
                 B1 
                 B1 + B6 
                   
                   
               
               
                 SCB2 
                 B2 
                 B2 + B7 
                   
                   
               
               
                 SCB3 
                 B3 
                 B3 + B8 
                   
                   
               
               
                 SCB4 
                 B4 
                 B4 + B9 
                   
                   
               
               
                 SCB5 
                 B5 
                  B5 + B10 
                   
                   
               
               
                 SCB6 
                 B6 
                 — 
                   
                   
               
               
                 SCB7 
                 B7 
                 — 
                   
                   
               
               
                 SCB8 
                 B8 
                 — 
                   
                   
               
               
                 SCB9 
                 B9 
                 — 
                   
                   
               
               
                 SCB10 
                  B10 
                 — 
               
               
                   
               
            
           
         
       
         
         
           
             More specifically, Table 4 shows an example of 2 bits being allocated in order to indicate the SCCC block mode. For example, when the SCCC block mode value is equal to ‘00’, this indicates that the SCCC block and the MPH block are identical to one another. Also, when the SCCC block mode value is equal to ‘01’, this indicates that each SCCC block is configured of 2 MPH blocks. 
           
         
       
    
     As described above, if one data group is configured of 2 SCCC blocks, although it is not indicated in Table 7, this information may also be indicated as the SCCC block mode. For example, when the SCCC block mode value is equal to ‘10’, this indicates that each SCCC block is configured of 5 MPH blocks and that one data group is configured of 2 SCCC blocks. Herein, the number of MPH blocks included in an SCCC block and the position of each MPH block may vary depending upon the settings made by the system designer. Therefore, the present invention will not be limited to the examples given herein. Accordingly, the SCCC mode information may also be expanded. 
     An example of a coding rate information of the SCCC block, i.e., SCCC outer code mode, is shown in Table 8 below. 
     
       
         
           
               
               
             
               
                 TABLE 8 
               
               
                   
               
               
                 SCCC outer 
                   
               
               
                 code mode (2 bits) 
                 Description 
               
               
                   
               
             
            
               
                 00 
                 Outer code rate of SCCC block is ½ rate 
               
               
                 01 
                 Outer code rate of SCCC block is ¼ rate 
               
               
                 10 
                 Reserved 
               
               
                 11 
                 Reserved 
               
               
                   
               
            
           
         
       
         
         
           
             More specifically, Table 8 shows an example of 2 bits being allocated in order to indicate the coding rate information of the SCCC block. For example, when the SCCC outer code mode value is equal to ‘00’, this indicates that the coding rate of the corresponding SCCC block is 1/2. And, when the SCCC outer code mode value is equal to ‘01’, this indicates that the coding rate of the corresponding SCCC block is 1/4. 
           
         
       
    
     If the SCCC block mode value of Table 7 indicates ‘00’, the SCCC outer code mode may indicate the coding rate of each MPH block with respect to each MPH block. In this case, since it is assumed that one data group includes 10 MPH blocks and that 2 bits are allocated for each SCCC block mode, a total of 20 bits are required for indicating the SCCC block modes of the 10 MPH modes. In another example, when the SCCC block mode value of Table 7 indicates ‘00’, the SCCC outer code mode may indicate the coding rate of each region with respect to each region within the data group. In this case, since it is assumed that one data group includes 4 regions (i.e., regions A, B, C, and D) and that 2 bits are allocated for each SCCC block mode, a total of 8 bits are required for indicating the SCCC block modes of the 4 regions. In another example, when the SCCC block mode value of Table 7 is equal to ‘01’, each of the regions A, B, C, and D within the data group has the same SCCC outer code mode. 
     Meanwhile, an example of an SCCC output block length (SOBL) for each SCCC block, when the SCCC block mode value is equal to ‘00’, is shown in Table 9 below. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 9 
               
             
            
               
                   
                   
               
               
                   
                   
                   
                 SIBL 
               
            
           
           
               
               
               
               
               
            
               
                   
                 SCCC Block 
                 SOBL 
                 ½ rate 
                 ¼ rate 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 SCB1 (B1) 
                 528 
                 264 
                 132 
               
               
                   
                 SCB2 (B2) 
                 1536 
                 768 
                 384 
               
               
                   
                 SCB3 (B3) 
                 2376 
                 1188 
                 594 
               
               
                   
                 SCB4 (B4) 
                 2388 
                 1194 
                 597 
               
               
                   
                 SCB5 (B5) 
                 2772 
                 1386 
                 693 
               
               
                   
                 SCB6 (B6) 
                 2472 
                 1236 
                 618 
               
               
                   
                 SCB7 (B7) 
                 2772 
                 1386 
                 693 
               
               
                   
                 SCB8 (B8) 
                 2508 
                 1254 
                 627 
               
               
                   
                 SCB9 (B9) 
                 1416 
                 708 
                 354 
               
               
                   
                 SCB10 (B10) 
                 480 
                 240 
                 120 
               
               
                   
                   
               
            
           
         
       
         
         
           
             More specifically, when given the SCCC output block length (SOBL) for each SCCC block, an SCCC input block length (SIBL) for each corresponding SCCC block may be decided based upon the outer coding rate of each SCCC block. The SOBL is equivalent to the number of SCCC output (or outer-encoded) bytes for each SCCC block. And, the SIBL is equivalent to the number of SCCC input (or payload) bytes for each SCCC block. Table 10 below shows an example of the SOBL and SIBL for each SCCC block, when the SCCC block mode value is equal to ‘01’. 
           
         
       
    
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 10 
               
             
            
               
                   
                   
               
               
                   
                   
                   
                 SIBL 
               
            
           
           
               
               
               
               
               
            
               
                   
                 SCCC Block 
                 SOBL 
                 ½ rate 
                 ¼ rate 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 SCB1 (B1 + B6) 
                 528 
                 264 
                 132 
               
               
                   
                 SCB2 (B2 + B7) 
                 1536 
                 768 
                 384 
               
               
                   
                 SCB3 (B3 + B8) 
                 2376 
                 1188 
                 594 
               
               
                   
                 SCB4 (B4 + B9) 
                 2388 
                 1194 
                 597 
               
               
                   
                 SCB5 (B5 + B10) 
                 2772 
                 1386 
                 693 
               
               
                   
                   
               
            
           
         
       
     
     In order to do so, as shown in  FIG. 24 , the block processor  302  includes a RS frame portion-SCCC block converter  511 , a byte-bit converter  512 , a convolution encoder  513 , a symbol interleaver  514 , a symbol-byte converter  515 , and an SCCC block-MPH block converter  516 . The convolutional encoder  513  and the symbol interleaver  514  are virtually concatenated with the trellis encoding module in the post-processor in order to configure an SCCC block. More specifically, the RS frame portion-SCCC block converter  511  divides the RS frame portions, which are being inputted, into multiple SCCC blocks using the SIBL of Table 9 and Table 10 based upon the RS code mode, SCCC block mode, and SCCC outer code mode. Herein, the MPH frame encoder  301  may output only primary RS frame portions or both primary RS frame portions and secondary RS frame portions in accordance with the RS frame mode. 
     When the RS Frame mode is set to ‘00’, a portion of the primary RS Frame equal to the amount of data, which are to be SCCC outer encoded and mapped to 10 MPH blocks (B 1  to B 10 ) of a data group, will be provided to the block processor  302 . When the SCCC block mode value is equal to ‘00’, then the primary RS frame portion will be split into 10 SCCC Blocks according to Table 9. Alternatively, when the SCCC block mode value is equal to ‘01’, then the primary RS frame will be split into 5 SCCC blocks according to Table 10. 
     When the RS frame mode value is equal to ‘01’, then the block processor  302  may receive two RS frame portions. The RS frame mode value of ‘01’ will not be used with the SCCC block mode value of ‘01’. The first portion from the primary RS frame will be SCCC-outer-encoded as SCCC Blocks SCB 3 , SCB 4 , SCB 5 , SCB 6 , SCB 7 , and SCB 8  by the block processor  302 . The SCCC Blocks SCB 3  and SCB 8  will be mapped to region B and the SCCC blocks SCB 4 , SCB 5 , SCB 6 , and SCB 7  shall be mapped to region A by the group formatter  303 . The second portion from the secondary RS frame will also be SCCC-outer-encoded, as SCB 1 , SCB 2 , SCB 9 , and SCB 10 , by the block processor  302 . The group formatter  303  will map the SCCC blocks SCB 1  and SCB 10  to region D as the MPH blocks B 1  and B 10 , respectively. Similarly, the SCCC blocks SCB 2  and SCB 9  will be mapped to region C as the MPH blocks B 2  and B 9 . 
     The byte-bit converter  512  identifies the mobile service data bytes of each SCCC block outputted from the RS frame portion-SCCC block converter  511  as data bits, which are then outputted to the convolution encoder  513 . The convolution encoder  513  performs one of 1/2-rate encoding and 1/4-rate encoding on the inputted mobile service data bits. 
       FIG. 25  illustrates a detailed block diagram of the convolution encoder  513 . The convolution encoder  513  includes two delay units  521  and  523  and three adders  522 ,  524 , and  525 . Herein, the convolution encoder  513  encodes an input data bit U and outputs the coded bit U to 5 bits (u 0  to u 4 ). At this point, the input data bit U is directly outputted as uppermost bit u 0  and simultaneously encoded as lower bit u 1 u 2 u 3 u 4  and then outputted. More specifically, the input data bit U is directly outputted as the uppermost bit u 0  and simultaneously outputted to the first and third adders  522  and  525 . 
     The first adder  522  adds the input data bit U and the output bit of the first delay unit  521  and, then, outputs the added bit to the second delay unit  523 . Then, the data bit delayed by a pre-determined time (e.g., by 1 clock) in the second delay unit  523  is outputted as a lower bit u 1  and simultaneously fed-back to the first delay unit  521 . The first delay unit  521  delays the data bit fed-back from the second delay unit  523  by a pre-determined time (e.g., by 1 clock). Then, the first delay unit  521  outputs the delayed data bit as a lower bit u 2  and, at the same time, outputs the fed-back data to the first adder  522  and the second adder  524 . The second adder  524  adds the data bits outputted from the first and second delay units  521  and  523  and outputs the added data bits as a lower bit u 3 . The third adder  525  adds the input data bit U and the output of the second delay unit  523  and outputs the added data bit as a lower bit u 4 . 
     At this point, the first and second delay units  521  and  523  are reset to ‘0’, at the starting point of each SCCC block. The convolution encoder  513  of  FIG. 25  may be used as a 1/2-rate encoder or a 1/4-rate encoder. More specifically, when a portion of the output bit of the convolution encoder  513 , shown in  FIG. 25 , is selected and outputted, the convolution encoder  513  may be used as one of a 1/2-rate encoder and a 1/4-rate encoder. Table 11 below shown an example of output symbols of the convolution encoder  513 . 
     
       
         
           
               
               
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                   
                   
                 ¼ rate 
               
            
           
           
               
               
               
               
            
               
                 Region 
                 ½ rate 
                 SCCC block mode = ‘00’ 
                 SCCC block mode = ‘01’ 
               
               
                   
               
               
                 A, B 
                 (u0, u1) 
                 (u0, u2), (u1, u3) 
                 (u0, u2), (u1, u4) 
               
               
                 C, D 
                   
                 (u0, u1), (u3, u4) 
               
               
                   
               
            
           
         
       
     
     For example, at the 1/2-coding rate, 1 output symbol (i.e., u 0  and u 1  bits) may be selected and outputted. And, at the 1/4-coding rate, depending upon the SCCC block mode, 2 output symbols (i.e., 4 bits) may be selected and outputted. For example, when the SCCC block mode value is equal to ‘01’, and when an output symbol configured of u 0  and u 2  and another output symbol configured of u 1  and u 4  are selected and outputted, a 1/4-rate coding result may be obtained. 
     The mobile service data encoded at the coding rate of 1/2 or 1/4 by the convolution encoder  513  are outputted to the symbol interleaver  514 . The symbol interleaver  514  performs block interleaving, in symbol units, on the output data symbol of the convolution encoder  513 . More specifically, the symbol interleaver  514  is a type of block interleaver. Any interleaver performing structural rearrangement (or realignment) may be applied as the symbol interleaver  514  of the block processor. However, in the present invention, a variable length symbol interleaver that can be applied even when a plurality of lengths is provided for the symbol, so that its order may be rearranged, may also be used. 
       FIG. 26  illustrates a symbol interleaver according to an embodiment of the present invention. Particularly,  FIG. 26  illustrates an example of the symbol interleaver when B=2112 and L=4096. Herein, B indicates a block length in symbols that are outputted for symbol interleaving from the convolution encoder  513 . And, L represents a block length in symbols that are actually interleaved by the symbol interleaver  514 . At this point, the block length in symbols B inputted to the symbol interleaver  514  is equivalent to 4×SOBL . More specifically, since one symbol is configured of 2 bits, the value of B may be set to be equal to 4×SOBL. 
     In the present invention, when performing the symbol-interleaving process, the conditions of L=2 m  (wherein m is an integer) and of L≧B should be satisfied. If there is a difference in value between B and L, (L−B) number of null (or dummy) symbols is added, thereby creating an interleaving pattern, as shown in P′(i) of  FIG. 26 . Therefore, B becomes a block size of the actual symbols that are inputted to the symbol interleaver  514  in order to be interleaved. L becomes an interleaving unit when the interleaving process is performed by an interleaving pattern created from the symbol interleaver  514 . 
     Equation 6 shown below describes the process of sequentially receiving B number of symbols, the order of which is to be rearranged, and obtaining an L value satisfying the conditions of L=2 m  (wherein m is an integer) and of L≧B, thereby creating the interleaving so as to realign (or rearrange) the symbol order.
 
In relation to all places, wherein 0≦i≦B−1,
 
P′(i)={89×i×(i+1)/2} mod L
 
Herein, L≧B ,L=2 m , wherein m is an integer.   Equation 6
 
     As shown in P′(i) of  FIG. 26 , the order of B number of input symbols and (L−B) number of null symbols is rearranged by using the above-mentioned Equation 6. Then, as shown in P(i) of  FIG. 26 , the null byte places are removed, so as to rearrange the order. Starting with the lowest value of i, the P(i) are shifted to the left in order to fill the empty entry locations. Thereafter, the symbols of the aligned interleaving pattern P(i) are outputted to the symbol-byte converter  515  in order. Herein, the symbol-byte converter  515  converts to bytes the mobile service data symbols, having the rearranging of the symbol order completed and then outputted in accordance with the rearranged order, and thereafter outputs the converted bytes to the SCCC block-MPH block converter  516 . The SCCC block-MPH block converter  516  converts the symbol-interleaved SCCC blocks to MPH blocks, which are then outputted to the group formatter  303 . 
     If the SCCC block mode value is equal to ‘00’, the SCCC block is mapped at a one-to-one (1:1) correspondence with each MPH block within the data group. In another example, if the SCCC block mode value is equal to ‘01’, each SCCC block is mapped with two MPH blocks within the data group. For example, the SCCC block SCB 1  is mapped with (B 1 , B 6 ), the SCCC block SCB 2  is mapped with (B 2 , B 7 ), the SCCC block SCB 3  is mapped with (B 3 , B 8 ), the SCCC block SCB 4  is mapped with (B 4 , B 9 ), and the SCCC block SCB 5  is mapped with (B 5 , B 10 ). The MPH block that is outputted from the SCCC block-MPH block converter  516  is configured of mobile service data and FEC redundancy. In the present invention, the mobile service data as well as the FEC redundancy of the MPH block will be collectively considered as mobile service data. 
     Group Formatter 
     The group formatter  303  inserts data of MPH blocks outputted from the block processor  302  to the corresponding MPH blocks within the data group, which is formed in accordance with a pre-defined rule. Also, in association with the data-deinterleaving process, the group formatter  303  inserts various place holders (or known data place holders) in the corresponding region within the data group. More specifically, apart from the encoded mobile service data outputted from the block processor  302 , the group formatter  303  also inserts MPEG header place holders, non-systematic RS parity place holders, main service data place holders, which are associated with the data deinterleaving in a later process, as shown in  FIG. 5 . 
     Herein, the main service data place holders are inserted because the mobile service data bytes and the main service data bytes are alternately mixed with one another in regions B to D based upon the input of the data deinterleaver, as shown in  FIG. 5 . For example, based upon the data outputted after data deinterleaving, the place holder for the MPEG header may be allocated at the very beginning of each packet. Also, in order to configure an intended group format, dummy bytes may also be inserted. Furthermore, the group formatter  303  inserts place holders for initializing the trellis encoding module  256  in the corresponding regions. For example, the initialization data place holders may be inserted in the beginning of the known data sequence. Additionally, the group formatter  303  may also insert signaling information, which are encoded and outputted from the signaling encoder  304 , in corresponding regions within the data group. At this point, reference may be made to the signaling information when the group formatter  303  inserts each data type and respective place holders in the data group. The process of encoding the signaling information and inserting the encoded signaling information to the data group will be described in detail in a later process. 
     After inserting each data type and respective place holders in the data group, the group formatter  303  may deinterleave the data and respective place holders, which have been inserted in the data group, as an inverse process of the data interleaver, thereby outputting the deinterleaved data and respective place holders to the packet formatter  305 . More specifically, when the data and respective place holders within the data group, which is configured (or structured) as shown in  FIG. 5 , are deinterleaved by the group formatter  303  and outputted to the packet formatter  305 , the structure of the data group may be identical to the structure shown in  FIG. 7 . In order to do so, the group formatter  303  may include a group format organizer  527 , and a data deinterleaver  529 , as shown in  FIG. 27 . The group format organizer  527  inserts data and respective place holders in the corresponding regions within the data group, as described above. And, the data deinterleaver  529  deinterleaves the inserted data and respective place holders as an inverse process of the data interleaver. 
     The packet formatter  305  removes the main service data place holders and the RS parity place holders that were allocated for the deinterleaving process from the deinterleaved data being inputted. Then, the packet formatter  305  groups the remaining portion and inserts the 3-byte MPEG header place holder in an MPEG header having a null packet PID (or an unused PID from the main service data packet). Furthermore, the packet formatter  305  adds a synchronization data byte at the beginning of each 187-byte data packet. Also, when the group formatter  303  inserts known data place holders, the packet formatter  303  may insert actual known data in the known data place holders, or may directly output the known data place holders without any modification in order to make replacement insertion in a later process. Thereafter, the packet formatter  305  identifies the data within the packet-formatted data group, as described above, as a 188-byte unit mobile service data packet (i.e., MPEG TS packet), which is then provided to the packet multiplexer  240 . 
     Based upon the control of the control unit  200 , the packet multiplexer  240  multiplexes the data group packet-formatted and outputted from the packet formatter  306  and the main service data packet outputted from the packet jitter mitigator  220 . Then, the packet multiplexer  240  outputs the multiplexed data packets to the data randomizer  251  of the post-processor  250 . More specifically, the control unit  200  controls the time-multiplexing of the packet multiplexer  240 . If the packet multiplexer  240  receives 118 mobile service data packets from the packet formatter  305 , 37 mobile service data packets are placed before a place for inserting VSB field synchronization. Then, the remaining 81 mobile service data packets are placed after the place for inserting VSB field synchronization. The multiplexing method may be adjusted by diverse variables of the system design. The multiplexing method and multiplexing rule of the packet multiplexer  240  will be described in more detail in a later process. 
     Also, since a data group including mobile service data in-between the data bytes of the main service data is multiplexed (or allocated) during the packet multiplexing process, the shifting of the chronological position (or place) of the main service data packet becomes relative. Also, a system object decoder (i.e., MPEG decoder) for processing the main service data of the receiving system, receives and decodes only the main service data and recognizes the mobile service data packet as a null data packet. 
     Therefore, when the system object decoder of the receiving system receives a main service data packet that is multiplexed with the data group, a packet jitter occurs. 
     At this point, since a multiple-level buffer for the video data exists in the system object decoder and the size of the buffer is relatively large, the packet jitter generated from the packet multiplexer  240  does not cause any serious problem in case of the video data. However, since the size of the buffer for the audio data in the object decoder is relatively small, the packet jitter may cause considerable problem. More specifically, due to the packet jitter, an overflow or underflow may occur in the buffer for the main service data of the receiving system (e.g., the buffer for the audio data). Therefore, the packet jitter mitigator  220  re-adjusts the relative position of the main service data packet so that the overflow or underflow does not occur in the system object decoder. 
     In the present invention, examples of repositioning places for the audio data packets within the main service data in order to minimize the influence on the operations of the audio buffer will be described in detail. The packet jitter mitigator  220  repositions the audio data packets in the main service data section so that the audio data packets of the main service data can be as equally and uniformly aligned and positioned as possible. Additionally, when the positions of the main service data packets are relatively re-adjusted, associated program clock reference (PCR) values may also be modified accordingly. The PCR value corresponds to a time reference value for synchronizing the time of the MPEG decoder. Herein, the PCR value is inserted in a specific region of a TS packet and then transmitted. 
     In the example of the present invention, the packet jitter mitigator  220  also performs the operation of modifying the PCR value. The output of the packet jitter mitigator  220  is inputted to the packet multiplexer  240 . As described above, the packet multiplexer  240  multiplexes the main service data packet outputted from the packet jitter mitigator  220  with the mobile service data packet outputted from the pre-processor  230  into a burst structure in accordance with a pre-determined multiplexing rule. Then, the packet multiplexer  240  outputs the multiplexed data packets to the data randomizer  251  of the post-processor  250 . 
     If the inputted data correspond to the main service data packet, the data randomizer  251  performs the same randomizing process as that of the conventional randomizer. More specifically, the synchronization byte within the main service data packet is deleted. Then, the remaining 187 data bytes are randomized by using a pseudo random byte generated from the data randomizer  251 . Thereafter, the randomized data are outputted to the RS encoder/non-systematic RS encoder  252 . 
     On the other hand, if the inputted data correspond to the mobile service data packet, the data randomizer  251  may randomize only a portion of the data packet. For example, if it is assumed that a randomizing process has already been performed in advance on the mobile service data packet by the pre-processor  230 , the data randomizer  251  deletes the synchronization byte from the 4-byte MPEG header included in the mobile service data packet and, then, performs the randomizing process only on the remaining 3 data bytes of the MPEG header. Thereafter, the randomized data bytes are outputted to the RS encoder/non-systematic RS encoder  252 . More specifically, the randomizing process is not performed on the remaining portion of the mobile service data excluding the MPEG header. In other words, the remaining portion of the mobile service data packet is directly outputted to the RS encoder/non-systematic RS encoder  252  without being randomized. Also, the data randomizer  251  may or may not perform a randomizing process on the known data (or known data place holders) and the initialization data place holders included in the mobile service data packet. 
     The RS encoder/non-systematic RS encoder  252  performs an RS encoding process on the data being randomized by the data randomizer  251  or on the data bypassing the data randomizer  251 , so as to add 20 bytes of RS parity data. Thereafter, the processed data are outputted to the data interleaver  253 . Herein, if the inputted data correspond to the main service data packet, the RS encoder/non-systematic RS encoder  252  performs the same systematic RS encoding process as that of the conventional broadcasting system, thereby adding the 20-byte RS parity data at the end of the 187-byte data. Alternatively, if the inputted data correspond to the mobile service data packet, the RS encoder/non-systematic RS encoder  252  performs a non-systematic RS encoding process. At this point, the 20-byte RS parity data obtained from the non-systematic RS encoding process are inserted in a pre-decided parity byte place within the mobile service data packet. 
     The data interleaver  253  corresponds to a byte unit convolutional interleaver. The output of the data interleaver  253  is inputted to the parity replacer  254  and to the non-systematic RS encoder  255 . Meanwhile, a process of initializing a memory within the trellis encoding module  256  is primarily required in order to decide the output data of the trellis encoding module  256 , which is located after the parity replacer  254 , as the known data pre-defined according to an agreement between the receiving system and the transmitting system. More specifically, the memory of the trellis encoding module  256  should first be initialized before the received known data sequence is trellis-encoded. At this point, the beginning portion of the known data sequence that is received corresponds to the initialization data place holder and not to the actual known data. Herein, the initialization data place holder has been included in the data by the group formatter within the pre-processor  230  in an earlier process. Therefore, the process of generating initialization data and replacing the initialization data place holder of the corresponding memory with the generated initialization data are required to be performed immediately before the inputted known data sequence is trellis-encoded. 
     Additionally, a value of the trellis memory initialization data is decided and generated based upon a memory status of the trellis encoding module  256 . Further, due to the newly replaced initialization data, a process of newly calculating the RS parity and replacing the RS parity, which is outputted from the data interleaver  253 , with the newly calculated RS parity is required. Therefore, the non-systematic RS encoder  255  receives the mobile service data packet including the initialization data place holders, which are to be replaced with the actual initialization data, from the data interleaver  253  and also receives the initialization data from the trellis encoding module  256 . 
     Among the inputted mobile service data packet, the initialization data place holders are replaced with the initialization data, and the RS parity data that are added to the mobile service data packet are removed and processed with non-systematic RS encoding. Thereafter, the new RS parity obtained by performing the non-systematic RS encoding process is outputted to the parity replacer  255 . Accordingly, the parity replacer  255  selects the output of the data interleaver  253  as the data within the mobile service data packet, and the parity replacer  255  selects the output of the non-systematic RS encoder  255  as the RS parity. The selected data are then outputted to the trellis encoding module  256 . 
     Meanwhile, if the main service data packet is inputted or if the mobile service data packet, which does not include any initialization data place holders that are to be replaced, is inputted, the parity replacer  254  selects the data and RS parity that are outputted from the data interleaver  253 . Then, the parity replacer  254  directly outputs the selected data to the trellis encoding module  256  without any modification. The trellis encoding module  256  converts the byte-unit data to symbol units and performs a 12-way interleaving process so as to trellis-encode the received data. Thereafter, the processed data are outputted to the synchronization multiplexer  260 . 
       FIG. 28  illustrates a detailed diagram of one of 12 trellis encoders included in the trellis encoding module  256 . Herein, the trellis encoder includes first and second multiplexers  531  and  541 , first and second adders  532  and  542 , and first to third memories  533 ,  542 , and  544 . More specifically, the first to third memories  533 ,  542 , and  544  are initialized by a set of trellis initialization data inserted in an initialization data place holder by the parity replacer  254  and, then, outputted. More specifically, when the first two 2-bit symbols, which are converted from each trellis initialization data byte, are inputted, the input bits of the trellis encoder will be replaced by the memory values of the trellis encoder, as shown in  FIG. 28 . 
     Since 2 symbols (i.e., 4 bits) are required for trellis initialization, the last 2 symbols (i.e., 4 bits) from the trellis initialization bytes are not used for trellis initialization and are considered as a symbol from a known data byte and processed accordingly. When the trellis encoder is in the initialization mode, the input comes from an internal trellis status (or state) and not from the parity replacer  254 . When the trellis encoder is in the normal mode, the input symbol provided from the parity replacer  254  will be processed. The trellis encoder provides the converted (or modified) input data for trellis initialization to the non-systematic RS encoder  255 . 
     More specifically, when a selection signal designates a normal mode, the first multiplexer  531  selects an upper bit X 2  of the input symbol. And, when a selection signal designates an initialization mode, the first multiplexer  531  selects the output of the first memory  533  and outputs the selected output data to the first adder  532 . The first adder  532  adds the output of the first multiplexer  531  and the output of the first memory  533 , thereby outputting the added result to the first memory  533  and, at the same time, as a most significant (or uppermost) bit Z 2 . The first memory  533  delays the output data of the first adder  532  by 1 clock, thereby outputting the delayed data to the first multiplexer  531  and the first adder  532 . 
     Meanwhile, when a selection signal designates a normal mode, the second multiplexer  541  selects a lower bit X 1  of the input symbol. And, when a selection signal designates an initialization mode, the second multiplexer  541  selects the output of the second memory  542 , thereby outputting the selected result to the second adder  543  and, at the same time, as a lower bit Z 1 . The second adder  543  adds the output of the second multiplexer  541  and the output of the second memory  542 , thereby outputting the added result to the third memory  544 . The third memory  544  delays the output data of the second adder  543  by 1 clock, thereby outputting the delayed data to the second memory  542  and, at the same time, as a least significant (or lowermost) bit Z 0 . The second memory  542  delays the output data of the third memory  544  by 1 clock, thereby outputting the delayed data to the second adder  543  and the second multiplexer  541 . 
     The synchronization multiplexer  260  inserts a field synchronization signal and a segment synchronization signal to the data outputted from the trellis encoding module  256  and, then, outputs the processed data to the pilot inserter  271  of the transmission unit  270 . Herein, the data having a pilot inserted therein by the pilot inserter  271  are modulated by the modulator  272  in accordance with a pre-determined modulating method (e.g., a VSB method). Thereafter, the modulated data are transmitted to each receiving system though the radio frequency (RF) up-converter  273 . 
     Multiplexing Method of Packet Multiplexer  240   
     Data of the error correction encoded and 1/H-rate encoded primary RS frame (i.e., when the RS frame mode value is equal to ‘00’) or primary/secondary RS frame (i.e., when the RS frame mode value is equal to ‘01’), are divided into a plurality of data groups by the group formatter  303 . Then, the divided data portions are assigned to at least one of regions A to D of each data group or to an MPH block among the MPH blocks B 1  to B 10 , thereby being deinterleaved. Then, the deinterleaved data group passes through the packet formatter  305 , thereby being multiplexed with the main service data by the packet multiplexer  240  based upon a de-decided multiplexing rule. The packet multiplexer  240  multiplexes a plurality of consecutive data groups, so that the data groups are assigned to be spaced as far apart from one another as possible within the sub-frame. For example, when it is assumed that 3 data groups are assigned to a sub-frame, the data groups are assigned to a 1 st  slot (Slot # 0 ), a 5 th  slot (Slot # 4 ), and a 9 th  slot (Slot # 8 ) in the sub-frame, respectively. 
     As described-above, in the assignment of the plurality of consecutive data groups, a plurality of parades are multiplexed and outputted so as to be spaced as far apart from one another as possible within a sub-MPH frame. For example, the method of assigning data groups and the method of assigning parades may be identically applied to all sub-frames for each MPH frame or differently applied to each MPH frame. 
       FIG. 10  illustrates an example of a plurality of data groups included in a single parade, wherein the number of data groups included in a sub-frame is equal to ‘3’, and wherein the data groups are assigned to an MPH frame by the packet multiplexer  240 . Referring to  FIG. 10 , 3 data groups are sequentially assigned to a sub-frame at a cycle period of 4 slots. Accordingly, when this process is equally performed in the 5 sub-frames included in the corresponding MPH frame, 15 data groups are assigned to a single MPH frame. Herein, the 15 data groups correspond to data groups included in a parade. 
     When data groups of a parade are assigned as shown in  FIG. 10 , the packet multiplexer  240  may either assign main service data to each data group, or assign data groups corresponding to different parades between each data group. More specifically, the packet multiplexer  240  may assign data groups corresponding to multiple parades to one MPH frame. Basically, the method of assigning data groups corresponding to multiple parades is very similar to the method of assigning data groups corresponding to a single parade. In other words, the packet multiplexer  240  may assign data groups included in other parades to an MPH frame according to a cycle period of 4 slots. At this point, data groups of a different parade may be sequentially assigned to the respective slots in a circular method. Herein, the data groups are assigned to slots starting from the ones to which data groups of the previous parade have not yet been assigned. For example, when it is assumed that data groups corresponding to a parade are assigned as shown in  FIG. 10 , data groups corresponding to the next parade may be assigned to a sub-frame starting either from the 12 th  slot of a sub-frame. 
       FIG. 11  illustrates an example of assigning and transmitting 3 parades (Parade # 0 , Parade # 1 , and Parade # 2 ) to an MPH frame. For example, when the 1 st  parade (Parade # 0 ) includes 3 data groups for each sub-frame, the packet multiplexer  240  may obtain the positions of each data groups within the sub-frames by substituting values ‘0’ to ‘2’ for i in Equation 1. More specifically, the data groups of the 1 st  parade (Parade # 0 ) are sequentially assigned to the 1 st , 5 th , and 9 th  slots (Slot # 0 , Slot # 4 , and Slot # 8 ) within the sub-frame. Also, when the 2 nd  parade includes 2 data groups for each sub-frame, the packet multiplexer  240  may obtain the positions of each data groups within the sub-frames by substituting values ‘3’ and ‘4’ for i in Equation 1. More specifically, the data groups of the 2 nd  parade (Parade # 1 ) are sequentially assigned to the 2 nd  and 12 th  slots (Slot # 3  and Slot # 11 ) within the sub-frame. Finally, when the 3 rd  parade includes 2 data groups for each sub-frame, the packet multiplexer  240  may obtain the positions of each data groups within the sub-frames by substituting values ‘5’ and ‘6’ for i in Equation 1. More specifically, the data groups of the 3 rd  parade (Parade # 2 ) are sequentially assigned and outputted to the 7 th  and 11 th  slots (Slot # 6  and Slot # 10 ) within the sub-frame. 
     As described above, the packet multiplexer  240  may multiplex and output data groups of multiple parades to a single MPH frame, and, in each sub-frame, the multiplexing process of the data groups may be performed serially with a group space of 4 slots from left to right. Therefore, a number of groups of one parade per sub-frame (NOG) may correspond to any one integer from ‘1’ to ‘8’. Herein, since one MPH frame includes 5 sub-frames, the total number of data groups within a parade that can be allocated to an MPH frame may correspond to any one multiple of ‘5’ ranging from ‘5’ to ‘40’. 
     Processing Signaling Information 
     The present invention assigns signaling information areas for inserting signaling information to some areas within each data group.  FIG. 29  illustrates an example of assigning signaling information areas for inserting signaling information starting from the 1 st  segment of the 4 th  MPH block (B 4 ) to a portion of the 2 nd  segment. More specifically, 276(=207+69) bytes of the 4 th  MPH block (B 4 ) in each data group are assigned as the signaling information area. In other words, the signaling information area consists of 207 bytes of the 1 st  segment and the first 69 bytes of the 2 nd  segment of the 4 th  MPH block (B 4 ). For example, the 1 st  segment of the 4 th  MPH block (B 4 ) corresponds to the 17 th  or 173 rd  segment of a VSB field. The signaling information that is to be inserted in the signaling information area is FEC-encoded by the signaling encoder  304 , thereby inputted to the group formatter  303 . 
     The group formatter  303  inserts the signaling information, which is FEC-encoded and outputted by the signaling encoder  304 , in the signaling information area within the data group. Herein, the signaling information may be identified by two different types of signaling channels: a transmission parameter channel (TPC) and a fast information channel (FIC). Herein, the TPC information corresponds to signaling information including transmission parameters, such as RS frame-associated information, SCCC-associated information, and MPH frame-associated information. However, the signaling information presented herein is merely exemplary. And, since the adding or deleting of signaling information included in the TPC may be easily adjusted and modified by one skilled in the art, the present invention will, therefore, not be limited to the examples set forth herein. Furthermore, the FIC is provided to enable a fast service acquisition of data receivers, and the FIC includes cross layer information between the physical layer and the upper layer(s). 
       FIG. 30  illustrates a detailed block diagram of the signaling encoder  304  according to the present invention. Referring to  FIG. 30 , the signaling encoder  304  includes a TPC encoder  561 , an FIC encoder  562 , a block interleaver  563 , a multiplexer  564 , a signaling randomizer  565 , and a PCCC encoder  566 . The TPC encoder  561  receives 10-bytes of TPC data and performs (18,10)-RS encoding on the 10-bytes of TPC data, thereby adding 8 bytes of parity data to the 10 bytes of TPC data. The 18 bytes of RS-encoded TPC data are outputted to the multiplexer  564 . The FIC encoder  562  receives 37-bytes of FIC data and performs (51,37)-RS encoding on the 37-bytes of FIC data, thereby adding 14 bytes of parity data to the 37 bytes of FIC data. Thereafter, the 51 bytes of RS-encoded FIC data are inputted to the block interleaver  563 , thereby being interleaved in predetermined block units. 
     Herein, the block interleaver  563  corresponds to a variable length block interleaver. The block interleaver  563  interleaves the FIC data within each sub-frame in TNoG(column)×51 (row) block units and then outputs the interleaved data to the multiplexer  564 . Herein, the TNoG corresponds to the total number of data groups being assigned to all sub-frames within an MPH frame. The block interleaver  563  is synchronized with the first set of FIC data in each sub-frame. The block interleaver  563  writes 51 bytes of incoming (or inputted) RS codewords in a row direction (i.e., row-by-row) and left-to-right and up-to-down directions and reads 51 bytes of RS codewords in a column direction (i.e., column-by-column) and left-to-right and up-to-down directions, thereby outputting the RS codewords. 
     The multiplexer  564  multiplexes the RS-encoded TPC data from the TPC encoder  561  and the block-interleaved FIC data from the block interleaver  563  along a time axis. Then, the multiplexer  564  outputs 69 bytes of the multiplexed data to the signaling randomizer  565 . The signaling randomizer  565  randomizes the multiplexed data and outputs the randomized data to the PCCC encoder  566 . The signaling randomizer  565  may use the same generator polynomial of the randomizer used for mobile service data. Also, initialization occurs in each data group. The PCCC encoder  566  corresponds to an inner encoder performing PCCC-encoding on the randomized data (i.e., signaling information data). The PCCC encoder  566  may include 6 even component encoders and 6 odd component encoders. 
       FIG. 31  illustrates an example of a syntax structure of TPC data being inputted to the TPC encoder  561 . The TPC data are inserted in the signaling information area of each data group and then transmitted. The TPC data may include a sub-frame_number field, a slot_number field, a parade_id field, a starting_group_number (SGN) field, a number_of_groups (NoG) field, a parade_repetition_cycle (PRC) field, an RS_frame_mode field, an RS_code_mode_primary field, an RS_code_mode_secondary field, an SCCC_block_mode field, an SCCC_outer_code_mode_A field, an SCCC_outer_code_mode_B field, an SCCC_outer_code_mode_C field, an SCCC_outer_code_mode_D field, an FIC_version field, a parade_continuity_counter field, and a TNoG field. 
     The Sub-Frame_number field corresponds to the current Sub-Frame number within the MPH frame, which is transmitted for MPH frame synchronization. The value of the Sub-Frame_number field may range from 0 to 4. The Slot_number field indicates the current slot number within the sub-frame, which is transmitted for MPH frame synchronization. Also, the value of the Sub-Frame_number field may range from 0 to 15. The Parade_id field identifies the parade to which this group belongs. The value of this field may be any 7-bit value. Each parade in a MPH transmission shall have a unique Parade_id field. 
     Communication of the Parade_id between the physical layer and the management layer may be performed by means of an Ensemble_id field formed by adding one bit to the left of the Parade_id field. If the Ensemble_id field is used for the primary Ensemble delivered through this parade, the added MSB shall be equal to ‘0’. Otherwise, if the Ensemble_id field is used for the secondary ensemble, the added MSB shall be equal to ‘1’. Assignment of the Parade_id field values may occur at a convenient level of the system, usually in the management layer. The starting_group_number (SGN) field shall be the first Slot_number for a parade to which this group belongs, as determined by Equation 1 (i.e., after the Slot numbers for all preceding parades have been calculated). The SGN and NoG shall be used according to Equation 1 to obtain the slot numbers to be allocated to a parade within the sub-frame. 
     The number_of_Groups (NoG) field shall be the number of groups in a sub-frame assigned to the parade to which this group belongs, minus 1, e.g., NoG=0 implies that one group is allocated (or assigned) to this parade in a sub-frame. The value of NoG may range from 0 to 7. This limits the amount of data that a parade may take from the main (legacy) service data, and consequently the maximum data that can be carried by one parade. The slot numbers assigned to the corresponding Parade can be calculated from SGN and NoG, using Equation 1. By taking each parade in sequence, the specific slots for each parade will be determined, and consequently the SGN for each succeeding parade. For example, if for a specific parade SGN=3 and NoG=3 (010b for 3-bit field of NoG), substituting i=3, 4, and 5 in Equation 1 provides slot numbers  12 ,  2 , and  6 . The Parade_repetition_cycle (PRC) field corresponds to the cycle time over which the parade is transmitted, minus 1, specified in units of MPH frames, as described in Table 12. 
     
       
         
           
               
               
             
               
                 TABLE 12 
               
               
                   
               
               
                 PRC 
                 Description 
               
               
                   
               
             
            
               
                 000 
                 This parade shall be transmitted once every MPH frame. 
               
               
                 001 
                 This parade shall be transmitted once every 2 MPH frames. 
               
               
                 010 
                 This parade shall be transmitted once every 3 MPH frames. 
               
               
                 011 
                 This parade shall be transmitted once every 4 MPH frames. 
               
               
                 100 
                 This parade shall be transmitted once every 5 MPH frames. 
               
               
                 101 
                 This parade shall be transmitted once every 6 MPH frames. 
               
               
                 110 
                 This parade shall be transmitted once every 7 MPH frames. 
               
               
                 111 
                 Reserved 
               
               
                   
               
            
           
         
       
     
     The RS_Frame_mode field shall be as defined in Table 1. The RS_code_mode_primary field shall be the RS code mode for the primary RS frame. Herein, the RS code mode is defined in Table 6. The RS_code_mode_secondary field shall be the RS code mode for the secondary RS frame. Herein, the RS code mode is defined in Table 6. The SCCC_Block_mode field shall be as defined in Table 7. The SCCC_outer_code_mode_A field corresponds to the SCCC outer code mode for Region A. The SCCC outer code mode is defined in Table 8. The SCCC_outer_code_mode_B field corresponds to the SCCC outer code mode for Region B. The SCCC_outer_code_mode_C field corresponds be the SCCC outer code mode for Region C. And, the SCCC_outer_code_mode_D field corresponds to the SCCC outer code mode for Region D. 
     The FIC_version field may be supplied by the management layer (which also supplies the FIC data). The Parade_continuity_counter field counter may increase from 0 to 15 and then repeat its cycle. This counter shall increment by 1 every (PRC+1) MPH frames. For example, as shown in Table 12, PRC=011 (decimal 3) implies that Parade_continuity_counter increases every fourth MPH frame. The TNoG field may be identical for all sub-frames in an MPH Frame. However, the information included in the TPC data presented herein is merely exemplary. And, since the adding or deleting of information included in the TPC may be easily adjusted and modified by one skilled in the art, the present invention will, therefore, not be limited to the examples set forth herein. 
     Since the TPC parameters (excluding the Sub-Frame_number field and the Slot_number field) for each parade do not change their values during an MPH frame, the same information is repeatedly transmitted through all MPH groups belonging to the corresponding parade during an MPH frame. This allows very robust and reliable reception of the TPC data. Because the Sub-Frame_number and the Slot_number are increasing counter values, they also are robust due to the transmission of regularly expected values. 
     Furthermore, the FIC information is provided to enable a fast service acquisition of data receivers, and the FIC information includes cross layer information between the physical layer and the upper layer(s). 
       FIG. 32  illustrates an example of a transmission scenario of the TPC data and the FIC data. The values of the Sub-Frame_number field, Slot_number field, Parade_id field, Parade_repetition_cycle field, and Parade_continuity_counter field may corresponds to the current MPH frame throughout the 5 sub-frames within a specific MPH frame. Some of TPC parameters and FIC data are signaled in advance. The SGN, NoG and all FEC modes may have values corresponding to the current MPH frame in the first two sub-frames. The SGN, NoG and all FEC modes may have values corresponding to the frame in which the parade next appears throughout the 3 rd , 4 th  and 5 th  sub-frames of the current MPH frame. This enables the MPH receivers to receive (or acquire) the transmission parameters in advance very reliably. 
     For example, when Parade_repetition_cycle=‘000’, the values of the 3 rd , 4 th , and 5 th  sub-frames of the current MPH frame correspond to the next MPH frame. Also, when Parade_repetition_cycle=‘011’, the values of the 3 rd , 4 th , and 5 th  sub-frames of the current MPH frame correspond to the 4 th  MPH frame and beyond. The FIC_version field and the FIC_data field may have values that apply to the current MPH Frame during the 1 st  sub-frame and the 2 nd  sub-frame, and they shall have values corresponding to the MPH frame immediately following the current MPH frame during the 3 rd , 4 th , and 5 th  sub-frames of the current MPH frame. 
     Meanwhile, the receiving system may turn the power on only during a slot to which the data group of the designated (or desired) parade is assigned, and the receiving system may turn the power off during the remaining slots, thereby reducing power consumption of the receiving system. Such characteristic is particularly useful in portable or mobile receivers, which require low power consumption. For example, it is assumed that data groups of a 1 st  parade with NOG=3, a 2 nd  parade with NOG=2, and a 3 rd  parade with NOG=3 are assigned to one MPH frame, as shown in  FIG. 33 . It is also assumed that the user has selected a mobile service included in the 1 st  parade using the keypad provided on the remote controller or terminal. In this case, the receiving system turns the power on only during a slot that data groups of the 1 st  parade is assigned, as shown in  FIG. 33 , and turns the power off during the remaining slots, thereby reducing power consumption, as described above. At this point, the power is required to be turned on briefly earlier than the slot to which the actual designated data group is assigned (or allocated). This is to enable the tuner or demodulator to converge in advance. 
     Assignment of Known Data (or Training Signal) 
     In addition to the payload data, the MPH transmission system inserts long and regularly spaced training sequences into each group. The regularity is an especially useful feature since it provides the greatest possible benefit for a given number of training symbols in high-Doppler rate conditions. The length of the training sequences is also chosen to allow fast acquisition of the channel during bursted power-saving operation of the demodulator. Each group contains 6 training sequences. The training sequences are specified before trellis-encoding. The training sequences are then trellis-encoded and these trellis-encoded sequences also are known sequences. This is because the trellis encoder memories are initialized to pre-determined values at the beginning of each sequence. The form of the 6 training sequences at the byte level (before trellis-encoding) is shown in  FIG. 34 . This is the arrangement of the training sequence at the group formatter  303 . 
     The 1 st  training sequence is located at the last 2 segments of the 3 rd  MPH block (B 3 ). The 2 nd  training sequence may be inserted at the 2 nd  and 3 rd  segments of the 4 th  MPH block (B 4 ). The 2 nd  training sequence is next to the signaling area, as shown in  FIG. 5 . Then, the 3 rd  training sequence, the 4 th  training sequence, the 5 th  training sequence, and the 6 th  training sequence may be placed at the last 2 segments of the 4 th , 5 th , 6 th , and 7 th  MPH blocks (B 4 , B 5 , B 6 , and B 7 ), respectively. As shown in  FIG. 34 , the 1 st  training sequence, the 3 rd  training sequence, the 4 th  training sequence, the 5 th  training sequence, and the 6 th  training sequence are spaced 16 segments apart from one another. Referring to  FIG. 34 , the dotted area indicates trellis initialization data bytes, the lined area indicates training data bytes, and the white area includes other bytes such as the FEC-coded MPH service data bytes, FEC-coded signaling data, main service data bytes, RS parity data bytes (for backwards compatibility with legacy ATSC receivers) and/or dummy data bytes. 
       FIG. 35  illustrates the training sequences (at the symbol level) after trellis-encoding by the trellis encoder. Referring to  FIG. 35 , the dotted area indicates data segment sync symbols, the lined area indicates training data symbols, and the white area includes other symbols, such as FEC-coded mobile service data symbols, FEC-coded signaling data, main service data symbols, RS parity data symbols (for backwards compatibility with legacy ATSC receivers), dummy data symbols, trellis initialization data symbols, and/or the first part of the training sequence data symbols. Due to the intra-segment interleaving of the trellis encoder, various types of data symbols will be mixed in the white area. 
     After the trellis-encoding process, the last 1416 (=588+828) symbols of the 1 st  training sequence, the 3 rd  training sequence, the 4 th  training sequence, the 5 th  training sequence, and the 6 th  training sequence commonly share the same data pattern. Including the data segment synchronization symbols in the middle of and after each sequence, the total length of each common training pattern is 1424 symbols. The 2 nd  training sequence has a first 528-symbol sequence and a second 528-symbol sequence that have the same data pattern. More specifically, the 528-symbol sequence is repeated after the 4-symbol data segment synchronization signal. At the end of each training sequence, the memory contents of the twelve modified trellis encoders shall be set to zero(0). 
     Demodulating Unit within Receiving System 
       FIG. 36  illustrates an example of a demodulating unit in a digital broadcast receiving system according to the present invention. The demodulating unit of  FIG. 36  uses known data information, which is inserted in the mobile service data section and, then, transmitted by the transmitting system, so as to perform carrier synchronization recovery, frame synchronization recovery, and channel equalization, thereby enhancing the receiving performance. Also the demodulating unit may turn the power on only during a slot to which the data group of the designated (or desired) parade is assigned, thereby reducing power consumption of the receiving system. 
     Referring to  FIG. 36 , the demodulating unit includes a demodulator  1002 , an equalizer  1003 , a known sequence detector  1004 , a block decoder  1005 , a RS frame decoder  1006 , a derandomizer  1007 . The demodulating unit may further include a data deinterleaver  1009 , a RS decoder  1010 , and a data derandomizer  1011 . The demodulating unit may further include a signaling information decoder  1013 . The receiving system also may further include a power controller  5000  for controlling power supply of the demodulating unit. 
     Herein, for simplicity of the description of the present invention, the RS frame decoder  1006 , and the derandomizer  1007  will be collectively referred to as a mobile service data processing unit. And, the data deinterleaver  1009 , the RS decoder  1010 , and the data derandomizer  1011  will be collectively referred to as a main service data processing unit. More specifically, a frequency of a particular channel tuned by a tuner down converts to an intermediate frequency (IF) signal. Then, the down-converted data  1001  outputs the down-converted IF signal to the demodulator  1002  and the known sequence detector  1004 . At this point, the down-converted data  1001  is inputted to the demodulator  1002  and the known sequence detector  1004  via analog/digital converter ADC (not shown). The ADC converts pass-band analog IF signal into pass-band digital IF signal. 
     The demodulator  1002  performs self gain control, carrier recovery, and timing recovery processes on the inputted pass-band digital IF signal, thereby modifying the IF signal to a base-band signal. Then, the demodulator  1002  outputs the newly created base-band signal to the equalizer  1003  and the known sequence detector  1004 . The equalizer  1003  compensates the distortion of the channel included in the demodulated signal and then outputs the error-compensated signal to the block decoder  1005 . 
     At this point, the known sequence detector  1004  detects the known sequence place inserted by the transmitting end from the input/output data of the demodulator  1002  (i.e., the data prior to the demodulation process or the data after the demodulation process). Thereafter, the place information along with the symbol sequence of the known data, which are generated from the detected place, is outputted to the demodulator  1002  and the equalizer  1003 . Also, the known data detector  1004  outputs a set of information to the block decoder  1005 . This set of information is used to allow the block decoder  1005  of the receiving system to identify the mobile service data that are processed with additional encoding from the transmitting system and the main service data that are not processed with additional encoding. In addition, although the connection status is not shown in  FIG. 36 , the information detected from the known data detector  1004  may be used throughout the entire receiving system and may also be used in the RS frame decoder  1006 . 
     The demodulator  1002  uses the known data symbol sequence during the timing and/or carrier recovery, thereby enhancing the demodulating performance. Similarly, the equalizer  1003  uses the known data so as to enhance the equalizing performance. Moreover, the decoding result of the block decoder  1005  may be fed-back to the equalizer  1003 , thereby enhancing the equalizing performance. 
     Power On/Off Control 
     The data demodulated in the demodulator  1002  or the data equalized in the channel equalizer  1003  is inputted to the signaling information decoder  1013 . The known data information detected in the known sequence detector  1004  is inputted to the signaling information decoder  1013 . 
     The signaling information decoder  1013  extracts and decodes signaling information from the inputted data, the decoded signaling information provides to blocks requiring the signaling information. For example, the SCCC-associated information may output to the block decoder  1005 , and the RS frame-associated information may output to the RS frame decoder  1006 . The MPH frame-associated information may output to the known sequence detector  1004  and the power controller  5000 . 
     Herein, the RS frame-associated information may include RS frame mode information and RS code mode information. The SCCC-associated information may include SCCC block mode information and SCCC outer code mode information. The MPH frame-associated information may include sub-frame count information, slot count information, parade_id information, SGN information, NoG information, and so on, as shown in  FIG. 32 . 
     More specifically, the signaling information between first known data area and second known data area can know by using known data information being outputted in the known sequence detector  1004 . Therefore, the signaling information decoder  1013  may extract and decode signaling information from the data being outputted in the demodulator  1002  or the channel equalizer  1003 . 
     The power controller  5000  is inputted the MPH frame-associated information from the signaling information decoder  1013 , and controls power of the tuner and the demodulating unit. 
     According to the embodiment of the present invention, the power controller  5000  turns the power on only during a slot to which a slot of the parade including user-selected mobile service is assigned. The power controller  5000  then turns the power off during the remaining slots. 
     For example, it is assumed that data groups of a 1 st  parade with NOG=3, a 2 nd  parade with NOG=2, and a 3 rd  parade with NOG=3 are assigned to one MPH frame, as shown in  FIG. 33 . It is also assumed that the user has selected a mobile service included in the 1 st  parade using the keypad provided on the remote controller or terminal. In this case, the power controller  5000  turns the power on only during a slot that data groups of the 1 st  parade is assigned, as shown in  FIG. 33 , and turns the power off during the remaining slots, thereby reducing power consumption. 
     Demodulator and Known Sequence Detector 
     At this point, the transmitting system may receive a data frame (or VSB frame) including a data group which known data sequence (or training sequence) is periodically inserted therein. Herein, the data group is divided into regions A to D, as shown in  FIG. 5 . More specifically, in the example of the present invention, each region A, B, C, and D are further divided into MPH blocks B 4  to B 7 , MPH blocks B 3  and B 8 , MPH blocks B 2  and B 9 , MPH blocks B 1  and B 10 , respectively. 
       FIG. 37  illustrates an example of known data sequence being periodically inserted and transmitted in-between actual data by the transmitting system. Referring to  FIG. 37 , AS represents the number of valid data symbols, and BS represents the number of known data symbols. Therefore, BS number of known data symbols are inserted and transmitted at a period of (AS+BS) symbols. Herein, AS may correspond to mobile service data, main service data, or a combination of mobile service data and main service data. In order to be differentiated from the known data, data corresponding to AS will hereinafter be referred to as valid data. 
     Referring to  FIG. 37 , known data sequence having the same pattern are included in each known data section that is being periodically inserted. Herein, the length of the known data sequence having identical data patterns may be either equal to or different from the length of the entire (or total) known data sequence of the corresponding known data section (or block). If the two lengths are different from one another, the length of the entire known data sequence should be longer than the length of the known data sequence having identical data patterns. In this case, the same known data sequences are included in the entire known data sequence. The known sequence detector  1004  detects the position of the known data being periodically inserted and transmitted as described above. At the same time, the known sequence detector  1004  may also estimate initial frequency offset during the process of detecting known data. In this case, the demodulator  1002  may estimate with more accuracy carrier frequency offset from the information on the known data position (or known sequence position indicator) and initial frequency offset estimation value, thereby compensating the estimated initial frequency offset. 
       FIG. 38  illustrates a detailed block diagram of a demodulator according to the present invention. Referring to  FIG. 38 , the demodulator includes a phase splitter  1010 , a numerically controlled oscillator (NCO)  1020 , a first multiplier  1030 , a resampler  1040 , a second multiplier  1050 , a matched filter  1060 , a DC remover  1070 , a timing recovery unit  1080 , a carrier recovery unit  1090 , and a phase compensator  1110 . Herein, the known sequence detector  1004  includes a known sequence detector and initial frequency offset estimator  1004 - 1  for estimating known data information and initial frequency offset. Also referring to  FIG. 38 , the phase splitter  1010  receives a pass band digital signal and splits the received signal into a pass band digital signal of a real number element and a pass band digital signal of an imaginary number element both having a phase of 90 degrees between one another. In other words, the pass band digital signal is split into complex signals. The split portions of the pass band digital signal are then outputted to the first multiplier  1030 . Herein, the real number signal outputted from the phase splitter  1010  will be referred to as an ‘I’ signal, and the imaginary number signal outputted from the phase splitter  1010  will be referred to as a ‘Q’ signal, for simplicity of the description of the present invention. 
     The first multiplier  1030  multiplies the I and Q pass band digital signals, which are outputted from the phase splitter  1010 , to a complex signal having a frequency proportional to a constant being outputted from the NCO  1020 , thereby changing the I and Q pass band digital signals to baseband digital complex signals. Then, the baseband digital signals of the first multiplier  1030  are inputted to the resampler  1040 . The resampler  1040  resamples the signals being outputted from the first multiplier  1030  so that the signal corresponds to the timing clock provided by the timing recovery unit  1080 . Thereafter, the resampler  1040  outputs the resampled signals to the second multiplier  1050 . 
     For example, when the analog/digital converter uses a 25 MHz fixed oscillator, the baseband digital signal having a frequency of 25 MHz, which is created by passing through the analog/digital converter, the phase splitter  1010 , and the first multiplier  1030 , is processed with an interpolation process by the resampler  1040 . Thus, the interpolated signal is recovered to a baseband digital signal having a frequency twice that of the receiving signal of a symbol clock (i.e., a frequency of 21.524476 MHz). Alternatively, if the analog/digital converter uses the timing clock of the timing recovery unit  1080  as the sampling frequency (i.e., if the analog/digital converter uses a variable frequency) in order to perform an A/D conversion process, the resampler  1040  is not required and may be omitted. 
     The second multiplier  1050  multiplies an output frequency of the carrier recovery unit  1090  with the output of the resampler  1040  so as to compensate any remaining carrier included in the output signal of the resampler  1040 . Thereafter, the compensated carrier is outputted to the matched filter  1060  and the timing recovery unit  1080 . The signal matched-filtered by the matched filter  1060  is inputted to the DC remover  1070 , the known sequence detector and initial frequency offset estimator  1004 - 1 , and the carrier recovery unit  1090 . 
     The known sequence detector and initial frequency offset estimator  1004 - 1  detects the place (or position) of the known data sequences that are being periodically or non-periodically transmitted. Simultaneously, the known sequence detector and initial frequency offset estimator  1004 - 1  estimates an initial frequency offset during the known sequence detection process. More specifically, while the transmission data frame is being received, as shown in  FIG. 5 , the known sequence detector and initial frequency offset estimator  1004 - 1  detects the position (or place) of the known data included in the transmission data frame. Then, the known sequence detector and initial frequency offset estimator  1004 - 1  outputs the detected information on the known data place (i.e., a known sequence position indicator) to the timing recovery unit  1080 , the carrier recovery unit  1090 , and the phase compensator  1110  of the demodulator  1002  and the equalizer  1003 . Furthermore, the known sequence detector and initial frequency offset estimator  1004 - 1  estimates the initial frequency offset, which is then outputted to the carrier recovery unit  1090 . At this point, the known sequence detector and initial frequency offset estimator  1004 - 1  may either receive the output of the matched filter  1060  or receive the output of the resampler  1040 . This may be optionally decided depending upon the design of the system designer. 
     The timing recovery unit  1080  uses the output of the second multiplier  1050  and the known sequence position indicator detected from the known sequence detector and initial frequency offset estimator  1004 - 1 , so as to detect the timing error and, then, to output a sampling clock being in proportion with the detected timing error to the resampler  1040 , thereby adjusting the sampling timing of the resampler  1040 . At this point, the timing recovery unit  1080  may receive the output of the matched filter  1060  instead of the output of the second multiplier  1050 . This may also be optionally decided depending upon the design of the system designer. 
     Meanwhile, the DC remover  1070  removes a pilot tone signal (i.e., DC signal), which has been inserted by the transmitting system, from the matched-filtered signal. Thereafter, the DC remover  1070  outputs the processed signal to the phase compensator  1110 . The phase compensator  1110  uses the data having the DC removed by the DC remover  1070  and the known sequence position indicator detected by the known sequence detector and initial frequency offset estimator  1004 - 1  to estimate the frequency offset and, then, to compensate the phase change included in the output of the DC remover  1070 . The data having its phase change compensated are inputted to the equalizer  1003 . Herein, the phase compensator  1110  is optional. If the phase compensator  1110  is not provided, then the output of the DC remover  1070  is inputted to the equalizer  1003  instead. 
       FIG. 39  includes detailed block diagrams of the timing recovery unit  1080 , the carrier recovery unit  1090 , and the phase compensator  1110  of the demodulator. According to an embodiment of the present invention, the carrier recovery unit  1090  includes a buffer  1091 , a frequency offset estimator  1092 , a loop filter  1093 , a holder  1094 , an adder  1095 , and a NCO  1096 . Herein, a decimator may be included before the buffer  1091 . The timing recovery unit  1080  includes a decimator  1081 , a buffer  1082 , a timing error detector  1083 , a loop filter  1084 , a holder  1085 , and a NCO  1086 . Finally, the phase compensator  1110  includes a buffer  1111 , a frequency offset estimator  1112 , a holder  1113 , a NCO  1114 , and a multiplier  1115 . Furthermore, a decimator  1200  may be included between the phase compensator  1110  and the equalizer  1003 . The decimator  1200  may be outputted in front of the DC remover  1070  instead of at the outputting end of the phase compensator  1110 . 
     Herein, the decimators correspond to components required when a signal being inputted to the demodulator is oversampled to N times by the analog/digital converter. More specifically, the integer N represents the sampling rate of the received signal. For example, when the input signal is oversampled to 2 times (i.e., when N=2) by the analog/digital converter, this indicates that two samples are included in one symbol. In this case, each of the decimators corresponds to a 1/2 decimator. Depending upon whether or not the oversampling process of the received signal has been performed, the signal may bypass the decimators. 
     Meanwhile, the output of the second multiplier  1050  is temporarily stored in the decimator  1081  and the buffer  1082  both included in the timing recovery unit  1080 . Subsequently, the temporarily stored output data are inputted to the timing error detector  1083  through the decimator  1081  and the buffer  1082 . Assuming that the output of the second multiplier  1050  is oversampled to N times its initial state, the decimator  1081  decimates the output of the second multiplier  1050  at a decimation rate of 1/N. Then, the 1/N-decimated data are inputted to the buffer  1082 . In other words, the decimator  1081  performs decimation on the input signal in accordance with a VSB symbol cycle. Furthermore, the decimator  1081  may also receive the output of the matched filter  1060  instead of the output of the second multiplier  1050 . The timing error detector  1083  uses the data prior to or after being processed with matched-filtering and the known sequence position indicator outputted from the known sequence detector and initial frequency offset estimator  1004 - 1  in order to detect a timing error. Thereafter, the detected timing error is outputted to the loop filter  1084 . Accordingly, the detected timing error information is obtained once during each repetition cycle of the known data sequence. 
     For example, if a known data sequence having the same pattern is periodically inserted and transmitted, as shown in  FIG. 37 , the timing error detector  1083  may use the known data in order to detect the timing error. There exists a plurality of methods for detecting timing error by using the known data. In the example of the present invention, the timing error may be detected by using a correlation characteristic between the known data and the received data in the time domain, the known data being already known in accordance with a pre-arranged agreement between the transmitting system and the receiving system. The timing error may also be detected by using the correlation characteristic of the two known data types being received in the frequency domain. Thus, the detected timing error is outputted. In another example, a spectral lining method may be applied in order to detect the timing error. Herein, the spectral lining method corresponds to a method of detecting timing error by using sidebands of the spectrum included in the received signal. 
     The loop filter  1084  filters the timing error detected by the timing error detector  1083  and, then, outputs the filtered timing error to the holder  1085 . The holder  1085  holds (or maintains) the timing error filtered and outputted from the loop filter  1084  during a pre-determined known data sequence cycle period and outputs the processed timing error to the NCO  1086 . Herein, the order of positioning of the loop filter  1084  and the holder  1085  may be switched with one another. In additionally, the function of the holder  1085  may be included in the loop filter  1084 , and, accordingly, the holder  1085  may be omitted. The NCO  1086  accumulates the timing error outputted from the holder  1085 . Thereafter, the NCO  1086  outputs the phase element (i.e., a sampling clock) of the accumulated timing error to the resampler  1040 , thereby adjusting the sampling timing of the resampler  1040 . 
     Meanwhile, the buffer  1091  of the carrier recovery unit  1090  may receive either the data inputted to the matched filter  1060  or the data outputted from the matched filter  1060  and, then, temporarily store the received data. Thereafter, the temporarily stored data are outputted to the frequency offset estimator  1092 . If a decimator is provided in front of the buffer  1091 , the input data or output data of the matched filter  1060  are decimated by the decimator at a decimation rate of 1/N. Thereafter, the decimated data are outputted to the buffer  1091 . For example, when the input data or output data of the matched filter  1060  are oversampled to 2 times (i.e., when N=2), this indicates that the input data or output data of the matched filter  1060  are decimated at a rate of 1/2 by the decimator  1081  and then outputted to the buffer  1091 . More specifically, when a decimator is provided in front of the buffer  1091 , the carrier recovery unit  1090  operates in symbol units. Alternatively, if a decimator is not provided, the carrier recovery unit  1090  operates in oversampling units. 
     The frequency offset estimator  1092  uses the input data or output data of the matched filter  1060  and the known sequence position indicator outputted from the known sequence detector and initial frequency offset estimator  1004 - 1  in order to estimate the frequency offset. Then, the estimated frequency offset is outputted to the loop filter  1093 . Therefore, the estimated frequency offset value is obtained once every repetition period of the known data sequence. The loop filter  1093  performs low pass filtering on the frequency offset value estimated by the frequency offset estimator  1092  and outputs the low pass-filtered frequency offset value to the holder  1094 . The holder  1094  holds (or maintains) the low pass-filtered frequency offset value during a pre-determined known data sequence cycle period and outputs the frequency offset value to the adder  1095 . Herein, the positions of the loop filter  1093  and the holder  1094  may be switched from one to the other. Furthermore, the function of the holder  1085  may be included in the loop filter  1093 , and, accordingly, the holder  1094  may be omitted. 
     The adder  1095  adds the value of the initial frequency offset estimated by the known sequence detector and initial frequency offset estimator  1004 - 1  to the frequency offset value outputted from the loop filter  1093  (or the holder  1094 ). Thereafter, the added offset value is outputted to the NCO  1096 . Herein, if the adder  1095  is designed to also receive the constant being inputted to the NCO  1020 , the NCO  1020  and the first multiplier  1030  may be omitted. In this case, the second multiplier  1050  may simultaneously perform changing signals to baseband signals and removing remaining carrier. 
     The NCO  1096  generates a complex signal corresponding to the frequency offset outputted from the adder  1095 , which is then outputted to the second multiplier  1050 . Herein, the NCO  1096  may include a ROM. In this case, the NCO  1096  generates a compensation frequency corresponding to the frequency offset being outputted from the adder  1095 . Then, the NCO  1096  reads a complex cosine corresponding to the compensation frequency from the ROM, which is then outputted to the second multiplier  1050 . The second multiplier  1050  multiplies the output of the NCO  1094  included in the carrier recovery unit  1090  to the output of the resampler  1040 , so as to remove the carrier offset included in the output signal of the resampler  1040 . 
       FIG. 40  illustrates a detailed block diagram of the frequency offset estimator  1092  of the carrier recovery unit  1090  according to an embodiment of the present invention. Herein, the frequency offset estimator  1092  operates in accordance with the known sequence position indicator detected from the known sequence detector and initial frequency offset estimator  1004 - 1 . At this point, if the input data or output data of the matched filter  1060  are inputted through the decimator, the frequency offset estimator  1092  operates in symbol units. Alternatively, if a decimator is not provided, the frequency offset estimator  1092  operates in oversampling units. In the example given in the description of the present invention, the frequency offset estimator  1092  operates in symbol units. Referring to  FIG. 40 , the frequency offset estimator  1092  includes a controller  1310 , a first N symbol buffer  1301 , a K symbol delay  1302 , a second N symbol buffer  1303 , a conjugator  1304 , a multiplier  1305 , an accumulator  1306 , a phase detector  1307 , a multiplier  1308 , and a multiplexer  1309 . The frequency offset estimator  1092  having the above-described structure, as shown in  FIG. 40 , will now be described in detail with respect to an operation example during a known data section. 
     The first N symbol buffer  1301  may store a maximum of N number of symbol being inputted thereto. The symbol data that are temporarily stored in the first N symbol buffer  1301  are then inputted to the multiplier  1305 . At the same time, the inputted symbol is inputted to the K symbol delay  1302  so as to be delayed by K symbols. Thereafter, the delayed symbol passes through the second N symbol buffer  1303  so as to be conjugated by the conjugator  1304 . Thereafter, the conjugated symbol is inputted to the multiplier  1305 . The multiplier  1305  multiplies the output of the first N symbol buffer  1301  and the output of the conjugator  1304 . Then, the multiplier  1305  outputs the multiplied result to the accumulator  1306 . Subsequently, the accumulator  1306  accumulates the output of the multiplier  1305  during N symbol periods, thereby outputted the accumulated result to the phase detector  1307 . 
     The phase detector  1307  extracts the corresponding phase information from the output of the accumulator  1306 , which is then outputted to the multiplier  1308 . The multiplier  1308  then divides the phase information by K, thereby outputting the divided result to the multiplexer  1309 . Herein, the result of the phase information divided by becomes the frequency offset estimation value. More specifically, at the point where the input of the known data ends or at a desired point, the frequency offset estimator  1092  accumulates during an N symbol period multiplication of the complex conjugate of N number of the input data stored in the first N symbol buffer  1301  and the complex conjugate of the N number of the input data that are delayed by K symbols and stored in the second N symbol buffer  1303 . Thereafter, the accumulated value is divided by K, thereby extracting the frequency offset estimation value. 
     Based upon a control signal of the controller  1310 , the multiplexer  1309  selects either the output of the multiplier  1308  or ‘0’ and, then, outputs the selected result as the final frequency offset estimation value. The controller  1310  receives the known data sequence position indicator from the known sequence detector and initial frequency offset estimator  1004 - 1  in order to control the output of the multiplexer  1309 . More specifically, the controller  1310  determines based upon the known data sequence position indicator whether the frequency offset estimation value being outputted from the multiplier  1308  is valid. If the controller  1310  determines that the frequency offset estimation value is valid, the multiplexer  1309  selects the output of the multiplier  1308 . Alternatively, if the controller  1310  determines that the frequency offset estimation value is invalid, the controller  1310  generates a control signal so that the multiplexer  1309  selects ‘0’. At this point, it is preferable that the input signals stored in the first N symbol buffer  1301  and in the second N symbol buffer  1303  correspond to signals each being transmitted by the same known data and passing through almost the same channel. Otherwise, due to the influence of the transmission channel, the frequency offset estimating performance may be largely deteriorated. 
     Further, the values N and K of the frequency offset estimator  1092  (shown in  FIG. 40 ) may be diversely decided. This is because a particular portion of the known data that are identically repeated may be used herein. For example, when the data having the structure described in  FIG. 37  are being transmitted, N may be set as BS (i.e., N=BS), and K may be set as (AS+BS) (i.e., K=AS+BS)). The frequency offset estimation value range of the frequency offset estimator  1092  is decided in accordance with the value K. If the value K is large, then the frequency offset estimation value range becomes smaller. Alternatively, if the value K is small, then the frequency offset estimation value range becomes larger. Therefore, when the data having the structure of  FIG. 37  is transmitted, and if the repetition cycle (AS+BS) of the known data is long, then the frequency offset estimation value range becomes smaller. 
     In this case, even if the initial frequency offset is estimated by the known sequence detector and initial frequency offset estimator  1004 - 1 , and if the estimated value is compensated by the second multiplier  1050 , the remaining frequency offset after being compensated will exceed the estimation range of the frequency offset estimator  1092 . In order to overcome such problems, the known data sequence that is regularly transmitted may be configured of a repetition of a same data portion by using a cyclic extension process. For example, if the known data sequence shown in  FIG. 37  is configured of two identical portions having the length of BS/2, then the N and K values of the frequency offset estimator  1092  (shown in  FIG. 40 ) may be respectively set as B/2 and B/2 (i.e., N=BS/2 and K=BS/2). In this case, the estimation value range may become larger than when using repeated known data. 
     Meanwhile, the known sequence detector and initial frequency offset estimator  1004 - 1  detects the place (o position) of the known data sequences that are being periodically or non-periodically transmitted. Simultaneously, the known sequence detector and initial frequency offset estimator  1004 - 1  estimates an initial frequency offset during the known sequence detection process. The known data sequence position indicator detected by the known sequence detector and initial frequency offset estimator  1004 - 1  is outputted to the timing recovery unit  1080 , the carrier recovery unit  1090 , and the phase compensator  1110  of the demodulator  1002 , and to the equalizer  1003 . Thereafter, the estimated initial frequency offset is outputted to the carrier recovery unit  1090 . At this point, the known sequence detector and initial frequency offset estimator  1004 - 1  may either receive the output of the matched filter  1060  or receive the output of the resampler  1040 . This may be optionally decided depending upon the design of the system designer. Herein, the frequency offset estimator shown in  FIG. 40  may be directly applied in the known sequence detector and initial frequency offset estimator  1004 - 1  or in the phase compensator  1110  of the frequency offset estimator. 
       FIG. 41  illustrates a detailed block diagram showing a known sequence detector and initial frequency offset estimator according to an embodiment of the present invention. More specifically,  FIG. 41  illustrates an example of an initial frequency offset being estimated along with the known sequence position indicator. Herein,  FIG. 41  shows an example of an inputted signal being oversampled to N times of its initial state. In other words, N represents the sampling rate of a received signal. Referring to  FIG. 41 , the known sequence detector and initial frequency offset estimator includes N number of partial correlators  1411  to  141 N configured in parallel, a known data place detector and frequency offset decider  1420 , a known data extractor  1430 , a buffer  1440 , a multiplier  1450 , a NCO  1460 , a frequency offset estimator  1470 , and an adder  1480 . Herein, the first partial correlator  1411  consists of a 1/N decimator, and a partial correlator. The second partial correlator  1412  consists of a 1 sample delay, a 1/N decimator, and a partial correlator. And, the N th  partial correlator  141 N consists of a N−1 sample delay, a 1/N decimator, and a partial correlator. These are used to match (or identify) the phase of each of the samples within the oversampled symbol with the phase of the original (or initial) symbol, and to decimate the samples of the remaining phases, thereby performing partial correlation on each sample. More specifically, the input signal is decimated at a rate of 1/N for each sampling phase, so as to pass through each partial correlator. 
     For example, when the input signal is oversampled to 2 times (i.e., when N=2), this indicates that two samples are included in one signal. In this case, two partial correlators (e.g.,  1411  and  1412 ) are required, and each 1/N decimator becomes a 1/2 decimator. At this point, the 1/N decimator of the first partial correlator  1411  decimates (or removes), among the input samples, the samples located in-between symbol places (or positions). Then, the corresponding 1/N decimator outputs the decimated sample to the partial correlator. Furthermore, the 1 sample delay of the second partial correlator  1412  delays the input sample by 1 sample (i.e., performs a 1 sample delay on the input sample) and outputs the delayed input sample to the 1/N decimator. Subsequently, among the samples inputted from the 1 sample delay, the 1/N decimator of the second partial correlator  1412  decimates (or removes) the samples located in-between symbol places (or positions). Thereafter, the corresponding 1/N decimator outputs the decimated sample to the partial correlator. 
     After each predetermined period of the VSB symbol, each of the partial correlators outputs a correlation value and an estimation value of the coarse frequency offset estimated at that particular moment to the known data place detector and frequency offset decider  1420 . The known data place detector and frequency offset decider  1420  stores the output of the partial correlators corresponding to each sampling phase during a data group cycle or a pre-decided cycle. Thereafter, the known data place detector and frequency offset decider  1420  decides a position (or place) corresponding to the highest correlation value, among the stored values, as the place (or position) for receiving the known data. Simultaneously, the known data place detector and frequency offset decider  1420  finally decides the estimation value of the frequency offset estimated at the moment corresponding to the highest correlation value as the coarse frequency offset value of the receiving system. At this point, the known sequence position indicator is inputted to the known data extractor  1430 , the timing recovery unit  1080 , the carrier recovery unit  1090 , the phase compensator  1110 , and the equalizer  1003 , and the coarse frequency offset is inputted to the adder  1480  and the NCO  1460 . 
     In the meantime, while the N numbers of partial correlators  1411  to  141 N detect the known data place (or known sequence position) and estimate the coarse frequency offset, the buffer  1440  temporarily stores the received data and outputs the temporarily stored data to the known data extractor  1430 . The known data extractor  1430  uses the known sequence position indicator, which is outputted from the known data place detector and frequency offset decider  1420 , so as to extract the known data from the output of the buffer  1440 . Thereafter, the known data extractor  1430  outputs the extracted data to the multiplier  1450 . The NCO  1460  generates a complex signal corresponding to the coarse frequency offset being outputted from the known data place detector and frequency offset decider  1420 . Then, the NCO  1460  outputs the generated complex signal to the multiplier  1450 . 
     The multiplier  1450  multiplies the complex signal of the NCO  1460  to the known data being outputted from the known data extractor  1430 , thereby outputting the known data having the coarse frequency offset compensated to the frequency offset estimator  1470 . The frequency offset estimator  1470  estimates a fine frequency offset from the known data having the coarse frequency offset compensated. Subsequently, the frequency offset estimator  1470  outputs the estimated fine frequency offset to the adder  1480 . The adder  1480  adds the coarse frequency offset to the fine frequency offset. Thereafter, the adder  1480  decides the added result as a final initial frequency offset, which is then outputted to the adder  1095  of the carrier recovery unit  1090  included in the demodulator  1002 . More specifically, during the process of acquiring initial synchronization, the present invention may estimate and use the coarse frequency offset as well as the fine frequency offset, thereby enhancing the estimation performance of the initial frequency offset. 
     It is assumed that the known data is inserted within the data group and then transmitted, as shown in  FIG. 5 . Then, the known sequence detector and initial frequency offset estimator  1004 - 1  may use the known data that have been additionally inserted between the A 1  area and the A 2  area, so as to estimate the initial frequency offset. The known position indicator, which was periodically inserted within the A area estimated by the known sequence detector and initial frequency offset estimator  1004 - 1 , is inputted to the timing error detector  1083  of the timing error recovery unit  1080 , to the frequency offset estimator  1092  of the carrier recovery unit  1090 , to the frequency offset estimator  1112  of the phase compensator  1110 , and to the equalizer  1003 . 
       FIG. 42  illustrates a block diagram showing the structure of one of the partial correlators shown in  FIG. 41 . During the step of detecting known data, since a frequency offset is included in the received signal, each partial correlator divides the known data, which is known according to an agreement between the transmitting system and the receiving system, to K number of parts each having an L symbol length, thereby correlating each divided part with the corresponding part of the received signal. In order to do so, each partial correlator includes K number of phase and size detector  1511  to  151 K each formed in parallel, an adder  1520 , and a coarse frequency offset estimator  1530 . 
     The first phase and size detector  1511  includes an L symbol buffer  1511 - 2 , a multiplier  1511 - 3 , an accumulator  1511 - 4 , and a squarer  1511 - 5 . Herein, the first phase and size detector  1511  calculates the correlation value of the known data having a first L symbol length among the K number of sections. Also, the second phase and size detector  1512  includes an L symbol delay  1512 - 1 , an L symbol buffer  1512 - 2 , a multiplier  1512 - 3 , an accumulator  1512 - 4 , and a squarer  1512 - 5 . Herein, the second phase and size detector  1512  calculates the correlation value of the known data having a second L symbol length among the K number of sections. Finally, the N th  phase and size detector  151 K includes a (K- 1 )L symbol delay  151 K- 1 , an L symbol buffer  151 K- 2 , a multiplier  151 K- 3 , an accumulator  151 K- 4 , and a squarer  151 K- 5 . Herein, the N th  phase and size detector  151 K calculates the correlation value of the known data having an N th  L symbol length among the K number of sections. 
     Referring to  FIG. 42 , {P 0 , P 1 , . . . , P KL-1 } each being multiplied with the received signal in the multiplier represents the known data known by both the transmitting system and the receiving system (i.e., the reference known data generated from the receiving system). And, * represents a complex conjugate. For example, in the first phase and size detector  1511 , the signal outputted from the 1/N decimator of the first partial correlator  1411 , shown in  FIG. 41 , is temporarily stored in the L symbol buffer  1511 - 2  of the first phase and size detector  1511  and then inputted to the multiplier  1511 - 3 . The multiplier  1511 - 3  multiplies the output of the L symbol buffer  1511 - 2  with the complex conjugate of the known data parts P 0 , P 1 , . . . , P KL-1 , each having a first L symbol length among the known K number of sections. Then, the multiplied result is outputted to the accumulator  1511 - 4 . During the L symbol period, the accumulator  1511 - 4  accumulates the output of the multiplier  1511 - 3  and, then, outputs the accumulated value to the squarer  1511 - 5  and the coarse frequency offset estimator  1530 . The output of the accumulator  1511 - 4  is a correlation value having a phase and a size. Accordingly, the squarer  1511 - 5  calculates an absolute value of the output of the multiplier  1511 - 4  and squares the calculated absolute value, thereby obtaining the size of the correlation value. The obtained size is then inputted to the adder  1520 . 
     The adder  1520  adds the output of the squares corresponding to each size and phase detector  1511  to  151 K. Then, the adder  1520  outputs the added result to the known data place detector and frequency offset decider  1420 . Also, the coarse frequency offset estimator  1530  receives the output of the accumulator corresponding to each size and phase detector  1511  to  151 K, so as to estimate the coarse frequency offset at each corresponding sampling phase. Thereafter, the coarse frequency offset estimator  1530  outputs the estimated offset value to the known data place detector and frequency offset decider  1420 . 
     When the K number of inputs that are outputted from the accumulator of each phase and size detector  1511  to  151 K are each referred to as {Z 0 , Z 1 , . . . , Z K-1 } the output of the coarse frequency offset estimator  1530  may be obtained by using Equation 7 shown below. 
     
       
         
           
             
               
                 
                   
                     ω 
                     0 
                   
                   = 
                   
                     
                       1 
                       L 
                     
                     ⁢ 
                     arg 
                     ⁢ 
                     
                       { 
                       
                         
                           ∑ 
                           
                             n 
                             = 
                             1 
                           
                           
                             K 
                             - 
                             1 
                           
                         
                         ⁢ 
                         
                           
                             ( 
                             
                               
                                 Z 
                                 n 
                               
                               
                                  
                                 
                                   Z 
                                   n 
                                 
                                  
                               
                             
                             ) 
                           
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             
                               ( 
                               
                                 
                                   Z 
                                   
                                     n 
                                     - 
                                     1 
                                   
                                 
                                 
                                    
                                   
                                     Z 
                                     
                                       n 
                                       - 
                                       1 
                                     
                                   
                                    
                                 
                               
                               ) 
                             
                             * 
                           
                         
                       
                       } 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   7 
                 
               
             
           
         
       
     
     The known data place detector and frequency offset decider  1420  stores the output of the partial correlator corresponding to each sampling phase during an enhanced data group cycle or a pre-decided cycle. Then, among the stored correlation values, the known data place detector and frequency offset decider  1420  decides the place (or position) corresponding to the highest correlation value as the place for receiving the known data. 
     Furthermore, the known data place detector and frequency offset decider  1420  decides the estimated value of the frequency offset taken (or estimated) at the point of the highest correlation value as the coarse frequency offset value of the receiving system. For example, if the output of the partial correlator corresponding to the second partial correlator  1412  is the highest value, the place corresponding to the highest value is decided as the known data place. Thereafter, the coarse frequency offset estimated by the second partial correlator  1412  is decided as the final coarse frequency offset, which is then outputted to the demodulator  1002 . 
     Meanwhile, the output of the second multiplier  1050  is temporarily stored in the decimator  1081  and the buffer  1082  both included in the timing recovery unit  1080 . Subsequently, the temporarily stored output data are inputted to the timing error detector  1083  through the decimator  1081  and the buffer  1082 . Assuming that the output of the second multiplier  1050  is oversampled to N times its initial state, the decimator  1081  decimates the output of the second multiplier  1050  at a decimation rate of 1/N. Then, the 1/N-decimated data are inputted to the buffer  1082 . In other words, the decimator  1081  performs decimation on the input signal in accordance with a VSB symbol cycle. Furthermore, the decimator  1081  may also receive the output of the matched filter  1060  instead of the output of the second multiplier  1050 . 
     The timing error detector  1083  uses the data prior to or after being processed with matched-filtering and the known sequence position indicator outputted from the known data detector and initial frequency offset estimator  1004 - 1  in order to detect a timing error. Thereafter, the detected timing error is outputted to the loop filter  1084 . Accordingly, the detected timing error information is obtained once during each repetition cycle of the known data sequence. 
     For example, if a known data sequence having the same pattern is periodically inserted and transmitted, as shown in  FIG. 37 , the timing error detector  1083  may use the known data in order to detect the timing error. There exists a plurality of methods for detecting timing error by using the known data. 
     In the example of the present invention, the timing error may be detected by using a correlation characteristic between the known data and the received data in the time domain, the known data being already known in accordance with a pre-arranged agreement between the transmitting system and the receiving system. The timing error may also be detected by using the correlation characteristic of the two known data types being received in the frequency domain. Thus, the detected timing error is outputted. In another example, a spectral lining method may be applied in order to detect the timing error. Herein, the spectral lining method corresponds to a method of detecting timing error by using sidebands of the spectrum included in the received signal. 
     The loop filter  1084  filters the timing error detected by the timing error detector  1083  and, then, outputs the filtered timing error to the holder  1085 . 
     The holder  1085  holds (or maintains) the timing error filtered and outputted from the loop filter  1084  during a pre-determined known data sequence cycle period and outputs the processed timing error to the NCO  1086 . Herein, the order of positioning of the loop filter  1084  and the holder  1085  may be switched with one another. In additionally, the function of the holder  1085  may be included in the loop filter  1084 , and, accordingly, the holder  1085  may be omitted. 
     The NCO  1086  accumulates the timing error outputted from the holder  1085 . Thereafter, the NCO  1086  outputs the phase element (i.e., a sampling clock) of the accumulated timing error to the resampler  1040 , thereby adjusting the sampling timing of the resampler  1040 . 
       FIG. 43  illustrates an example of the timing recovery unit included in the demodulator  1002  shown in  FIG. 36 . Referring to  FIG. 43 , the timing recovery unit  1080  includes a first timing error detector  1611 , a second timing error detector  1612 , a multiplexer  1613 , a loop-filter  1614 , and an NCO  1615 . The timing recovery unit  1080  would be beneficial when the input signal is divided into a first area in which known data having a predetermined length are inserted at predetermined position(s) and a second area that includes no known data. Assuming that the first timing error detector  1611  detects a first timing error using a sideband of a spectrum of an input signal and the second timing error detector  1612  detects a second timing error using the known data, the multiplexer  1613  can output the first timing error for the first area and can output the second timing error for the second area. The multiplexer  1613  may output both of the first and second timing errors for the first area in which the known data are inserted. By using the known data a more reliable timing error can be detected and the performance of the timing recovery unit  1080  can be enhanced. 
     This disclosure describes two ways of detecting a timing error. One way is to detect a timing error using correlation in the time domain between known data pre-known to a transmitting system and a receiving system (reference known data) and the known data actually received by the receiving system, and the other way is to detect a timing error using correlation in the frequency domain between two known data actually received by the receiving system. In  FIG. 44 , a timing error is detected by calculating correlation between the reference known data pre-known to and generated by the receiving system and the known data actually received. In  FIG. 44 , correlation between an entire portion of the reference know data sequence and an entire portion of the received known data sequence is calculated. The correlation output has a peak value at the end of each known data sequence actually received. 
     In  FIG. 45 , a timing error is detected by calculating correlation values between divided portions of the reference known data sequence and divided portions of the received known data sequence, respectively. The correlation output has a peak value at the end of each divided portion of the received known data sequence. The correlation values may be added as a total correlation value as shown  FIG. 45 , and the total correlation value can be used to calculate the timing error. When an entire portion of the received known data is used for correlation calculation, the timing error can be obtained for each data block. If the correlation level of the entire portion of the known data sequence is low, a more precise correlation can be obtained by using divided portions of the known data sequence as shown in  FIG. 45 . 
     The use of a final correlation value which is obtained based upon a plurality of correlation values of divided portions of a received known data sequence may reduce the carrier frequency error. In addition, the process time for the timing recovery can be greatly reduced when the plurality of correlation values are used to calculate the timing error. For example, when the reference known data sequence which is pre-known to the transmitting system and receiving system is divided into K portions, K correlation values between the K portions of the reference known data sequence and the corresponding divided portions of the received known data sequence can be calculated, or any combination(s) of the correlation values can be used. Therefore, the period of the timing error detection can be reduced when the divided portions of the known data sequence are used instead of the entire portion of the sequence. 
     The timing error can be calculated from the peak value of the correlation values. The timing error is obtained for each data block if an entire portion of the known data sequence is used as shown in  FIG. 46 . On the other hand, if K divided portions of the known data sequence are used for correlation calculation, K correlation values and corresponding peak values can be obtained. This indicates that the timing error can be detected K times. 
     A method of detecting a timing error using the correlation between the reference known data and the received known data shown will now be described in more detail.  FIG. 46  illustrates correlation values between the reference known data and the received known data. The correlation values correspond to data samples sampled at a rate two times greater than the symbol clock. When the random data effect is minimized and there is no timing clock error, the correlation values between the reference known data and the received known data are symmetrical. However, if a timing phase error exists, the correlation values adjacent to the peak value are not symmetrical as shown in  FIG. 46 . Therefore, the timing error can be obtained by using a difference (timing phase error shown in  FIG. 46 ) between the correlation values before and after the peak value. 
       FIG. 47  illustrates an example of the timing error detector shown in  FIG. 43 . The timing error detector includes a correlator  1701 , a down sampler  1702 , an absolute value calculator  1703 , a delay  1704 , and a subtractor  1705 . The correlator  1701  receives a known data sequence sampled at a rate at least two times higher than the symbol clock frequency and calculates the correlation values between the received known data sequence and a reference known data sequence. The down sampler  1702  performs down sampling on the correlation values and obtains samples having a symbol frequency. For example, if the data inputted to the correlator  1701  is pre-sampled at a sampling rate of 2, then the down sampler  1702  performs down sampling at a rate of 1/2 to obtain samples having the symbol frequency. The absolute value calculator  1703  calculates absolute values (or square values) of the down-sampled correlation values. These absolute values are inputted to the delay  1704  and the subtractor  1705 . The delay  1704  delays the absolute values for a symbol and the subtractor then outputs a timing error by subtracting the delayed absolute value from the values outputted from the absolute value calculator  1703 . 
     The arrangement of the correlator  1701 , the down sampler  1702 , the absolute value calculator  1703 , and the delay  1704 , and the subtractor  1705  shown in  FIG. 47  can be modified. For example, the timing phase error can be calculated in the order of the down sampler  1702 , the correlator  1701 , and the absolute value calculator  1703 , or in the order of the correlator  1701 , the absolute value calculator  1703 , and the down sampler  1702 . 
     The timing error can also be obtained using the frequency characteristic of the known data. When there is a timing frequency error, a phase of the input signal increases at a fixed slope as the frequency of the signal increases and this slope is different for current and next data block. Therefore, the timing error can be calculated based on the frequency characteristic of two different known data blocks. In  FIG. 48 , a current known data sequence (right) and a previous known data sequence (left) are converted into first and second frequency domain signals, respectively, using a Fast Fourier Transform (FFT) algorithm. The conjugate value of the first frequency domain signal is then multiplied with the second frequency domain signal in order to obtain the correlation value between two frequency domain signals. In other words, the correlation between the frequency value of the previous known data sequence and the frequency value of the current known data sequence is used to detect a phase change between the known data blocks for each frequency. In this way the phase distortion of a channel can be eliminated. 
     The frequency response of a complex VSB signal does not have a full symmetric distribution as shown in  FIG. 46 . Rather, its distribution is a left or right half of the distribution and the frequency domain correlation values also have a half distribution. In order to the phase difference between the frequency domain correlation values, the frequency domain having the correlation values can be divided into two sub-areas and a phase of a combined correlation value in each sub-area can be obtained. Thereafter, the difference between the phases of sub-areas can be used to calculate a timing frequency error. When a phase of a combined correlation values is used for each frequency, the magnitude of each correlation value is proportional to reliability and a phase component of each correlation value is reflected to the final phase component in proportion to the magnitude. 
       FIG. 49  illustrates another example of the timing error detector shown in  FIG. 43 . The timing error detector shown in  FIG. 49  includes a Fast Fourier Transform (FFT) unit  1801 , a first delay  1802 , a conjugator  1803 , a multiplier  1804 , an accumulator (adder)  1805 , a phase detector  1806 , a second delay  1807 , and a subtractor  1808 . The first delay  1802  delays for one data block and the second delay  1807  delays for 1/4 data block. One data block includes a frequency response of a sequence of N known data symbol sequences. When a known data region is known and the data symbols are received, the FFT unit  1801  converts complex values of consecutive N known data symbol sequences into complex values in the frequency domain. The first delay  1802  delays the frequency domain complex values for a time corresponding to one data block, and the conjugator  1803  generate conjugate values of the delayed complex values. The multiplier  1804  multiplies the current block of known data outputted from the FFT unit  1801  with the previous block of known data outputted from the conjugator  1803 . The output of the multiplier  1804  represents frequency region correlation values within a known data block. 
     Since the complex VSB data exist only on a half of the frequency domain, the accumulator  1805  divides a data region in the known data block into two sub-regions, and accumulates correlation values for each sub-region. The phase detector  1806  detects a phase of the accumulated correlation value for each sub-region. The second delay  1807  delays the detected phase for a time corresponding to a 1/4 data block. The subtractor  1808  obtains a phase difference between the delayed phase and the phase outputted from the accumulator  1806  and outputs the phase difference as a timing frequency error. 
     In the method of calculating a timing error by using a peak of correlation between the reference known data and the received known data in the time domain, the contribution of the correlation values may affect a channel when the channel is a multi path channel. However, this can be greatly eliminated if the timing error is obtained using the correlation between two received known data. In addition, the timing error can be detected using an entire portion of the known data sequence inserted by the transmitting system, or it can be detected using a portion of the known data sequence which is robust to random or noise data. 
     Meanwhile, the DC remover  1070  removes pilot tone signal (i.e., DC signal), which has been inserted by the transmitting system, from the matched-filtered signal. Thereafter, the DC remover  1070  outputs the processed signal to the phase compensator  1110 . 
       FIG. 50  illustrates a detailed block diagram of a DC remover according to an embodiment of the present invention. Herein, identical signal processing processes are performed on each of a real number element (or in-phase (I)) and an imaginary number element (or a quadrature (Q)) of the inputted complex signal, thereby estimating and removing the DC value of each element. In order to do so, the DC remover shown in  FIG. 50  includes a first DC estimator and remover  1900  and a second DC estimator and remover  1950 . Herein, the first DC estimator and remover  1900  includes an R sample buffer  1901 , a DC estimator  1902 , an M sample holder  1903 , a C sample delay  1904 , and a subtractor  1905 . Herein, the first DC estimator and remover  1900  estimates and removes the DC of the real number element (i.e., an in-phase DC). Furthermore, the second DC estimator and remover  1950  includes an R sample buffer  1951 , a DC estimator  1952 , an M sample holder  1953 , a C sample delay  1954 , and a subtractor  1955 . The second DC estimator and remover  1950  estimates and removes the DC of the imaginary number element (i.e., a quadrature DC). In the present invention, the first DC estimator and remover  1900  and the second DC estimator and remover  1950  may receive different input signals. However, each DC estimator and remover  1900  and  1950  has the same structure. Therefore, a detailed description of the first DC estimator and remover  1900  will be presented herein, and the second DC estimator and remover  1950  will be omitted for simplicity. 
     More specifically, the in-phase signal matched-filtered by the matched filter  1060  is inputted to the R sample buffer  1901  of the first DC estimator and remover  1900  within the DC remover  1070  and is then stored. The R sample buffer  1901  is a buffer having the length of R sample. Herein, the output of the R sample buffer  1901  is inputted to the DC estimator  1902  and the C sample delay  1904 . The DC estimator  1902  uses the data having the length of R sample, which are outputted from the buffer  1901 , so as to estimate the DC value by using Equation 8 shown below. 
     
       
         
           
             
               
                 
                   
                     y 
                     ⁡ 
                     
                       [ 
                       n 
                       ] 
                     
                   
                   = 
                   
                     
                       1 
                       R 
                     
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           0 
                         
                         
                           R 
                           - 
                           1 
                         
                       
                       ⁢ 
                       
                         x 
                         ⁡ 
                         
                           [ 
                           
                             k 
                             + 
                             
                               M 
                               * 
                               n 
                             
                           
                           ] 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   8 
                 
               
             
           
         
       
     
     In the above-described Equation 8, x[n] represents the inputted sample data stored in the buffer  1901 . And, y[n] indicates the DC estimation value. More specifically, the DC estimator  1902  accumulates R number of sample data stored in the buffer  1901  and estimates the DC value by dividing the accumulated value by R. At this point, the stored input sample data set is shifted as much as M sample. Herein, the DC estimation value is outputted once every M samples. 
       FIG. 51  illustrates a shifting of the input sample data used for DC estimation. For example, when M is equal to 1 (i.e., M=1), the DC estimator  1902  estimates the DC value each time a sample is shifted to the buffer  1901 . Accordingly, each estimated result is outputted for each sample. If M is equal to R (i.e., M=R), the DC estimator  1902  estimates the DC value each time R number of samples are shifted to the buffer  1901 . Accordingly, each estimated result is outputted for each cycle of R samples. Therefore, in this case, the DC estimator  1902  corresponds to a DC estimator that operates in a block unit of R samples. Herein, any value within the range of 1 and R may correspond to the value M. 
     As described above, since the output of the DC estimator  1902  is outputted after each cycle of M samples, the M sample holder  1903  holds the DC value estimated from the DC estimator  1902  for a period of M samples. Then, the estimated DC value is outputted to the subtractor  1905 . Also, the C sample delay  1904  delays the input sample data stored in the buffer  1901  by C samples, which are then outputted to the subtractor  1905 . The subtractor  1905  subtracts the output of the M sample holder  1903  from the output of the C sample delay  1904 . Thereafter, the subtractor  1905  outputs the signal having the in-phase DC removed. 
     Herein, the C sample delay  1904  decides which portion of the input sample data is to be compensated with the output of the DC estimator  1902 . More specifically, the DC estimator and remover  1900  may be divided into a DC estimator  1902  for estimating the DC and the subtractor for compensating the input sample data within the estimated DC value. At this point, the C sample delay  1904  decides which portion of the input sample data is to be compensated with the estimated DC value. For example, when C is equal to 0 (i.e., C=0), the beginning of the R samples is compensated with the estimated DC value obtained by using R samples. Alternatively, when C is equal to R (i.e., C=R), the end of the R samples is compensated with the estimated DC value obtained by using R samples. Similarly, the data having the DC removed are inputted to the buffer  1111  and the frequency offset estimator  1112  of the phase compensator  1110 . 
     Meanwhile,  FIG. 52  illustrates a detailed block diagram of a DC remover according to another embodiment of the present invention. Herein, identical signal processing processes are performed on each of a real number element (or in-phase (I)) and an imaginary number element (or a quadrature (Q)) of the inputted complex signal, thereby estimating and removing the DC value of each element. In order to do so, the DC remover shown in  FIG. 52  includes a first DC estimator and remover  2100  and a second DC estimator and remover  2150 .  FIG. 52  corresponds to an infinite impulse response (IIR) structure. 
     Herein, the first DC estimator and remover  2100  includes a multiplier  2101 , an adder  2102 , an 1 sample delay  2103 , a multiplier  2104 , a C sample delay  2105 , and a subtractor  2106 . Also, the second DC estimator and remover  2150  includes a multiplier  2151 , an adder  2152 , an 1 sample delay  2153 , a multiplier  2154 , a C sample delay  2155 , and a subtractor  2156 . In the present invention, the first DC estimator and remover  2100  and the second DC estimator and remover  2150  may receive different input signals. However, each DC estimator and remover  2100  and  2150  has the same structure. Therefore, a detailed description of the first DC estimator and remover  2100  will be presented herein, and the second DC estimator and remover  2150  will be omitted for simplicity. 
     More specifically, the in-phase signal matched-filtered by the matched filter  1060  is inputted to the multiplier  2101  and the C sample delay  2105  of the first DC estimator and remover  2100  within the DC remover  1070 . The multiplier  2101  multiplies a pre-determined constant a to the in-phase signal that is being inputted. Then, the multiplier  2101  outputs the multiplied result to the adder  2102 . The adder  2102  adds the output of the multiplier  2101  to the output of the multiplier  2104  that is being fed-back. Thereafter, the adder  2102  outputs the added result to the 1 sample delay  2103  and the subtractor  2106 . More specifically, the output of the adder  2102  corresponds to the estimated in-phase DC value. 
     The 1 sample delay  2103  delays the estimated DC value by 1 sample and outputs the DC value delayed by 1 sample to the multiplier  2104 . The multiplier  2104  multiplies a pre-determined constant (1−α) to the DC value delayed by 1 sample. Then, the multiplier  2104  feeds-back the multiplied result to the adder  2102 . 
     Subsequently, the C sample delay  2105  delays the in-phase sample data by C samples and, then, outputs the delayed in-phase sample data to the subtractor  2106 . The subtractor  2106  subtracts the output of the adder  2102  from the output of the C sample delay  2105 , thereby outputting the signal having the in-phase DC removed therefrom. 
     Similarly, the data having the DC removed are inputted to the buffer  1111  and the frequency offset estimator  1112  of the phase compensator  1110  of  FIG. 39 . 
     The frequency offset estimator  1112  uses the known sequence position indicator outputted from the known sequence detector and initial frequency offset estimator  1004 - 1  in order to estimate the frequency offset from the known data sequence that is being inputted, the known data sequence having the DC removed by the DC remover  1070 . Then, the frequency offset estimator  1112  outputs the estimated frequency offset to the holder  1113 . Similarly, the frequency offset estimation value is obtained at each repetition cycle of the known data sequence. 
     Therefore, the holder  1113  holds the frequency offset estimation value during a cycle period of the known data sequence and then outputs the frequency offset estimation value to the NCO  1114 . The NCO  1114  generates a complex signal corresponding to the frequency offset held by the holder  1113  and outputs the generated complex signal to the multiplier  1115 . 
     The multiplier  1115  multiplies the complex signal outputted from the NCO  1114  to the data being delayed by a set period of time in the buffer  1111 , thereby compensating the phase change included in the delayed data. The data having the phase change compensated by the multiplier  1115  pass through the decimator  1200  so as to be inputted to the equalizer  1003 . At this point, since the frequency offset estimated by the frequency offset estimator  1112  of the phase compensator  1110  does not pass through the loop filter, the estimated frequency offset indicates the phase difference between the known data sequences. In other words, the estimated frequency offset indicates a phase offset. 
     Channel Equalizer 
     The demodulated data using the known data in the demodulator  1002  is inputted to the channel equalizer  1003 . The demodulated data is inputted to the known sequence detector  1004 . 
     The equalizer  1003  may perform channel equalization by using a plurality of methods. An example of estimating a channel impulse response (CIR) so as to perform channel equalization will be given in the description of the present invention. Most particularly, an example of estimating the CIR in accordance with each region within the data group, which is hierarchically divided and transmitted from the transmitting system, and applying each CIR differently will also be described herein. Furthermore, by using the known data, the place and contents of which is known in accordance with an agreement between the transmitting system and the receiving system, and/or the field synchronization data, so as to estimate the CIR, the present invention may be able to perform channel equalization with more stability. 
     Herein, the data group that is inputted for the equalization process is divided into regions A to D, as shown in  FIG. 5 . More specifically, in the example of the present invention, each region A, B, C, and D are further divided into MPH blocks B 4  to B 7 , MPH blocks B 3  and B 8 , MPH blocks B 2  and B 9 , MPH blocks B 1  and B 10 , respectively. 
     More specifically, a data group can be assigned and transmitted a maximum the number of 4 in a VSB frame in the transmitting system. In this case, all data group do not include field synchronization data. In the present invention, the data group including the field synchronization data performs channel-equalization using the field synchronization data and known data. And the data group not including the field synchronization data performs channel-equalization using the known data. For example, the data of the MPH block B 3  including the field synchronization data performs channel-equalization using the CIR calculated from the field synchronization data area and the CIR calculated from the first known data area. Also, the data of the MPH blocks B 1  and B 2  performs channel-equalization using the CIR calculated from the field synchronization data area and the CIR calculated from the first known data area. Meanwhile, the data of the MPH blocks B 4  to B 6  not including the field synchronization data performs channel-equalization using CIRS calculated from the first known data area and the third known data area. 
     As described above, the present invention uses the CIR estimated from the field synchronization data and the known data sequences in order to perform channel equalization on data within the data group. At this point, each of the estimated CIRs may be directly used in accordance with the characteristics of each region within the data group. Alternatively, a plurality of the estimated CIRs may also be either interpolated or extrapolated so as to create a new CIR, which is then used for the channel equalization process. 
     Herein, when a value F(Q) of a function F(x) at a particular point Q and a value F(S) of the function F(x) at another particular point S are known, interpolation refers to estimating a function value of a point within the section between points Q and S. Linear interpolation corresponds to the simplest form among a wide range of interpolation operations. The linear interpolation described herein is merely exemplary among a wide range of possible interpolation methods. And, therefore, the present invention is not limited only to the examples set forth herein. 
     Alternatively, when a value F(Q) of a function F(x) at a particular point Q and a value F(S) of the function F(x) at another particular point S are known, extrapolation refers to estimating a function value of a point outside of the section between points Q and S. Linear extrapolation is the simplest form among a wide range of extrapolation operations. Similarly, the linear extrapolation described herein is merely exemplary among a wide range of possible extrapolation methods. And, therefore, the present invention is not limited only to the examples set forth herein. 
       FIG. 53  illustrates a block diagram of a channel equalizer according to another embodiment of the present invention. Herein, by estimating and compensating a remaining carrier phase error from a channel-equalized signal, the receiving system of the present invention may be enhanced. Referring to  FIG. 53 , the channel equalizer includes a first frequency domain converter  3100 , a channel estimator  3110 , a second frequency domain converter  3121 , a coefficient calculator  3122 , a distortion compensator  3130 , a time domain converter  3140 , a remaining carrier phase error remover  3150 , a noise canceller (NC)  3160 , and a decision unit  3170 . 
     Herein, the first frequency domain converter  3100  includes an overlap unit  3101  overlapping inputted data, and a fast fourier transform (FFT) unit  3102  converting the data outputted from the overlap unit  3101  to frequency domain data. 
     The channel estimator  3110  includes a CIR estimator, a phase compensator  3112 , a pre-CIR cleaner  3113 , CIR interpolator/extrapolator  3114 , a post-CIR cleaner, and a zero-padding unit. 
     The second frequency domain converter  3121  includes a fast fourier transform (FFT) unit converting the CIR being outputted from the channel estimator  3110  to frequency domain CIR. 
     The time domain converter  3140  includes an IFFT unit  3141  converting the data having the distortion compensated by the distortion compensator  3130  to time domain data, and a save unit  3142  extracting only valid data from the data outputted from the IFFT unit  3141 . 
     The remaining carrier phase error remover  3150  includes an error compensator  3151  removing the remaining carrier phase error included in the channel equalized data, and a remaining carrier phase error estimator  3152  using the channel equalized data and the decision data of the decision unit  3170  so as to estimate the remaining carrier phase error, thereby outputting the estimated error to the error compensator  3151 . Herein, any device performing complex number multiplication may be used as the distortion compensator  3130  and the error compensator  3151 . 
     At this point, since the received data correspond to data modulated to VSB type data, 8-level scattered data exist only in the real number element. Therefore, referring to  FIG. 53 , all of the signals used in the noise canceller  3160  and the decision unit  3170  correspond to real number (or in-phase) signals. However, in order to estimate and compensate the remaining carrier phase error and the phase noise, both real number (in-phase) element and imaginary number (quadrature) element are required. Therefore, the remaining carrier phase error remover  3150  receives and uses the quadrature element as well as the in-phase element. Generally, prior to performing the channel equalization process, the demodulator  902  within the receiving system performs frequency and phase recovery of the carrier. However, if a remaining carrier phase error that is not sufficiently compensated is inputted to the channel equalizer, the performance of the channel equalizer may be deteriorated. Particularly, in a dynamic channel environment, the remaining carrier phase error may be larger than in a static channel environment due to the frequent and sudden channel changes. Eventually, this acts as an important factor that deteriorates the receiving performance of the present invention. 
     Furthermore, a local oscillator (not shown) included in the receiving system should preferably include a single frequency element. However, the local oscillator actually includes the desired frequency elements as well as other frequency elements. Such unwanted (or undesired) frequency elements are referred to as phase noise of the local oscillator. Such phase noise also deteriorates the receiving performance of the present invention. It is difficult to compensate such remaining carrier phase error and phase noise from the general channel equalizer. Therefore, the present invention may enhance the channel equaling performance by including a carrier recovery loop (i.e., a remaining carrier phase error remover  3150 ) in the channel equalizer, as shown in  FIG. 53 , in order to remove the remaining carrier phase error and the phase noise. 
     More specifically, the receiving data demodulated in  FIG. 53  are overlapped by the overlap unit  3101  of the first frequency domain converter  3100  at a pre-determined overlapping ratio, which are then outputted to the FFT unit  3102 . The FFT unit  3102  converts the overlapped time domain data to overlapped frequency domain data through by processing the data with FFT. Then, the converted data are outputted to the distortion compensator  3130 . 
     The distortion compensator  3130  performs a complex number multiplication on the overlapped frequency domain data outputted from the FFT unit  3102  included in the first frequency domain converter  3100  and the equalization coefficient calculated from the coefficient calculator  3122 , thereby compensating the channel distortion of the overlapped data outputted from the FFT unit  3102 . Thereafter, the compensated data are outputted to the IFFT unit  3141  of the time domain converter  3140 . The IFFT unit  3141  performs IFFT on the overlapped data having the channel distortion compensated, thereby converting the overlapped data to time domain data, which are then outputted to the error compensator  3151  of the remaining carrier phase error remover  3150 . 
     The error compensator  3151  multiplies a signal compensating the estimated remaining carrier phase error and phase noise with the valid data extracted from the time domain. Thus, the error compensator  3151  removes the remaining carrier phase error and phase noise included in the valid data. 
     The data having the remaining carrier phase error compensated by the error compensator  3151  are outputted to the remaining carrier phase error estimator  3152  in order to estimate the remaining carrier phase error and phase noise and, at the same time, outputted to the noise canceller  3160  in order to remove (or cancel) the noise. 
     The remaining carrier phase error estimator  3152  uses the output data of the error compensator  3151  and the decision data of the decision unit  3170  to estimate the remaining carrier phase error and phase noise. Thereafter, the remaining carrier phase error estimator  3152  outputs a signal for compensating the estimated remaining carrier phase error and phase noise to the error compensator  3151 . In this embodiment of the present invention, an inverse number of the estimated remaining carrier phase error and phase noise is outputted as the signal for compensating the remaining carrier phase error and phase noise. 
       FIG. 54  illustrates a detailed block diagram of the remaining carrier phase error estimator  3152  according to an embodiment of the present invention. Herein, the remaining carrier phase error estimator  3152  includes a phase error detector  3211 , a loop filter  3212 , a numerically controlled oscillator (NCO)  3213 , and a conjugator  3214 . Referring to  FIG. 54 , the decision data, the output of the phase error detector  3211 , and the output of the loop filter  3212  are all real number signals. And, the output of the error compensator  3151 , the output of the NCO  3213 , and the output of the conjugator  3214  are all complex number signals. 
     The phase error detector  3211  receives the output data of the error compensator  3151  and the decision data of the decision unit  3170  in order to estimate the remaining carrier phase error and phase noise. Then, the phase error detector  3211  outputs the estimated remaining carrier phase error and phase noise to the loop filter. 
     The loop filter  3212  then filters the remaining carrier phase error and phase noise, thereby outputting the filtered result to the NCO  3213 . The NCO  3213  generates a cosine corresponding to the filtered remaining carrier phase error and phase noise, which is then outputted to the conjugator  3214 . 
     The conjugator  3214  calculates the conjugate value of the cosine wave generated by the NCO  3213 . Thereafter, the calculated conjugate value is outputted to the error compensator  3151 . At this point, the output data of the conjugator  3214  becomes the inverse number of the signal compensating the remaining carrier phase error and phase noise. In other words, the output data of the conjugator  3214  becomes the inverse number of the remaining carrier phase error and phase noise. 
     The error compensator  3151  performs complex number multiplication on the equalized data outputted from the time domain converter  3140  and the signal outputted from the conjugator  3214  and compensating the remaining carrier phase error and phase noise, thereby removing the remaining carrier phase error and phase noise included in the equalized data. Meanwhile, the phase error detector  3211  may estimate the remaining carrier phase error and phase noise by using diverse methods and structures. According to this embodiment of the present invention, the remaining carrier phase error and phase noise are estimated by using a decision-directed method. 
     If the remaining carrier phase error and phase noise are not included in the channel-equalized data, the decision-directed phase error detector according to the present invention uses the fact that only real number values exist in the correlation values between the channel-equalized data and the decision data. More specifically, if the remaining carrier phase error and phase noise are not included, and when the input data of the phase error detector  3211  are referred to as x i +jx q , the correlation value between the input data of the phase error detector  3211  and the decision data may be obtained by using Equation 9 shown below:
 
E{(x i +jx q )({circumflex over (x)} i +j{circumflex over (x)} q )*}  Equation 9
 
     At this point, there is no correlation between x i  and x q . Therefore, the correlation value between x i  and x q  is equal to 0. Accordingly, if the remaining carrier phase error and phase noise are not included, only the real number values exist herein. However, if the remaining carrier phase error and phase noise are included, the real number element is shown in the imaginary number value, and the imaginary number element is shown in the real number value. Thus, in this case, the imaginary number element is shown in the correlation value. Therefore, it can be assumed that the imaginary number portion of the correlation value is in proportion with the remaining carrier phase error and phase noise. Accordingly, as shown in Equation 10 below, the imaginary number of the correlation value may be used as the remaining carrier phase error and phase noise.
 
Phase Error=imag{(x i +jx q )({circumflex over (x)} i +j{circumflex over (x)} q )*}
 
Phase Error=x q {circumflex over (x)} i −x i {circumflex over (x)} q    Equation 10
 
       FIG. 55  illustrates a block diagram of a phase error detector  3211  obtaining the remaining carrier phase error and phase noise. Herein, the phase error detector  3211  includes a Hilbert converter  3311 , a complex number configurator  3312 , a conjugator  3313 , a multiplier  3314 , and a phase error output  3315 . More specifically, the Hilbert converter  3311  creates an imaginary number decision data {circumflex over (x)} q  by performing a Hilbert conversion on the decision value {circumflex over (x)} i  of the decision unit  3170 . The generated imaginary number decision value is then outputted to the complex number configurator  3312 . The complex number configurator  3312  uses the decision data {circumflex over (x)} i  and {circumflex over (x)} q  to configure the complex number decision data {circumflex over (x)} i +j{circumflex over (x)} q , which are then outputted to the conjugator  3313 . The conjugator  3313  conjugates the output of the complex number configurator  3312 , thereby outputting the conjugated value to the multiplier  3314 . The multiplier  3314  performs a complex number multiplication on the output data of the error compensator  3151  and the output data {circumflex over (x)} i −j{circumflex over (x)} q  of the conjugator  3313 , thereby obtaining the correlation between the output data x i +jx q  of the error compensator  3151  and the decision value {circumflex over (x)} i −j{circumflex over (x)} q  of the decision unit  3170 . The correlation data obtained from the multiplier  3314  are then inputted to the phase error output  3315 . The phase error output  3315  outputs the imaginary number portion x q {circumflex over (x)} i −x i {circumflex over (x)} q  of the correlation data outputted from the multiplier  3314  as the remaining carrier phase error and phase noise. 
     The phase error detector shown in  FIG. 55  is an example of a plurality of phase error detecting methods. Therefore, other types of phase error detectors may be used in the present invention. Therefore, the present invention is not limited only to the examples and embodiments presented in the description of the present invention. Furthermore, according to another embodiment of the present invention, at least 2 phase error detectors are combined so as to detect the remaining carrier phase error and phase noise. 
     Accordingly, the output of the remaining carrier phase error remover  3150  having the detected remaining carrier phase error and phase noise removed as described above, is configured of an addition of the original (or initial) signal having the channel equalization, the remaining carrier phase error and phase noise, and the signal corresponding to a white noise being amplified to a colored noise during the channel equalization. 
     Therefore, the noise canceller  3160  receives the output data of the remaining carrier phase error remover  3150  and the decision data of the decision unit  3170 , thereby estimating the colored noise. Then, the noise canceller  3160  subtracts the estimated colored noise from the data having the remaining carrier phase error and phase noise removed therefrom, thereby removing the noise amplified during the equalization process. 
     In order to do so, the noise canceller  3160  includes a subtractor and a noise predictor. More specifically, the subtractor subtracts the noise predicted by the noise predictor from the output data of the residual carrier phase error estimator  3150 . Then, the subtractor outputs the signal from which amplified noise is cancelled (or removed) for data recovery and, simultaneously, outputs the same signal to the decision unit  3170 . The noise predictor calculates a noise element by subtracting the output of the decision unit  3170  from the signal having residual carrier phase error removed therefrom by the residual carrier phase error estimator  3150 . Thereafter, the noise predictor uses the calculated noise element as input data of a filter included in the noise predictor. Also, the noise predictor uses the filter (not shown) in order to predict any color noise element included in the output symbol of the residual carrier phase error estimator  3150 . Accordingly, the noise predictor outputs the predicted color noise element to the subtractor. 
     The data having the noise removed (or cancelled) by the noise canceller  3160  are outputted for the data decoding process and, at the same time, outputted to the decision unit  3170 . 
     The decision unit  3170  selects one of a plurality of pre-determined decision data sets (e.g., 8 decision data sets) that is most approximate to the output data of the noise canceller  3160 , thereby outputting the selected data to the remaining carrier phase error estimator  3152  and the noise canceller  3160 . 
     Meanwhile, the received data are inputted to the overlap unit  3101  of the first frequency domain converter  3100  included in the channel equalizer and, at the same time, inputted to the CIR estimator  3111  of the channel estimator  3110 . 
     The CIR estimator  3111  uses a training sequence, for example, data being inputted during the known data section and the known data in order to estimate the CIR, thereby outputting the estimated CIR to the phase compensator  3112 . If the data to be channel-equalizing is the data within the data group including field synchronization data, the training sequence using in the CIR estimator  3111  may become the field synchronization data and known data. Meanwhile, if the data to be channel-equalizing is the data within the data group not including field synchronization data, the training sequence using in the CIR estimator  3111  may become only the known data. 
     For example, the CIR estimator  3111  estimates CIR using the known data correspond to reference known data generated during the known data section by the receiving system in accordance with an agreement between the receiving system and the transmitting system. For this, the CIR estimator  3111  is provided known data position information from the known sequence detector  1004 . Also the CIR estimator  3111  may be provided field synchronization position information from the known sequence detector  1004 . 
     Furthermore, in this embodiment of the present invention, the CIR estimator  3111  estimates the CIR by using the least square (LS) method. 
     The LS estimation method calculates a cross correlation value p between the known data that have passed through the channel during the known data section and the known data that are already known by the receiving end. Then, a cross correlation matrix R of the known data is calculated. Subsequently, a matrix operation is performed on R −1 ·p so that the cross correlation portion within the cross correlation value p between the received data and the initial known data, thereby estimating the CIR of the transmission channel. 
     The phase compensator  3112  compensates the phase change of the estimated CIR. Then, the phase compensator  3112  outputs the compensated CIR to the linear interpolator  3113 . At this point, the phase compensator  3112  may compensate the phase change of the estimated CIR by using a maximum likelihood method. 
     More specifically, the remaining carrier phase error and phase noise that are included in the demodulated received data and, therefore, being inputted change the phase of the CIR estimated by the CIR estimator  3111  at a cycle period of one known data sequence. At this point, if the phase change of the inputted CIR, which is to be used for the linear interpolation process, is not performed in a linear form due to a high rate of the phase change, the channel equalizing performance of the present invention may be deteriorated when the channel is compensated by calculating the equalization coefficient from the CIR, which is estimated by a linear interpolation method. 
     Therefore, the present invention removes (or cancels) the amount of phase change of the CIR estimated by the CIR estimator  3111  so that the distortion compensator  3130  allows the remaining carrier phase error and phase noise to bypass the distortion compensator  3130  without being compensated. Accordingly, the remaining carrier phase error and phase noise are compensated by the remaining carrier phase error remover  3150 . 
     For this, the present invention removes (or cancels) the amount of phase change of the CIR estimated by the phase compensator  3112  by using a maximum likelihood method. 
     The basic idea of the maximum likelihood method relates to estimating a phase element mutually (or commonly) existing in all CIR elements, then to multiply the estimated CIR with an inverse number of the mutual (or common) phase element, so that the channel equalizer, and most particularly, the distortion compensator  3130  does not compensate the mutual phase element. 
     More specifically, when the mutual phase element is referred to as θ, the phase of the newly estimated CIR is rotated by θ as compared to the previously estimated CIR. When the CIR of a point t is referred to as h i (t), the maximum likelihood phase compensation method obtains a phase θ ML  corresponding to when h i (t) is rotated by θ, the squared value of the difference between the CIR of h i (t) and the CIR of h i (t+1), i.e., the CIR of a point (t+1), becomes a minimum value. Herein, when i represents a tap of the estimated CIR, and when N represents a number of taps of the CIR being estimated by the CIR estimator  3111 , the value of θ ML  is equal to or greater than 0 and equal to or less than N−1. This value may be calculated by using Equation 11 shown below: 
     
       
         
           
             
               
                 
                   
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                   12 
                 
               
             
           
         
       
     
     The above Equation 12 may be simplified as shown in Equation 13 below: 
     
       
         
           
             
               
                 
                   
                     
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                   13 
                 
               
             
           
         
       
     
     More specifically, Equation 13 corresponds to the θ ML  value that is to be estimated by the argument of the correlation value between h i (t) and h i (t+1). 
       FIG. 56  illustrates a phase compensator according to an embodiment of the present invention, wherein the mutual phase element θ ML  is calculated as described above, and wherein the estimated phase element is compensated at the estimated CIR. Referring to  FIG. 56 , the phase compensator includes a correlation calculator  3410 , a phase change estimator  3420 , a compensation signal generator  3430 , and a multiplier  3440 . 
     The correlation calculator  3410  includes a first N symbol buffer  3411 , an N symbol delay  3412 , a second N symbol buffer  3413 , a conjugator  3414 , and a multiplier  3415 . More specifically, the first N symbol buffer  3411  included in the correlation calculator  3410  is capable of storing the data being inputted from the CIR estimator  3111  in symbol units to a maximum limit of N number of symbols. The symbol data being temporarily stored in the first N symbol buffer  3411  are then inputted to the multiplier  3415  included in the correlation calculator  3410  and to the multiplier  3440 . 
     At the same time, the symbol data being outputted from the CIR estimator  3111  are delayed by N symbols from the N symbol delay  3412 . Then, the delayed symbol data pass through the second N symbol buffer  3413  and inputted to the conjugator  3414 , so as to be conjugated and then inputted to the multiplier  3415 . 
     The multiplier  3415  multiplies the output of the first N symbol buffer  3411  and the output of the conjugator  3414 . Then, the multiplier  3415  outputs the multiplied result to an accumulator  3421  included in the phase change estimator  3420 . 
     More specifically, the correlation calculator  3410  calculates a correlation between a current CIR h i (t+1) having the length of N and a previous CIR h i (t) also having the length of N. then, the correlation calculator  3410  outputs the calculated correlation value to the accumulator  3421  of the phase change estimator  3420 . 
     The accumulator  3421  accumulates the correlation values outputted from the multiplier  3415  during an N symbol period. Then, the accumulator  3421  outputs the accumulated value to the phase detector  3422 . The phase detector  3422  then calculates a mutual phase element θ ML  from the output of the accumulator  3421  as shown in the above-described Equation 11. Thereafter, the calculated θ ML  value is outputted to the compensation signal generator  3430 . 
     The compensation signal generator  3430  outputs a complex signal e −jθ     ML    having a phase opposite to that of the detected phase as the phase compensation signal to the multiplier  3440 . The multiplier  3440  multiplies the current CIR h i (t+1) being outputted from the first N symbol buffer  3411  with the phase compensation signal e −jθ     ML   , thereby removing the amount of phase change of the estimated CIR. 
     The CIR having its phase change compensated, as described above, passes through a first cleaner (or pre-CIR cleaner)  3113  or bypasses the first cleaner  3113 , thereby being inputted to a CIR calculator (or CIR interpolator-extrapolator)  3114 . The CIR interpolator-extrapolator  3114  either interpolates or extrapolates an estimated CIR, which is then outputted to a second cleaner (or post-CIR cleaner)  3115 . Herein, the estimated CIR corresponds to a CIR having its phase change compensated. The first cleaner  3113  may or may not operate depending upon whether the CIR interpolator-extrapolator  3114  interpolates or extrapolates the estimated CIR. For example, if the CIR interpolator-extrapolator  3114  interpolates the estimated CIR, the first cleaner  3113  does not operate. Conversely, if the CIR interpolator-extrapolator  3114  extrapolates the estimated CIR, the first cleaner  3113  operates. 
     More specifically, the CIR estimated from the known data includes a channel element that is to be obtained as well as a jitter element caused by noise. Since such jitter element deteriorates the performance of the equalizer, it preferable that a coefficient calculator  3122  removes the jitter element before using the estimated CIR. Therefore, according to the embodiment of the present invention, each of the first and second cleaners  3113  and  3115  removes a portion of the estimated CIR having a power level lower than the predetermined threshold value (i.e., so that the estimated CIR becomes equal to ‘0’). Herein, this removal process will be referred to as a “CIR cleaning” process. 
     The CIR interpolator-extrapolator  3114  performs CIR interpolation by multiplying a CIR estimated from the CIR estimator  3112  by a coefficient and by multiplying a CIR having its phase change compensated from the phase compensator (or maximum likelihood phase compensator)  3112  by another coefficient, thereby adding the multiplied values. At this point, some of the noise elements of the CIR may be added to one another, thereby being cancelled. Therefore, when the CIR interpolator-extrapolator  3114  performs CIR interpolation, the original (or initial) CIR having noise elements remaining therein. In other words, when the CIR interpolator-extrapolator  3114  performs CIR interpolation, an estimated CIR having its phase change compensated by the phase compensator  3112  bypasses the first cleaner  3113  and is inputted to the CIR interpolator-extrapolator  3114 . Subsequently, the second cleaner  3115  cleans the CIR interpolated by the CIR interpolator-extrapolator  3114 . 
     Conversely, the CIR interpolator-extrapolator  3114  performs CIR extrapolation by using a difference value between two CIRs, each having its phase change compensated by the phase compensator  3112 , so as to estimate a CIR positioned outside of the two CIRs. Therefore, in this case, the noise element is rather amplified. Accordingly, when the CIR interpolator-extrapolator  3114  performs CIR extrapolation, the CIR cleaned by the first cleaner  3113  is used. More specifically, when the CIR interpolator-extrapolator  3114  performs CIR extrapolation, the extrapolated CIR passes through the second cleaner  3115 , thereby being inputted to the zero-padding unit  3116 . 
     Meanwhile, when a second frequency domain converter (or fast fourier transform (FFT2))  3121  converts the CIR, which has been cleaned and outputted from the second cleaner  3115 , to a frequency domain, the length and of the inputted CIR and the FFT size may not match (or be identical to one another). In other words, the CIR length may be smaller than the FFT size. In this case, the zero-padding unit  3116  adds a number of zeros ‘0’s corresponding to the difference between the FFT size and the CIR length to the inputted CIR, thereby outputting the processed CIR to the second frequency domain converter (FFT2)  3121 . Herein, the zero-padded CIR may correspond to one of the interpolated CIR, extrapolated CIR, and the CIR estimated in the known data section. 
     The second frequency domain converter  3121  performs FFT on the CIR being outputted from the zero padding unit  3116 , thereby converting the CIR to a frequency domain CIR. Then, the second frequency domain converter  3121  outputs the converted CIR to the coefficient calculator  3122 . 
     The coefficient calculator  3122  uses the frequency domain CIR being outputted from the second frequency domain converter  3121  to calculate the equalization coefficient. Then, the coefficient calculator  3122  outputs the calculated coefficient to the distortion compensator  3130 . Herein, for example, the coefficient calculator  3122  calculates a channel equalization coefficient of the frequency domain that can provide minimum mean square error (MMSE) from the CIR of the frequency domain, which is outputted to the distortion compensator  3130 . 
     The distortion compensator  3130  performs a complex number multiplication on the overlapped data of the frequency domain being outputted from the FFT unit  3102  of the first frequency domain converter  3100  and the equalization coefficient calculated by the coefficient calculator  3122 , thereby compensating the channel distortion of the overlapped data being outputted from the FFT unit  3102 . 
       FIG. 57  illustrates a block diagram of a channel equalizer according to another embodiment of the present invention. In other words,  FIG. 57  illustrates a block diagram showing another example of a channel equalizer by using different CIR estimation and application methods in accordance with regions A, B, C, and D, when the data group is divided into the structure shown in  FIG. 5 . 
     More specifically, as shown in  FIG. 5 , known data that are sufficiently are being periodically transmitted in regions A/B (i.e., MPH blocks B 3  to B 8 ). Therefore, an indirect equalizing method using the CIR may be used herein. However, in regions C/D (i.e., MPH blocks B 1 , B 2 , B 9 , and B 10 ), the known data are neither able to be transmitted at a sufficiently long length nor able to be periodically and equally transmitted. Therefore, it is inadequate to estimate the CIR by using the known data. Accordingly, in regions C/D, a direct equalizing method in which an error is obtained from the output of the equalizer, so as to update the coefficient. 
     The examples presented in the embodiments of the present invention shown in  FIG. 57  include a method of performing indirect channel equalization by using a cyclic prefix on the data of regions A/B, and a method of performing direct channel equalization by using an overlap &amp; save method on the data of regions C/D. 
     Accordingly, referring to  FIG. 57 , the frequency domain channel equalizer includes a frequency domain converter  3510 , a distortion compensator  3520 , a time domain converter  3530 , a first coefficient calculating unit  3540 , a second coefficient calculating unit  3550 , and a coefficient selector  3560 . 
     Herein, the frequency domain converter  3510  includes an overlap unit  3511 , a select unit  3512 , and a first FFT unit  3513 . 
     The time domain converter  3530  includes an IFFT unit  3531 , a save unit  3532 , and a select unit  3533 . 
     The first coefficient calculating unit  3540  includes a CIR estimator  3541 , an average calculator  3542 , and second FFT unit  3543 , and a coefficient calculator  3544 . 
     The second coefficient calculating unit  3550  includes a decision unit  3551 , a select unit  3552 , a subtractor  3553 , a zero-padding unit  3554 , a third FFT unit  3555 , a coefficient updater  3556 , and a delay unit  3557 . 
     Also, a multiplexer (MUX), which selects data that are currently being inputted as the input data depending upon whether the data correspond to regions A/B or to regions C/D, may be used as the select unit  3512  of the frequency domain converter  3510 , the select unit  3533  of the time domain converter  3530 , and the coefficient selector  3560 . 
     In the channel equalizer having the above-described structure, as shown in  FIG. 57 , if the data being inputted correspond to the data of regions A/B, the select unit  3512  of the frequency domain converter  3510  selects the input data and not the output data of the overlap unit  3511 . In the same case, the select unit  3533  of the time domain converter  3530  selects the output data of the IFFT unit  3531  and not the output data of the save unit  3532 . The coefficient selector  3560  selects the equalization coefficient being outputted from the first coefficient calculating unit  3540 . 
     Conversely, if the data being inputted correspond to the data of regions C/D, the select unit  3512  of the frequency domain converter  3510  selects the output data of the overlap unit  3511  and not the input data. In the same case, the select unit  3533  of the time domain converter  3530  selects the output data of the save unit  3532  and not the output data of the IFFT unit  3531 . The coefficient selector  3560  selects the equalization coefficient being outputted from the second coefficient calculating unit  3550 . 
     More specifically, the received data are inputted to the overlap unit  3511  and select unit  3512  of the frequency domain converter  3510 , and to the first coefficient calculating unit  3540 . If the inputted data correspond to the data of regions A/B, the select unit  3512  selects the received data, which are then outputted to the first FFT unit  3513 . On the other hand, if the inputted data correspond to the data of regions C/D, the select unit  3512  selects the data that are overlapped by the overlap unit  3513  and are, then, outputted to the first FFT unit  3513 . The first FFT unit  3513  performs FFT on the time domain data that are outputted from the select unit  3512 , thereby converting the time domain data to frequency domain data. Then, the converted data are outputted to the distortion compensator  3520  and the delay unit  3557  of the second coefficient calculating unit  3550 . 
     The distortion compensator  3520  performs complex multiplication on frequency domain data outputted from the first FFT unit  3513  and the equalization coefficient outputted from the coefficient selector  3560 , thereby compensating the channel distortion detected in the data that are being outputted from the first FFT unit  3513 . 
     Thereafter, the distortion-compensated data are outputted to the IFFT unit  3531  of the time domain converter  3530 . The IFFT unit  3531  of the time domain converter  3530  performs IFFT on the channel-distortion-compensated data, thereby converting the compensated data to time domain data. The converted data are then outputted to the save unit  3532  and the select unit  3533 . If the inputted data correspond to the data of regions A/B, the select unit  3533  selects the output data of the IFFT unit  3531 . On the other hand, if the inputted data correspond to regions C/D, the select unit  3533  selects the valid data extracted from the save unit  3532 . Thereafter, the selected data are outputted to be decoded and, simultaneously, outputted to the second coefficient calculating unit  3550 . 
     The CIR estimator  3541  of the first coefficient calculating unit  3540  uses the data being received during the known data section and the known data of the known data section, the known data being already known by the receiving system in accordance with an agreement between the receiving system and the transmitting system, in order to estimate the CIR. Subsequently, the estimated CIR is outputted to the average calculator  3542 . The average calculator  3542  calculates an average value of the CIRs that are being inputted consecutively. Then, the calculated average value is outputted to the second FFT unit  3543 . For example, referring to  FIG. 37 , the average value of the CIR value estimated at point T 1  and the CIR value estimated at point T 2  is used for the channel equalization process of the general data existing between point T 1  and point T 2 . Accordingly, the calculated average value is outputted to the second FFT unit  3543 . 
     The second FFT unit  3543  performs FFT on the CIR of the time domain that is being inputted, so as to convert the inputted CIR to a frequency domain CIR. Thereafter, the converted frequency domain CIR is outputted to the coefficient calculator  3544 . The coefficient calculator  3544  calculates a frequency domain equalization coefficient that satisfies the condition of using the CIR of the frequency domain so as to minimize the mean square error. The calculated equalizer coefficient of the frequency domain is then outputted to the coefficient calculator  3560 . 
     The decision unit  3551  of the second coefficient calculating unit  3550  selects one of a plurality of decision values (e.g., 8 decision values) that is most approximate to the equalized data and outputs the selected decision value to the select unit  3552 . Herein, a multiplexer may be used as the select unit  3552 . In a general data section, the select unit  3552  selects the decision value of the decision unit  3551 . Alternatively, in a known data section, the select unit  3552  selects the known data and outputs the selected known data to the subtractor  3553 . The subtractor  3553  subtracts the output of the select unit  3533  included in the time domain converter  3530  from the output of the select unit  652  so as to calculate (or obtain) an error value. Thereafter, the calculated error value is outputted to the zero-padding unit  3554 . 
     The zero-padding unit  3554  adds (or inserts) the same amount of zeros (0) corresponding to the overlapped amount of the received data in the inputted error. Then, the error extended with zeros (0) is outputted to the third FFT unit  3555 . The third FFT unit  3555  converts the error of the time domain having zeros (0) added (or inserted) therein, to the error of the frequency domain. Thereafter, the converted error is outputted to the coefficient update unit  3556 . The coefficient update unit  3556  uses the received data of the frequency domain that have been delayed by the delay unit  3557  and the error of the frequency domain so as to update the previous equalization coefficient. Thereafter, the updated equalization coefficient is outputted to the coefficient selector  3560 . 
     At this point, the updated equalization coefficient is stored so as that it can be used as a previous equalization coefficient in a later process. If the input data correspond to the data of regions A/B, the coefficient selector  3560  selects the equalization coefficient calculated from the first coefficient calculating unit  3540 . On the other hand, if the input data correspond to the data of regions C/D, the coefficient selector  3560  selects the equalization coefficient updated by the second coefficient calculating unit  3550 . Thereafter, the selected equalization coefficient is outputted to the distortion compensator  3520 . 
       FIG. 58  illustrates a block diagram of a channel equalizer according to another embodiment of the present invention. In other words,  FIG. 58  illustrates a block diagram showing another example of a channel equalizer by using different CIR estimation and application methods in accordance with regions A, B, C, and D, when the data group is divided into the structure shown in  FIG. 5 . In this example, a method of performing indirect channel equalization by using an overlap &amp; save method on the data of regions A/B, and a method of performing direct channel equalization by using an overlap &amp; save method on the data of regions C/D are illustrated. 
     Accordingly, referring to  FIG. 58 , the frequency domain channel equalizer includes a frequency domain converter  3610 , a distortion compensator  3620 , a time domain converter  3630 , a first coefficient calculating unit  3640 , a second coefficient calculating unit  3650 , and a coefficient selector  3660 . 
     Herein, the frequency domain converter  3610  includes an overlap unit  3611  and a first FFT unit  3612 . 
     The time domain converter  3630  includes an IFFT unit  3631  and a save unit  3632 . 
     The first coefficient calculating unit  3640  includes a CIR estimator  3641 , an interpolator  3642 , a second FFT unit  3643 , and a coefficient calculator  3644 . 
     The second coefficient calculating unit  3650  includes a decision unit  3651 , a select unit  3652 , a subtractor  3653 , a zero-padding unit  3654 , a third FFT unit  3655 , a coefficient updater  3656 , and a delay unit  3657 . 
     Also, a multiplexer (MUX), which selects data that are currently being inputted as the input data depending upon whether the data correspond to regions A/B or to regions C/D, may be used as the coefficient selector  3660 . More specifically, if the input data correspond to the data of regions A/B, the coefficient selector  3660  selects the equalization coefficient calculated from the first coefficient calculating unit  3640 . On the other hand, if the input data correspond to the data of regions C/D, the coefficient selector  3660  selects the equalization coefficient updated by the second coefficient calculating unit  3650 . 
     In the channel equalizer having the above-described structure, as shown in  FIG. 58 , the received data are inputted to the overlap unit  3611  of the frequency domain converter  3610  and to the first coefficient calculating unit  3640 . The overlap unit  3611  overlaps the input data to a pre-determined overlapping ratio and outputs the overlapped data to the first FFT unit  3612 . The first FFT unit  3612  performs FFT on the overlapped time domain data, thereby converting the overlapped time domain data to overlapped frequency domain data. Then, the converted data are outputted to the distortion compensator  3620  and the delay unit  3657  of the second coefficient calculating unit  3650 . 
     The distortion compensator  3620  performs complex multiplication on the overlapped frequency domain data outputted from the first FFT unit  3612  and the equalization coefficient outputted from the coefficient selector  3660 , thereby compensating the channel distortion detected in the overlapped data that are being outputted from the first FFT unit  3612 . Thereafter, the distortion-compensated data are outputted to the IFFT unit  3631  of the time domain converter  3630 . The IFFT unit  3631  of the time domain converter  3630  performs IFFT on the distortion-compensated data, thereby converting the compensated data to overlapped time domain data. The converted overlapped data are then outputted to the save unit  3632 . The save unit  3632  extracts only the valid data from the overlapped time domain data, which are then outputted for data decoding and, at the same time, outputted to the second coefficient calculating unit  3650  in order to update the coefficient. 
     The CIR estimator  3641  of the first coefficient calculating unit  3640  uses the data received during the known data section and the known data in order to estimate the CIR. Subsequently, the estimated CIR is outputted to the interpolator  3642 . The interpolator  3642  uses the inputted CIR to estimate the CIRs (i.e., CIRs of the region that does not include the known data) corresponding to the points located between the estimated CIRs according to a predetermined interpolation method. Thereafter, the estimated result is outputted to the second FFT unit  3643 . The second FFT unit  3643  performs FFT on the inputted CIR, so as to convert the inputted CIR to a frequency domain CIR. Thereafter, the converted frequency domain CIR is outputted to the coefficient calculator  3644 . The coefficient calculator  3644  calculates a frequency domain equalization coefficient that satisfies the condition of using the CIR of the frequency domain so as to minimize the mean square error. The calculated equalizer coefficient of the frequency domain is then outputted to the coefficient calculator  3660 . 
     The structure and operations of the second coefficient calculating unit  3650  is identical to those of the second coefficient calculating unit  3550  shown in  FIG. 57 . Therefore, the description of the same will be omitted for simplicity. 
     If the input data correspond to the data of regions A/B, the coefficient selector  3660  selects the equalization coefficient calculated from the first coefficient calculating unit  3640 . On the other hand, if the input data correspond to the data of regions C/D, the coefficient selector  3660  selects the equalization coefficient updated by the second coefficient calculating unit  3650 . Thereafter, the selected equalization coefficient is outputted to the distortion compensator  3620 . 
       FIG. 59  illustrates a block diagram of a channel equalizer according to another embodiment of the present invention. In other words,  FIG. 59  illustrates a block diagram showing another example of a channel equalizer by using different CIR estimation and application methods in accordance with regions A, B, C, and D, when the data group is divided into the structure shown in  FIG. 5 . For example, in regions A/B, the present invention uses the known data in order to estimate the CIR by using a least square (LS) method, thereby performing the channel equalization process. On the other hand, in regions C/D, the present invention estimates the CIR by using a least mean square (LMS) method, thereby performing the channel equalization process. More specifically, since the periodic known data do not exist in regions C/D, as in regions A/B, the same channel equalization process as that of regions A/B cannot be performed in regions C/D. Therefore, the channel equalization process may only be performed by using the LMS method. 
     Referring to  FIG. 59 , the channel equalizer includes an overlap unit  3701 , a first fast fourier transform (FFT) unit  3702 , a distortion compensator  3703 , an inverse fast fourier transform (IFFT) unit  3704 , a save unit  3705 , a first CIR estimator  3706 , a CIR interpolator  3707 , a decision unit  3708 , a second CIR estimator  3710 , a selection unit  3711 , a second FFT unit  3712 , and a coefficient calculator  3713 . Herein, any device performed complex number multiplication may be used as the distortion compensator  3703 . In the channel equalizer having the above-described structure, as shown in  FIG. 59 , the overlap unit  3701  overlaps the data being inputted to the channel equalizer to a predetermined overlapping ratio and then outputs the overlapped data to the first FFT unit  3702 . The first FFT unit  3702  converts (or transforms) the overlapped data of the time domain to overlapped data of the frequency domain by using fast fourier transform (FFT). Then, the converted data are outputted to the distortion compensator  3703 . 
     The distortion converter  3703  performs complex multiplication on the equalization coefficient calculated from the coefficient calculator  3713  and the overlapped data of the frequency domain, thereby compensating the channel distortion of the overlapped data being outputted from the first FFT unit  3702 . Thereafter, the distortion-compensated data are outputted to the IFFT unit  3704 . The IFFT unit  3704  performs inverse fast fourier transform (IFFT) on the distortion-compensated overlapped data, so as to convert the corresponding data back to data (i.e., overlapped data) of the time domain. Subsequently, the converted data are outputted to the save unit  3705 . The save unit  3705  extracts only the valid data from the overlapped data of the time domain. Then, the save unit  3705  outputs the extracted valid data for a data decoding process and, at the same time, outputs the extracted valid data to the decision unit  3708  for a channel estimation process. 
     The decision unit  3708  selects one of a plurality of decision values (e.g., 8 decision values) that is most approximate to the equalized data and outputs the selected decision value to the select unit  3709 . Herein, a multiplexer may be used as the select unit  3709 . In a general data section, the select unit  3709  selects the decision value of the decision unit  3708 . Alternatively, in a known data section, the select unit  3709  selects the known data and outputs the selected known data to the second CIR estimator  3710 . 
     Meanwhile, the first CIR estimator  3706  uses the data that are being inputted in the known data section and the known data so as to estimate the CIR. 
     Thereafter, the first CIR estimator  3706  outputs the estimated CIR to the CIR interpolator  3707 . Herein, the known data correspond to reference known data created during the known data section by the receiving system in accordance to an agreement between the transmitting system and the receiving system. At this point, according to an embodiment of the present invention, the first CIR estimator  3706  uses the LS method to estimate the CIR. The LS estimation method calculates a cross correlation value p between the known data that have passed through the channel during the known data section and the known data that are already known by the receiving end. Then, a cross correlation matrix R of the known data is calculated. Subsequently, a matrix operation is performed on R −1 ·p so that the cross correlation portion within the cross correlation value p between the received data and the initial known data, thereby estimating the CIR of the transmission channel. 
     The CIR interpolator  3707  receives the CIR from the first CIR estimator  3706 . And, in the section between two sets of known data, the CIR is interpolated in accordance with a pre-determined interpolation method. Then, the interpolated CIR is outputted. At this point, the pre-determined interpolation method corresponds to a method of estimating a particular set of data at an unknown point by using a set of data known by a particular function. For example, such method includes a linear interpolation method. The linear interpolation method is only one of the most simple interpolation methods. A variety of other interpolation methods may be used instead of the above-described linear interpolation method. It is apparent that the present invention is not limited only to the example set forth in the description of the present invention. More specifically, the CIR interpolator  3707  uses the CIR that is being inputted in order to estimate the CIR of the section that does not include any known data by using the pre-determined interpolation method. Thereafter, the estimated CIR is outputted to the select unit  3711 . 
     The second CIR estimator  3710  uses the input data of the channel equalizer and the output data of the select unit  3709  in order to estimate the CIR. Then, the second CIR estimator  3710  outputs the estimated CIR to the select unit  3711 . At this point, according to an embodiment of the present invention, the CIR is estimated by using the LMS method. The LMS estimation method will be described in detail in a later process. 
     In regions A/B (i.e., MPH blocks B 3  to B 8 ), the select unit  3711  selects the CIR outputted from the CIR interpolator  3707 . And, in regions C/D (i.e., MPH blocks B 1 , B 2 , B 9 , and B 10 ), the select unit  3711  selects the CIR outputted from the second CIR estimator  3710 . Thereafter, the select unit  3711  outputs the selected CIR to the second FFT unit  3712 . 
     The second FFT unit  3712  converts the CIR that is being inputted to a CIR of the frequency domain, which is then outputted to the coefficient calculator  3713 . The coefficient calculator  3713  uses the CIR of the frequency domain that is being inputted, so as to calculate the equalization coefficient and to output the calculated equalization coefficient to the distortion compensator  3703 . At this point, the coefficient calculator  3713  calculates a channel equalization coefficient of the frequency domain that can provide minimum mean square error (MMSE) from the CIR of the frequency domain. At this point, the second CIR estimator  3710  may use the CIR estimated in regions A/B as the CIR at the beginning of regions C/D. For example, the CIR value of MPH block B 8  may be used as the CIR value at the beginning of the MPH block B 9 . Accordingly, the convergence speed of regions C/D may be reduced. 
     The basic principle of estimating the CIR by using the LMS method in the second CIR estimator  3710  corresponds to receiving the output of an unknown transmission channel and to updating (or renewing) the coefficient of an adaptive filter (not shown) so that the difference value between the output value of the unknown channel and the output value of the adaptive filter is minimized. More specifically, the coefficient value of the adaptive filter is renewed so that the input data of the channel equalizer is equal to the output value of the adaptive filter (not shown) included in the second CIR estimator  3710 . Thereafter, the filter coefficient is outputted as the CIR after each FFT cycle. 
     Referring to  FIG. 60 , the second CIR estimator  3710  includes a delay unit T, a multiplier, and a coefficient renewal unit for each tab. Herein, the delay unit T sequentially delays the output data {circumflex over (x)}(n) of the select unit  3709 . The multiplier multiplies respective output data outputted from each delay unit T with error data e(n). The coefficient renewal unit renews the coefficient by using the output corresponding to each multiplier. Herein, the multipliers that are being provided as many as the number of tabs will be referred to as a first multiplying unit for simplicity. Furthermore, the second CIR estimator  3710  further includes a plurality of multipliers each multiplying the output data of the select unit  3709  and the output data of the delay unit T (wherein the output data of the last delay unit are excluded) with the output data corresponding to each respective coefficient renewal unit. These multipliers are also provided as many as the number of tabs. This group of multipliers will be referred to as a second multiplying unit for simplicity. 
     The second CIR estimator  3710  further includes an adder and a subtractor. Herein, the adder adds all of the data outputted from each multipliers included in the second multiplier unit. Then, the added value is outputted as the estimation value ŷ(n) of the data inputted to the channel equalizer. The subtractor calculates the difference between the output data ŷ(n) of the adder and the input data y(n) of the channel equalizer. Thereafter, the calculated difference value is outputted as the error data e(n). Referring to  FIG. 60 , in a general data section, the decision value of the equalized data is inputted to the first delay unit included in the second CIR estimator  3710  and to the first multiplier included in the second multiplier. In the known data section, the known data are inputted to the first delay unit included in the second CIR estimator  3710  and to the first multiplier included in the second multiplier unit. The input data {circumflex over (x)}(n) are sequentially delayed by passing through a number of serially connected delay units T, the number corresponding to the number of tabs. The output data of each delay unit T and the error data e(n) are multiplied by each corresponding multiplier included in the first multiplier unit. Thereafter, the coefficients are renewed by each respective coefficient renewal unit. 
     Each coefficient that is renewed by the corresponding coefficient renewal unit is multiplied with the input data the output data {circumflex over (x)}(n) and also with the output data of each delay unit T with the exception of the last delay. Thereafter, the multiplied value is inputted to the adder. The adder then adds all of the output data outputted from the second multiplier unit and outputs the added value to the subtractor as the estimation value ŷ(n) of the input data of the channel equalizer. The subtractor calculates a difference value between the estimation value ŷ(n) and the input data y(n) of the channel equalizer. The difference value is then outputted to each multiplier of the first multiplier unit as the error data e(n). At this point, the error data e(n) is outputted to each multiplier of the first multiplier unit by passing through each respective delay unit T. As described above, the coefficient of the adaptive filter is continuously renewed. And, the output of each coefficient renewal unit is outputted as the CIR of the second CIR estimator  3710  after each FFT cycle. 
     Block Decoder 
     Meanwhile, if the data being inputted to the block decoder  1005 , after being channel-equalized by the equalizer  1003 , correspond to the data having both block encoding and trellis encoding performed thereon (i.e., the data within the RS frame, the signaling information data, etc.) by the transmitting system, trellis decoding and block decoding processes are performed on the inputted data as inverse processes of the transmitting system. Alternatively, if the data being inputted to the block decoder  1005  correspond to the data having only trellis encoding performed thereon (i.e., the main service data), and not the block encoding, only the trellis decoding process is performed on the inputted data as the inverse process of the transmitting system. 
     The trellis decoded and block decoded data by the block decoder  1005  are then outputted to the RS frame decoder  1006 . More specifically, the block decoder  1005  removes the known data, data used for trellis initialization, and signaling information data, MPEG header, which have been inserted in the data group, and the RS parity data, which have been added by the RS encoder/non-systematic RS encoder or non-systematic RS encoder of the transmitting system. Then, the block decoder  1005  outputs the processed data to the RS frame decoder  1006 . Herein, the removal of the data may be performed before the block decoding process, or may be performed during or after the block decoding process. 
     Meanwhile, the data trellis-decoded by the block decoder  1005  are outputted to the data deinterleaver  1009 . At this point, the data being trellis-decoded by the block decoder  1005  and outputted to the data deinterleaver  1009  may not only include the main service data but may also include the data within the RS frame and the signaling information. Furthermore, the RS parity data that are added by the transmitting system after the pre-processor  230  may also be included in the data being outputted to the data deinterleaver  1009 . 
     According to another embodiment of the present invention, data that are not processed with block decoding and only processed with trellis encoding by the transmitting system may directly bypass the block decoder  1005  so as to be outputted to the data deinterleaver  1009 . In this case, a trellis decoder should be provided before the data deinterleaver  1009 . More specifically, if the inputted data correspond to the data having only trellis encoding performed thereon and not block encoding, the block decoder  1005  performs Viterbi (or trellis) decoding on the inputted data so as to output a hard decision value or to perform a hard-decision on a soft decision value, thereby outputting the result. 
     Meanwhile, if the inputted data correspond to the data having both block encoding process and trellis encoding process performed thereon, the block decoder  1005  outputs a soft decision value with respect to the inputted data. 
     In other words, if the inputted data correspond to data being processed with block encoding by the block processor  302  and being processed with trellis encoding by the trellis encoding module  256 , in the transmitting system, the block decoder  1005  performs a decoding process and a trellis decoding process on the inputted data as inverse processes of the transmitting system. At this point, the RS frame encoder of the pre-processor included in the transmitting system may be viewed as an outer (or external) encoder. And, the trellis encoder may be viewed as an inner (or internal) encoder. When decoding such concatenated codes, in order to allow the block decoder  1005  to maximize its performance of decoding externally encoded data, the decoder of the internal code should output a soft decision value. 
       FIG. 61  illustrates a detailed block diagram of the block decoder  1005  according to an embodiment of the present invention. Referring to  FIG. 61 , the block decoder  1005  includes a feedback controller  4010 , an input buffer  4011 , a trellis decoding unit (or 12-way trellis coded modulation (TCM) decoder or inner decoder)  4012 , a symbol-byte converter  4013 , an outer block extractor  4014 , a feedback deformatter  4015 , a symbol deinterleaver  4016 , an outer symbol mapper  4017 , a symbol decoder  4018 , an inner symbol mapper  4019 , a symbol interleaver  4020 , a feedback formatter  4021 , and an output buffer  4022 . Herein, just as in the transmitting system, the trellis decoding unit  4012  may be viewed as an inner (or internal) decoder. And, the symbol decoder  4018  may be viewed as an outer (or external) decoder. 
     The input buffer  4011  temporarily stores the mobile service data symbols being channel-equalized and outputted from the equalizer  1003 . (Herein, the mobile service data symbols may include symbols corresponding to the signaling information, RS parity data symbols and CRC data symbols added during the encoding process of the RS frame.) Thereafter, the input buffer  4011  repeatedly outputs the stored symbols for M number of times to the trellis decoding unit  4012  in a turbo block (TDL) size required for the turbo decoding process. 
     The turbo decoding length (TDL) may also be referred to as a turbo block. Herein, a TDL should include at least one SCCCC block size. Therefore, as defined in  FIG. 5 , when it is assumed that one MPH block is a 16-segment unit, and that a combination of 10 MPH blocks form one SCCC block, a TDL should be equal to or larger than the maximum possible combination size. For example, when it is assumed that 2 MPH blocks form one SCCC block, the TDL may be equal to or larger than 32 segments (i.e., 828*32=26496 symbols). Herein, M indicates a number of repetitions for turbo-decoding pre-decided by the feed-back controller  4010 . 
     Also, M represents a number of repetitions of the turbo decoding process, the number being predetermined by the feedback controller  4010 . 
     Additionally, among the values of symbols being channel-equalized and outputted from the equalizer  1003 , the input symbol values corresponding to a section having no mobile service data symbols (including RS parity data symbols during RS frame encoding and CRC data symbols) included therein, bypass the input buffer  4011  without being stored. More specifically, since trellis-encoding is performed on input symbol values of a section wherein SCCC block-encoding has not been performed, the input buffer  4011  inputs the inputted symbol values of the corresponding section directly to the trellis encoding module  4012  without performing any storage, repetition, and output processes. The storage, repetition, and output processes of the input buffer  4011  are controlled by the feedback controller  4010 . Herein, the feedback controller  4010  refers to SCCC-associated information (e.g., SCCC block mode and SCCC outer code mode), which are outputted from the signaling information decoding unit  1013 , in order to control the storage and output processes of the input buffer  4011 . 
     The trellis decoding unit  4012  includes a 12-way TCM decoder. Herein, the trellis decoding unit  4012  performs 12-way trellis decoding as inverse processes of the 12-way trellis encoder. 
     More specifically, the trellis decoding unit  4012  receives a number of output symbols of the input buffer  4011  and soft-decision values of the feedback formatter  4021  equivalent to each TDL, so as to perform the TCM decoding process. 
     At this point, based upon the control of the feedback controller  4010 , the soft-decision values outputted from the feedback formatter  4021  are matched with a number of mobile service data symbol places so as to be in a one-to-one (1:1) correspondence. Herein, the number of mobile service data symbol places is equivalent to the TDL being outputted from the input buffer  4011 . 
     More specifically, the mobile service data being outputted from the input buffer  4011  are matched with the turbo decoded data being inputted, so that each respective data place can correspond with one another. Thereafter, the matched data are outputted to the trellis decoding unit  4012 . For example, if the turbo decoded data correspond to the third symbol within the turbo block, the corresponding symbol (or data) is matched with the third symbol included in the turbo block, which is outputted from the input buffer  4011 . Subsequently, the matched symbol (or data) is outputted to the trellis decoding unit  4012 . 
     In order to do so, while the regressive turbo decoding is in process, the feedback controller  4010  controls the input buffer  4011  so that the input buffer  4011  stores the corresponding turbo block data. Also, by delaying data (or symbols), the soft decision value (e.g., LLR) of the symbol outputted from the symbol interleaver  4020  and the symbol of the input buffer  4011  corresponding to the same place (or position) within the block of the output symbol are matched with one another to be in a one-to-one correspondence. Thereafter, the matched symbols are controlled so that they can be inputted to the TCM decoder through the respective path. This process is repeated for a predetermined number of turbo decoding cycle periods. Then, the data of the next turbo block are outputted from the input buffer  4011 , thereby repeating the turbo decoding process. 
     The output of the trellis decoding unit  4012  signifies a degree of reliability of the transmission bits configuring each symbol. For example, in the transmitting system, since the input data of the trellis encoding module correspond to two bits as one symbol, a log likelihood ratio (LLR) between the likelihood of a bit having the value of ‘1’ and the likelihood of the bit having the value of ‘0’ may be respectively outputted (in bit units) to the upper bit and the lower bit. Herein, the log likelihood ratio corresponds to a log value for the ratio between the likelihood of a bit having the value of ‘1’ and the likelihood of the bit having the value of ‘0’. Alternatively, a LLR for the likelihood of 2 bits (i.e., one symbol) being equal to “00”, “01”, “10”, and “11” may be respectively outputted (in symbol units) to all 4 combinations of bits (i.e., 00, 01, 10, 11). Consequently, this becomes the soft decision value that indicates the degree of reliability of the transmission bits configuring each symbol. A maximum a posteriori probability (MAP) or a soft-out Viterbi algorithm (SOVA) may be used as a decoding algorithm of each TCM decoder within the trellis decoding unit  4012 . 
     The output of the trellis decoding unit  4012  is inputted to the symbol-byte converter  4013  and the outer block extractor  4014 . 
     The symbol-byte converter  4013  performs a hard-decision process of the soft decision value that is trellis decoded and outputted from the trellis decoding unit  4012 . Thereafter, the symbol-byte converter  4013  groups 4 symbols into byte units, which are then outputted to the data deinterleaver  1009  of  FIG. 36 . More specifically, the symbol-byte converter  4013  performs hard-decision in bit units on the soft decision value of the symbol outputted from the trellis decoding unit  4012 . Therefore, the data processed with hard-decision and outputted in bit units from the symbol-byte converter  4013  not only include main service data, but may also include mobile service data, known data, RS parity data, and MPEG headers. 
     Among the soft decision values of TDL size of the trellis decoding unit  4012 , the outer block extractor  4014  identifies the soft decision values of B size of corresponding to the mobile service data symbols (wherein symbols corresponding to signaling information, RS parity data symbols that are added during the encoding of the RS frame, and CRC data symbols are included) and outputs the identified soft decision values to the feedback deformatter  4015 . 
     The feedback deformatter  4015  changes the processing order of the soft decision values corresponding to the mobile service data symbols. This is an inverse process of an initial change in the processing order of the mobile service data symbols, which are generated during an intermediate step, wherein the output symbols outputted from the block processor  302  of the transmitting system are being inputted to the trellis encoding module  256  (e.g., when the symbols pass through the group formatter, the data deinterleaver, the packet formatter, and the data interleaver). Thereafter, the feedback deformatter  1015  performs reordering of the process order of soft decision values corresponding to the mobile service data symbols and, then, outputs the processed mobile service data symbols to the symbol deinterleaver  4016 . 
     This is because a plurality of blocks exist between the block processor  302  and the trellis encoding module  256 , and because, due to these blocks, the order of the mobile service data symbols being outputted from the block processor  302  and the order of the mobile service data symbols being inputted to the trellis encoding module  256  are not identical to one another. Therefore, the feedback deformatter  4015  reorders (or rearranges) the order of the mobile service data symbols being outputted from the outer block extractor  4014 , so that the order of the mobile service data symbols being inputted to the symbol deinterleaver  4016  matches the order of the mobile service data symbols outputted from the block processor  302  of the transmitting system. The reordering process may be embodied as one of software, middleware, and hardware. 
       FIG. 62  illustrates a detailed block view of the feedback deformatter  4015  according to an embodiment of the present invention. Herein, the feedback deformatter  4015  includes a data deinterleaver  5011 , a packet deformatter  5012 , a data interleaver  5013 , and a group deformatter  5014 . Referring to  FIG. 62 , the soft decision value of the mobile service data symbol, which is extracted by the outer block extractor  4014 , is outputted directly to the data deinterleaver  5011  of the feedback deformatter  4015  without modification. However, data place holders (or null data) are inserted in data places (e.g., main service data places, known data places, signaling information places, RS parity data places, and MPEG header places), which are removed by the outer block extractor  4014 , thereby being outputted to the data deinterleaver  5011  of the feedback deformatter  4015 . 
     The data deinterleaver  5011  performs an inverse process of the data interleaver  253  included in the transmitting system. More specifically, the data deinterleaver  5011  deinterleaves the inputted data and outputs the deinterleaved data to the packet deformatter  5012 . The packet deformatter  5012  performs an inverse process of the packet formatter  305 . More specifically, among the data that are deinterleaved and outputted from the data deinterleaver  5011 , the packet deformatter  5012  removes the place holder corresponding to the MPEG header, which had been inserted to the packet formatter  305 . The output of the packet deformatter  5012  is inputted to the data interleaver  5013 , and the data interleaver  5013  interleaves the data being inputted, as an inverse process of the data deinterleaver  529  included in the transmitting system. Accordingly, data having a data structure as shown in  FIG. 5 , are outputted to the group deformatter  5014 . 
     The data deformatter  5014  performs an inverse process of the group formatter  303  included in the transmitting system. More specifically, the group formatter  5014  removes the place holders corresponding to the main service data, known data, signaling information data, and RS parity data. Then, the group formatter  5014  outputs only the reordered (or rearranged) mobile service data symbols to the symbol deinterleaver  4016 . According to another embodiment of the present invention, when the feedback deformatter  4015  is embodied using a memory map, the process of inserting and removing place holder to and from data places removed by the outer block extractor  4014  may be omitted. 
     The symbol deinterleaver  4016  performs deinterleaving on the mobile service data symbols having their processing orders changed and outputted from the feedback deformatter  4015 , as an inverse process of the symbol interleaving process of the symbol interleaver  514  included in the transmitting system. The size of the block used by the symbol deinterleaver  4016  during the deinterleaving process is identical to interleaving size of an actual symbol (i.e., B) of the symbol interleaver  514 , which is included in the transmitting system. This is because the turbo decoding process is performed between the trellis decoding unit  4012  and the symbol decoder  4018 . Both the input and output of the symbol deinterleaver  4016  correspond to soft decision values, and the deinterleaved soft decision values are outputted to the outer symbol mapper  4017 . 
     The operations of the outer symbol mapper  4017  may vary depending upon the structure and coding rate of the convolution encoder  513  included in the transmitting system. For example, when data are 1/2-rate encoded by the convolution encoder  513  and then transmitted, the outer symbol mapper  4017  directly outputs the input data without modification. In another example, when data are 1/4-rate encoded by the convolution encoder  513  and then transmitted, the outer symbol mapper  4017  converts the input data so that it can match the input data format of the symbol decoder  4018 . For this, the outer symbol mapper  4017  may be inputted SCCC-associated information (i.e., SCCC block mode and SCCC outer code mode) from the signaling information decoder  1013 . Then, the outer symbol mapper  4017  outputs the converted data to the symbol decoder  4018 . 
     The symbol decoder  4018  (i.e., the outer decoder) receives the data outputted from the outer symbol mapper  4017  and performs symbol decoding as an inverse process of the convolution encoder  513  included in the transmitting system. At this point, two different soft decision values are outputted from the symbol decoder  4018 . One of the outputted soft decision values corresponds to a soft decision value matching the output symbol of the convolution encoder  513  (hereinafter referred to as a “first decision value”). The other one of the outputted soft decision values corresponds to a soft decision value matching the input bit of the convolution encoder  513  (hereinafter referred to as a “second decision value”). 
     More specifically, the first decision value represents a degree of reliability the output symbol (i.e., 2 bits) of the convolution encoder  513 . Herein, the first soft decision value may output (in bit units) a LLR between the likelihood of 1 bit being equal to ‘1’ and the likelihood of 1 bit being equal to ‘0’ with respect to each of the upper bit and lower bit, which configures a symbol. Alternatively, the first soft decision value may also output (in symbol units) a LLR for the likelihood of 2 bits being equal to “00”, “01”, “10”, and “11” with respect to all possible combinations. The first soft decision value is fed-back to the trellis decoding unit  4012  through the inner symbol mapper  4019 , the symbol interleaver  4020 , and the feedback formatter  4021 . On the other hand, the second soft decision value indicates a degree of reliability the input bit of the convolution encoder  513  included in the transmitting system. Herein, the second soft decision value is represented as the LLR between the likelihood of 1 bit being equal to ‘1’ and the likelihood of 1 bit being equal to ‘0’. Thereafter, the second soft decision value is outputted to the outer buffer  4022 . In this case, a maximum a posteriori probability (MAP) or a soft-out Viterbi algorithm (SOVA) may be used as the decoding algorithm of the symbol decoder  4018 . 
     The first soft decision value that is outputted from the symbol decoder  4018  is inputted to the inner symbol mapper  4019 . The inner symbol mapper  4019  converts the first soft decision value to a data format corresponding the input data of the trellis decoding unit  4012 . Thereafter, the inner symbol mapper  4019  outputs the converted soft decision value to the symbol interleaver  4020 . The operations of the inner symbol mapper  4019  may also vary depending upon the structure and coding rate of the convolution encoder  513  included in the transmitting system. 
     The symbol interleaver  4020  performs symbol interleaving, as shown in  FIG. 26 , on the first soft decision value that is outputted from the inner symbol mapper  4019 . Then, the symbol interleaver  4020  outputs the symbol-interleaved first soft decision value to the feedback formatter  4021 . Herein, the output of the symbol interleaver  4020  also corresponds to a soft decision value. 
     With respect to the changed processing order of the soft decision values corresponding to the symbols that are generated during an intermediate step, wherein the output symbols outputted from the block processor  302  of the transmitting system are being inputted to the trellis encoding module (e.g., when the symbols pass through the group formatter, the data deinterleaver, the packet formatter, the RS encoder, and the data interleaver), the feedback formatter  4021  alters (or changes) the order of the output values outputted from the symbol interleaver  4020 . Subsequently, the feedback formatter  4020  outputs values to the trellis decoding unit  4012  in the changed order. The reordering process of the feedback formatter  4021  may configure at least one of software, hardware, and middleware. For example, the feedback formatter  4021  may configure to be performed as an inverse process of  FIG. 62 . 
     The soft decision values outputted from the symbol interleaver  4020  are matched with the positions of mobile service data symbols each having the size of TDL, which are outputted from the input buffer  4011 , so as to be in a one-to-one correspondence. Thereafter, the soft decision values matched with the respective symbol position are inputted to the trellis decoding unit  4012 . At this point, since the main service data symbols or the RS parity data symbols and known data symbols of the main service data do not correspond to the mobile service data symbols, the feedback formatter  4021  inserts null data in the corresponding positions, thereby outputting the processed data to the trellis decoding unit  4012 . Additionally, each time the symbols having the size of TDL are turbo decoded, no value is fed-back by the symbol interleaver  4020  starting from the beginning of the first decoding process. Therefore, the feedback formatter  4021  is controlled by the feedback controller  4010 , thereby inserting null data into all symbol positions including a mobile service data symbol. Then, the processed data are outputted to the trellis decoding unit  4012 . 
     The output buffer  4022  receives the second soft decision value from the symbol decoder  4018  based upon the control of the feedback controller  4010 . Then, the output buffer  4022  temporarily stores the received second soft decision value. Thereafter, the output buffer  4022  outputs the second soft decision value to the RS frame decoder  10006 . For example, the output buffer  4022  overwrites the second soft decision value of the symbol decoder  4018  until the turbo decoding process is performed for M number of times. Then, once all M number of turbo decoding processes is performed for a single TDL, the corresponding second soft decision value is outputted to the RS frame decoder  1006 . 
     The feedback controller  4010  controls the number of turbo decoding and turbo decoding repetition processes of the overall block decoder, shown in  FIG. 61 . More specifically, once the turbo decoding process has been repeated for a predetermined number of times, the second soft decision value of the symbol decoder  4018  is outputted to the RS frame decoder  1006  through the output buffer  4022 . Thus, the block decoding process of a turbo block is completed. In the description of the present invention, this process is referred to as a regressive turbo decoding process for simplicity. 
     At this point, the number of regressive turbo decoding rounds between the trellis decoding unit  4012  and the symbol decoder  4018  may be defined while taking into account hardware complexity and error correction performance. Accordingly, if the number of rounds increases, the error correction performance may be enhanced. However, this may lead to a disadvantageous of the hardware becoming more complicated (or complex). 
     Meanwhile, the data deinterleaver  1009 , the RS decoder  1010 , and the data derandomizer  1011  correspond to blocks required for receiving the main service data. Therefore, the above-mentioned blocks may not be necessary (or required) in the structure of a digital broadcast receiving system for receiving mobile service data only. 
     The data deinterleaver  1009  performs an inverse process of the data interleaver included in the transmitting system. In other words, the data deinterleaver  1009  deinterleaves the main service data outputted from the block decoder  1005  and outputs the deinterleaved main service data to the RS decoder  1010 . The data being inputted to the data deinterleaver  1009  include main service data, as well as mobile service data, known data, RS parity data, and an MPEG header. At this point, among the inputted data, only the main service data and the RS parity data added to the main service data packet may be outputted to the RS decoder  1010 . Also, all data outputted after the data derandomizer  1011  may all be removed with the exception for the main service data. In the embodiment of the present invention, only the main service data and the RS parity data added to the main service data packet are inputted to the RS decoder  1010 . 
     The RS decoder  1010  performs a systematic RS decoding process on the deinterleaved data and outputs the processed data to the data derandomizer  1011 . 
     The data derandomizer  1011  receives the output of the RS decoder  1010  and generates a pseudo random data byte identical to that of the randomizer included in the digital broadcast transmitting system. Thereafter, the data derandomizer  1011  performs a bitwise exclusive OR (XOR) operation on the generated pseudo random data byte, thereby inserting the MPEG synchronization bytes to the beginning of each packet so as to output the data in 188-byte main service data packet units. 
     RS Frame Decoder 
     The data outputted from the block decoder  1005  are in portion units. More specifically, in the transmitting system, the RS frame is divided into several portions, and the mobile service data of each portion are assigned either to regions A/B/C/D within the data group or to any one of regions A/B and regions C/D , thereby being transmitted to the receiving system. Therefore, the RS frame decoder  1006  groups several portions included in a parade so as to form an RS frame. Alternatively, the RS frame decoder  1006  may also group several portions included in a parade so as to form two RS frames. Thereafter, error correction decoding is performed in RS frame units. 
     For example, when the RS frame mode value is equal to ‘00’, then one parade transmits one RS frame. At this point, one RS frame is divided into several portions, and the mobile service data of each portion are assigned to regions A/B/C/D of the corresponding data group, thereby being transmitted. In this case, the MPH frame decoder  1006  extracts mobile service data from regions A/B/C/D of the corresponding data group, as shown in  FIG. 63(a) . Subsequently, the MPH frame decoder  1006  may perform the process of forming (or creating) a portion on a plurality of data group within a parade, thereby forming several portions. Then, the several portions of mobile service data may be grouped to form an RS frame. Herein, if stuffing bytes are added to the last portion, the RS frame may be formed after removing the stuffing byte. 
     In another example, when the RS frame mode value is equal to ‘01’, then one parade transmits two RS frames (i.e., a primary RS frame and a secondary RS frame). At this point, a primary RS frame is divided into several primary portions, and the mobile service data of each primary portion are assigned to regions A/B of the corresponding data group, thereby being transmitted. Also, a secondary RS frame is divided into several secondary portions, and the mobile service data of each secondary portion are assigned to regions C/D of the corresponding data group, thereby being transmitted. 
     In this case, the MPH frame decoder  1006  extracts mobile service data from regions A/B of the corresponding data group, as shown in  FIG. 63(b) . Subsequently, the MPH frame decoder  1006  may perform the process of forming (or creating) a primary portion on a plurality of data group within a parade, thereby forming several primary portions. Then, the several primary portions of mobile service data may be grouped to form a primary RS frame. Herein, if stuffing bytes are added to the last primary portion, the primary RS frame may be formed after removing the stuffing byte. Also, the MPH frame decoder  1006  extracts mobile service data from regions C/D of the corresponding data group. Subsequently, the MPH frame decoder  1006  may perform the process of forming (or creating) a secondary portion on a plurality of data group within a parade, thereby forming several secondary portions. Then, the several secondary portions of mobile service data may be grouped to form a secondary RS frame. Herein, if stuffing bytes are added to the last secondary portion, the secondary RS frame may be formed after removing the stuffing byte. 
     More specifically, the RS frame decoder  1006  receives the RS-encoded and/or CRC-encoded mobile service data of each portion from the block decoder  1005 . Then, the RS frame decoder  1006  groups several portions, which are inputted based upon RS frame-associated information outputted from the signaling information decoder  1013 , thereby performing error correction. By referring to the RS frame mode value included in the RS frame-associated information, the RS frame decoder  1006  may form an RS frame and may also be informed of the number of RS code parity data bytes and the code size. Herein, the RS code is used to configure (or form) the RS frame. The RS frame decoder  1006  also refers to the RS frame-associated information in order to perform an inverse process of the RS frame encoder, which is included in the transmitting system, thereby correcting the errors within the RS frame. Thereafter, the RS frame decoder  1006  adds 1 MPEG synchronization data byte to the error-correction mobile service data packet. In an earlier process, the 1 MPEG synchronization data byte was removed from the mobile service data packet during the RS frame encoding process. Finally, the RS frame decoder  1006  outputs the processed mobile service data packet to the derandomizer  1007 . 
       FIG. 64  illustrates, when the RS frame mode value is equal to ‘00’, an exemplary process of grouping several portion being transmitted to a parade, thereby forming an RS frame and an RS frame reliability map, and an exemplary process of performing a row de-permutation process in super frame units as an inverse process of the transmitting system, thereby re-distinguishing (or identifying) the row-de-permuted RS frame and RS frame reliability map. More specifically, the RS frame decoder  1006  receives and groups a plurality of mobile service data bytes, so as to form an RS frame. According to the present invention, in transmitting system, the mobile service data correspond to data RS-encoded in RS frame units and also correspond to data row-permuted in super frame units. At this point, the mobile service data may already be error correction encoded (e.g., CRC-encoded). Alternatively, the error correction encoding process may be omitted. 
     It is assumed that, in the transmitting system, an RS frame having the size of (N+2)×(187+P) bytes is divided into M number of portions, and that the M number of mobile service data portions are assigned and transmitted to regions A/B/C/D in M number of data groups, respectively. In this case, in the receiving system, each mobile service data portion is grouped, as shown in  FIG. 64(a) , thereby forming an RS frame having the size of (N+2)×(187+P) bytes. At this point, when stuffing bytes (S) are added to at least one portion included in the corresponding RS frame and then transmitted, the stuffing bytes are removed, thereby configuring an RS frame and an RS frame reliability map. For example, as shown in  FIG. 23 , when S number of stuffing bytes are added to the corresponding portion, the S number of stuffing bytes are removed, thereby configuring the RS frame and the RS frame reliability map. 
     Herein, when it is assumed that the block decoder  1005  outputs a soft decision value for the decoding result, the RS frame decoder  1006  may decide the ‘0’ and ‘1’ of the corresponding bit by using the codes of the soft decision value. 8 bits that are each decided as described above are grouped to create 1 data byte. If the above-described process is performed on all soft decision values of several portions (or data groups) included in a parade, the RS frame having the size of (N+2)×(187+P) bytes may be configured. 
     Additionally, the present invention uses the soft decision value not only to configure the RS frame but also to configure a reliability map. 
     Herein, the reliability map indicates the reliability of the corresponding data byte, which is configured by grouping 8 bits, the 8 bits being decided by the codes of the soft decision value. 
     For example, when the absolute value of the soft decision value exceeds a pre-determined threshold value, the value of the corresponding bit, which is decided by the code of the corresponding soft decision value, is determined to be reliable. Conversely, when the absolute value of the soft decision value does not exceed the pre-determined threshold value, the value of the corresponding bit is determined to be unreliable. Thereafter, if even a single bit among the 8 bits, which are decided by the codes of the soft decision value and group to configure one data byte, is determined to be unreliable, the corresponding data byte is marked on the reliability map as an unreliable data byte. 
     Herein, determining the reliability of one data byte is only exemplary. More specifically, when a plurality of data bytes (e.g., at least 4 data bytes) are determined to be unreliable, the corresponding data bytes may also be marked as unreliable data bytes within the reliability map. Conversely, when all of the data bits within the one data byte are determined to be reliable (i.e., when the absolute value of the soft decision values of all 8 bits included in the one data byte exceed the predetermined threshold value), the corresponding data byte is marked to be a reliable data byte on the reliability map. Similarly, when a plurality of data bytes (e.g., at least 4 data bytes) are determined to be reliable, the corresponding data bytes may also be marked as reliable data bytes within the reliability map. The numbers proposed in the above-described example are merely exemplary and, therefore, do not limit the scope or spirit of the present invention. 
     The process of configuring the RS frame and the process of configuring the reliability map both using the soft decision value may be performed at the same time. Herein, the reliability information within the reliability map is in a one-to-one correspondence with each byte within the RS frame. For example, if a RS frame has the size of (N+2)×(187+P) bytes, the reliability map is also configured to have the size of (N+2)×(187+P) bytes.  FIG. 64 (a′) and  FIG. 64 (b′) respectively illustrate the process steps of configuring the reliability map according to the present invention. 
     At this point, the RS frame of  FIG. 64(b)  and the RS frame reliability map of  FIG. 64 (b′) are interleaved in super frame units (as shown in  FIG. 21 ). Therefore, the RS frame and the RS frame reliability maps are grouped to create a super frame and a super frame reliability map. Subsequently, as shown in  FIG. 64(c)  and  FIG. 64 (c′), a de-permutation (or deinterleaving) process is performed in super frame units on the RS frame and the RS frame reliability maps, as an inverse process of the transmitting system. Then, when the de-permutation process is performed in super frame units, the processed data are divided into de-permuted (or deinterleaved) RS frames having the size of (N+2)×(187+P) bytes and de-permuted RS frame reliability maps having the size of (N+2)×(187+P) bytes, as shown in  FIG. 64(d)  and  FIG. 64 (d′). Subsequently, the RS frame reliability map is used on the divided RS frames so as to perform error correction. 
       FIG. 65  illustrates example of the error correction processed according to embodiments of the present invention.  FIG. 65  illustrates an example of performing an error correction process when the transmitting system has performed both RS encoding and CRC encoding processes on the RS frame. 
     As shown in  FIG. 65(a)  and  FIG. 65 (a′), when the RS frame having the size of (N+2)×(187+P) bytes and the RS frame reliability map having the size of (N+2)×(187+P) bytes are created, a CRC syndrome checking process is performed on the created RS frame, thereby verifying whether any error has occurred in each row. Subsequently, as shown in  FIG. 65(b) , a 2-byte checksum is removed to configure an RS frame having the size of N×(187+P) bytes. Herein, the presence (or existence) of an error is indicated on an error flag corresponding to each row. Similarly, since the portion of the reliability map corresponding to the CRC checksum has hardly any applicability, this portion is removed so that only N×(187+P) number of the reliability information bytes remain, as shown in  FIG. 65 (b′). 
     After performing the CRC syndrome checking process, as described above, a RS decoding process is performed in a column direction. Herein, a RS erasure correction process may be performed in accordance with the number of CRC error flags. More specifically, as shown in  FIG. 65(c) , the CRC error flag corresponding to each row within the RS frame is verified. Thereafter, the RS frame decoder  1006  determines whether the number of rows having a CRC error occurring therein is equal to or smaller than the maximum number of errors on which the RS erasure correction may be performed, when performing the RS decoding process in a column direction. The maximum number of errors corresponds to P number of parity bytes inserted when performing the RS encoding process. In the embodiment of the present invention, it is assumed that 48 parity bytes have been added to each column (i.e., P=48). 
     If the number of rows having the CRC errors occurring therein is smaller than or equal to the maximum number of errors (i.e., 48 errors according to this embodiment) that can be corrected by the RS erasure decoding process, a (235,187)-RS erasure decoding process is performed in a column direction on the RS frame having (187+P) number of N-byte rows (i.e., 235 N-byte rows), as shown in  FIG. 65(d) . Thereafter, as shown in  FIG. 65(e) , the 48-byte parity data that have been added at the end of each column are removed. Conversely, however, if the number of rows having the CRC errors occurring therein is greater than the maximum number of errors (i.e., 48 errors) that can be corrected by the RS erasure decoding process, the RS erasure decoding process cannot be performed. In this case, the error may be corrected by performing a general RS decoding process. In addition, the reliability map, which has been created based upon the soft decision value along with the RS frame, may be used to further enhance the error correction ability (or performance) of the present invention. 
     More specifically, the RS frame decoder  1006  compares the absolute value of the soft decision value of the block decoder  1005  with the pre-determined threshold value, so as to determine the reliability of the bit value decided by the code of the corresponding soft decision value. Also, 8 bits, each being determined by the code of the soft decision value, are grouped to form one data byte. Accordingly, the reliability information on this one data byte is indicated on the reliability map. Therefore, as shown in  FIG. 65(c) , even though a particular row is determined to have an error occurring therein based upon a CRC syndrome checking process on the particular row, the present invention does not assume that all bytes included in the row have errors occurring therein. The present invention refers to the reliability information of the reliability map and sets only the bytes that have been determined to be unreliable as erroneous bytes. In other words, with disregard to whether or not a CRC error exists within the corresponding row, only the bytes that are determined to be unreliable based upon the reliability map are set as erasure points. 
     According to another method, when it is determined that CRC errors are included in the corresponding row, based upon the result of the CRC syndrome checking result, only the bytes that are determined by the reliability map to be unreliable are set as errors. More specifically, only the bytes corresponding to the row that is determined to have errors included therein and being determined to be unreliable based upon the reliability information, are set as the erasure points. Thereafter, if the number of error points for each column is smaller than or equal to the maximum number of errors (i.e., 48 errors) that can be corrected by the RS erasure decoding process, an RS erasure decoding process is performed on the corresponding column. Conversely, if the number of error points for each column is greater than the maximum number of errors (i.e., 48 errors) that can be corrected by the RS erasure decoding process, a general decoding process is performed on the corresponding column 
     More specifically, if the number of rows having CRC errors included therein is greater than the maximum number of errors (i.e., 48 errors) that can be corrected by the RS erasure decoding process, either an RS erasure decoding process or a general RS decoding process is performed on a column that is decided based upon the reliability information of the reliability map, in accordance with the number of erasure points within the corresponding column. For example, it is assumed that the number of rows having CRC errors included therein within the RS frame is greater than 48. And, it is also assumed that the number of erasure points decided based upon the reliability information of the reliability map is indicated as 40 erasure points in the first column and as 50 erasure points in the second column. In this case, a (235,187)-RS erasure decoding process is performed on the first column. Alternatively, a (235,187)-RS decoding process is performed on the second column. When error correction decoding is performed on all column directions within the RS frame by using the above-described process, the 48-byte parity data which were added at the end of each column are removed, as shown in  FIG. 65(e) . 
     As described above, even though the total number of CRC errors corresponding to each row within the RS frame is greater than the maximum number of errors that can be corrected by the RS erasure decoding process, when the number of bytes determined to have a low reliability level, based upon the reliability information on the reliability map within a particular column, while performing error correction decoding on the particular column. Herein, the difference between the general RS decoding process and the RS erasure decoding process is the number of errors that can be corrected. More specifically, when performing the general RS decoding process, the number of errors corresponding to half of the number of parity bytes (i.e., (number of parity bytes)/2) that are inserted during the RS encoding process may be error corrected (e.g., 24 errors may be corrected). Alternatively, when performing the RS erasure decoding process, the number of errors corresponding to the number of parity bytes that are inserted during the RS encoding process may be error corrected (e.g., 48 errors may be corrected). 
     After performing the error correction decoding process, as described above, a RS frame configured of 187 N-byte rows (or packet) may be obtained as shown in  FIG. 65(e) . The RS frame having the size of N×187 bytes is outputted by the order of N number of 187-byte units. At this point, 1 MPEG synchronization byte, which had been removed by the transmitting system, is added to each 187-byte packet, as shown in  FIG. 65(f) . Therefore, a 188-byte unit mobile service data packet is outputted. 
     As described above, the RS frame decoded mobile service data is outputted to the data derandomizer  1007 . The data derandomizer  1007  performs a derandomizing process, which corresponds to the inverse process of the randomizer included in the transmitting system, on the received mobile service data. Thereafter, the derandomized data are outputted, thereby obtaining the mobile service data transmitted from the transmitting system. In the present invention, the RS frame decoder  1006  may perform the data derandomizing function. An MPH frame decoder may be configured of M number of RS frame decoders provided in parallel, wherein the number of RS frame encoders is equal to the number of parades (=M) within an MPH frame, a multiplexer for multiplexing each portion and being provided to each input end of the M number of RS frame decoders, and a demultiplexer for demultiplexing each portion and being provided to each output end of the M number of RS frame decoders. 
     General Digital Broadcast Receiving System 
       FIG. 66  illustrates a block diagram showing a structure of a digital broadcast receiving system according to an embodiment of the present invention. Herein, the demodulating unit of  FIG. 36  may be applied in the digital broadcast receiving system. Referring to  FIG. 66 , the digital broadcast receiving system includes a tuner  6001 , a demodulating unit  6002 , a demultiplexer  6003 , an audio decoder  6004 , a video decoder  6005 , a native TV application manager  6006 , a channel manager  6007 , a channel map  6008 , a first memory  6009 , an SI and/or data decoder  6010 , a second memory  6011 , a system manager  6012 , a data broadcast application manager  6013 , a storage controller  6014 , a third memory  6015 , and a GPS module  6020 . Herein, the first memory  6009  corresponds to a non-volatile random access memory (NVRAM) (or a flash memory). The third memory  6015  corresponds to a large-scale storage device, such as a hard disk drive (HDD), a memory chip, and so on. 
     The tuner  6001  tunes a frequency of a specific channel through any one of an antenna, cable, and satellite. Then, the tuner  6001  down-converts the tuned frequency to an intermediate frequency (IF), which is then outputted to the demodulating unit  6002 . At this point, the tuner  6001  is controlled by the channel manager  6007 . Additionally, the result and strength of the broadcast signal of the tuned channel are also reported to the channel manager  6007 . The data that are being received by the frequency of the tuned specific channel include main service data, mobile service data, and table data for decoding the main service data and mobile service data. 
     According to the embodiment of the present invention, audio data and video data for mobile broadcast programs may be applied as the mobile service data. Such audio data and video data are compressed by various types of encoders so as to be transmitted to a broadcasting station. In this case, the video decoder  6004  and the audio decoder  6005  will be provided in the receiving system so as to correspond to each of the encoders used for the compression process. Thereafter, the decoding process will be performed by the video decoder  6004  and the audio decoder  6005 . Then, the processed video and audio data will be provided to the users. Examples of the encoding/decoding scheme for the audio data may include AC 3, MPEG 2 AUDIO, MPEG 4 AUDIO, AAC, AAC+, HE AAC, AAC SBR, MPEG-Surround, and BSAC. And, examples of the encoding/decoding scheme for the video data may include MPEG 2 VIDEO, MPEG 4 VIDEO, H.264, SVC, and VC-1. 
     Depending upon the embodiment of the present invention, examples of the mobile service data may include data provided for data service, such as Java application data, HTML application data, XML data, and so on. The data provided for such data services may correspond either to a Java class file for the Java application, or to a directory file designating positions (or locations) of such files. Furthermore, such data may also correspond to an audio file and/or a video file used in each application. The data services may include weather forecast services, traffic information services, stock information services, services providing information quiz programs providing audience participation services, real time poll, user interactive education programs, gaming services, services providing information on soap opera (or TV series) synopsis, characters, original sound track, filing sites, services providing information on past sports matches, profiles and accomplishments of sports players, product information and product ordering services, services providing information on broadcast programs by media type, airing time, subject, and so on. The types of data services described above are only exemplary and are not limited only to the examples given herein. Furthermore, depending upon the embodiment of the present invention, the mobile service data may correspond to meta data. For example, the meta data be written in XML format so as to be transmitted through a DSM-CC protocol. 
     The demodulating unit  6002  performs VSB-demodulation and channel equalization on the signal being outputted from the tuner  6001 , thereby identifying the main service data and the mobile service data. Thereafter, the identified main service data and mobile service data are outputted in TS packet units. An example of the demodulating unit  6002  is shown in  FIG. 36  to  FIG. 65 . Therefore, the structure and operation of the demodulator will be described in detail in a later process. However, this is merely exemplary and the scope of the present invention is not limited to the example set forth herein. In the embodiment given as an example of the present invention, only the mobile service data packet outputted from the demodulating unit  6002  is inputted to the demultiplexer  6003 . In this case, the main service data packet is inputted to another demultiplexer (not shown) that processes main service data packets. Herein, the storage controller  6014  is also connected to the other demultiplexer in order to store the main service data after processing the main service data packets. The demultiplexer of the present invention may also be designed to process both mobile service data packets and main service data packets in a single demultiplexer. 
     The storage controller  6014  is interfaced with the demultiplexer so as to control instant recording, reserved (or pre-programmed) recording, time shift, and so on of the mobile service data and/or main service data. For example, when one of instant recording, reserved (or pre-programmed) recording, and time shift is set and programmed in the receiving system (or receiver) shown in  FIG. 66 , the corresponding mobile service data and/or main service data that are inputted to the demultiplexer are stored in the third memory  6015  in accordance with the control of the storage controller  6014 . The third memory  6015  may be described as a temporary storage area and/or a permanent storage area. Herein, the temporary storage area is used for the time shifting function, and the permanent storage area is used for a permanent storage of data according to the user&#39;s choice (or decision). 
     When the data stored in the third memory  6015  need to be reproduced (or played), the storage controller  6014  reads the corresponding data stored in the third memory  6015  and outputs the read data to the corresponding demultiplexer (e.g., the mobile service data are outputted to the demultiplexer  6003  shown in  FIG. 66 ). At this point, according to the embodiment of the present invention, since the storage capacity of the third memory  6015  is limited, the compression encoded mobile service data and/or main service data that are being inputted are directly stored in the third memory  6015  without any modification for the efficiency of the storage capacity. In this case, depending upon the reproduction (or reading) command, the data read from the third memory  6015  pass trough the demultiplexer so as to be inputted to the corresponding decoder, thereby being restored to the initial state. 
     The storage controller  6014  may control the reproduction (or play), fast-forward, rewind, slow motion, instant replay functions of the data that are already stored in the third memory  6015  or presently being buffered. Herein, the instant replay function corresponds to repeatedly viewing scenes that the viewer (or user) wishes to view once again. The instant replay function may be performed on stored data and also on data that are currently being received in real time by associating the instant replay function with the time shift function. If the data being inputted correspond to the analog format, for example, if the transmission mode is NTSC, PAL, and so on, the storage controller  6014  compression encodes the inputted data and stored the compression-encoded data to the third memory  6015 . In order to do so, the storage controller  6014  may include an encoder, wherein the encoder may be embodied as one of software, middleware, and hardware. Herein, an MPEG encoder may be used as the encoder according to an embodiment of the present invention. The encoder may also be provided outside of the storage controller  6014 . 
     Meanwhile, in order to prevent illegal duplication (or copies) of the input data being stored in the third memory  6015 , the storage controller  6014  scrambles (or encrypts) the input data and stores the scrambled (or encrypted) data in the third memory  6015 . Accordingly, the storage controller  6014  may include a scramble algorithm (or encryption algorithm) for scrambling the data stored in the third memory  6015  and a descramble algorithm (or decryption algorithm) for descrambling (or decrypting) the data read from the third memory  6015 . The scrambling method may include using an arbitrary key (e.g., control word) to modify a desired set of data, and also a method of mixing signals. 
     Meanwhile, the demultiplexer  6003  receives the real-time data outputted from the demodulating unit  6002  or the data read from the third memory  6015  and demultiplexes the received data. In the example given in the present invention, the demultiplexer  6003  performs demultiplexing on the mobile service data packet. Therefore, in the present invention, the receiving and processing of the mobile service data will be described in detail. However, depending upon the many embodiments of the present invention, not only the mobile service data but also the main service data may be processed by the demultiplexer  6003 , the audio decoder  6004 , the video decoder  6005 , the native TV application manager  6006 , the channel manager  6007 , the channel map  6008 , the first memory  6009 , the SI and/or data decoder  6010 , the second memory  6011 , a system manager  6012 , the data broadcast application manager  6013 , the storage controller  6014 , the third memory  6015 , and the GPS module  6020 . Thereafter, the processed data may be used to provide diverse services to the users. 
     The demultiplexer  6003  demultiplexes mobile service data and system information (SI) tables from the mobile service data packet inputted in accordance with the control of the SI and/or data decoder  6010 . Thereafter, the demultiplexed mobile service data and SI tables are outputted to the SI and/or data decoder  6010  in a section format. In this case, it is preferable that data for the data service are used as the mobile service data that are inputted to the SI and/or data decoder  6010 . In order to extract the mobile service data from the channel through which mobile service data are transmitted and to decode the extracted mobile service data, system information is required. Such system information may also be referred to as service information. The system information may include channel information, event information, etc. In the embodiment of the present invention, the PSI/PSIP tables are applied as the system information. However, the present invention is not limited to the example set forth herein. More specifically, regardless of the name, any protocol transmitting system information in a table format may be applied in the present invention. 
     The PSI table is an MPEG-2 system standard defined for identifying the channels and the programs. The PSIP table is an advanced television systems committee (ATSC) standard that can identify the channels and the programs. The PSI table may include a program association table (PAT), a conditional access table (CAT), a program map table (PMT), and a network information table (NIT). Herein, the PAT corresponds to special information that is transmitted by a data packet having a PID of ‘0’. The PAT transmits PID information of the PMT and PID information of the NIT corresponding to each program. The CAT transmits information on a paid broadcast system used by the transmitting system. The PMT transmits PID information of a transport stream (TS) packet, in which program identification numbers and individual bit sequences of video and audio data configuring the corresponding program are transmitted, and the PID information, in which PCR is transmitted. The NIT transmits information of the actual transmission network. 
     The PSIP table may include a virtual channel table (VCT), a system time table (STT), a rating region table (RRT), an extended text table (ETT), a direct channel change table (DCCT), an event information table (EIT), and a master guide table (MGT). The VCT transmits information on virtual channels, such as channel information for selecting channels and information such as packet identification (PID) numbers for receiving the audio and/or video data. More specifically, when the VCT is parsed, the PID of the audio/video data of the broadcast program may be known. Herein, the corresponding audio/video data are transmitted within the channel along with the channel name and the channel number. 
       FIG. 67  illustrates a VCT syntax according to an embodiment of the present invention. The VCT syntax of  FIG. 67  is configured by including at least one of a table_id field, a section_syntax_indicator field, a private_indicator field, a section_length field, a transport_stream_id field, a version_number field, a current_next_indicator field, a section_number field, a last_section_number field, a protocol_version field, and a num_channels_in_section field. 
     The VCT syntax further includes a first ‘for’ loop repetition statement that is repeated as much as the num_channels_in_section field value. The first repetition statement may include at least one of a short_name field, a major_channel_number field, a minor_channel_number field, a modulation_mode field, a carrier_frequency field, a channel_TSID field, a program_number field, an ETM_location field, an access_controlled field, a hidden field, a service_type field, a source_id field, a descriptor_length field, and a second ‘for’ loop statement that is repeated as much as the number of descriptors included in the first repetition statement. Herein, the second repetition statement will be referred to as a first descriptor loop for simplicity. The descriptor descriptors( ) included in the first descriptor loop is separately applied to each virtual channel. 
     Furthermore, the VCT syntax may further include an additional_descriptor_length field, and a third ‘for’ loop statement that is repeated as much as the number of descriptors additionally added to the VCT. For simplicity of the description of the present invention, the third repetition statement will be referred to as a second descriptor loop. The descriptor additional_descriptors( ) included in the second descriptor loop is commonly applied to all virtual channels described in the VCT. 
     As described above, referring to  FIG. 67 , the table_id field indicates a unique identifier (or identification) (ID) that can identify the information being transmitted to the table as the VCT. More specifically, the table_id field indicates a value informing that the table corresponding to this section is a VCT. For example, a 0xC8 value may be given to the table_id field. 
     The version_number field indicates the version number of the VCT. The section_number field indicates the number of this section. The last_section_number field indicates the number of the last section of a complete VCT. And, the num_channel_in_section field designates the number of the overall virtual channel existing within the VCT section. Furthermore, in the first ‘for’ loop repetition statement, the short name field indicates the name of a virtual channel. The major_channel_number field indicates a ‘major’ channel number associated with the virtual channel defined within the first repetition statement, and the minor_channel_number field indicates a ‘minor’ channel number. More specifically, each of the channel numbers should be connected to the major and minor channel numbers, and the major and minor channel numbers are used as user reference numbers for the corresponding virtual channel. 
     The program_number field is shown for connecting the virtual channel having an MPEG-2 program association table (PAT) and program map table (PMT) defined therein, and the program_number field matches the program number within the PAT/PMT. Herein, the PAT describes the elements of a program corresponding to each program number, and the PAT indicates the PID of a transport packet transmitting the PMT. The PMT described subordinate information, and a PID list of the transport packet through which a program identification number and a separate bit sequence, such as video and/or audio data configuring the program, are being transmitted. 
       FIG. 68  illustrates a service_type field according to an embodiment of the present invention. The service_type field indicates the service type provided in a corresponding virtual channel. Referring to  FIG. 68 , it is provided that the service_type field should only indicate an analog television, a digital television, digital audio data, and digital video data. Also, according to the embodiment of the present invention, it may be provided that a mobile broadcast program should be designated to the service_type field. The service_type field, which is parsed by the SI and/or data decoder  6010  may be provided to a receiving system, as shown in  FIG. 66 , and used accordingly. According to other embodiments of the present invention, the parsed service_type field may also be provided to each of the audio decoder  6004  and video decoder  6005 , so as to be used in the decoding process. 
     The source_id field indicates a program source connected to the corresponding virtual channel. Herein, a source refers to a specific source, such as an image, a text, video data, or sound. The source_id field value has a unique value within the transport stream transmitting the VCT. Meanwhile, a service location descriptor may be included in a descriptor loop (i.e., descriptor { }) within a next ‘for’ loop repetition statement. The service location descriptor may include a stream type, PID, and language code for each elementary stream. 
       FIG. 69  illustrates a service location descriptor according to an embodiment of the present invention. As shown in  FIG. 69 , the service location descriptor may include a descriptor_tag field, a descriptor_length field, and a PCR_PID field. Herein, the PCR_PID field indicates the PID of a transport stream packet within a program specified by a program_number field, wherein the transport stream packet includes a valid PCR field. Meanwhile, the service location descriptor includes a number_elements field so as to indicate a number of PIDs used in the corresponding program. The number of repetition of a next ‘for’ descriptor loop repetition statement can be decided, depending upon the value of the number_elements field. Referring to  FIG. 69 , the ‘for’ loop repetition statement includes a stream_type field, an elementary_PID field, and an ISO_639_language_code field. Herein, the stream_type field indicates the stream type of the corresponding elementary stream (i.e., video/audio data). The elementary_PID field indicates the PID of the corresponding elementary stream. The ISO_639_language_code field indicates a language code of the corresponding elementary stream. 
       FIG. 70  illustrates examples that may be assigned to the stream_type field according to the present invention. As shown in  FIG. 70 , ISO/IEC 11172 Video, ITU-T Rec. H.262|ISO/IEC 13818-2 Video or ISO/IEC 11172-2 constrained parameter video stream, ISO/IEC 11172 Audio, ISO/IEC 13818-3 Audio, ITU-T Rec. H.222.0|ISO/IEC 13818-1 private_sections, ITU-T Rec. H.222.0|ISO/IEC 13818-1 PES packets containing private data, ISO/IEC 13522 MHEG, ITU-T Rec. H.222.0|ISO/IEC 13818-1 Annex A DSM CC, ITU-T Rec. H.222.1, ISO/IEC 13818-6 type A, ISO/IEC 13818-6 type B, ISO/IEC 13818-6 type C, ISO/IEC 13818-6 type D, ISO/IEC 13818-1 auxiliary, and so on may be applied as the stream type. Meanwhile, according to the embodiment of the present invention, MPH video stream: Non-hierarchical mode, MPH audio stream: Non-hierarchical mode, MPH Non-A/V stream: Non-hierarchical mode, MPH High Priority video stream: Hierarchical mode, MPH High Priority audio stream: Hierarchical mode, MPH Low Priority video stream: Hierarchical mode, MPH Low priority audio stream: Hierarchical mode, and so on may further be applied as the stream type. 
     As described above, “MPH” corresponds to the initials of “mobile”, “pedestrian”, and “handheld” and represents the opposite concept of a fixed-type system. Therefore, the MPH video stream: Non-hierarchical mode, the MPH audio stream: Non-hierarchical mode, the MPH Non-A/V stream: Non-hierarchical mode, the MPH High Priority video stream: Hierarchical mode, the MPH High Priority audio stream: Hierarchical mode, the MPH Low Priority video stream: Hierarchical mode, and the MPH Low priority audio stream: Hierarchical mode correspond to stream types that are applied when mobile broadcast programs are being transmitted and received. Also the Hierarchical mode and the Non-hierarchical mode each correspond to values that are used in stream types having different priority levels. Herein, the priority level is determined based upon a hierarchical structure applied in any one of the encoding or decoding method. 
     Therefore, when a hierarchical structure-type codec is used, a field value including the hierarchical mode and the non-hierarchical mode is respectively designated so as to identify each stream. Such stream type information is parsed by the SI and/or data decoder  6010 , so as to be provided to the video and audio decoders  6004  and  6005 . Thereafter, each of the video and audio decoders  6004  and  6005  uses the parsed stream type information in order to perform the decoding process. Other stream types that may be applied in the present invention may include MPEG 4 AUDIO, AC 3, AAC, AAC+, BSAC, HE AAC, AAC SBR, and MPEG-S for the audio data, and may also include MPEG 2 VIDEO, MPEG 4 VIDEO, H.264, SVC, and VC-1 for the video data. 
     Furthermore, referring to  FIG. 70 , in fields using the hierarchical mode and the non-hierarchical mode, such as the MPH video stream: Non-hierarchical mode and the MPH audio stream: Non-hierarchical mode, examples of using the MPEG 4 AUDIO, AC 3, AAC, AAC+, BSAC, HE AAC, AAC SBR, and MPEG-S for the audio data, and the MPEG 2 VIDEO, MPEG 4 VIDEO, H.264, SVC, and VC-1 for the video data may also be respectively used as replacements for each of the audio stream and the video stream may be considered as other embodiments of the present invention and may, therefore, be included in the scope of the present invention. Meanwhile, the stream_type field may be provided as one of the fields within the PMT. And, in this case, it is apparent that such stream_type field includes the above-described syntax. The STT transmits information on the current data and timing information. The RRT transmits information on region and consultation organs for program ratings. The ETT transmits additional description of a specific channel and broadcast program. The EIT transmits information on virtual channel events (e.g., program title, program start time, etc.). 
       FIG. 71  illustrates a bit stream syntax for an event information table (EIT) according to the present invention. In this embodiment, the EIT shown in  FIG. 71  corresponds to a PSIP table including information on a title, start time, duration, and so on of an event in a virtual channel. Referring to  FIG. 71 , the EIT is configured of a plurality of fields including a table_id field, a section_syntax_indicator field, a private_indicator field, a source_ID, a version_numbers_in_section field, a current_next_indicator field, and a num_event field. More specifically, the table_id field is an 8-bit field having the value of ‘oxCB’, which indicates that the corresponding section is included in the EIT. The section_syntax_indicator field is a 1-bit field having the value of ‘1’. This indicates that the corresponding section passes through the section_length field and is in accordance with a generic section syntax. The private_indicator field corresponds to a 1-bit field having the value of ‘1’. 
     Also, the source_ID corresponds to an ID identifying a virtual channel that carries an event shown in the above-described table. The version_numbers_in_section field indicates the version of an element included in the event information table. In the present invention, with respect to the previous version number, an event change information included in the event information table, wherein the event change information has a new version number is recognized as the latest change in information. The current_next_indicator field indicates whether the event information included in the corresponding EIT is a current information or a next information. And, finally, the num_event field represents the number of events included in the channel having a source ID. More specifically, an event loop shown below is repeated as many times as the number of events. 
     The above-described EIT field is commonly applied to at least one or more events included in one EIT syntax. A loop statement, which is included as “for(j=0; j&lt;num_event_in_section;j++) { }”, describes the characteristics of each event. The following fields represent detailed information of each individual event. Therefore, the following fields are individually applied to each corresponding event described by the EIT syntax. An event_ID included in an event loop is an identifier for identifying each individual event. The number of the event ID corresponds to a portion of the identifier for even extended text message (i.e., ETM_ID). A start_time field indicates the starting time of an event. Therefore, the start_time field collects the starting time information of a program provided from an electronic program information. A length_in_seconds field indicates the duration of an event. Therefore, the length_in_seconds field collects the ending time information of a program provided from an electronic program information. More specifically, the ending time information is collected by adding the start_time field value and the length_in_seconds field value. A title_text( )field may be used to indicate the tile of a broadcast program. 
     Meanwhile, the descriptor applied to each event may be included in the EIT. Herein, a descriptors_length field indicates the length of a descriptor. Also, a descriptor loop (i.e., descriptor{ }) included in a ‘for’ loop repetition statement includes at least one of an AC-3 audio descriptor, an MPEG 2 audio descriptor, an MPEG 4 audio descriptor, an AAC descriptor, an AAC+ descriptor, an HE AAC descriptor, an AAC SBR descriptor, an MPEG surround descriptor, a BSAC descriptor, an MPEG 2 video descriptor, an MPEG 4 video descriptor, an H.264 descriptor, an SVC descriptor, and a VC-1 descriptor. Herein, each descriptor describes information on audio/video codec applied to each event. Such codec information may be provided to the audio/video decoder  6004  and  6005  and used in the decoding process. 
     Finally, the DCCT/DCCSCT transmits information associated with automatic (or direct) channel change. And, the MGT transmits the versions and PID information of the above-mentioned tables included in the PSIP. Each of the above-described tables included in the PSI/PSIP is configured of a basic unit referred to as a “section”, and a combination of one or more sections forms a table. For example, the VCT may be divided into 256 sections. Herein, one section may include a plurality of virtual channel information. However, a single set of virtual channel information is not divided into two or more sections. At this point, the receiving system may parse and decode the data for the data service that are transmitting by using only the tables included in the PSI, or only the tables included in the PSIP, or a combination of tables included in both the PSI and the PSIP. In order to parse and decode the mobile service data, at least one of the PAT and PMT included in the PSI, and the VCT included in the PSIP is required. For example, the PAT may include the system information for transmitting the mobile service data, and the PID of the PMT corresponding to the mobile service data (or program number). The PMT may include the PID of the TS packet used for transmitting the mobile service data. The VCT may include information on the virtual channel for transmitting the mobile service data, and the PID of the TS packet for transmitting the mobile service data. 
     Meanwhile, depending upon the embodiment of the present invention, a DVB-SI may be applied instead of the PSIP. The DVB-SI may include a network information table (NIT), a service description table (SDT), an event information table (EIT), and a time and data table (TDT). The DVB-SI may be used in combination with the above-described PSI. Herein, the NIT divides the services corresponding to particular network providers by specific groups. The NIT includes all tuning information that are used during the IRD set-up. The NIT may be used for informing or notifying any change in the tuning information. The SDT includes the service name and different parameters associated with each service corresponding to a particular MPEG multiplex. The EIT is used for transmitting information associated with all events occurring in the MPEG multiplex. The EIT includes information on the current transmission and also includes information selectively containing different transmission streams that may be received by the IRD. And, the TDT is used for updating the clock included in the IRD. 
     Furthermore, three selective SI tables (i.e., a bouquet associate table (BAT), a running status table (RST), and a stuffing table (ST)) may also be included. More specifically, the bouquet associate table (BAT) provides a service grouping method enabling the IRD to provide services to the viewers. Each specific service may belong to at least one ‘bouquet’ unit. A running status table (RST) section is used for promptly and instantly updating at least one event execution status. The execution status section is transmitted only once at the changing point of the event status. Other SI tables are generally transmitted several times. The stuffing table (ST) may be used for replacing or discarding a subsidiary table or the entire SI tables. 
     In the present invention, when the mobile service data correspond to audio data and video data, it is preferable that the mobile service data included (or loaded) in a payload within a TS packet correspond to PES type mobile service data. According to another embodiment of the present invention, when the mobile service data correspond to the data for the data service (or data service data), the mobile service data included in the payload within the TS packet consist of a digital storage media-command and control (DSM-CC) section format. However, the TS packet including the data service data may correspond either to a packetized elementary stream (PES) type or to a section type. More specifically, either the PES type data service data configure the TS packet, or the section type data service data configure the TS packet. The TS packet configured of the section type data will be given as the example of the present invention. At this point, the data service data are includes in the digital storage media-command and control (DSM-CC) section. Herein, the DSM-CC section is then configured of a 188-byte unit TS packet. 
     Furthermore, the packet identification of the TS packet configuring the DSM-CC section is included in a data service table (DST). When transmitting the DST, ‘0x95’ is assigned as the value of a stream_type field included in the service location descriptor of the PMT or the VCT. More specifically, when the PMT or VCT stream_type field value is ‘0x95’, the receiving system may acknowledge the reception of the data broadcast program including mobile service data. At this point, the mobile service data may be transmitted by a data/object carousel method. The data/object carousel method corresponds to repeatedly transmitting identical data on a regular basis. 
     At this point, according to the control of the SI and/or data decoder  6010 , the demultiplexer  6003  performs section filtering, thereby discarding repetitive sections and outputting only the non-repetitive sections to the SI and/or data decoder  6010 . The demultiplexer  6003  may also output only the sections configuring desired tables (e.g., VCT or EIT) to the SI and/or data decoder  6010  by section filtering. Herein, the VCT or EIT may include a specific descriptor for the mobile service data. However, the present invention does not exclude the possibilities of the mobile service data being included in other tables, such as the PMT. The section filtering method may include a method of verifying the PID of a table defined by the MGT, such as the VCT, prior to performing the section filtering process. Alternatively, the section filtering method may also include a method of directly performing the section filtering process without verifying the MGT, when the VCT includes a fixed PID (i.e., a base PID). At this point, the demultiplexer  6003  performs the section filtering process by referring to a table_id field, a version_number field, a section_number field, etc. 
     As described above, the method of defining the PID of the VCT broadly includes two different methods. Herein, the PID of the VCT is a packet identifier required for identifying the VCT from other tables. The first method consists of setting the PID of the VCT so that it is dependent to the MGT. In this case, the receiving system cannot directly verify the VCT among the many PSI and/or PSIP tables. Instead, the receiving system must check the PID defined in the MGT in order to read the VCT. Herein, the MGT defines the PID, size, version number, and so on, of diverse tables. The second method consists of setting the PID of the VCT so that the PID is given a base PID value (or a fixed PID value), thereby being independent from the MGT. In this case, unlike in the first method, the VCT according to the present invention may be identified without having to verify every single PID included in the MGT. Evidently, an agreement on the base PID must be previously made between the transmitting system and the receiving system. 
     Meanwhile, in the embodiment of the present invention, the demultiplexer  6003  may output only an application information table (AIT) to the SI and/or data decoder  6010  by section filtering. The AIT includes information on an application being operated in the receiver for the data service. The AIT may also be referred to as an XAIT, and an AMT. Therefore, any table including application information may correspond to the following description. When the AIT is transmitted, a value of ‘0x05’ may be assigned to a stream_type field of the PMT. The AIT may include application information, such as application name, application version, application priority, application ID, application status (i.e., auto-start, user-specific settings, kill, etc.), application type (i.e., Java or HTML), position (or location) of stream including application class and data files, application platform directory, and location of application icon. 
     In the method for detecting application information for the data service by using the AIT, component_tag, original network_id, transport_stream_id, and service_id fields may be used for detecting the application information. The component_tag field designates an elementary stream carrying a DSI of a corresponding object carousel. The original_network_id field indicates a DVB-SI original_network_id of the TS providing transport connection. The transport_stream_id field indicates the MPEG TS of the TS providing transport connection, and the service_id field indicates the DVB-SI of the service providing transport connection. Information on a specific channel may be obtained by using the original_network_id field, the transport_stream_id field, and the service_id field. The data service data, such as the application data, detected by using the above-described method may be stored in the second memory  6011  by the SI and/or data decoder  6010 . 
     The SI and/or data decoder  6010  parses the DSM-CC section configuring the demultiplexed mobile service data. Then, the mobile service data corresponding to the parsed result are stored as a database in the second memory  6011 . The SI and/or data decoder  6010  groups a plurality of sections having the same table identification (table_id) so as to configure a table, which is then parsed. Thereafter, the parsed result is stored as a database in the second memory  6011 . At this point, by parsing data and/or sections, the SI and/or data decoder  6010  reads all of the remaining actual section data that are not section-filtered by the demultiplexer  6003 . Then, the SI and/or data decoder  6010  stores the read data to the second memory  6011 . The second memory  6011  corresponds to a table and data/object carousel database storing system information parsed from tables and mobile service data parsed from the DSM-CC section. Herein, a table_id field, a section_number field, and a last_section_number field included in the table may be used to indicate whether the corresponding table is configured of a single section or a plurality of sections. For example, TS packets having the PID of the VCT are grouped to form a section, and sections having table identifiers allocated to the VCT are grouped to form the VCT. When the VCT is parsed, information on the virtual channel to which mobile service data are transmitted may be obtained. 
     Also, according to the present invention, the SI and/or data decoder  6010  parses the SLD of the VCT, thereby transmitting the stream type information of the corresponding elementary stream to the audio decoder  6004  or the video decoder  6005 . In this case, the corresponding audio decoder  6004  or video decoder  6005  uses the transmitted stream type information so as to perform the audio or video decoding process. Furthermore, according to the present invention, the SI and/or data decoder  6010  parses an AC-3 audio descriptor, an MPEG 2 audio descriptor, an MPEG 4 audio descriptor, an AAC descriptor, an AAC+ descriptor, an HE AAC descriptor, an AAC SBR descriptor, an MPEG surround descriptor, a BSAC descriptor, an MPEG 2 video descriptor, an MPEG 4 video descriptor, an H.264 descriptor, an SVC descriptor, a VC-1 descriptor, and so on, of the EIT, thereby transmitting the audio or video codec information of the corresponding event to the audio decoder  6004  or video decoder  6005 . In this case, the corresponding audio decoder  6004  or video decoder  6005  uses the transmitted audio or video codec information in order to perform an audio or video decoding process. 
     The obtained application identification information, service component identification information, and service information corresponding to the data service may either be stored in the second memory  6011  or be outputted to the data broadcasting application manager  6013 . In addition, reference may be made to the application identification information, service component identification information, and service information in order to decode the data service data. Alternatively, such information may also prepare the operation of the application program for the data service. Furthermore, the SI and/or data decoder  6010  controls the demultiplexing of the system information table, which corresponds to the information table associated with the channel and events. Thereafter, an A/V PID list may be transmitted to the channel manager  6007 . 
     The channel manager  6007  may refer to the channel map  6008  in order to transmit a request for receiving system-related information data to the SI and/or data decoder  6010 , thereby receiving the corresponding result. In addition, the channel manager  6007  may also control the channel tuning of the tuner  6001 . Furthermore, the channel manager  6007  may directly control the demultiplexer  6003 , so as to set up the A/V PID, thereby controlling the audio decoder  6004  and the video decoder  6005 . 
     The audio decoder  6004  and the video decoder  6005  may respectively decode and output the audio data and video data demultiplexed from the main service data packet. Alternatively, the audio decoder  6004  and the video decoder  6005  may respectively decode and output the audio data and video data demultiplexed from the mobile service data packet. Meanwhile, when the mobile service data include data service data, and also audio data and video data, it is apparent that the audio data and video data demultiplexed by the demultiplexer  6003  are respectively decoded by the audio decoder  6004  and the video decoder  6005 . For example, an audio-coding (AC)-3 decoding algorithm, an MPEG-2 audio decoding algorithm, an MPEG-4 audio decoding algorithm, an AAC decoding algorithm, an AAC+ decoding algorithm, an HE AAC decoding algorithm, an AAC SBR decoding algorithm, an MPEG surround decoding algorithm, and a BSAC decoding algorithm may be applied to the audio decoder  6004 . Also, an MPEG-2 video decoding algorithm, an MPEG-4 video decoding algorithm, an H.264 decoding algorithm, an SVC decoding algorithm, and a VC-1 decoding algorithm may be applied to the video decoder  6005 . Accordingly, the decoding process may be performed. 
     Meanwhile, the native TV application manager  6006  operates a native application program stored in the first memory  6009 , thereby performing general functions such as channel change. The native application program refers to software stored in the receiving system upon shipping of the product. More specifically, when a user request (or command) is transmitted to the receiving system through a user interface (UI), the native TV application manger  6006  displays the user request on a screen through a graphic user interface (GUI), thereby responding to the user&#39;s request. The user interface receives the user request through an input device, such as a remote controller, a key pad, a jog controller, an a touchscreen provided on the screen, and then outputs the received user request to the native TV application manager  6006  and the data broadcasting application manager  6013 . Furthermore, the native TV application manager  6006  controls the channel manager  6007 , thereby controlling channel-associated operations, such as the management of the channel map  6008 , and controlling the SI and/or data decoder  6010 . The native TV application manager  6006  also controls the GUI of the overall receiving system, thereby storing the user request and status of the receiving system in the first memory  6009  and restoring the stored information. 
     The channel manager  6007  controls the tuner  6001  and the SI and/or data decoder  6010 , so as to managing the channel map  6008  so that it can respond to the channel request made by the user. More specifically, channel manager  6007  sends a request to the SI and/or data decoder  6010  so that the tables associated with the channels that are to be tuned are parsed. The results of the parsed tables are reported to the channel manager  6007  by the SI and/or data decoder  6010 . Thereafter, based on the parsed results, the channel manager  6007  updates the channel map  6008  and sets up a PID in the demultiplexer  6003  for demultiplexing the tables associated with the data service data from the mobile service data. 
     The system manager  6012  controls the booting of the receiving system by turning the power on or off. Then, the system manager  6012  stores ROM images (including downloaded software images) in the first memory  6009 . More specifically, the first memory  6009  stores management programs such as operating system (OS) programs required for managing the receiving system and also application program executing data service functions. The application program is a program processing the data service data stored in the second memory  6011  so as to provide the user with the data service. If the data service data are stored in the second memory  6011 , the corresponding data service data are processed by the above-described application program or by other application programs, thereby being provided to the user. The management program and application program stored in the first memory  6009  may be updated or corrected to a newly downloaded program. Furthermore, the storage of the stored management program and application program is maintained without being deleted even if the power of the system is shut down. Therefore, when the power is supplied, the programs may be executed without having to be newly downloaded once again. 
     The application program for providing data service according to the present invention may either be initially stored in the first memory  6009  upon the shipping of the receiving system, or be stored in the first memory  6009  after being downloaded. The application program for the data service (i.e., the data service providing application program) stored in the first memory  6009  may also be deleted, updated, and corrected. Furthermore, the data service providing application program may be downloaded and executed along with the data service data each time the data service data are being received. 
     When a data service request is transmitted through the user interface, the data broadcasting application manager  6013  operates the corresponding application program stored in the first memory  6009  so as to process the requested data, thereby providing the user with the requested data service. And, in order to provide such data service, the data broadcasting application manager  6013  supports the graphic user interface (GUI). Herein, the data service may be provided in the form of text (or short message service (SMS)), voice message, still image, and moving image. The data broadcasting application manager  6013  may be provided with a platform for executing the application program stored in the first memory  6009 . The platform may be, for example, a Java virtual machine for executing the Java program. Hereinafter, an example of the data broadcasting application manager  6013  executing the data service providing application program stored in the first memory  6009 , so as to process the data service data stored in the second memory  6011 , thereby providing the user with the corresponding data service will now be described in detail. 
     Assuming that the data service corresponds to a traffic information service, the data service according to the present invention is provided to the user of a receiver that is not equipped with an electronic map and/or a GPS system in the form of at least one of a text (or short message service (SMS)), a voice message, a graphic message, a still image, and a moving image. In this case, when a GPS module  6020  is mounted on the receiving system, as shown in  FIG. 66 , the GPS module  6020  receives satellite signals transmitted from a plurality of low earth orbit satellites and extracts the current position (or location) information (e.g., longitude, latitude, altitude), thereby outputting the extracted information to the data broadcasting application manager  6013 . 
     At this point, it is assumed that the electronic map including information on each link and nod and other diverse graphic information are stored in one of the second memory  6011 , the first memory  6009 , and another memory that is not shown. More specifically, according to the request made by the data broadcasting application manager  6013 , the data service data stored in the second memory  6011  are read and inputted to the data broadcasting application manager  6013 . The data broadcasting application manager  6013  translates (or deciphers) the data service data read from the second memory  6011 , thereby extracting the necessary information according to the contents of the message and/or a control signal. In other words, the data broadcasting application manager  6013  uses the current position information and the graphic information, so that the current position information can be processed and provided to the user in a graphic format. 
       FIG. 72  illustrates a block diagram showing the structure of a digital broadcast (or television) receiving system according to another embodiment of the present invention. Referring to  FIG. 72 , the digital broadcast receiving system includes a tuner  7001 , a demodulating unit  7002 , a demultiplexer  7003 , a first descrambler  7004 , an audio decoder  7005 , a video decoder  7006 , a second descrambler  7007 , an authentication unit  7008 , a native TV application manager  7009 , a channel manager  7010 , a channel map  7011 , a first memory  7012 , a data decoder  7013 , a second memory  7014 , a system manager  7015 , a data broadcasting application manager  7016 , a storage controller  7017 , a third memory  7018 , a telecommunication module  7019 , and a GPS module  7020 . Herein, the third memory  7018  is a mass storage device, such as a hard disk drive (HDD) or a memory chip. Also, during the description of the digital broadcast (or television or DTV) receiving system shown in  FIG. 72 , the components that are identical to those of the digital broadcast receiving system of  FIG. 66  will be omitted for simplicity. 
     As described above, in order to provide services for preventing illegal duplication (or copies) or illegal viewing of the enhanced data and/or main data that are transmitted by using a broadcast network, and to provide paid broadcast services, the transmitting system may generally scramble and transmit the broadcast contents. Therefore, the receiving system needs to descramble the scrambled broadcast contents in order to provide the user with the proper broadcast contents. Furthermore, the receiving system may generally be processed with an authentication process with an authentication means before the descrambling process. Hereinafter, the receiving system including an authentication means and a descrambling means according to an embodiment of the present invention will now be described in detail. 
     According to the present invention, the receiving system may be provided with a descrambling means receiving scrambled broadcasting contents and an authentication means authenticating (or verifying) whether the receiving system is entitled to receive the descrambled contents. Hereinafter, the descrambling means will be referred to as first and second descramblers  7004  and  7007 , and the authentication means will be referred to as an authentication unit  7008 . Such naming of the corresponding components is merely exemplary and is not limited to the terms suggested in the description of the present invention. For example, the units may also be referred to as a decryptor. Although  FIG. 72  illustrates an example of the descramblers  7004  and  7007  and the authentication unit  7008  being provided inside the receiving system, each of the descramblers  7004  and  7007  and the authentication unit  7008  may also be separately provided in an internal or external module. Herein, the module may include a slot type, such as a SD or CF memory, a memory stick type, a USB type, and so on, and may be detachably fixed to the receiving system. 
     As described above, when the authentication process is performed successfully by the authentication unit  7008 , the scrambled broadcasting contents are descrambled by the descramblers  7004  and  7007 , thereby being provided to the user. At this point, a variety of the authentication method and descrambling method may be used herein. However, an agreement on each corresponding method should be made between the receiving system and the transmitting system. Hereinafter, the authentication and descrambling methods will now be described, and the description of identical components or process steps will be omitted for simplicity. 
     The receiving system including the authentication unit  7008  and the descramblers  7004  and  7007  will now be described in detail. The receiving system receives the scrambled broadcasting contents through the tuner  7001  and the demodulating unit  7002 . Then, the system manager  7015  decides whether the received broadcasting contents have been scrambled. Herein, the demodulating unit  7002  may be included as a demodulating means according to embodiment of the present invention as described in  FIG. 36  to  FIG. 65 . However, the present invention is not limited to the examples given in the description set forth herein. If the system manager  7015  decides that the received broadcasting contents have been scrambled, then the system manager  7015  controls the system to operate the authentication unit  7008 . As described above, the authentication unit  7008  performs an authentication process in order to decide whether the receiving system according to the present invention corresponds to a legitimate host entitled to receive the paid broadcasting service. Herein, the authentication process may vary in accordance with the authentication methods. 
     For example, the authentication unit  7008  may perform the authentication process by comparing an IP address of an IP datagram within the received broadcasting contents with a specific address of a corresponding host. At this point, the specific address of the corresponding receiving system (or host) may be a MAC address. More specifically, the authentication unit  7008  may extract the IP address from the decapsulated IP datagram, thereby obtaining the receiving system information that is mapped with the IP address. At this point, the receiving system should be provided, in advance, with information (e.g., a table format) that can map the IP address and the receiving system information. Accordingly, the authentication unit  7008  performs the authentication process by determining the conformity between the address of the corresponding receiving system and the system information of the receiving system that is mapped with the IP address. In other words, if the authentication unit  7008  determines that the two types of information conform to one another, then the authentication unit  7008  determines that the receiving system is entitled to receive the corresponding broadcasting contents. 
     In another example, standardized identification information is defined in advance by the receiving system and the transmitting system. Then, the identification information of the receiving system requesting the paid broadcasting service is transmitted by the transmitting system. Thereafter, the receiving system determines whether the received identification information conforms with its own unique identification number, so as to perform the authentication process. More specifically, the transmitting system creates a database for storing the identification information (or number) of the receiving system requesting the paid broadcasting service. Then, if the corresponding broadcasting contents are scrambled, the transmitting system includes the identification information in the EMM, which is then transmitted to the receiving system. 
     If the corresponding broadcasting contents are scrambled, messages (e.g., entitlement control message (ECM), entitlement management message (EMM)), such as the CAS information, mode information, message position information, that are applied to the scrambling of the broadcasting contents are transmitted through a corresponding data header or another data packet. The ECM may include a control word (CW) used for scrambling the broadcasting contents. At this point, the control word may be encoded with an authentication key. The EMM may include an authentication key and entitlement information of the corresponding data. Herein, the authentication key may be encoded with a receiving system-specific distribution key. In other words, assuming that the enhanced data are scrambled by using the control word, and that the authentication information and the descrambling information are transmitted from the transmitting system, the transmitting system encodes the CW with the authentication key and, then, includes the encoded CW in the entitlement control message (ECM), which is then transmitted to the receiving system. Furthermore, the transmitting system includes the authentication key used for encoding the CW and the entitlement to receive data (or services) of the receiving system (i.e., a standardized serial number of the receiving system that is entitled to receive the corresponding broadcasting service or data) in the entitlement management message (EMM), which is then transmitted to the receiving system. 
     Accordingly, the authentication unit  7008  of the receiving system extracts the identification information of the receiving system and the identification information included in the EMM of the broadcasting service that is being received. Then, the authentication unit  7008  determines whether the identification information conform to each other, so as to perform the authentication process. More specifically, if the authentication unit  7008  determines that the information conform to each other, then the authentication unit  7008  eventually determines that the receiving system is entitled to receive the request broadcasting service. 
     In yet another example, the authentication unit  7008  of the receiving system may be detachably fixed to an external module. In this case, the receiving system is interfaced with the external module through a common interface (CI). In other words, the external module may receive the data scrambled by the receiving system through the common interface, thereby performing the descrambling process of the received data. Alternatively, the external module may also transmit only the information required for the descrambling process to the receiving system. The common interface is configured on a physical layer and at least one protocol layer. Herein, in consideration of any possible expansion of the protocol layer in a later process, the corresponding protocol layer may be configured to have at least one layer that can each provide an independent function. 
     The external module may either consist of a memory or card having information on the key used for the scrambling process and other authentication information but not including any descrambling function, or consist of a card having the above-mentioned key information and authentication information and including the descrambling function. Both the receiving system and the external module should be authenticated in order to provide the user with the paid broadcasting service provided (or transmitted) from the transmitting system. Therefore, the transmitting system can only provide the corresponding paid broadcasting service to the authenticated pair of receiving system and external module. 
     Additionally, an authentication process should also be performed between the receiving system and the external module through the common interface. More specifically, the module may communicate with the system manager  7015  included in the receiving system through the common interface, thereby authenticating the receiving system. Alternatively, the receiving system may authenticate the module through the common interface. Furthermore, during the authentication process, the module may extract the unique ID of the receiving system and its own unique ID and transmit the extracted IDs to the transmitting system. Thus, the transmitting system may use the transmitted ID values as information determining whether to start the requested service or as payment information. Whenever necessary, the system manager  7015  transmits the payment information to the remote transmitting system through the telecommunication module  7019 . 
     The authentication unit  7008  authenticates the corresponding receiving system and/or the external module. Then, if the authentication process is successfully completed, the authentication unit  7008  certifies the corresponding receiving system and/or the external module as a legitimate system and/or module entitled to receive the requested paid broadcasting service. In addition, the authentication unit  7008  may also receive authentication-associated information from a mobile telecommunications service provider to which the user of the receiving system is subscribed, instead of the transmitting system providing the requested broadcasting service. In this case, the authentication-association information may either be scrambled by the transmitting system providing the broadcasting service and, then, transmitted to the user through the mobile telecommunications service provider, or be directly scrambled and transmitted by the mobile telecommunications service provider. Once the authentication process is successfully completed by the authentication unit  7008 , the receiving system may descramble the scrambled broadcasting contents received from the transmitting system. At this point, the descrambling process is performed by the first and second descramblers  7004  and  7007 . Herein, the first and second descramblers  7004  and  7007  may be included in an internal module or an external module of the receiving system. 
     The receiving system is also provided with a common interface for communicating with the external module including the first and second descramblers  7004  and  7007 , so as to perform the descrambling process. More specifically, the first and second descramblers  7004  and  7007  may be included in the module or in the receiving system in the form of hardware, middleware or software. Herein, the descramblers  7004  and  7007  may be included in any one of or both of the module and the receiving system. If the first and second descramblers  7004  and  7007  are provided inside the receiving system, it is advantageous to have the transmitting system (i.e., at least any one of a service provider and a broadcast station) scramble the corresponding data using the same scrambling method. 
     Alternatively, if the first and second descramblers  7004  and  7007  are provided in the external module, it is advantageous to have each transmitting system scramble the corresponding data using different scrambling methods. In this case, the receiving system is not required to be provided with the descrambling algorithm corresponding to each transmitting system. Therefore, the structure and size of receiving system may be simplified and more compact. Accordingly, in this case, the external module itself may be able to provide CA functions, which are uniquely and only provided by each transmitting systems, and functions related to each service that is to be provided to the user. The common interface enables the various external modules and the system manager  7015 , which is included in the receiving system, to communicate with one another by a single communication method. Furthermore, since the receiving system may be operated by being connected with at least one or more modules providing different services, the receiving system may be connected to a plurality of modules and controllers. 
     In order to maintain successful communication between the receiving system and the external module, the common interface protocol includes a function of periodically checking the status of the opposite correspondent. By using this function, the receiving system and the external module is capable of managing the status of each opposite correspondent. This function also reports the user or the transmitting system of any malfunction that may occur in any one of the receiving system and the external module and attempts the recovery of the malfunction. 
     In yet another example, the authentication process may be performed through software. More specifically, when a memory card having CAS software downloaded, for example, and stored therein in advanced is inserted in the receiving system, the receiving system receives and loads the CAS software from the memory card so as to perform the authentication process. In this example, the CAS software is read out from the memory card and stored in the first memory  7012  of the receiving system. Thereafter, the CAS software is operated in the receiving system as an application program. According to an embodiment of the present invention, the CAS software is mounted on (or stored) in a middleware platform and, then executed. A Java middleware will be given as an example of the middleware included in the present invention. Herein, the CAS software should at least include information required for the authentication process and also information required for the descrambling process. 
     Therefore, the authentication unit  7008  performs authentication processes between the transmitting system and the receiving system and also between the receiving system and the memory card. At this point, as described above, the memory card should be entitled to receive the corresponding data and should include information on a normal receiving system that can be authenticated. For example, information on the receiving system may include a unique number, such as a standardized serial number of the corresponding receiving system. Accordingly, the authentication unit  7008  compares the standardized serial number included in the memory card with the unique information of the receiving system, thereby performing the authentication process between the receiving system and the memory card. 
     If the CAS software is first executed in the Java middleware base, then the authentication between the receiving system and the memory card is performed. For example, when the unique number of the receiving system stored in the memory card conforms to the unique number of the receiving system read from the system manager  7015 , then the memory card is verified and determined to be a normal memory card that may be used in the receiving system. At this point, the CAS software may either be installed in the first memory  7012  upon the shipping of the present invention, or be downloaded to the first memory  7012  from the transmitting system or the module or memory card, as described above. Herein, the descrambling function may be operated by the data broadcasting application manger  7016  as an application program. 
     Thereafter, the CAS software parses the EMM/ECM packets outputted from the demultiplexer  7003 , so as to verify whether the receiving system is entitled to receive the corresponding data, thereby obtaining the information required for descrambling (i.e., the CW) and providing the obtained CW to the descramblers  7004  and  7007 . More specifically, the CAS software operating in the Java middleware platform first reads out the unique (or serial) number of the receiving system from the corresponding receiving system and compares it with the unique number of the receiving system transmitted through the EMM, thereby verifying whether the receiving system is entitled to receive the corresponding data. Once the receiving entitlement of the receiving system is verified, the corresponding broadcasting service information transmitted to the ECM and the entitlement of receiving the corresponding broadcasting service are used to verify whether the receiving system is entitled to receive the corresponding broadcasting service. Once the receiving system is verified to be entitled to receive the corresponding broadcasting service, the authentication key transmitted to the EMM is used to decode (or decipher) the encoded CW, which is transmitted to the ECM, thereby transmitting the decoded CW to the descramblers  7004  and  7007 . Each of the descramblers  7004  and  7007  uses the CW to descramble the broadcasting service. 
     Meanwhile, the CAS software stored in the memory card may be expanded in accordance with the paid service which the broadcast station is to provide. Additionally, the CAS software may also include other additional information other than the information associated with the authentication and descrambling. Furthermore, the receiving system may download the CAS software from the transmitting system so as to upgrade (or update) the CAS software originally stored in the memory card. As described above, regardless of the type of broadcast receiving system, as long as an external memory interface is provided, the present invention may embody a CAS system that can meet the requirements of all types of memory card that may be detachably fixed to the receiving system. Thus, the present invention may realize maximum performance of the receiving system with minimum fabrication cost, wherein the receiving system may receive paid broadcasting contents such as broadcast programs, thereby acknowledging and regarding the variety of the receiving system. Moreover, since only the minimum application program interface is required to be embodied in the embodiment of the present invention, the fabrication cost may be minimized, thereby eliminating the manufacturer&#39;s dependence on CAS manufacturers. Accordingly, fabrication costs of CAS equipments and management systems may also be minimized. 
     Meanwhile, the descramblers  7004  and  7007  may be included in the module either in the form of hardware or in the form of software. In this case, the scrambled data that being received are descrambled by the module and then demodulated. Also, if the scrambled data that are being received are stored in the third memory  7018 , the received data may be descrambled and then stored, or stored in the memory at the point of being received and then descrambled later on prior to being played (or reproduced). Thereafter, in case scramble/descramble algorithms are provided in the storage controller  7017 , the storage controller  7017  scrambles the data that are being received once again and then stores the re-scrambled data to the third memory  7018 . 
     In yet another example, the descrambled broadcasting contents (transmission of which being restricted) are transmitted through the broadcasting network. Also, information associated with the authentication and descrambling of data in order to disable the receiving restrictions of the corresponding data are transmitted and/or received through the telecommunications module  7019 . Thus, the receiving system is able to perform reciprocal (or two-way) communication. The receiving system may either transmit data to the telecommunication module within the transmitting system or be provided with the data from the telecommunication module within the transmitting system. Herein, the data correspond to broadcasting data that are desired to be transmitted to or from the transmitting system, and also unique information (i.e., identification information) such as a serial number of the receiving system or MAC address. 
     The telecommunication module  7019  included in the receiving system provides a protocol required for performing reciprocal (or two-way) communication between the receiving system, which does not support the reciprocal communication function, and the telecommunication module included in the transmitting system. Furthermore, the receiving system configures a protocol data unit (PDU) using a tag-length-value (TLV) coding method including the data that are to be transmitted and the unique information (or ID information). Herein, the tag field includes indexing of the corresponding PDU. The length field includes the length of the value field. And, the value field includes the actual data that are to be transmitted and the unique number (e.g., identification number) of the receiving system. 
     The receiving system may configure a platform that is equipped with the Java platform and that is operated after downloading the Java application of the transmitting system to the receiving system through the network. In this case, a structure of downloading the PDU including the tag field arbitrarily defined by the transmitting system from a storage means included in the receiving system and then transmitting the downloaded PDU to the telecommunication module  7019  may also be configured. Also, the PDU may be configured in the Java application of the receiving system and then outputted to the telecommunication module  7019 . The PDU may also be configured by transmitting the tag value, the actual data that are to be transmitted, the unique information of the corresponding receiving system from the Java application and by performing the TLV coding process in the receiving system. This structure is advantageous in that the firmware of the receiving system is not required to be changed even if the data (or application) desired by the transmitting system is added. 
     The telecommunication module within the transmitting system either transmits the PDU received from the receiving system through a wireless data network or configures the data received through the network into a PDU which is transmitted to the host. At this point, when configuring the PDU that is to be transmitted to the host, the telecommunication module within the transmitting end may include unique information (e.g., IP address) of the transmitting system which is located in a remote location. Additionally, in receiving and transmitting data through the wireless data network, the receiving system may be provided with a common interface, and also provided with a WAP, CDMA 1×EV-DO, which can be connected through a mobile telecommunication base station, such as CDMA and GSM, and also provided with a wireless LAN, mobile internet, WiBro, WiMax, which can be connected through an access point. The above-described receiving system corresponds to the system that is not equipped with a telecommunication function. However, a receiving system equipped with telecommunication function does not require the telecommunication module  7019 . 
     The broadcasting data being transmitted and received through the above-described wireless data network may include data required for performing the function of limiting data reception. Meanwhile, the demultiplexer  7003  receives either the real-time data outputted from the demodulating unit  7002  or the data read from the third memory  7018 , thereby performing demultiplexing. In this embodiment of the present invention, the demultiplexer  7003  performs demultiplexing on the enhanced data packet. Similar process steps have already been described earlier in the description of the present invention. Therefore, a detailed of the process of demultiplexing the enhanced data will be omitted for simplicity. 
     The first descrambler  7004  receives the demultiplexed signals from the demultiplexer  7003  and then descrambles the received signals. At this point, the first descrambler  7004  may receive the authentication result received from the authentication unit  7008  and other data required for the descrambling process, so as to perform the descrambling process. The audio decoder  7005  and the video decoder  7006  receive the signals descrambled by the first descrambler  7004 , which are then decoded and outputted. Alternatively, if the first descrambler  7004  did not perform the descrambling process, then the audio decoder  7005  and the video decoder  7006  directly decode and output the received signals. In this case, the decoded signals are received and then descrambled by the second descrambler  7007  and processed accordingly. 
     Other Embodiment of Transmitting System 
     In other embodiment of a transmitting system, it is intended to transmit mobile service data based on Internet Protocol (IP). 
     In the embodiment of the present invention, main service data are transmitted based on MPEG-2, and mobile service data are transmitted based on IP. 
       FIG. 73  illustrates an example of a protocol stack for providing a main service based on MPEG-2. 
     In  FIG. 73 , A/V streamings for a main service are elementary streams (ES), and are packetized in a packetized elementary stream (PES). The PES packets are again packetized in MPEG-2 TS of 188-byte unit. Signaling information such as PSI/PSIP data, which includes configuration information of each service, is sectioned. In other words, signaling information such as the PSI/PSIP tables is divided into a plurality of sections. For example, VCT within the PSIP can be divided into 256 sections. At this time, although one section can include several kinds of virtual channel information, one kind of virtual channel information is not divided into two or more sections. Hereinafter, a table type of signaling information will be referred to as program table information or program table in the present invention. 
     Data broadcasting is sectioned by a digital storage media-command and control (DSM-CC) scheme. The DSM-CC section is again packetized in MPEG-2 TS of 188-byte unit. The IP datagram for IP multicast is encapsulated in a DSM-CC addressable section structure, and the encapsulated DSM-CC addressable section is again packetized in MPEG-2 TS of 188-byte unit. The TS packetization is performed in a network layer. 
     The PES type TS packets or the section type TS packets packetized as above are modulated in a physical layer in accordance with a previously determined transmission scheme, for example, VSB transmission scheme, and then transmitted to the receiving system. In other words, the physical layer provides a main service using the VSB transmission scheme, and corresponds to a first layer of an open systems interconnection (OSI) model. 
       FIG. 74  illustrates an example of a protocol stack for a mobile service based on IP.  FIG. 74  is an example of a protocol stack for a mobile service through encapsulated IP datagrams. 
     In other words, in  FIG. 74 , signaling information for a mobile service is encapsulated in a section structure such as PSI/PSIP. A/V streaming for a mobile service is packetized in IP layer in accordance with a real time protocol (RTP) scheme as shown in (a) of  FIG. 75 . The RTP packets are again packetized in accordance with a user datagram protocol (UDP) scheme, and the RTP/UDP packets are again packetized in accordance with the IP scheme to obtain RTP/UDP/IP packet data. For convenience of description, the packetized RTP/UDP/IP packet data will be referred to as IP datagram in the present invention. 
     The IP datagram is encapsulated in a DSM-CC addressable section structure, and the encapsulated DSM-CC addressable section is again packetized in MPEG-2 TS of 188-byte unit as shown in (b) of  FIG. 75 . 
     (a) and (b) of  FIG. 75  illustrate examples of TS packet mapping of the IP datagram through the DSM-CC addressable section. 
     In other words, one addressable section is additionally provided with an RTP header, a UDP header, an IP header, and an addressable section header at the front of A/V data, and is also additionally provided with stuffing data (optional), and CRC at the rear of A/V data, as shown in (a) of  FIG. 75 . This addressable section is divided in a fixed length, i.e., 184-byte unit, as shown in (b) of  FIG. 75 , and is additionally provided with a TS packet header of 4 bytes to constitute TS packets of 188 bytes. 
     In  FIG. 74 , file/data download is packetized in accordance with a file transfer protocol scheme, and the file transfer protocol packet is again packetized in accordance with an asynchronous layered coding/layered coding transport (ALC/LCT) scheme. The ALC/LCT packet is again packetized in accordance with a UDP scheme, and the ALC/LCT/UDP packet is again packetized in accordance with an IP scheme to obtain ALC/LCT/UDP/IP packet data. For convenience of description, the packetized ALC/LCT/UDP/IP packet data will be referred to as the IP datagram in the present invention. The IP datagram is encapsulated in a DSM-CC addressable section structure, and the encapsulated DSM-CC addressable section is again packetized in MPEG-2 TS of 188-byte unit. 
     Furthermore, the UDP multicast is packetized in accordance with the UDP scheme, and the UDP packet is again packetized in accordance with the IP scheme. The IP datagram packetized in accordance with the IP scheme is encapsulated in a DSM-CC addressable section structure, and the encapsulated DSM-CC addressable section is again packetized in MPEG-2 TS of 188-byte unit. 
     The MPEG-2 TS packets are modulated in a mobile physical layer in accordance with a previously determined transmission scheme, for example, VSB transmission scheme, and then transmitted to the receiving system. 
     If the IP based mobile service is provided as shown in  FIG. 74 , all the data can be divided into the IP datagram and program table information of a section format (i.e., the PSI/PSIP data). 
     Since the IP datagram and the program table information such as the PSI/PSIP data are transmitted in MPEG-2 TS format, they may be accompanied with overhead. In other words, information of the TS packet header included per TS packet may act as overhead. 
     In order to solve this overhead,  FIG. 76  illustrates another example of a protocol stack for a mobile service based on IP. 
     In  FIG. 76 , an adaptation layer is included between the IP layer and the physical layer, so that the IP datagram and program table information (i.e., the PSI/PSIP data) can be transmitted without MPEG-2 TS format. Since an upper layer including the IP layer of  FIG. 76  has the same structure as that of  FIG. 75 , its detailed description will be omitted. 
     In  FIG. 76 , signaling information for a mobile service is encapsulated in program table information structure such as a PSI/PSIP section, and will be referred to as PSI/PSIP data or program table information for convenience of description. A/V streaming for a mobile service is additionally provided with an RTP header, a UDP header, and an IP header, sequentially, as shown in  FIG. 77 , so as to constitute one IP datagram. As another embodiment of the present invention, a transmission parameter of signaling information for a mobile service may be constituted by the IP datagram. 
     The adaptation layer is a data link layer which divides the IP datagram from the program table information and connects the divided data with each other to allow the upper layer to process the data. 
     In other words, the adaptation layer generates RS frame, which includes program table information, IP datagram, and identification information to divide program table information and the IP datagram. 
       FIG. 78  illustrates another example of the RS frame generated in the adaptation layer according to the embodiment of the present invention. 
     In one RS frame, a length of column (i.e., the number of rows) is 187 bytes, and a length of row (i.e., the number of columns) is N bytes, wherein the N may depend on signaling information such as a transmission parameter. The transmission parameter (or TPC information) can include sub-frame information, slot information, parade related information (for example, parade ID, parade repetition period, etc.), data group information with sub-frame, RS frame mode information, RS code mode information, SCCC block information, SCCC outer code mode information, FIC version information, etc. 
     Also, the N may depend on regions within a data group to which the RS frame will be allocated. This is because that the probability of error is reduced in the order of A&gt;B&gt;C&gt;D within the data group. 
     According to the embodiment of the present invention, the N is equal to or greater than 187. In other words, the RS frame of  FIG. 78  has a byte size of N(row)*187(column). 
     For convenience of description, each row of the N bytes will be referred to as MPH service data packet in the present invention. The MPH service data packet can be comprised of MPH header of 2 bytes and payload of N−2 bytes. In this case, the MPH header region of 2 bytes is allocated exemplarily. Since the MPH header region may depend on a designer, the present invention is not limited to the above example. 
     The RS frame is generated by program table information of N−2(row)*187(column) byte size and/or IP datagram. Also, one RS frame can include program table information and IP datagram corresponding to one or more mobile services. For example, program table information and IP datagram of two kinds of mobile services such as news and stock can be included in one RS frame. 
     The program table information or the IP datagram is allocated to payload within the MPH service data packet constituting the RS frame. 
     At this time, according to the embodiment of the present invention, the program table information and the IP datagram are not together allocated to one MPH service data packet. 
     In  FIG. 78 , the program table information are allocated to two MPH service data packets within one RS frame, and the IP datagram is allocated to the other MPH service data packets. 
     In  FIG. 78 , the position of the MPH service data packets within one RS frame, to which the program table information such as the PSI/PSIP data are allocated, and the number of the MPH service data packets are illustrated exemplarily. Since the position of the MPH service data packets and the number of the MPH service data packets may depend on a designer, the present invention will not be limited to the above example. 
     When the program table information or the IP datagram is allocated to one MPH service data packet, if the corresponding MPH service data packet including the MPH header does not reach N bytes, stuffing bytes can be allocated to the other part. For example, after the program table information are allocated to one MPH service data packet, the length of the MPH service data packet including the MPH header is N−20 bytes, stuffing bytes can be allocated to the other 20 bytes. 
     Also, the program table information can include a plurality of tables, for example, PMT, PAT, VCT, MGT, RRT, ETT, and EIT data. The plurality of table data within the program table information may sequentially be allocated to one MPH service data packet in a predetermined order as shown in  FIG. 78 . Alternatively, the data corresponding to one table may be allocated to one MPH service data packet. 
       FIG. 79  illustrates an example of fields allocated to the MPH header region within the MPH service data packet according to the embodiment of the present invention. Examples of the fields include a type_indicator field, an error_indicator field, a priority field (or stuff indicator), and a pointer field. 
     The type_indicator field can allocate 3 bits, for example, and expresses a type of data allocated to payload within the corresponding MPH service data packet. In other words, the type_indicator field indicates whether data of the payload is IP datagram or signaling information such as program table information. 
     At this time, each data type constitutes one logical channel. In the logical channel which transmits the IP datagram, several mobile services are multiplexed and then transmitted. Each mobile service undergoes demultiplexing in the IP layer. 
     The error_indicator field can allocate 1 bit, for example, and expresses whether the corresponding MPH service data packet has an error. For example, if the error_indicator field has a value of 0, it means that there is no error in the corresponding MPH service data packet. If the error_indicator field has a value of 1, it means that there may be an error in the corresponding MPH service data packet. 
     The priority field can allocate 1 bit, for example, and expresses region information within a data group to which data of payload within the corresponding MPH service data packet will be inserted. For example, if the priority field has a value of 1, it means that the data of payload within the corresponding MPH service data packet is data to be inserted to A/B region within the data group. If the priority field has a value of 0, it means that the data of payload within the corresponding MPH service data packet is data to be inserted to C/D region within the data group. The stuff indicator instead of the priority field can be assigned. The stuff indicator field may indicate whether Stuff byte exists in the payload of MPH service data packet. 
     The pointer field can allocate 11 bits, for example, and expresses position information where new data (i.e., new signaling information or new IP datagram) starts in the corresponding MPH service data packet. 
     For example, if IP datagram  1  and IP datagram  2  are allocated to the first MPH service data packet within the RS frame as shown in  FIG. 78 , the pointer field value expresses the start position of the IP datagram  2  within the MPH service data packet. 
     Also, if there is no new data in the corresponding MPH service data packet, the corresponding field value is expressed as a maximum value exemplarily. In the present invention, since 11 bits are allocated to the pointer field, if 2047 is expressed as the pointer field value, it means that there is no new data in the packet. 
     It is to be understood that the order, the position, and the meaning of the field allocated to the header within the MPH service data packet illustrated in  FIG. 79  are exemplarily illustrated for understanding of the present invention. Since the order, the position and the meaning of the field allocated to the header within the MPH service data packet and the number of additionally allocated fields can easily be modified by those skilled in the art, the present invention will not be limited to the above example. 
       FIG. 80(a)  and  FIG. 80(b)  illustrate another examples of an RS frame according to the embodiment of the present invention. (a) of  FIG. 80  illustrates an example of RS frame to be allocated to A/B region within the data group, and (b) of  FIG. 80  illustrates an example of RS frame to be allocated to C/D region within the data group. 
     In (a) and (b) of  FIG. 80 , a column length (i.e., the number of rows) of the RS frame to be allocated to the A/B region and a column length (i.e., the number of rows) of the RS frame to be allocated to the C/D region are 187 equally. However, row lengths (i.e, the number of columns) may be different from each other. In the present invention, the data group is exemplarily divided into the regions A, B, C and D depending on interference level of the main service data. Interference of the main service data is reduced in the order of the A&gt;B&gt;C&gt;D regions. If interference of the main service data becomes smaller, receiving performance becomes better. 
     In the present invention, the RS frame to be allocated to the A/B region within the data group will be referred to as primary RS frame, and the RS frame to be allocated to the C/D region within the data group will be referred to as secondary RS frame. 
     According to the embodiment of the present invention, when the row length of the primary RS frame to be allocated to the A/B region within the data group is N1 bytes and the row length of the secondary RS frame to be allocated to the C/D region within the data group is N2 bytes, a condition of N1&gt;N2 is satisfied. In this case, N1 and N2 can be varied depending on the transmission parameter or a region of the data group, to which the corresponding RS frame will be transmitted. 
     For convenience of the description, each row of the N1 and N2 bytes will be referred to as the MPH service data packet. The MPH service data packet within the RS frame to be allocated to the A/B region within the data group can be comprised of MPH header of 2 bytes and payload of N1−2 bytes. Also, the MPH service data packet within the RS frame to be allocated to the C/D region within the data group can be comprised of MPH header of 2 bytes and payload of N2−2 bytes. 
     In this case, the MPH header of 2 bytes is only example. Since the allocation bytes of the MPH header can be varied depending on a designer, the present invention will not be limited to the above example. The order, position, and meaning of the fields allocated to the MPH header of each MPH service data packet in  FIG. 79  can be applied to those of (a) and (b) of  FIG. 80 . 
     In the present invention, the primary RS frame for the A/B region and the secondary RS frame for the C/D region within the data group include at least one of the program table information and the IP datagram. Also, one RS frame can include IP datagram corresponding to one or more mobile services. 
     The primary RS frame in (a) of  FIG. 80  exemplarily includes program table information and IP datagram for two kinds of mobile services. On the other hand, the secondary RS frame in  FIG. 80(b)  exemplarily includes IP datagram for two kinds of mobile services. 
     In (a) of  FIG. 80 , program table information for two kinds of mobile services are allocated to two MPH service data packets within one RS frame, and IP datagram for two kinds of mobile services is allocated to the other MPH service data packet. 
     The position of the MPH service data packet within the RS frame, to which the program table information are allocated, and the number of the MPH service data packets are exemplarily illustrated in (a) of  FIG. 80 . Since they can be varied depending on a designer, the present invention will not be limited to the above example. 
     Corresponding parts of  FIG. 78  can be applied to the other parts, which are not described in (a) and (b) of  FIG. 80 . 
     In the embodiment of the present invention, the RS frame of  FIG. 78  or  FIG. 80(a)  and  FIG. 80(b)  is generated in the MPH frame encoder  301  of the pre-processor  230 . 
     The MPH service data packet within the RS frame as shown in  FIG. 78  or (a) and (b) of  FIG. 80  is again extended to a plurality of MPH service data packets. 
       FIG. 81(a)  to  FIG. 81(f)  illustrate examples of a procedure of extending the MPH service data packet to a plurality of MPH service data packets. 
     In (a) to (f) of  FIG. 81 , N MPH service data packets within the RS frame having N(row)*187(column) byte size are exemplarily extended to 2N MPH service data packets. 
     If the RS frame having N(row)*187(column) byte size is divided into 187-byte unit in a row direction as shown in (a) of  FIG. 81 , one RS frame is divided into N temporary packets of 187 bytes as shown in (b) of  FIG. 81 . In other words, If N temporary packets of 187 bytes divided as shown in (b) of  FIG. 81  are sequentially collected, the RS frame as shown in (a) of  FIG. 81  is obtained. 
     The temporary packets of 187 bytes divided as shown in (b) of  FIG. 81  are again divided into a plurality of temporary packets. At this time, when the temporary packets of 187 bytes are divided into a plurality of packets, the plurality of packets may have the same size or different sizes. 
     In (c) of  FIG. 81 , the temporary packets of 187 bytes are exemplarily divided into temporary packets of 102 bytes and temporary packets of 85 bytes. This is only one example, and the scope of the present invention will not be limited to the above numerical values. 
     For convenience of the description in the present invention, the temporary packets of 102 bytes will be referred to as first temporary packets, and the temporary packets of 85 bytes will be referred to as second temporary packets. 
     In the present invention, as shown in (d) of  FIG. 81 , a temporary header mph_stl_header of 8 bytes is additionally provided at the front of the first temporary packets, and dummy bytes of 74 bytes are additionally provided at the rear of the first temporary packets, whereby the first temporary packets of 184 bytes are obtained. Also, a temporary header of 8 bytes is additionally provided at the front of the second temporary packets, and dummy bytes of 91 bytes are additionally provided at the rear of the second temporary packets, whereby the second temporary packets of 184 bytes are obtained. 
     In other words, one temporary packet of 187 bytes is extended to two temporary packets of 184 bytes. 
       FIG. 82  illustrates an example of fields allocated to header regions of the first and second temporary packets according to the present invention. The fields can include parade_id field, region_id field, pkt_number field, max_pkt_number field, parade_size field, sccc_mode field, and rs_mode field. 
     The parade_id field can allocate 8 bits, for example, and represents unique identifier (id) of parade to which the corresponding RS frame will be transmitted. 
     The region_id field can allocate 1 bit, for example, and represents information of a region to which the corresponding RS frame will be transmitted. For example, if the region_id field has a value of ‘0’, the RS frame is allocated to the A/B region. If the region_id field has a value of ‘1’, the RS frame is allocated to the C/D region. 
     A reserved field of 7 bits can be allocated next to the region_id field for future use. 
     The pkt_number field can allocate 16 bits, for example, and represents the order of 184-byte packets extended to two time as shown in (d) of  FIG. 81 . For example, the pkt_number field has a value of 0 to max_packet number (for example, 2N−1). At this time, the pkt_number field value of even numbers including 0 is expressed in the packets extended from 102 bytes, and the pkt_number field value of odd numbers is expressed in the packets extended from 85 bytes. 
     The max_packet_number field can allocate 16 bits, for example, and represents a maximum value where the pkt_number field value will reach in the corresponding RS frame. For example, 2N−1 can be expressed as the max_packet_number field value. 
     The parade_size field can allocate 5 bits, for example, and represents one parade size. 
     The sccc_mode field can allocate 3 bits, for example, and represents a coding rate of each region within the data group. For example, the SCCC outer code mode within the TPC information of  FIG. 31  can be expressed as it is. 
     The rs_mode field can allocate 4 bits, for example, and represents RS code mode of each region within the data group. 
     A reserved field of 6 bits can be allocated next to the rs_mode field for future use. 
     The order, position, and meaning of the fields allocated to the temporary header within the extended temporary packets illustrated in  FIG. 82  are only examples for understanding of the present invention. Since the order, position, and meaning of the fields allocated to the temporary header and the number of additionally allocated fields can easily be varied depending on a designer, the present invention will not be limited to the above examples. 
     As described above, if the temporary header of 8 bytes and dummy bytes of 74 bytes or 91 bytes are added to the first and second temporary packets, the RS frame of N(row)*187(column) bytes can be extended to 2N packets of 184 bytes as shown in (e) of  FIG. 81 . Namely, the RS frame of N(row)*187(column) bytes is extended to RS frame of 184 (row)*2N(column) bytes. 
     A MPEG header of 4 bytes as shown in  FIG. 81(f)  in added in each 184-byte packet within the extended RS frame as shown in  FIG. 81(e)  to configure 188-byte TS packet. Namely, the RS frame of 184(row)*2N(column) bytes is again extended to RS frame of 188(row)*2N(column) bytes. 
     According to the embodiment of the present invention, the generation of the RS frame illustrated in  FIG. 78  to  FIG. 82  and extension of each packet within the generated RS frame are performed by a service multiplexer. 
       FIG. 83  illustrates another example of a service multiplexer according to the embodiment of the present invention. 
     The service multiplexer of  FIG. 83  is located in a studio of each broadcasting station, and can include a PSI/PSIP generator  8010 , an RS frame generator  8020 , a studio-to-transmitter link (STL) adaptor  8030 , and a transport multiplexer  8040 . 
     The transport multiplexer  8040  can include a main service multiplexer  8041 , and a transport stream (TS) packet multiplexer  8042 . 
     The RS frame generator  8020  corresponds to the adaptation layer of  FIG. 76 , and receives IP datagram and program table information of at least one kind of mobile service to constitute the RS frame as shown in  FIG. 78  or (a) and (b) of  FIG. 80 . 
     For example, in case of  FIG. 78 , the RS frame is the same as that 187 MPH service data packets are comprised of MPH header of 2 bytes and payload of N−2 bytes. 
     The RS frame generated by the RS frame generator  8020  is input to the STL adaptor  8030 . 
     The STL adaptor  8030  performs the procedure of (a) to (f) of  FIG. 81  for the RS frame output from the RS frame generator  8020  to extend  187  packets of N bytes to 2N TS packets of 188 bytes. 
     For convenience of the description, the TS packets of 188 bytes extended from the STL adaptor  8030  will be referred to as the mobile service data packets in the present invention. 
     Furthermore, at least one kind of main service data and the PSI/PSIP data generated for the main service by the PSI/PSIP generator  8010  are input to the main service multiplexer  8041  of the transport multiplexer  8040 . The main service multiplexer  8041  respectively encapsulates the input main service data and PSI/PSIP data in MPEG-2 TS packet format, and multiplexes the TS packets to output the multiplexed TS packets to the TS packet multiplexer  8042 . For convenience of the description, the data packets output from the main service multiplexer  8041  will be referred to as the main service data packets. 
     At this time, in order that the transmitter identifies the main service data packets from the mobile service data packets to process them, identification information is required. A value previously determined by agreement between the transmitter and the receiver may be used as the identification information, or separate data may be used as the identification information. Also, a value obtained by modifying a value of a previously set position within the corresponding data packet may be used as the identification information. 
     According to the embodiment of the present invention, different packet identifiers (PIDs) can respectively be allocated to the main service data packets and the mobile service data packets. 
     To this end, when the STL adaptor  8030  adds the MPEG header per packet of 184 bytes, PID agreed between the STL adaptor and the transmitter (exciter) can be set in the MPEG header. 
     According to another embodiment of the present invention, the main service data packets can be identified from the mobile service data packets by a synchronization byte value of the mobile service data packets, which is obtained by modifying synchronization bytes within the MPEG header of the mobile service data packets. 
     Since anything that can identify the main service data packets from the mobile service data packets can be used as the identification information, the present invention will not be limited to the above embodiments. 
     Meanwhile, the transport multiplexer used in the existing digital broadcasting system can be used as the transport multiplexer  8040 . Namely, in order to multiplex the mobile service data with the main service data and transmit them, a data rate of the main service is limited to a data rate of M Mbps, and L Mbps corresponding to the other data rate is allocated to the mobile service output from the STL adaptor  8030 . In this case, the existing transport multiplexer can be used as it is without any change. Then, the TS packet multiplexer  8042  multiplexes the main service data packets output from the main service multiplexer  8041  at a data rate of M Mbps with the mobile service data packets output from the STL adaptor  8030  at a data rate of L Mbps and transmits the multiplexed data packets to the transmitter. 
     However, there may be a case where the output data rate of the TS packet multiplexer  8042  does not reach 19.39 Mbps even though the output data rate L Mbps of the STL adaptor  8030  and the output data rate M Mbps of the main service multiplexer  8041  are added to each other. 
     In this case, the TS packet multiplexer  8042  receives null data packets of a data rate of (19.39-M-L) Mbps, multiplexes the null data packets with the main service data packets and the mobile service data packets, and output the multiplexed data packets. Even in this case, the identification information is included in the null data packets so that the transmitter can identify the null data packets. 
     In this case, the output data rate of the TS packet multiplexer  8042  can be adjusted to 19.39 Mbps. 
     In other words, since the mobile service data are extended by additional encoding in the transmitter, even though the STL adaptor  8030  allocates 187 bytes to two TS packets to obtain data of L Mbps, if the data rate of L Mbps is added to the output data rate of the main service multiplexer  8041 , the output data rate of the TS packet multiplexer  8042  may be smaller than 19.39 Mbps. In this case, the null data packets are added to the service data packets by the difference so that the output data rate of the TS packet multiplexer  8042  is adjusted to 19.39 Mbps. 
     In order that the transmitter can identify the main service data, the mobile service data, and the null data from one another, the service multiplexer can insert identification information. Since a method of inserting the identification information can refer to the service multiplexer of  FIG. 14 , its detailed description will be omitted. 
     As an example of the above transmitter, the transmitter of  FIG. 15  can be used. In this case, if the data packets are received from the service multiplexer, the demultiplexer  210  identifies whether the received data packets are the main service data packets, the mobile service data packets or the null data packets, by using the identification information (for example, PID within MPEG header) included in the corresponding data packets. 
     The null data packets identified by the demultiplexer  210  are disused without being processed, and the main service data packets are output to the packet jitter mitigator  220 . Since the operation after the main service data packets are processed can refer to the transmitter of  FIG. 15 , its detailed description will be omitted. 
     The mobile service data packets identified by the demultiplexer  210  are input to the pre-processor  230 . 
     The pre-processor  230  performs an inverse procedure of the procedure of (a) to (f) in  FIG. 81  to constitute the RS frame as shown in  FIG. 78  or the RS frame as shown in (a) and (b) of  FIG. 80 . 
     For example, the pre-processor  230  removes the MPEG header of 4 bytes added to the mobile service data packets, and collects all the data having the pkt_number field value of 0 to max_pkt_number among the data of which the parade_id field value and the region_id field value of the MPH header added to the first and second temporary packets of 184-byte unit is the same, whereby one RS frame having N*187 byte size can be obtained as shown in (a) of  FIG. 81 . mph_stl_header and the dummy bytes are not included in the RS frame. At this time, transmission parameters required pre-processing/post-processing of the corresponding RS frame can be determined as parade related information of mph_stl_header. Also, the transmission parameters are transmitted to the receiving system by being included in the region previously set within the data group, or by being included in the field synchronization region. In this case, examples of the transmission parameters include sub-frame information, slot information, parade related information (for example, parade ID, parade repetition period, etc.), data group information with sub-frame, RS frame mode information, RS code mode information, SCCC block information, SCCC outer code mode information, and FIC version information. 
     The procedure of constituting the RS frame from the mobile service data packets can be performed before or after randomizing in the MPH frame encoder  301  of the pre-processor  230 . If the procedure of constituting the RS frame is performed before randomizing, randomizing can be performed in MPH service data packet unit of N bytes. If the procedure of constituting the RS frame is performed after randomizing, randomizing can be performed in mobile service data packet unit of 187 bytes. 
     According to the embodiment of the present invention, the MPH frame encoder  301  performs an inverse procedure of (a) to (f) of  FIG. 81  after data randomizing, whereby the RS frame as shown in  FIG. 78  or the RS frame as shown in (a) and (b) of  FIG. 80  is constituted. 
     If the RS frame is constituted as shown in  FIG. 78  or (a) and (b) of  FIG. 80 , the MPH frame encoder  301  performs at least one of error encoding and error detection encoding in RS frame unit. In this case, it is possible to disperse burst error that can occur due to change of electric wave environment while giving robustness to the mobile service data, thereby coping with the electric wave environment which is rapidly changed. 
     Furthermore, the MPH frame encoder  301  can constitute a super frame by collecting a plurality of RS frames, and can perform row permutation in a super frame unit. 
     Error correction encoding, error detection encoding, and row permutation, which are performed by the MPH frame encoder  301 , will refer to the aforementioned description, and their detailed description will be omitted. 
     Furthermore, each block within the pre-processor next to the MPH frame encoder  301  will refer to the aforementioned description, and its detailed description will be omitted. 
     The packet multiplexer  240  provided at the output of the pre-processor  230  and the packet jitter mitigator  220  multiplexes the mobile service data packets output from the pre-processor  230  and the main service data packets output from the packet jitter mitigator  220  in accordance with the multiplexing method which is previously defined, and outputs the multiplexed data to the data randomizer  251  of the post-processor  250 . 
       FIG. 84  illustrates an example of a multiplexing method of the packet multiplexer  240 . In other words,  FIG. 84  illustrates an example of multiplexing the main service data and the mobile service data so that three parades exist in one sub-frame and one or more mobile services are transmitted from each parade. 
     Each parade is repeated per parade_id to transmit the same mobile service. At this time, this transmission path will be referred to as a parade in the present invention. In other words, one or more parades are temporally multiplexed in one physical channel determined by frequency. 
     For example, mobile service  1  and mobile service  2  can be transmitted from parade alpha, mobile service  3  and mobile service  4  can be transmitted from parade beta, and mobile service  5  can be transmitted from parade gamma 
     At this time, each parade has information of unique ID (parade_id), parade repetition cycle, parade size (NoG), etc. This information can be transmitted to the receiving system by being included in a specific region of the RS frame as the transmission parameter (or TPC information). 
     At this time, one parade may transmit either one RS frame as shown in  FIG. 78  or two RS frames, i.e., a primary RS frame and a secondary RS frame as shown in (a) and (b) of  FIG. 80 . If one parade transmits both the primary RS frame and the secondary RS frame as shown in (a) and (b) of  FIG. 80 , the information that can identify the two RS frames can be transmitted to the receiving system by being included in the specific region of the RS frame as the transmission parameter (or TPC information). 
     The receiving system can control parade demultiplexing using this transmission parameter. In this case, region_id can be transmitted as information that can identify the primary RS frame from the secondary RS frame within one parade. The region_id represents information of a region within the data group to which data of the corresponding RS frame will be transmitted. For example, if the region_id has a value of 0, the data of the RS frame is allocated to the A/B region within the data group. If the region_id field has a value of 1, the RS frame is allocated to the C/D region. 
     At this time, the data of the A/B region and the data of the C/D region are those corresponding to the same parade, and a hierarchical mobile service or separate mobile services can be constituted using these data. According to the embodiment of the present invention, the A/B region and the C/D region within the data group are allocated to one parade. 
     The data of the RS frame transmitted to one parade constitute two logical channels through the MPH service data packets. One channel is for PSI/PSIP information, and the other channel is for IP datagram. The IP datagram is only transmitted to the channel for IP datagram. Multiplexing between components constituting the mobile service and multiplexing of the mobile services transmitted to one parade are performed in the IP layer. 
     The receiving system can identify each ensemble by combination of the parade_id and the region_id. The receiving system can also generate ensemble identifier (ensemble_id) by combination of the parade_id and the region_id. 
     In other words, one RS frame transmits one ensemble. The ensemble is a collection of services requiring the same quality of service (QoS) and encoded with the same FEC codes. 
     For example, if one parade is comprised of one RS frame, the ensemble, the RS frame, and the parade can be mapped at 1:1:1. For another example, if one parade is comprised of the primary RS frame and the secondary RS frame, the primary ensemble can be mapped with the primary RS frame and the secondary ensemble can be mapped with the secondary RS frame. In other words, the primary ensemble is transmitted through the primary RS frame of one parade, and the secondary ensemble is transmitted through the secondary RS frame of the parade. 
     Therefore, if the parade_id is combined with the region_id, the primary ensemble and the secondary ensemble can be identified from each other within one parade. 
     As another method of identifying the ensemble, at least one bit is added to the parade_id, for example, the left of the parade_id, so as to constitute ensemble_id, whereby each ensemble can be identified from another ensemble using the ensemble_id. In this case, the ensemble identifier (i.e., ensemble_id) includes parade identifier (i.e., parade_id). 
     For example, if the ensemble_id is for the primary Ensemble delivered through this Parade, the added MSB shall be ‘0’. Otherwise, if it is for the secondary Ensemble, the added MSB shall be ‘1’. 
     The receiving system can perform parade demultiplexing and power control using the parade_id. Also, the receiving system can perform demultiplexing of the ensemble by combining the parade_id with the region_id, or can perform demultiplexing of the ensemble using the ensemble_id obtained by adding one bit to the left of the parade_id. 
     In  FIG. 85 , an example of a procedure of temporally multiplexing three parades (parade alpha, parade beta, and parade gamma) in a physical channel determined by one frequency and multiplexing each parade with two logical channels (program table information channel and IP datagram channel) is illustrated using a protocol stack. 
     If the mobile service data are transmitted in a parade format as described above, the receiving system receives the mobile service data by turning on the power in only a slot to which parade of a desired mobile service is allocated and does not receive the data in the other slots by turning off the power in the other slots. As a result, power consumption of the receiving system can be reduced. This feature is especially useful for a portable receiver, which requires less power consumption. 
     For example, the mobile service which the receiving system desires to receive exists in parade alpha, the receiving system turns on the power in only the slot to which data of parade alpha is allocated as shown in (b) of  FIG. 84 . 
     Each block within the transmitter next to the packet multiplexer  240  will refer to the aforementioned description, and thus its detailed description will be omitted. 
       FIG. 86  is a block diagram illustrating another example of a receiving system according to the embodiment of the present invention. 
     The receiving system of  FIG. 86  can include a tuner  8301 , a demodulating unit  8302 , a demultiplexer  8303 , a program table buffer  8304 , a program table decoder  8305 , a program table database (DB)  8306 , an IP datagram buffer  8307 , an IP filter  8308 , a data handler  8309 , a middleware engine  8310 , an A/V decoder  8311 , an A/V post-processor  8312 , an application manager  8313 , and a user interface  8316 . The application manager  8313  can include a channel manager  8314  and a service manager  8315 . 
     In  FIG. 86 , a flow of data is marked with a solid line, and a flow of control is marked with a dotted line. 
     The tuner  8301  tunes a frequency of a specific channel through any one of antenna, cable, satellite, performs down-conversion for the tuned frequency into an intermediate frequency signal, and outputs the resultant signal to the demodulating unit  8302 . At this time, the tuner  8301  is controlled by the channel manager  8314  of the application manager  8313 , and reports the result and strength of a broadcasting signal of the tuned channel to the channel manager  8314 . Examples of the data received to the frequency of the specific channel include main service data, mobile service data, table data for decoding of the main service data and the mobile service data, and transmission parameter. 
     The demodulating unit  8302  performs VSB demodulation and channel equalization for the signal output from the tuner  8301 , and then outputs the resultant signal by dividing the signal into the main service data and the mobile service data. The aforementioned demodulating unit illustrated in  FIG. 36  can be used as an example of the demodulating unit  8302 . However, it is to be understood that the demodulating unit is only an example, and the scope of the present invention is not limited to the above example. 
     Meanwhile, the transmitter can transmit signaling information (or TPC information) including the transmission parameter to at least one of the field synchronization region, the base data region, and the mobile service data region. Accordingly, the demodulating unit  8302  can extract the transmission parameter from the field synchronization region, the base data region, and the mobile service data region. 
     The transmission parameter can include sub-frame information, slot information, parade related information (for example, parade ID, parade repetition period, etc.), data group information with sub-frame, RS frame mode information, RS code mode information, SCCC block information, SCCC outer code mode information, FIC version information, etc. 
     The demodulating unit  8302  performs block decoding, RS frame decoding, etc. using the extracted transmission parameter. For example, the demodulating unit  8302  performs block decoding of each region within the data group with reference to SCCC related information (for example, SCCC block information and SCCC outer code mode) within the transmission parameter, and performs RS frame decoding of each region within the data group with reference to RS related information (for example, RS code mode). 
     According to the embodiment of the present invention, the RS frame including the mobile service data demodulated by the demodulating unit  8302  is exemplarily input to the demultiplexer  8303 . 
     In other words, the data input to the demultiplexer  8303  has RS frame data format as shown in  FIG. 78  or (a) and (b) of  FIG. 80 . Namely, the RS frame decoder within the demodulating unit  8302  performs an inverse procedure of that performed in the RS frame encoder of the transmitting system to correct errors within the RS frame, and then outputs the resultant data to the data de-randomizer. The data de-randomizer performs de-randomizing for the error-corrected RS frame in the inverse procedure of the transmitting system. As a result, the data de-randomizer can obtain the RS frame as shown in  FIG. 78  or (a) and (b) of  FIG. 80 . 
     The demultiplexer  8303  may receive the RS frame of every parade, or may receive only the RS frame of the parade, which includes a desired mobile service, in accordance with the power control. For example, if the demultiplexer  8303  receives the RS frame of every parade, the demultiplexer  8303  can demultiplex the parade, which includes a desired mobile service, using the parade_id. 
     At this time, since one parade transmits one or two RS frames and one ensemble is mapped with one RS frame, if one parade transmits two RS frames, the demultiplexer  8303  needs to identify the RS frame, which transmits ensemble including mobile service data to be decoded, from the parade which includes a desired mobile service. That is, when the inputted one parade or the demultiplexed parade of a plurality of parades transmits both the primary ensemble and the secondary ensemble, the demultiplexer  8303  selects any one of the primary ensemble and the secondary ensemble. 
     For example, the demultiplexer  8303  can demultiplex the RS frame, which transmits ensemble including mobile service data to be decoded, by combining the parade_id with the region_id within the transmission parameter. For another example, the demultiplexer  8303  can demultiplex the RS frame, which transmits ensemble including mobile service data to be decoded, using the ensemble_id obtained by adding one bit to the left of the parade_id. 
     The demultiplexer  8303  identifies whether the corresponding MPH service data packets are program table information or IP datagram, with reference to the MPH header of the MPH service data packet within the RS frame corresponding to the ensemble, which includes mobile service data to be decoded. The identified program table information are output to the program table buffer  8304 , and the IP datagram is output to the IP datagram buffer  8307 . 
     The program table buffer  8304  temporarily stores the program table information of section type and then outputs the data to the program table decoder  8305 . 
     The program table decoder  8305  divides tables using table id and section length within the program table information and then parses the sections of the divided tables. Subsequently, the program table decoder  8305  stores the parsed result in the program table DB  8306 . For example, the program table decoder  8305  collects sections having the same table identifier table_id to constitute tables and then parses the tables to store the parsed result in the program table DB  8306 . 
     The IP datagram buffer  8307  temporarily stores the IP datagram and then outputs the IP datagram to the IP filter  8308 . 
     The IP filter  8308  filters the IP datagram only corresponding to a desired mobile service under the control of the service manager  8315  and outputs the filtered IP datagram to the A/V decoder  8311  and/or the data handler  8309 . If the transmission parameter (or TPC information) is transmitted to the IP datagram, the IP filter  8308  divides the IP datagram, which includes the transmission parameter, under the control of the service manager  8315 , and outputs the divided IP datagram to the corresponding block (for example, program table DB, application manager, data handler, etc.). 
     The A/V decoder  8311  divides audio and video from the IP datagram, decodes the divided audio and video through each decoding algorithm, and then outputs the decoded result to the A/V post-processor  8312 . For example, at least one of AC-3 decoding algorithm, MPEG 2 audio decoding algorithm, MPEG 4 audio decoding algorithm, AAC decoding algorithm, AAC+ decoding algorithm, HE AAC decoding algorithm, AAC SBR decoding algorithm, MPEG surround decoding algorithm, and BSAC decoding algorithm can be used as the audio decoding algorithm. At least one of MPEG 2 video decoding algorithm, MPEG 4 video decoding algorithm, H.264 decoding algorithm, SVC decoding algorithm, and VC-1 decoding algorithm can be used as the video decoding algorithm. 
     The data handler  8309  processes datagram required for data broadcasting from the IP datagram, and then allows the processed datagram to be mixed with A/V data through the middleware engine  8310 . According to the embodiment of the present invention, the middleware engine  8310  is a JAVA middleware engine. 
     The application manager  8313  receives key input of a TV viewer through the user interface (UI) and responds to the viewer&#39;s request through the graphic user interface (GUI) on the TV screen. Also, the application manager  8313  stores and recovers GUI control of the TV, user request, and TV system state in a memory (for example, NVRAM or Flash). 
     Also, the application manager  8313  receives parade related information, for example, parade_id from the demodulating unit  8302  or the IP filter  8308  and controls the demultiplexer  8303  to select the RS frame of the parade channel where a desired mobile service exists. Also, the application manager  8313  receives parade_id and region_id or ensemble_id from the demodulating unit  8302  or the IP filter  8308  and controls the demultiplexer  8303  to select the RS frame of ensemble including mobile service data to be decoded from the parade. The application manager  8313  controls the channel manager  8314  to perform channel related operation (channel map management and operation of program table decoder). 
     The channel manager  8314  manages a physical channel map and a logical channel map, and responds to the viewer&#39;s channel request by controlling the tuner  8301  and the program table decoder  8305 . Also, the channel manager  8314  requests the program table decoder  8305  to parse channel related table to be tuned and receives the result. Further, the channel manager  8314  updates the channel map based on the result, and transfers information of a desired mobile service to the service manager  8316  so that the service manager  8316  can control the IP filter  8308 . 
     The service manager  8316  takes IP datagram only corresponding to the user&#39;s desired mobile service from the IP datagram buffer  8307 , and transmits the IP datagram to the application layer. In this case, the service manager  8316  divides components (for example, audio and video streams) of the mobile service from the corresponding IP datagram and outputs the divided components to the A/V decoder  8311 . In other words, the IP layer demultiplexes audio and video streams within the IP datagram. 
       FIG. 87  illustrates an example of a procedure of identifying whether the MPH service data packet within the RS frame is IP datagram or program table information, through the demultiplexer  8303 . 
     In other words, the demultiplexer  8303  receives one MPH service data packet within the RS frame (step  9101 ), and parses type_indicator field of the MPH header within the corresponding MPH service data packet (step  9102 ). If the type_indicator field value is parsed, it is possible to identify whether the corresponding MPH service data packet is data constituting program table information section or IP datagram. 
     If it is determined that the corresponding MPH service data packet is data constituting program table information section in step  9103 , the current step proceeds to  FIG. 89  to output data included in payload within the corresponding MPH service data packet to the program table buffer  8304  (step  9106 ). 
     If it is determined that the corresponding MPH service data packet is IP datagram in step  9104 , the current step proceeds to  FIG. 88  to output data included in payload within the corresponding MPH service data packet to the IP datagram buffer  8307  (step  9107 ). If it is determined that the corresponding MPH service data packet is neither data constituting program table information section or nor IP datagram in step  9104 , since it is reserved data for extension of the system, the demultiplexer disuses the corresponding MPH service data packet and receives next packet (steps  9105  and  9108 ). 
       FIG. 88  is a flow chart performed when the type_indicator field indicates that the corresponding MPH service data packet is IP datagram. 
     In other words, if the type_indicator field of the MPH header within the MPH service data packet read out from the RS frame indicates that the data included in payload within the corresponding MPH service data packet is IP datagram (step  9201 ), it is identified whether the pointer field pt_field value expresses a maximum value (step  9202 ). 
     If the pointer field pt_field value expresses a maximum value in step  9202 , since all the data of payload within the corresponding MPH service data packet are those on a continuous line of the IP datagram ongoing from the previous MPH service data packet, the demultiplexer transfers the data of payload to the IP datagram buffer which is previously allocated (step  9204 ), and receives next MPH service data packet (step  9209 ). If it is determined that the pointer field value is not maximum value in step  9202 , it is determined whether the pointer field value is 0 (step  9203 ). If it is determined that the pointer field value is not 0 in step  9203 , since the previous data of the data indicated by the pointer field correspond to the IP datagram ongoing from the previous MPH service data packet, the data are copied in the previous IP datagram (step  9205 ). If it is determined that the pointer field value is 0 in step  9203 , since it represents start of new IP datagram, a new IP datagram buffer is allocated (step  9206 ). Afterwards, the data of payload are copied in the new IP datagram buffer (step  9207 ). 
     If one IP datagram is completed through the above steps (step  9208 ), a procedure of receiving a new IP datagram is repeated. If the IP datagram has not been completed, since next MPH service data packet will be followed by data, the current step proceeds to the next step for receiving next data packet. 
       FIG. 90  is a flow chart illustrating an example of a detailed procedure of  FIG. 88 . 
     In other words, if the MPH service data packet including IP datagram is received (step  9401 ), a length of the current IP datagram is compared with a size of valid data (valid_data_size) stored in the IP datagram buffer  8307  (IP_datagram_length&gt;valid_data_size) in step  9402 . At this time, if the length of the current IP datagram is greater than the size of the valid data, since it means that there exist data required to complete one IP datagram in payload of the corresponding MPH service data packet, the current step proceeds to step  9403 . If not so, since it means that new data should be received, the current step proceeds to step  9404  and then amount of data is set to 0′. In step  9403 , amount of data included in payload of the corresponding MPH service data packet is determined, and the data as much as the determined amount are transmitted to the IP datagram buffer  8307 . And, the current step proceeds to step  9405  so that the amount is compared with the pointer field value (amount&gt;pt_field). If the amount is equal to the pointer field value, it means that one IP datagram has been completed as a rule. However, since there may exist the possibility of error, the current step proceeds to step  9406  to test completeness. If the amount is different from the pt_field in step  9405 , since the payload of the corresponding packet is data belonging to the same IP datagram as designated in step  9403 , the current step returns to a routine for processing next MPH service data packet (step  9413 ). 
     If it is identified that completeness of data has not assured in step  9407 , the current step proceeds to step  9408  to report that error has occurred and then proceeds to step  9409 . In step  9409 , a length of IP datagram is identified from the data included in the IP datagram header by reading out data at the front from the part indicated by the pointer field pt_field. Also, a memory for the IP datagram is allocated, and valid_data_size is initiated to ‘0’. Afterwards, similarly to step  9403 , data are transferred to the IP datagram buffer  8307 , and valid_data_size is updated (step  9410 ). If the amount of the data transferred to the IP datagram buffer  8307  is equal to that of the IP datagram (step  9411 ), since it means that another IP datagram has been completely transmitted, the pointer field pt_field is transferred as much as the amount and completeness of the datagram is notified (step  9412 ). Afterwards, since there may exist data to be processed, the current step returns to step  9409 . If the size of the data copied in step  9411  is different from that of the IP datagram, since it means that it has reached the end of payload of the corresponding MPH service data packet, the current step proceeds to step  9413  to process next packet. 
       FIG. 89  is an example of a flow chart performed when the type_indicator field indicates that the corresponding MPH service data packet is program table information. The procedure of  FIG. 89  is the same as that of  FIG. 88  except that the program table information included in payload of the MPH service data packet are transmitted to the program table buffer  8304 . Accordingly, each part constituting  FIG. 89 , which is repeated with  FIG. 88 , will refer to the description of  FIG. 88 , and thus its detailed description will be omitted. 
       FIG. 91  is a flow chart illustrating an example of a detailed procedure of processing program table information of  FIG. 89 . The procedure of  FIG. 89  is the same as that of  FIG. 88  except that the program table information included in payload of the MPH service data packet are transmitted to the program table buffer  8304 . Accordingly, each part constituting  FIG. 89 , which is repeated with  FIG. 88 , will refer to the description of  FIG. 88 , and thus its detailed description will be omitted. 
     The procedure of  FIG. 91  is the same as that of  FIG. 90  except that the program table information are processed. Accordingly, each part constituting  FIG. 91 , which is repeated with  FIG. 90 , will refer to the description of  FIG. 90 , and thus its detailed description will be omitted. 
     As described above, the digital broadcasting system and the method of processing data according to the present invention has the following advantages. 
     The present invention is robust to error when mobile service data are transmitted through a channel, and can be compatible with the existing receiver. 
     Even a channel having ghost and strong noise can receive mobile service data without any error. 
     Since base data are transmitted by being inserted to a predetermined position of a data region, it is possible to improve receiving performance of the receiving system under the channel variable environment. 
     Since the mobile service data is multiplexed with the main service data in a parade format, it is possible to reduce the power of the receiving system. 
     In particular, the present invention is more effective when it is applied to a mobile receiver of which channel change is frequent and which requires robustness to noise. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.