Patent Publication Number: US-9894638-B2

Title: Digital broadcasting system and method of processing data in digital broadcasting system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 14/534,990, filed on Nov. 6, 2014, now U.S. Pat. No. 9,674,817, which is a continuation of U.S. application Ser. No. 14/191,019, filed on Feb. 26, 2014, now U.S. Pat. No. 8,917,727, which is a continuation of U.S. application Ser. No. 13/069,268, filed on Mar. 22, 2011, now U.S. Pat. No. 8,687,635, which is a continuation of U.S. application Ser. No. 12/235,583, filed on Sep. 22, 2008, now U.S. Pat. No. 7,936,786, which claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2008-0092361, filed on Sep. 19, 2008, and also claims the benefit of U.S. Provisional Application Ser. No. 60/973,773, filed on Sep. 20, 2007, 60/974,084, filed on Sep. 21, 2007, 60/977,379, filed on Oct. 4, 2007, 61/044,504, filed on Apr. 13, 2008, and 61/076,686, filed on Jun. 29, 2008, the contents of all of which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     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. 
     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 
     The present invention provides a data processing method comprising: receiving a broadcast signal including mobile service data and main service data; detecting known data from the broadcast signal; performing channel equalization on the mobile service data received by means of the detected known data; acquiring a Reed Solomon (RS) frame from the channel-equalized mobile service data; extracting a Generic Stream Encapsulation (GSE) packet from a GSE Base Band (BB) constructing one row of the RS frame, and calculating an IP datagram from the GSE packet; and displaying broadcast data using data contained in the calculated IP datagram. 
     The mobile service data may configure a data group, in which the data group is segmented into several areas, a known data sequence is linearly inserted into some areas from among the several areas, and initialization data for initializing a memory contained in a Trellis encoder of a transmitter is located at a start part of the known data sequence; and N number of the known data sequences are inserted into the some areas from among the several areas, and a transmission parameter is inserted between a first known data sequence and a second known data sequence from among the N known data sequences. 
     The calculating step may include: recovering a header of the IP datagram by releasing compression of data contained in a data field of the GSE packet. The header of the IP datagram may be compressed by a Robust Header Compression (ROHC). 
     The IP datagram is contained in a data field of at least one GSE packet. 
     In another aspect of the present invention, there is provided a data processing method comprising: encapsulating an IP datagram including mobile service data into at least one Generic Stream Encapsulation (GSE) packet; generating a mobile service data frame including the GSE packet; segmenting the generated mobile service data frame into data groups, and multiplexing the data groups with main service data; modulating the multiplexed data groups and the main service data into a broadcast signal; and transmitting the broadcast signal. The generating step may include: forming a Base Band (BB) frame with the GSE packet; and generating the mobile service data frame by constructing the BB frame in row units of the mobile service data frame. 
     The encapsulating step may include: compressing a header of the IP datagram. The header of the IP datagram may be compressed by a Robust Header Compression (ROHC). 
     In another aspect of the present invention, there is provided a digital broadcasting system comprising: a receiver for receiving a broadcast signal including mobile service data and main service data; a known data detector for detecting known data from the broadcast signal; an equalizer for performing channel equalization on the mobile service data received by means of the detected known data; a Reed Solomon (RS) frame decoder for acquiring a Reed Solomon (RS) frame from the channel-equalized mobile service data; a management processor for extracting a Generic Stream Encapsulation (GSE) packet from a GSE Base Band (BB) constructing one row of the RS frame, and calculating an IP datagram from the extracted GSE packet; and a presentation processor for displaying broadcast data using data contained in the calculated IP datagram. 
     The mobile service data may configure a data group, in which the data group is segmented into several areas, a known data sequence is linearly inserted into some areas from among the several areas, and initialization data for initializing a memory contained in a Trellis encoder of a transmitter is located at a start part of the known data sequence; and N number of the known data sequences are inserted into the some areas from among the several areas, and a transmission parameter is inserted between a first known data sequence and a second known data sequence from among the N known data sequences. 
     The management processor may release compression of data contained in a data field of the GSE packet, and may recover a header of the IP datagram. The management processor may release compression of the header of the IP datagram on the basis of a Robust Header Compression (ROHC). 
     The management processor may calculate the IP datagram from a data field of at least one GSE packet. 
    
    
     
       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 block diagram showing a general structure of a digital broadcasting receiving system according to an embodiment of the present invention; 
         FIG. 2  illustrates an exemplary structure of a data group according to the present invention; 
         FIG. 3  illustrates an RS frame according to an embodiment of the present invention; 
         FIG. 4  illustrates an example of an MH frame structure for transmitting and receiving mobile service data according to the present invention; 
         FIG. 5  illustrates an example of a general VSB frame structure; 
         FIG. 6  illustrates a example of mapping positions of the first 4 slots of a sub-frame in a spatial area with respect to a VSB frame; 
         FIG. 7  illustrates a example of mapping positions of the first 4 slots of a sub-frame in a chronological (or time) area with respect to a VSB frame; 
         FIG. 8  illustrates an exemplary order of data groups being assigned to one of 5 sub-frames configuring an MH frame according to the present invention; 
         FIG. 9  illustrates an example of a single parade being assigned to an MH frame according to the present invention; 
         FIG. 10  illustrates an example of 3 parades being assigned to an MH frame according to the present invention; 
         FIG. 11  illustrates an example of the process of assigning 3 parades shown in  FIG. 10  being expanded to 5 sub-frames within an MH frame; 
         FIG. 12  illustrates a data transmission structure according to an embodiment of the present invention, wherein signaling data are included in a data group so as to be transmitted; 
         FIG. 13  illustrates a hierarchical signaling structure according to an embodiment of the present invention; 
         FIG. 14  illustrates an exemplary FIC body format according to an embodiment of the present invention; 
         FIG. 15  illustrates an exemplary bit stream syntax structure with respect to an FIC segment according to an embodiment of the present invention; 
         FIG. 16  illustrates an exemplary bit stream syntax structure with respect to a payload of an FIC segment according to the present invention, when an FIC type field value is equal to ‘0’; 
         FIG. 17  illustrates an exemplary bit stream syntax structure of a service map table according to the present invention; 
         FIG. 18  illustrates an exemplary bit stream syntax structure of an MH audio descriptor according to the present invention; 
         FIG. 19  illustrates an exemplary bit stream syntax structure of an MH RTP payload type descriptor according to the present invention; 
         FIG. 20  illustrates an exemplary bit stream syntax structure of an MH current event descriptor according to the present invention; 
         FIG. 21  illustrates an exemplary bit stream syntax structure of an MH next event descriptor according to the present invention; 
         FIG. 22  illustrates an exemplary bit stream syntax structure of an MH system time descriptor according to the present invention; 
         FIG. 23  illustrates segmentation and encapsulation processes of a service map table according to the present invention; and 
         FIG. 24  illustrates a flow chart for accessing a virtual channel using FIC and SMT according to the present invention. 
         FIG. 25  illustrates a block diagram showing a general structure of a digital broadcasting receiving system according to another embodiment of the present invention; 
         FIG. 26  is a structural diagram illustrating a Reed Solomon (RS) frame according to another embodiment of the present invention; 
         FIG. 27  shows the relationship between Protocol Data Units (PDUs) and Generic Stream Encapsulation (GSE) packets according to the present invention; 
         FIG. 28  shows a header of the Generic Stream Encapsulation (GSE) packet according to the present invention; 
         FIG. 29  is a conceptual diagram illustrating a method for constructing the GSE packet according to the present invention; and 
         FIG. 30  is a flow chart illustrating a data processing method according to the present invention. 
         FIG. 31  is a flow chart illustrating a method of processing broadcast data in a transmitter according to an embodiment of the invention. 
     
    
    
     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. At this time, it is to be understood that the following detailed description of the present invention illustrated in the drawings and described with reference to the drawings are exemplary and explanatory and technical spirits of the present invention and main features and operation of the present invention will not be limited by the following detailed description. 
     Definition of Terms Used in the Present Invention 
     Although general terms, which are widely used considering functions in the present invention, have been selected in the present invention, they may be changed depending on intention of those skilled in the art, practices, or new technology. Also, in specific case, the applicant may optionally select the terms. In this case, the meaning of the terms will be described in detail in the description part of the invention. Therefore, it is to be understood that the terms should be defined based upon their meaning not their simple title and the whole description of the present invention. 
     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, “MH” corresponds to the initials of “mobile” and “handheld” and represents the opposite concept of a fixed-type system. Furthermore, the MH service data may include at least one of mobile 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 MH 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 MH 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. 
     Receiving System 
       FIG. 1  illustrates a block diagram showing a general structure of a digital broadcasting receiving system according to an embodiment of the present invention. The digital broadcast receiving system according to the present invention includes a baseband processor  100 , a management processor  200 , and a presentation processor  300 . 
     The baseband processor  100  includes an operation controller  110 , a tuner  120 , a demodulator  130 , an equalizer  140 , a known sequence detector (or known data detector)  150 , a block decoder (or mobile handheld block decoder)  160 , a promary Reed-Solomon (RS) frame decoder  170 , a secondary RS frame decoder  180 , and a signaling decoder  190 . The operation controller  110  controls the operation of each block included in the baseband processor  100 . 
     By tuning the receiving system to a specific physical channel frequency, the tuner  120  enables the receiving system to receive main service data, which correspond to broadcast signals for fixed-type broadcast receiving systems, and mobile service data, which correspond to broadcast signals for mobile broadcast receiving systems. At this point, the tuned frequency of the specific physical channel is down-converted to an intermediate frequency (IF) signal, thereby being outputted to the demodulator  130  and the known sequence detector  140 . The passband digital IF signal being outputted from the tuner  120  may only include main service data, or only include mobile service data, or include both main service data and mobile service data. 
     The demodulator  130  performs self-gain control, carrier wave recovery, and timing recovery processes on the passband digital IF signal inputted from the tuner  120 , thereby modifying the IF signal to a baseband signal. Then, the demodulator  130  outputs the baseband signal to the equalizer  140  and the known sequence detector  150 . The demodulator  130  uses the known data symbol sequence inputted from the known sequence detector  150  during the timing and/or carrier wave recovery, thereby enhancing the demodulating performance. 
     The equalizer  140  compensates channel-associated distortion included in the signal demodulated by the demodulator  130 . Then, the equalizer  140  outputs the distortion-compensated signal to the block decoder  160 . By using a known data symbol sequence inputted from the known sequence detector  150 , the equalizer  140  may enhance the equalizing performance. Furthermore, the equalizer  140  may receive feed-back on the decoding result from the block decoder  160 , thereby enhancing the equalizing performance. 
     The known sequence detector  150  detects known data place (or position) inserted by the transmitting system from the input/output data (i.e., data prior to being demodulated or data being processed with partial demodulation). Then, the known sequence detector  150  outputs the detected known data position information and known data sequence generated from the detected position information to the demodulator  130  and the equalizer  140 . Additionally, in order to allow the block decoder  160  to identify the mobile service data that have been processed with additional encoding by the transmitting system and the main service data that have not been processed with any additional encoding, the known sequence detector  150  outputs such corresponding information to the block decoder  160 . 
     If the data channel-equalized by the equalizer  140  and inputted to the block decoder  160  correspond to data processed with both block-encoding and trellis-encoding by the transmitting system (i.e., data within the RS frame, signaling data), the block decoder  160  may perform trellis-decoding and block-decoding as inverse processes of the transmitting system. On the other hand, if the data channel-equalized by the equalizer  140  and inputted to the block decoder  160  correspond to data processed only with trellis-encoding and not block-encoding by the transmitting system (i.e., main service data), the block decoder  160  may perform only trellis-decoding. 
     The signaling decoder  190  decoded signaling data that have been channel-equalized and inputted from the equalizer  140 . It is assumed that the signaling data inputted to the signaling decoder  190  correspond to data processed with both block-encoding and trellis-encoding by the transmitting system. Examples of such signaling data may include transmission parameter channel (TPC) data and fast information channel (FIC) data. Each type of data will be described in more detail in a later process. The FIC data decoded by the signaling decoder  190  are outputted to the FIC handler  215 . And, the TPC data decoded by the signaling decoder  190  are outputted to the TPC handler  214 . 
     Meanwhile, according to the present invention, the transmitting system uses RS frames by encoding units. Herein, the RS frame may be divided into a primary RS frame and a secondary RS frame. However, according to the embodiment of the present invention, the primary RS frame and the secondary RS frame will be divided based upon the level of importance of the corresponding data. 
     The primary RS frame decoder  170  receives the data outputted from the block decoder  160 . At this point, according to the embodiment of the present invention, the primary RS frame decoder  170  receives only the mobile service data that have been Reed-Solomon (RS)-encoded and/or cyclic redundancy check (CRC)-encoded from the block decoder  160 . 
     Herein, the primary RS frame decoder  170  receives only the mobile service data and not the main service data. The primary RS frame decoder  170  performs inverse processes of an RS frame encoder (not shown) included in the digital broadcast transmitting system, thereby correcting errors existing within the primary RS frame. More specifically, the primary RS frame decoder  170  forms a primary RS frame by grouping a plurality of data groups and, then, correct errors in primary RS frame units. In other words, the primary RS frame decoder  170  decodes primary RS frames, which are being transmitted for actual broadcast services. 
     Additionally, the secondary RS frame decoder  180  receives the data outputted from the block decoder  160 . At this point, according to the embodiment of the present invention, the secondary RS frame decoder  180  receives only the mobile service data that have been RS-encoded and/or CRC-encoded from the block decoder  160 . Herein, the secondary RS frame decoder  180  receives only the mobile service data and not the main service data. The secondary RS frame decoder  180  performs inverse processes of an RS frame encoder (not shown) included in the digital broadcast transmitting system, thereby correcting errors existing within the secondary RS frame. More specifically, the secondary RS frame decoder  180  forms a secondary RS frame by grouping a plurality of data groups and, then, correct errors in secondary RS frame units. In other words, the secondary RS frame decoder  180  decodes secondary RS frames, which are being transmitted for mobile audio service data, mobile video service data, guide data, and so on. 
     Meanwhile, the management processor  200  according to an embodiment of the present invention includes an MH physical adaptation processor  210 , an IP network stack  220 , a streaming handler  230 , a system information (SI) handler  240 , a file handler  250 , a multi-purpose internet main extensions (MIME) type handler  260 , and an electronic service guide (ESG) handler  270 , and an ESG decoder  280 , and a storage unit  290 . 
     The MH physical adaptation processor  210  includes a primary RS frame handler  211 , a secondary RS frame handler  212 , an MH transport packet (TP) handler  213 , a TPC handler  214 , an FIC handler  215 , and a physical adaptation control signal handler  216 . 
     The TPC handler  214  receives and processes baseband information required by modules corresponding to the MH physical adaptation processor  210 . The baseband information is inputted in the form of TPC data. Herein, the TPC handler  214  uses this information to process the FIC data, which have been sent from the baseband processor  100 . 
     The TPC data are transmitted from the transmitting system to the receiving system via a predetermined region of a data group. The TPC data may include at least one of an MH ensemble ID, an MH sub-frame number, a total number of MH groups (TNoG), an RS frame continuity counter, a column size of RS frame (N), and an FIC version number. 
     Herein, the MH ensemble ID indicates an identification number of each MH ensemble carried in the corresponding channel. The MH sub-frame number signifies a number identifying the MH sub-frame number in an MH frame, wherein each MH group associated with the corresponding MH ensemble is transmitted. The TNoG represents the total number of MH groups including all of the MH groups belonging to all MH parades included in an MH sub-frame. 
     The RS frame continuity counter indicates a number that serves as a continuity counter of the RS frames carrying the corresponding MH ensemble. Herein, the value of the RS frame continuity counter shall be incremented by 1 modulo 16 for each successive RS frame. 
     N represents the column size of an RS frame belonging to the corresponding MH ensemble. Herein, the value of N determines the size of each MH TP. 
     Finally, the FIC version number signifies the version number of an FIC body carried on the corresponding physical channel. 
     As described above, diverse TPC data are inputted to the TPC handler  214  via the signaling decoder  190  shown in  FIG. 1 . Then, the received TPC data are processed by the TPC handler  214 . The received TPC data may also be used by the FIC handler  215  in order to process the FIC data. 
     The FIC handler  215  processes the FIC data by associating the FIC data received from the baseband processor  100  with the TPC data. 
     The physical adaptation control signal handler  216  collects FIC data received through the FIC handler  215  and SI data received through RS frames. Then, the physical adaptation control signal handler  216  uses the collected FIC data and SI data to configure and process IP datagrams and access information of mobile broadcast services. Thereafter, the physical adaptation control signal handler  216  stores the processed IP datagrams and access information to the storage unit  290 . 
     The primary RS frame handler  211  identifies primary RS frames received from the primary RS frame decoder  170  of the baseband processor  100  for each row unit, so as to configure an MH TP. Thereafter, the primary RS frame handler  211  outputs the configured MH TP to the MH TP handler  213 . 
     The secondary RS frame handler  212  identifies secondary RS frames received from the secondary RS frame decoder  180  of the baseband processor  100  for each row unit, so as to configure an MH TP. Thereafter, the secondary RS frame handler  212  outputs the configured MH TP to the MH TP handler  213 . 
     The MH transport packet (TP) handler  213  extracts a header from each MH TP received from the primary RS frame handler  211  and the secondary RS frame handler  212 , thereby determining the data included in the corresponding MH TP. Then, when the determined data correspond to SI data (i.e., SI data that are not encapsulated to IP datagrams), the corresponding data are outputted to the physical adaptation control signal handler  216 . Alternatively, when the determined data correspond to an IP datagram, the corresponding data are outputted to the IP network stack  220 . 
     The IP network stack  220  processes broadcast data that are being transmitted in the form of IP datagrams. More specifically, the IP network stack  220  processes data that are inputted via user datagram protocol (UDP), real-time transport protocol (RTP), real-time transport control protocol (RTCP), asynchronous layered coding/layered coding transport (ALC/LCT), file delivery over unidirectional transport (FLUTE), and so on. Herein, when the processed data correspond to streaming data, the corresponding data are outputted to the streaming handler  230 . And, when the processed data correspond to data in a file format, the corresponding data are outputted to the file handler  250 . Finally, when the processed data correspond to SI-associated data, the corresponding data are outputted to the SI handler  240 . 
     The SI handler  240  receives and processes SI data having the form of IP datagrams, which are inputted to the IP network stack  220 . When the inputted data associated with SI correspond to MIME-type data, the inputted data are outputted to the MIME-type handler  260 . The MIME-type handler  260  receives the MIME-type SI data outputted from the SI handler  240  and processes the received MIME-type SI data. 
     The file handler  250  receives data from the IP network stack  220  in an object format in accordance with the ALC/LCT and FLUTE structures. The file handler  250  groups the received data to create a file format. Herein, when the corresponding file includes ESG, the file is outputted to the ESG handler  270 . On the other hand, when the corresponding file includes data for other file-based services, the file is outputted to the presentation controller  330  of the presentation processor  300 . 
     The ESG handler  270  processes the ESG data received from the file handler  250  and stores the processed ESG data to the storage unit  290 . Alternatively, the ESG handler  270  may output the processed ESG data to the ESG decoder  280 , thereby allowing the ESG data to be used by the ESG decoder  280 . 
     The storage unit  290  stores the system information (SI) received from the physical adaptation control signal handler  210  and the ESG handler  270  therein. Thereafter, the storage unit  290  transmits the stored SI data to each block. 
     The ESG decoder  280  either recovers the ESG data and SI data stored in the storage unit  290  or recovers the ESG data transmitted from the ESG handler  270 . Then, the ESG decoder  280  outputs the recovered data to the presentation controller  330  in a format that can be outputted to the user. 
     The streaming handler  230  receives data from the IP network stack  220 , wherein the format of the received data are in accordance with RTP and/or RTCP structures. The streaming handler  230  extracts audio/video streams from the received data, which are then outputted to the audio/video (A/V) decoder  310  of the presentation processor  300 . The audio/video decoder  310  then decodes each of the audio stream and video stream received from the streaming handler  230 . 
     The display module  320  of the presentation processor  300  receives audio and video signals respectively decoded by the A/V decoder  310 . Then, the display module  320  provides the received audio and video signals to the user through a speaker and/or a screen. 
     The presentation controller  330  corresponds to a controller managing modules that output data received by the receiving system to the user. 
     The channel service manager  340  manages an interface with the user, which enables the user to use channel-based broadcast services, such as channel map management, channel service connection, and so on. 
     The application manager  350  manages an interface with a user using ESG display or other application services that do not correspond to channel-based services. 
     Meanwhile, The streaming handler  230  may include a buffer temporarily storing audio/video data. The digital broadcasting reception system periodically sets reference time information to a system time clock, and then the stored audio/video data can be transferred to A/V decoder  310  at a constant bitrate. Accordingly, the audio/video data can be processed at a bitrate and audio/video service can be provided. 
       FIG. 31  illustrates a method of processing broadcast data in a transmitter according to an embodiment of the invention. 
     Data Format Structure 
     Meanwhile, the data structure used in the mobile broadcasting technology according to the embodiment of the present invention may include a data group structure and an RS frame structure, which will now be described in detail. 
       FIG. 2  illustrates an exemplary structure of a data group according to the present invention. 
       FIG. 2  shows an example of dividing a data group according to the data structure of the present invention into 10 MH blo In this example, each MH block has the length of 16 segments. Referring to  FIG. 2 , only the RS parity data are allocated to portions of the first 5 segments of the MH block  1  (B 1 ) and the last 5 segments of the MH 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 MH block may be included in any one of region A to region D depending upon the characteristic of each MH 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. 2 , MH block  4  (B 4 ) to MH block  7  (B 7 ) correspond to regions without interference of the main service data. MH block  4  (B 4 ) to MH block  7  (B 7 ) within the data group shown in  FIG. 2  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 MH block. In the description of the present invention, the region including MH block  4  (B 4 ) to MH 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 MH 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. 2 , MH block  3  (B 3 ) and MH 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 MH 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 MH block  3  (B 3 ), and another long known data sequence is inserted at the beginning of MH block  8  (B 8 ). In the present invention, the region including MH block  3  (B 3 ) and MH 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 MH 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. 2 , MH block  2  (B 2 ) and MH 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 MH block  2  (B 2 ) and MH block  9  (B 9 ). Herein, the region including MH block  2  (B 2 ) and MH block  9  (B 9 ) will be referred to as “region C (=B 2 +B 9 )”. 
     Finally, in the example shown in  FIG. 2 , MH block  1  (B 1 ) and MH 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 MH block  1  (B 1 ) and MH block  10  (B 10 ). Herein, the region including MH block  1  (B 1 ) and MH 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. 
     Additionally, the data group includes a signaling information area wherein signaling information is assigned (or allocated). 
     In the present invention, the signaling information area may start from the 1 st  segment of the 4 th  MH block (B 4 ) to a portion of the 2 nd  segment. 
     According to an embodiment of the present invention, the signaling information area for inserting signaling information may start from the 1 st  segment of the 4 th  MH block (B 4 ) to a portion of the 2 nd  segment. More specifically, 276(=207+69) bytes of the 4 th  MH 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  MH block (B 4 ). The 1 st  segment of the 4 th  MH block (B 4 ) corresponds to the 17 th  or 173 rd  segment of a VSB field. 
     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 data may include at least one of an MH ensemble ID, an MH sub-frame number, a total number of MH groups (TNoG), an RS frame continuity counter, a column size of RS frame (N), and an FIC version number. However, the TPC data (or information) presented herein are merely exemplary. And, since the adding or deleting of signaling information included in the TPC data 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). For example, when the data group includes 6 known data sequences, as shown in  FIG. 2 , the signaling information area is located between the first known data sequence and the second known data sequence. More specifically, the first known data sequence is inserted in the last 2 segments of the 3 rd  MH block (B 3 ), and the second known data sequence in inserted in the 2 nd  and 3 rd  segments of the 4 th  MH block (B 4 ). Furthermore, the 3 rd  to 6 th  known data sequences are respectively inserted in the last 2 segments of each of the 4 th , 5 th , 6 th , and 7 th  MH blocks (B 4 , B 5 , B 6 , and B 7 ). The 1 st  and 3 rd  to 6 th  known data sequences are spaced apart by 16 segments. 
       FIG. 3  illustrates an RS frame according to an embodiment of the present invention. 
     The RS frame shown in  FIG. 3  corresponds to a collection of one or more data groups. The RS frame is received for each MH frame in a condition where the receiving system receives the FIC and processes the received FIC and where the receiving system is switched to a time-slicing mode so that the receiving system can receive MH ensembles including ESG entry points. Each RS frame includes IP streams of each service or ESG, and SMT section data may exist in all RS frames. 
     The RS frame according to the embodiment of the present invention consists of at least one MH transport packet (TP). Herein, the MH TP includes an MH header and an MH payload. 
     The MH payload may include mobile service data as wekk as signaling data. More specifically, an MH payload may include only mobile service data, or may include only signaling data, or may include both mobile service data and signaling data. 
     According to the embodiment of the present invention, the MH header may identify (or distinguish) the data types included in the MH payload. More specifically, when the MH TP includes a first MH header, this indicates that the MH payload includes only the signaling data. Also, when the MH TP includes a second MH header, this indicates that the MH payload includes both the signaling data and the mobile service data. Finally, when MH TP includes a third MH header, this indicates that the MH payload includes only the mobile service data. 
     In the example shown in  FIG. 3 , the RS frame is assigned with IP datagrams (IP datagram 1 and IP datagram 2) for two service types. 
     The IP datagram in the MH-TP in the RS frame may include reference time information (for example, network time stamp (NTP)), the detailed description for the reference time information will be disclosed by being referred to  FIGS. 25 to 29 . 
     Data Transmission Structure 
       FIG. 4  illustrates a structure of a MH frame for transmitting and receiving mobile service data according to the present invention. 
     In the example shown in  FIG. 4 , one MH frame consists of 5 sub-frames, wherein each sub-frame includes 16 slots. In this case, the MH 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. 5  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 unit 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 the first 118 data packets within the slot correspond to a data group, 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. 6  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 spatial area. And,  FIG. 7  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 chronological (or time) area. 
     Referring to  FIG. 6  and  FIG. 7 , 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. 
       FIG. 8  illustrates an exemplary assignment order of data groups being assigned to one of 5 sub-frames, wherein the 5 sub-frames configure an MH frame. For example, the method of assigning data groups may be identically applied to all MH frames or differently applied to each MH 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 MH frame, the total number of data groups being assigned to an MH 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 MH 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. 8  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 =(4 i+ 0)mod 16
 
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≦j≦15).
 
     In the present invention, a collection of data groups included in a MH 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. 
     According to the embodiment 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. Such RS frame mode is transmitted as the above-described TPC data. 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. 
     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 MH frames or differently applied to each MH frame. 
     According to the embodiment of the present invention, the parades may be assigned differently for each MH frame and identically for all sub-frames within an MH frame. More specifically, the MH frame structure may vary by MH frame units. Thus, an ensemble rate may be adjusted on a more frequent and flexible basis. 
       FIG. 9  illustrates an example of multiple data groups of a single parade being assigned (or allocated) to an MH frame. More specifically,  FIG. 9  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 MH frame. 
     Referring to  FIG. 9 , 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 MH frame, 15 data groups are assigned to a single MH 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 (not shown) included in the transmitting system 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. 9 , 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 shown in  FIG. 9 , 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 MH 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 MH 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. 9 , 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. 10  illustrates an example of transmitting 3 parades (Parade #0, Parade #1, and Parade #2) to an MH frame. More specifically,  FIG. 10  illustrates an example of transmitting parades included in one of 5 sub-frames, wherein the 5 sub-frames configure one MH 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 MH 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 MH frame includes 5 sub-frames, the total number of data groups within a parade that can be allocated to an MH frame may correspond to any one multiple of ‘5’ ranging from ‘5’ to ‘40’. 
       FIG. 11  illustrates an example of expanding the assignment process of 3 parades, shown in  FIG. 10 , to 5 sub-frames within an MH frame. 
       FIG. 12  illustrates a data transmission structure according to an embodiment of the present invention, wherein signaling data are included in a data group so as to be transmitted. 
     As described above, an MH frame is divided into 5 sub-frames. Data groups corresponding to a plurality of parades co-exist in each sub-frame. Herein, the data groups corresponding to each parade are grouped by MH frame units, thereby configuring a single parade. The data structure shown in  FIG. 12  includes 3 parades, one ESG dedicated channel (EDC) parade (i.e., parade with NoG=1), and 2 service parades (i.e., parade with NoG=4 and parade with NoG=3). Also, a predetermined portion of each data group (i.e., 37 bytes/data group) is used for delivering (or sending) FIC information associated with mobile service data, wherein the FIC information is separately encoded from the RS-encoding process. The FIC region assigned to each data group consists of one FIC segments. Herein, each segment is interleaved by MH sub-frame units, thereby configuring an FIC body, which corresponds to a completed FIC transmission structure. However, whenever required, each segment may be interleaved by MH frame units and not by MH sub-frame units, thereby being completed in MH frame units. 
     Meanwhile, the concept of an MH ensemble is applied in the embodiment of the present invention, thereby defining a collection (or group) of services. Each MH ensemble carries the same QoS and is coded with the same FEC code. Also, each MH ensemble has the same unique identifier (i.e., ensemble ID) and corresponds to consecutiveRS frames. 
     As shown in  FIG. 12 , the FIC segment corresponding to each data group described service information of an MH ensemble to which the corresponding data group belongs. When FIC segments within a sub-frame are grouped and deinterleved, all service information of a physical channel through which the corresponding FICs are transmitted may be obtained. Therefore, the receiving system may be able to acquire the channel information of the corresponding physical channel, after being processed with physical channel tuning, during a sub-frame period. 
     Furthermore,  FIG. 12  illustrates a structure further including a separate EDC parade apart from the service parade and wherein electronic service guide (ESG) data are transmitted in the 1 st  slot of each sub-frame. 
     If the digital broadcasting reception system recognizes a frame start point or a frame end point of the MH frame (or the MH subframe), then the digital broadcasting reception system can set the reference time information to the system time clock at the frame start point or the frame end point. The reference time information can be the network time protocol (NTP) timestamp. The detailed description for the reference time information will be disclosed by being referred to  FIGS. 25 to 29 . 
     Hierarchical Signaling Structure 
       FIG. 13  illustrates a hierarchical signaling structure according to an embodiment of the present invention. As shown in  FIG. 13 , the mobile broadcasting techonology according to the embodiment of the present invention adopts a signaling method using FIC and SMT. In the description of the present invention, the signaling structure will be referred to as a hierarchical signaling structure. 
     Hereinafter, a detailed description on how the receiving system accesses a virtual channel via FIC and SMT will now be given with reference to  FIG. 13 . 
     The FIC body defined in an MH transport (M 1 ) identifies the physical location of each the data stream for each virtual channel and provides very high level descriptions of each virtual channel. 
     Being MH ensemble level signaling information, the service map table (SMT) provides MH ensemble level signaling information. The SMT provides the IP access information of each virtual channel belonging to the respective MH ensemble within which the SMT is carried. The SMT also provides all IP stream component level information required for the virtual channel service acquisition. 
     Referring to  FIG. 13 , each MH ensemble (i.e., Ensemble 0, Ensemble 1, . . . , Ensemble K) includes a stream information on each associated (or corresponding) virtual channel (e.g., virtual channel 0 IP stream, virtual channel 1 IP stream, and virtual channel 2 IP stream). For example, Ensemble 0 includes virtual channel 0 IP stream and virtual channel 1 IP stream. And, each MH ensemble includes diverse information on the associated virtual channel (i.e., Virtual Channel 0 Table Entry, Virtual Channel 0 Access Info, Virtual Channel 1 Table Entry, Virtual Channel 1 Access Info, Virtual Channel 2 Table Entry, Virtual Channel 2 Access Info, Virtual Channel N Table Entry, Virtual Channel N Access Info, and so on). 
     The FIC body payload includes information on MH ensembles (e.g., ensemble_id field, and referred to as “ensemble location” in  FIG. 13 ) and information on a virtual channel associated with the corresponding MH ensemble (e.g., when such information corresponds to a major_channel_num field and a minor_channel_num field, the information is expressed as Virtual Channel 0, Virtual Channel 1, Virtual Channel N in  FIG. 13 ). 
     The application of the signaling structure in the receiving system will now be described in detail. 
     When a user selects a channel he or she wishes to view (hereinafter, the user-selected channel will be referred to as “channel θ” for simplicity), the receiving system first parses the received FIC. Then, the receiving system acquires information on an MH ensemble (i.e., ensemble location), which is associated with the virtual channel corresponding to channel θ (hereinafter, the corresponding MH ensemble will be referred to as “MH ensemble θ” for simplicity). By acquiring slots only corresponding to the MH ensemble θ using the time-slicing method, the receiving system configures ensemble θ. The ensemble θ configured as described above, includes an SMT on the associated virtual channels (including channel θ) and IP streams on the corresponding virtual channels. Therefore, the receiving system uses the SMT included in the MH ensemble θ in order to acquire various information on channel θ (e.g., Virtual Channel θ Table Entry) and stream access information on channel θ (e.g., Virtual Channel 0 Access Info). The receiving system uses the stream access information on channel 0 to receive only the associated IP streams, thereby providing channel 0 services to the user. 
     Fast Information Channel (FIC) 
     The digital broadcast receiving system according to the present invention adopts the fast information channel (FIC) for a faster access to a service that is currently being broadcasted. 
     More specifically, the FIC handler  215  of  FIG. 1  parses the FIC body, which corresponds to an FIC transmission structure, and outputs the parsed result to the physical adaptation control signal handler  216 . 
       FIG. 14  illustrates an exemplary FIC body format according to an embodiment of the present invention. According to the embodiment of the present invention, the FIC format consists of an FIC body header and an FIC body payload. 
     Meanwhile, according to the embodiment of the present invention, data are transmitted through the FIC body header and the FIC body payload in FIC segment units. Each FIC segment has the size of 37 bytes, and each FIC segment consists of a 2-byte FIC segment header and a 35-byte FIC segment payload. More specifically, an FIC body configured of an FIC body header and an FIC body payload, is segmented in units of 35 data bytes, which are then carried in at least one FIC segment within the FIC segment payload, so as to be transmitted. 
     In the description of the present invention, an example of inserting one FIC segment in one data group, which is then transmitted, will be given. In this case, the receiving system receives a slot corresponding to each data group by using a time-slicing method. 
     The signaling decoder  190  included in the receiving system shown in  FIG. 1  collects each FIC segment inserted in each data group. Then, the signaling decoder  190  uses the collected FIC segments to created a single FIC body. Thereafter, the signaling decoder  190  performs a decoding process on the FIC body payload of the created FIC body, so that the decoded FIC body payload corresponds to an encoded result of a signaling encoder (not shown) included in the transmitting system. Subsequently, the decoded FIC body payload is outputted to the FIC handler  215 . The FIC handler  215  parses the FIC data included in the FIC body payload, and then outputs the parsed FIC data to the physical adaptation control signal handler  216 . The physical adaptation control signal handler  216  uses the inputted FIC data to perform processes associated with MH ensembles, virtual channels, SMTs, and so on. 
     According to an embodiment of the present invention, when an FIC body is segmented, and when the size of the last segmented portion is smaller than 35 data bytes, it is assumed that the lacking number of data bytes in the FIC segment payload is completed with by adding the same number of stuffing bytes therein, so that the size of the last FIC segment can be equal to 35 data bytes. 
     However, it is apparent that the above-described data byte values (i.e., 37 bytes for the FIC segment, 2 bytes for the FIC segment header, and 35 bytes for the FIC segment payload) are merely exemplary, and will, therefore, not limit the scope of the present invention. 
       FIG. 15  illustrates an exemplary bit stream syntax structure with respect to an FIC segment according to an embodiment of the present invention. 
     Herein, the FIC segment signifies a unit used for transmitting the FIC data. The FIC segment consists of an FIC segment header and an FIC segment payload. Referring to  FIG. 15 , the FIC segment payload corresponds to the portion starting from the ‘for’ loop statement. Meanwhile, the FIC segment header may include a FIC_type field, an error_indicator field, an FIC_seg_number field, and an FIC_last_seg_number field. A detailed description of each field will now be given. 
     The FIC_type field is a 2-bit field indicating the type of the corresponding FIC. 
     The error_indicator field is a 1-bit field, which indicates whether or not an error has occurred within the FIC segment during data transmission. If an error has occurred, the value of the error_indicator field is set to ‘1’. More specifically, when an error that has failed to be recovered still remains during the configuration process of the FIC segment, the error_indicator field value is set to ‘1’. The error_indicator field enables the receiving system to recognize the presence of an error within the FIC data. 
     The FIC_seg_number field is a 4-bit field. Herein, when a single FIC body is divided into a plurality of FIC segments and transmitted, the FIC_seg_number field indicates the number of the corresponding FIC segment. 
     Finally, the FIC_last_seg_number field is also a 4-bit field. The FIC_last_seg_number field indicates the number of the last FIC segment within the corresponding FIC body. 
       FIG. 16  illustrates an exemplary bit stream syntax structure with respect to a payload of an FIC segment according to the present invention, when an FIC type field value is equal to ‘0’. 
     According to the embodiment of the present invention, the payload of the FIC segment is divided into 3 different regions. A first region of the FIC segment payload exists only when the FIC_seg_number field value is equal to ‘0’. Herein, the first region may include a current_next_indicator field, an ESG_version field, and a transport_stream_id field. However, depending upon the embodiment of the present invention, it may be assumed that each of the 3 fields exists regardless of the FIC_seg_number field. 
     The current_next_indicator field is a 1-bit field. The current_next_indicator field acts as an indicator identifying whether the corresponding FIC data carry MH ensemble configuration information of an MH frame including the current FIC segment, or whether the corresponding FIC data carry MH ensemble configuration information of a next MH frame. 
     The ESG_version field is a 5-bit field indicating ESG version information. Herein, by providing version information on the service guide providing channel of the corresponding ESG, the ESG_version field enables the receiving system to notify whether or not the corresponding ESG has been updated. 
     Finally, the transport_stream_id field is a 16-bit field acting as a unique identifier of a broadcast stream through which the corresponding FIC segment is being transmitted. 
     A second region of the FIC segment payload corresponds to an ensemble loop region, which includes an ensemble_id field, an SI_version field, and a num_channel field. 
     More specifically, the ensemble_id field is an 8-bit field indicating identifiers of an MH ensemble through which MH services are transmitted. The MH services will be described in more detail in a later process. Herein, the ensemble_id field binds the MH services and the MH ensemble. 
     The SI_version field is a 4-bit field indicating version information of SI data included in the corresponding ensemble, which is being transmitted within the RS frame. 
     Finally, the num_channel field is an 8-bit field indicating the number of virtual channel being transmitted via the corresponding ensemble. 
     A third region of the FIC segment payload a channel loop region, which includes a channel_type field, a channel_activity field, a CA_indicator field, a stand_alone_service_indicator field, a major_channel_num field, and a minor_channel_num field. 
     The channel_type field is a 5-bit field indicating a service type of the corresponding virtual channel. For example, the channel_type field may indicates an audio/video channel, an audio/video and data channel, an audio-only channel, a data-only channel, a file download channel, an ESG delivery channel, a notification channel, and so on. 
     The channel_activity field is a 2-bit field indicating activity information of the corresponding virtual channel. More specifically, the channel_activity field may indicate whether the current virtual channel is providing the current service. 
     The CA_indicator field is a 1-bit field indicating whether or not a conditional access (CA) is applied to the current virtual channel. 
     The stand_alone_service_indicator field is also a 1-bit field, which indicates whether the service of the corresponding virtual channel corresponds to a stand alone service. 
     The major_channel_num field is an 8-bit field indicating a major channel number of the corresponding virtual channel. 
     Finally, the minor_channel_num field is also an 8-bit field indicating a minor channel number of the corresponding virtual channel. 
     Service Table Map 
       FIG. 17  illustrates an exemplary bit stream syntax structure of a service map table (hereinafter referred to as “SMT”) according to the present invention. 
     According to the embodiment of the present invention, the SMT is configured in an MPEG-2 private section format. However, this will not limit the scope and spirit of the present invention. The SMT according to the embodiment of the present invention includes description information for each virtual channel within a single MH ensemble. And, additional information may further be included in each descriptor area. 
     Herein, the SMT according to the embodiment of the present invention includes at least one field and is transmitted from the transmitting system to the receiving system. 
     As described in  FIG. 3 , the SMT section may be transmitted by being included in the MH TP within the RS frame. In this case, each of the RS frame decoders  170  and  180 , shown in  FIG. 1 , decodes the inputted RS frame, respectively. Then, each of the decoded RS frames is outputted to the respective RS frame handler  211  and  212 . Thereafter, each RS frame handler  211  and  212  identifies the inputted RS frame by row units, so as to create an MH TP, thereby outputting the created MH TP to the MH TP handler  213 . When it is determined that the corresponding MH TP includes an SMT section based upon the header in each of the inputted MH TP, the MH TP handler  213  parses the corresponding SMT section, so as to output the SI data within the parsed SMT section to the physical adaptation control signal handler  216 . However, this is limited to when the SMT is not encapsulated to IP datagrams. 
     Meanwhile, when the SMT is not encapsulated to IP datagrams, and when it is determined that the corresponding MH TP includes an SMT section based upon the header in each of the inputted MH TP, the MH TP handler  213  outputs the SMT section to the IP network stack  220 . Accordingly, the IP network stack  220  performs IP and UDP processes on the inputted SMT section and, then, outputs the processed SMT section to the SI handler  240 . The SI handler  240  parses the inputted SMT section and controls the system so that the parsed SI data can be stored in the storage unit  290 . 
     The following corresponds to example of the fields that may be transmitted through the SMT. 
     The table_id field corresponds to an 8-bit unsigned integer number, which indicates the type of table section. The table —id  field allows the corresponding table to be defined as the service map table (SMT). 
     The ensemble_id field is an 8-bit unsigned integer field, which corresponds to an ID value associated to the corresponding MH ensemble. Herein, the ensemble_id field may be assigned with a value ranging from range ‘0x00’ to ‘0x3F’. It is preferable that the value of the ensemble_id field is derived from the parade_id of the TPC data, which is carried from the baseband processor of MH physical layer subsystem. When the corresponding MH ensemble is transmitted through (or carried over) the primary RS frame, a value of ‘0’ may be used for the most significant bit (MSB), and the remaining 7 bits are used as the parade_id value of the associated MH parade (i.e., for the least significant 7 bits). Alternatively, when the corresponding MH ensemble is transmitted through (or carried over) the secondary RS frame, a value of ‘1’ may be used for the most significant bit (MSB). 
     The num_channels field is an 8-bit field, which specifies the number of virtual channels in the corresponding SMT section. 
     Meanwhile, the SMT according to the embodiment of the present invention provides information on a plurality of virtual channels using the ‘for’ loop statement. 
     The major_channel_num field corresponds to an 8-bit field, which represents the major channel number associated with the corresponding virtual channel. Herein, the major_channel_num field may be assigned with a value ranging from ‘0x00’ to ‘0xFF’. 
     The minor_channel_num field corresponds to an 8-bit field, which represents the minor channel number associated with the corresponding virtual channel. Herein, the minor_channel_num field may be assigned with a value ranging from ‘0x00’ to ‘0xFF’. 
     The short_channel_name field indicates the short name of the virtual channel. 
     The service_id field is a 16-bit unsigned integer number (or value), which identifies the virtual channel service. 
     The service_type field is a 6-bit enumerated type field, which designates the type of service carried in the corresponding virtual channel as defined in Table 2 below. 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 0x00 
                 [Reserved] 
               
               
                   
               
             
            
               
                 0x01 
                 MH_digital_television field: the virtual channel 
               
               
                   
                 carries television programming (audio, video 
               
               
                   
                 and optional associated data) conforming to 
               
               
                   
                 ATSC standards. 
               
               
                 0x02 
                 MH_audio field: the virtual channel carries 
               
               
                   
                 audio programming (audio service and optional 
               
               
                   
                 associated data) conforming to ATSC standards. 
               
               
                 0x03 
                 MH_data_only_service field: the virtual channel 
               
               
                   
                 carries a data service conforming to ATSC standards, 
               
               
                   
                 but no video or audio component. 
               
               
                 0x04 to 0xFF 
                 [Reserved for future ATSC usage] 
               
               
                   
               
            
           
         
       
     
     The virtual_channel_activity field is a 2-bit enumerated field identifying the activity status of the corresponding virtual channel. When the most significant bit (MSB) of the virtual_channel_activity field is ‘1’, the virtual channel is active, and when the most significant bit (MSB) of the virtual_channel_activity field is ‘0’, the virtual channel is inactive. Also, when the least significant bit (LSB) of the virtual_channel_activity field is ‘1’, the virtual channel is hidden (when set to 1), and when the least significant bit (LSB) of the virtual_channel_activity field is ‘0’, the virtual channel is not hidden. 
     The num_components field is a 5-bit field, which specifies the number of IP stream components in the corresponding virtual channel. 
     The IP_version_flag field corresponds to a 1-bit indicator. More specifically, when the value of the IP_version_flag field is set to ‘1’, this indicates that a source_IP_address field, a virtual_channel_target_IP_address field, and a component_target_IP_address field are IPv6 addresses. Alternatively, when the value of the IP_version_flag field is set to ‘0’, this indicates that the source_IP_address field, the virtual_channel_target_IP_address field, and the component_target_IP_address field are IPv4. 
     The source_IP_address_flag field is a 1-bit Boolean flag, which indicates, when set, that a source IP address of the corresponding virtual channel exist for a specific multicast source. 
     The virtual_channel_target_IP_address_flag field is a 1-bit Boolean flag, which indicates, when set, that the corresponding IP stream component is delivered through IP datagrams with target IP addresses different from the virtual_channel_target_IP_address. Therefore, when the flag is set, the receiving system (or receiver) uses the component_target_IP_address as the target_IP_address in order to access the corresponding IP stream component. Accordingly, the receiving system (or receiver) may ignore the virtual_channel_target_IP_address field included in the num_channels loop. 
     The source_IP_address field corresponds to a 32-bit or 128-bit field. Herein, the source_IP_address field will be significant (or present), when the value of the source_IP_address_flag field is set to ‘1’. However, when the value of the source_IP_address_flag field is set to ‘0’, the source_IP_address field will become insignificant (or absent). More specifically, when the source_IP_address_flag field value is set to ‘1’, and when the IP_version_flag field value is set to ‘0’, the source_IP_address field indicates a 32-bit IPv4 address, which shows the source of the corresponding virtual channel. Alternatively, when the IP_version_flag field value is set to ‘1’, the source_IP_address field indicates a 128-bit IPv6 address, which shows the source of the corresponding virtual channel. 
     The virtual_channel_target_IP_address field also corresponds to a 32-bit or 128-bit field. Herein, the virtual_channel_target_IP_address field will be significant (or present), when the value of the virtual_channel_target_IP_address_flag field is set to ‘1’. However, when the value of the virtual_channel_target_IP_address_flag field is set to ‘0’, the virtual_channel_target_IP_address_field will become insignificant (or absent). More specifically, when the virtual_channel_target_IP_address_flag field value is set to ‘1’, and when the IP_version_flag field value is set to ‘0’, the virtual_channel_target_IP_address field indicates a 32-bit target IPv4 address associated to the corresponding virtual channel. Alternatively, when the virtual_channel_target_IP_address_flag field value is set to ‘1’, and when the IP_version_flag field value is set to ‘1’, the virtual_channel_target_IP_address field indicates a 64-bit target IPv6 address associated to the corresponding virtual channel. If the virtual_channel_target_IP_address field is insignificant (or absent), the component_target_IP_address field within the num_channels loop should become significant (or present). And, in order to enable the receiving system to access the IP stream component, the component_target_IP_address field should be used. 
     Meanwhile, the SMT according to the embodiment of the present invention uses a ‘for’ loop statement in order to provide information on a plurality of components. 
     Herein, the RTP_payload_type field, which is assigned with 7 bits, identifies the encoding format of the component based upon Table 3 shown below. When the IP stream component is not encapsulated to RTP, the RTP_payload_type field shall be ignored (or deprecated). 
     Table 3 below shows an example of an RTP payload type. 
     
       
         
           
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 RTP_payload_type Meaning 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 35 
                 AVC video 
               
               
                   
                 36 
                 MH audio 
               
               
                   
                 37 to 72 
                 [Reserved for future ATSC use] 
               
               
                   
                   
               
            
           
         
       
     
     The component_target_IP_address_flag field is a 1-bit Boolean flag, which indicates, when set, that the corresponding IP stream component is delivered through IP datagrams with target IP addresses different from the virtual_channel_target_IP_address. Furthermore, when the component_target_IP_address_flag is set, the receiving system (or receiver) uses the component_target_IP_address field as the target IP address for accessing the corresponding IP stream component. Accordingly, the receiving system (or receiver) will ignore the virtual_channel_target_IP_address field included in the num_channels loop. 
     The component_target_IP_address field corresponds to a 32-bit or 128-bit field. Herein, when the value of the IP_version_flag field is set to ‘0’, the component_target_IP_address field indicates a 32-bit target IPv4 address associated to the corresponding IP stream component. And, when the value of the IP_version_flag field is set to ‘1’, the component_target_IP_address field indicates a 128-bit target IPv6 address associated to the corresponding IP stream component. 
     The port_num_count field is a 6-bit field, which indicates the number of UDP ports associated with the corresponding IP stream component. A target UDP port number value starts from the target_UDP_port_num field value and increases (or is incremented) by 1. For the RTP stream, the target UDP port number should start from the target_UDP_port_num field value and shall increase (or be incremented) by 2. This is to incorporate RTCP streams associated with the RTP streams. 
     The target_UDP_port_num field is a 16-bit unsigned integer field, which represents the target UDP port number for the corresponding IP stream component. When used for RTP streams, the value of the target_UDP_port_num field shall correspond to an even number. And, the next higher value shall represent the target UDP port number of the associated RTCP stream. 
     The component_level_descriptor( ) represents zero or more descriptors providing additional information on the corresponding IP stream component. 
     The virtual_channel_level_descriptor( ) represents zero or more descriptors providing additional information for the corresponding virtual channel. 
     The ensemble_level_descriptor( ) represents zero or more descriptors providing additional information for the MH ensemble, which is described by the corresponding SMT. 
       FIG. 18  illustrates an exemplary bit stream syntax structure of an MH audio descriptor according to the present invention. When at least one audio service is present as a component of the current event, the MH_audio_descriptor( ) shall be used as a component_level_descriptor of the SMT. The MH_audio_descriptor( ) may be capable of informing the system of the audio language type and stereo mode status. If there is no audio service associated with the current event, then it is preferable that the MH_audio_descriptor( ) is considered to be insignificant (or absent) for the current event. Each field shown in the bit stream syntax of  FIG. 18  will now be described in detail. 
     The descriptor_tag field is an 8-bit unsigned integer having a TBD value, which indicates that the corresponding descriptor is the MH_audio_descriptor( ). The descriptor_length field is also an 8-bit unsigned integer, which indicates the length (in bytes) of the portion immediately following the descriptor_length field up to the end of the MH_audio_descriptor( ). The channel configuration field corresponds to an 8-bit field indicating the number and configuration of audio channels. The values ranging from ‘1’ to ‘6’ respectively indicate the the number and configuration of audio channels as given for “Default bit stream index number” in Table 42 of ISO/IEC 13818-7:2006. All other values indicate that the number and configuration of audio channels are undefined. 
     The sample_rate_code field is a 3-bit field, which indicates the sample rate of the encoded audio data. Herein, the indication may correspond to one specific sample rate, or may correspond to a set of values that include the sample rate of the encoded audio data as defined in Table A3.3 of ATSC A/52B. The bit_rate_code field corresponds to a 6-bit field. Herein, among the 6 bits, the lower 5 bits indicate a nominal bit rate. More specifically, when the most significant bit (MSB) is ‘0’, the corresponding bit rate is exact. On the other hand, when the most significant bit (MSB) is ‘0’, the bit rate corresponds to an upper limit as defined in Table A3.4 of ATSC A/53B. The ISO_639_language_code field is a 24-bit (i.e., 3-byte) field indicating the language used for the audio stream component, in conformance with ISO 639.2/B [x]. When a specific language is not present in the corresponding audio stream component, the value of each byte will be set to ‘0x00’. 
       FIG. 19  illustrates an exemplary bit stream syntax structure of an MH RTP payload type descriptor according to the present invention. 
     The MH_RTP_payload_type_descriptor( ) specifies the RTP payload type. Yet, the MH_RTP_payload_type_descriptor( ) exists only when the dynamic value of the RTP_payload_type field within the num_components loop of the SMT is in the range of ‘96’ to ‘127’. The MH_RTP_payload_type_descriptor( ) is used as a component_level_descriptor of the SMT. 
     The MH_RTP_payload_type_descriptor translates (or matches) a dynamic RTP_payload_type field value into (or with) a MIME type. Accordingly, the receiving system (or receiver) may collect (or gather) the encoding format of the IP stream component, which is encapsulated in RTP. 
     The fields included in the MH_RTP_payload_type_descriptor( ) will now be described in detail. 
     The descriptor_tag field corresponds to an 8-bit unsigned integer having the value TBD, which identifies the current descriptor as the MH_RTP_payload_type_descriptor( ). 
     The descriptor_length field also corresponds to an 8-bit unsigned integer, which indicates the length (in bytes) of the portion immediately following the descriptor length field up to the end of the MH_RTP_payload_type_descriptor( ). 
     The RTP_payload_type field corresponds to a 7-bit field, which identifies the encoding format of the IP stream component. Herein, the dynamic value of the RTP_payload_type field is in the range of ‘96’ to ‘127’. 
     The MIME_type_length field specifies the length (in bytes) of the MIME_type field. 
     The MIME_type field indicates the MIME type corresponding to the encoding format of the IP stream component, which is described by the MH_RTP_payload_type_descriptor( ). 
       FIG. 20  illustrates an exemplary bit stream syntax structure of an MH current event descriptor according to the present invention. 
     The MH_current_event_descriptor( ) shall be used as the virtual_channel_level_descriptor( ) within the SMT. Herein, the MH_current_event_descriptor( ) provides basic information on the current event (e.g., the start time, duration, and title of the current event, etc.), which is transmitted via the respective virtual channel. 
     The fields included in the MH_current_event_descriptor( ) will now be described in detail. 
     The descriptor_tag field corresponds to an 8-bit unsigned integer having the value TBD, which identifies the current descriptor as the MH_current_event_descriptor( ). 
     The descriptor_length field also corresponds to an 8-bit unsigned integer, which indicates the length (in bytes) of the portion immediately following the descriptor_length field up to the end of the MH_current_event_descriptor( ). 
     The current_event_start_time field corresponds to a 32-bit unsigned integer quantity. The current_event_start_time field represents the start time of the current event and, more specifically, as the number of GPS seconds since 00:00:00 UTC, Jan. 6, 1980. 
     The current_event_duration field corresponds to a 24-bit field. Herein, the current_event_duration field indicates the duration of the current event in hours, minutes, and seconds (wherein the format is in 6 digits, 4-bit BCD=24 bits). 
     The title_length field specifies the length (in bytes) of the title_text field. Herein, the value ‘0’ indicates that there are no titles existing for the corresponding event. 
     The title_text field indicates the title of the corresponding event in event title in the format of a multiple string structure as defined in ATSC A/65C [x]. 
       FIG. 21  illustrates an exemplary bit stream syntax structure of an MH next event descriptor according to the present invention. 
     The optional MH_next_event_descriptor( ) shall be used as the virtual_channel_level_descriptor( ) within the SMT. Herein, the MH_next_event_descriptor( ) provides basic information on the next event (e.g., the start time, duration, and title of the next event, etc.), which is transmitted via the respective virtual channel. The fields included in the 
     MH_next_event_descriptor( ) will now be described in detail. 
     The descriptor_tag field corresponds to an 8-bit unsigned integer having the value TBD, which identifies the current descriptor as the MH_next_event_descriptor( ). 
     The descriptor length field also corresponds to an 8-bit unsigned integer, which indicates the length (in bytes) of the portion immediately following the descriptor_length field up to the end of the MH_next_event_descriptor( ). 
     The next_event_start_time field corresponds to a 32-bit unsigned integer quantity. The next_event_start_time field represents the start time of the next event and, more specifically, as the number of GPS seconds since 00:00:00 UTC, Jan. 6, 1980. 
     The next_event_duration field corresponds to a 24-bit field. Herein, the next_event_duration field indicates the duration of the next event in hours, minutes, and seconds (wherein the format is in 6 digits, 4-bit BCD=24 bits). 
     The title_length field specifies the length (in bytes) of the title_text field. Herein, the value ‘0’ indicates that there are no titles existing for the corresponding event. 
     The title_text field indicates the title of the corresponding event in event title in the format of a multiple string structure as defined in ATSC A/65C [x]. 
       FIG. 22  illustrates an exemplary bit stream syntax structure of an MH system time descriptor according to the present invention. 
     The MH_system_time_descriptor( ) shall be used as the ensemble_level_descriptor( ) within the SMT. Herein, the MH_system_time_descriptor( ) provides information on current time and date. 
     The MH_system_time_descriptor( ) also provides information on the time zone in which the transmitting system (or transmitter) transmitting the corresponding broadcast stream is located, while taking into consideration the mobile/portable characteristics of the MH service data. The fields included in the MH_system_time_descriptor( ) will now be described in detail. 
     The descriptor_tag field corresponds to an 8-bit unsigned integer having the value TBD, which identifies the current descriptor as the MH_system_time_descriptor( ). 
     The descriptor_length field also corresponds to an 8-bit unsigned integer, which indicates the length (in bytes) of the portion immediately following the descriptor_length field up to the end of the MH_system_time_descriptor( ). 
     The system_time field corresponds to a 32-bit unsigned integer quantity. The system_time field represents the current system time and, more specifically, as the number of GPS seconds since 00:00:00 UTC, Jan. 6, 1980. 
     The GPS_UTC_offset field corresponds to an 8-bit unsigned integer, which defines the current offset in whole seconds between GPS and UTC time standards. In order to convert GPS time to UTC time, the GPS_UTC_offset is subtracted from GPS time. Whenever the International Bureau of Weights and Measures decides that the current offset is too far in error, an additional leap second may be added (or subtracted). Accordingly, the GPS_UTC_offset field value will reflect the change. 
     The time_zone_offset_polarity field is a 1-bit field, which indicates whether the time of the time zone, in which the broadcast station is located, exceeds (or leads or is faster) or falls behind (or lags or is slower) than the UTC time. When the value of the time_zone_offset_polarity field is equal to ‘0’, this indicates that the time on the current time zone exceeds the UTC time. Therefore, the time_zone_offset_polarity field value is added to the UTC time value. Conversely, when the value of the time_zone_offset_polarity field is equal to ‘1’, this indicates that the time on the current time zone falls behind the UTC time. Therefore, the time_zone_offset_polarity field value is subtracted from the UTC time value. 
     The time_zone_offset field is a 31-bit unsigned integer quantity. More specifically, the time_zone_offset field represents, in GPS seconds, the time offset of the time zone in which the broadcast station is located, when compared to the UTC time. 
     The daylight_savings field corresponds to a 16-bit field providing information on the Summer Time (i.e., the Daylight Savings Time). The time_zone field corresponds to a (5×8)-bit field indicating the time zone, in which the transmitting system (or transmitter) transmitting the corresponding broadcast stream is located. 
       FIG. 23  illustrates segmentation and encapsulation processes of a service map table (SMT) according to the present invention. 
     According to the present invention, the SMT is encapsulated to UDP, while including a target IP address and a target UDP port number within the IP datagram. 
     More specifically, the SMT is first segmented into a predetermined number of sections, then encapsulated to a UDP header, and finally encapsulated to an IP header. In addition, the SMT section provides signaling information on all virtual channel included in the MH ensemble including the corresponding SMT section. At least one SMT section describing the MH ensemble is included in each RS frame included in the corresponding MH ensemble. Finally, each SMT section is identified by an ensemble_id included in each section. According to the embodiment of the present invention, by informing the receiving system of the target IP address and target UDP port number, the corresponding data (i.e., target IP address and target UDP port number) may be parsed without having the receiving system to request for other additional information. 
       FIG. 24  illustrates a flow chart for accessing a virtual channel using FIC and SMT according to the present invention. 
     More specifically, a physical channel is tuned (S 501 ). And, when it is determined that an MH signal exists in the tuned physical channel (S 502 ), the corresponding MH signal is demodulated (S 503 ). Additionally, FIC segments are grouped from the demodulated MH signal in sub-frame units (S 504  and S 505 ). 
     According to the embodiment of the present invention, an FIC segment is inserted in a data group, so as to be transmitted. More specifically, the FIC segment corresponding to each data group described service information on the MH ensemble to which the corresponding data group belongs. When the FIC segments are grouped in sub-frame units and, then, deinterleaved, all service information on the physical channel through which the corresponding FIC segment is transmitted may be acquired. Therefore, after the tuning process, the receiving system may acquire channel information on the corresponding physical channel during a sub-frame period. Once the FIC segments are grouped, in S 504  and S 505 , a broadcast stream through which the corresponding FIC segment is being transmitted is identified (S 506 ). For example, the broadcast stream may be identified by parsing the transport_stream_id field of the FIC body, which is configured by grouping the FIC segments. 
     Furthermore, an ensemble identifier, a major channel number, a minor channel number, channel type information, and so on, are extracted from the FIC body (S 507 ). And, by using the extracted ensemble information, only the slots corresponding to the designated ensemble are acquired by using the time-slicing method, so as to configure an ensemble (S 508 ). 
     Subsequently, the RS frame corresponding to the designated ensemble is decoded (S 509 ), and an IP socket is opened for SMT reception (S 510 ). 
     According to the example given in the embodiment of the present invention, the SMT is encapsulated to UDP, while including a target IP address and a target UDP port number within the IP datagram. More specifically, the SMT is first segmented into a predetermined number of sections, then encapsulated to a UDP header, and finally encapsulated to an IP header. According to the embodiment of the present invention, by informing the receiving system of the target IP address and target UDP port number, the receiving system parses the SMT sections and the descriptors of each SMT section without requesting for other additional information (S 511 ). 
     The SMT section provides signaling information on all virtual channel included in the MH ensemble including the corresponding SMT section. At least one SMT section describing the MH ensemble is included in each RS frame included in the corresponding MH ensemble. Also, each SMT section is identified by an ensemble_id included in each section. 
     Furthermore each SMT provides IP access information on each virtual channel subordinate to the corresponding MH ensemble including each SMT. Finally, the SMT provides IP stream component level information required for the servicing of the corresponding virtual channel. 
     Therefore, by using the information parsed from the SMT, the IP stream component belonging to the virtual channel requested for reception may be accessed (S 513 ). Accordingly, the service associated with the corresponding virtual channel is provided to the user (S 514 ). 
       FIG. 25  illustrates a block diagram showing a general structure of a digital broadcasting receiving system according to another embodiment of the present invention; 
     Referring to  FIG. 25 , the reception system according to another embodiment of the present invention includes a baseband processor  100 , a management processor  200 , and a presentation processor  300 . 
     The baseband processor  100  includes an operation controller  110 , a tuner  120 , a demodulator  130 , an equalizer  140 , a known sequence detector  150 , a Mobile Handheld block decoder  160 , a primary Reed-Solomon (RS) frame decoder  170 , a secondary RS frame decoder  180 , and a signaling decoder  190 . In this case, the operation controller  110 , the tuner  120 , the demodulator  130 , the equalizer  140 , the known sequence detector  150 , the Mobile Handheld block decoder  160 , the primary RS frame decoder  170 , the secondary RS frame decoder  180 , and the signaling decoder  190  shown in  FIG. 25  correspond to the operation controller  110 , the tuner  120 , the demodulator  130 , the equalizer  140 , the known sequence detector  150 , the mobile handheld block decoder  160 , the primary RS frame decoder  170 , the secondary RS frame decoder  180 , and the signaling decoder  190  shown in  FIG. 1 , respectively. Detailed descriptions of the above-mentioned components of  FIG. 25  are equal to those of  FIG. 1 , such that they will herein be omitted for the convenience of description. 
     The management processor  200  includes an MH physical adaptation processor  210 , an IP network stack  220 , a streaming handler  230 , an SI handler  240 , a file handler  250 , a MIME (Multipurpose Internet Mail Extensions) type handler  260 , an ESG handler  270 , an ESG decoder  280 , a storage unit  290 . In this case, the IP network stack  220 , the streaming handler  230 , the SI handler  240 , the file handler  250 , the MIME type handler  260 , the ESG handler  270 , the ESG decoder  280 , and the storage unit  290  shown in  FIG. 25  correspond to the IP network stack  220 , the streaming handler  230 , the SI handler  240 , the file handler  250 , the MIME type handler  260 , the ESG handler  270 , the ESG decoder  280 , and the storage unit  290  shown in  FIG. 1 . Detailed descriptions of the above-mentioned components of  FIG. 25  are equal to those of  FIG. 1 , such that they will herein be omitted for the convenience of description. 
     The MH physical adaptation processor  210  may include a primary RS handler  211 , a secondary RS frame handler  212 , a Generic Stream Encapsulation (GSE) handler  2513 , a TPC handler  214 , an FIC handler  215 , and a physical adaptation control signal handler  216 . 
     The primary RS frame handler  211  receives a primary RS frame from the primary RS frame decoder  170  of the baseband processor  100 , divides the received primary RS frame into Transport Packets (TPs) used as row units, and outputs the divided TPs to the GSE handler  2513 . 
     The secondary RS frame handler  212  receives a secondary RS frame from the secondary RS frame decoder  180  of the baseband processor  100 , divides the received secondary RS frame into transport packets (TPs) used as row units, and outputs the divided TPs to the GSE handler  2513 . 
     The GSE handler  2513  extracts the GSE packet from the TPs received from the primary and secondary RS frame handlers  211  and  212 , and calculates an IP datagram from the extracted GSE packet. The GSE handler  2513  outputs the IP datagram to the IP network stack  220 . 
     The TPC handler  214 , the FIC handler  215 , and the physical adaptation control signal handler  216  shown in  FIG. 25  correspond to the TPC handler  214 , the FIC handler  215 , and the physical adaptation control signal handler  216  shown in  FIG. 1 , respectively. Detailed descriptions of the above-mentioned components of  FIG. 25  are equal to those of  FIG. 1 , such that they will herein be omitted for the convenience of description. 
     The presentation processor  300  includes an A/V decoder  310 , a display module  320 , a presentation controller  330 , a channel service manager  340 , and an application manager  350 . In this case, the A/V decoder  310 , the display module  320 , the presentation controller  330 , the channel service manager  340 , and the application manager  350  shown in  FIG. 25  correspond to the A/V decoder  310 , the display module  320 , the presentation controller  330 , the channel service manager  340 , and the application manager  350  shown in  FIG. 1 . Detailed descriptions of the above-mentioned components of  FIG. 25  are equal to those of  FIG. 1 , such that they will herein be omitted for the convenience of description. 
       FIG. 26  is a structural diagram illustrating a Reed Solomon (RS) frame according to another embodiment of the present invention. 
     Referring to  FIG. 26 , the RS frame according to the present invention may include at least one GSE packet. If the at least one GSE packet is contained in the RS frame, there is no need for the RS frame to have an additional header for discriminating individual GSE packets. 
     There may be an allocation process for allowing one row of the RS frame to have one GSE packet. In this case, the RS frame includes 187 rows, such that it may include 187 GSE packets. If 11 rows of the RS frame are allocated to have one GSE packet, the RS frame may include 17 GSE packets. 
     The individual rows of the RS frame have variable lengths, such that one row of the RS frame may be allocated to a GSE BB (Base Band) frame. In other words, the GSE BB frame may construct one row of the RS frame. In this case, a header of the GSE BB frame is contained in one row of the RS frame, such that the resultant one row of the RS frame can be constructed. The GSE BB frame header may be deleted from one row of the RS frame, such that the resultant one row of the RS frame can be constructed. Although the GSE BB frame header is deleted, the GSE packet may be extracted from the GSE BB frame on the basis of a header of a first GSE packet contained in the GSE BB frame. The GSE BB frame indicates a frame defined on a physical layer including at least one RS packet. 
       FIG. 27  shows the relationship between Protocol Data Units (PDUs) and a Generic Stream Encapsulation (GSE) packet according to the present invention. 
     Referring to  FIG. 27 , the PDUs defined on the network layer may be contained in a data field of the GSE packet. In this case, one GSE packet may include at least one PDU, and a plurality of GSE packets may include a single PDU. If the single PDU is contained in the several GSE packets and is then encapsulated in the GSE packet, PDU fragmentation may be conducted. When the PDU is calculated from the GSE packet, a PDU reassembly may be conducted. For example, an IP datagram or an Ethernet frame may be used as an example of the PDU. 
     The GSE packet may be contained in a Base Band (BB) frame. One GSR packet may be contained in one BB frame, and several GSE packets may be contained in one BB frame. 
       FIG. 28  shows a header of the GSE packet according to the present invention. 
     Referring to  FIG. 28 , the GSE packet header may include at least one of a Start_Indicator(S) field, an End_Indicator(E) field, a Label_Type_Indicator(LT) field, a GSE_Length field, a Frag_ID field, a Total_Length field, a Protocol_Type field, a Label field, and an Extension_Header_Bytes field. The Start_Indicator(S) field may include specific information indicating a start part of the encapsulated PDU in the GSE packet, and may have the size of one bit. The End_Indicator(E) field may include specific information indicating the end of the encapsulated PDU in the GSE packet, and may have the size of one bit. The Label_Type_Indicator(LT) field may include padding information, and may have the size of 2 bits. The GSE_Length field may include specific information indicating the length of the GSE packet, and may have the size of 12 bits. The Frag_ID field may include specific information indicating whether the PDU fragment is contained in the GSE packet, and may have the size of 1 byte. If the Start_Indicator(S) field and the End_Indicator(E) field are established, the Frag_ID field may include specific information indicating the absence of the PDU fragment in the GSE packet. The Total_Length field may be contained in the header of the GSE packet including a first fragment of the fragmented PDU, may include total length information of the fragmented PDU, and may have the size of 2 bytes. The Protocol_Type field may include specific information indicating a type of the payload delivered by the PDU contained in the GSE packet, and may have the size of 2 bytes. The Label field may include label information used for an addressing operation, and may have the size of 3/6 bytes. The Extension_Header_Bytes may be reserved for the extended header format, and may have the size of 2 bytes or the size of at least 2 bytes. 
     If several GSE packets include one PDU, the GSE handler  2513  may reassemble PDU fragments contained in the several GSE packets on the basis of information contained in the Start_Indicator(S) field, the End_Indicator(E) field, the Frag_ID field, and the Total_Length field. That is, the GSE handler  2513  may extract PDU fragments from individual GSE packets from a first GSE packet including start information of the encapsulated PDU in the SE packet to the last GSE packet including end information of the encapsulated PDU in the GSE packet, and may reassemble the extracted PDU fragments, such that it may calculate the PDU. The GSE handler  2513  may check the size of the reassembled PDU on the basis of the information contained in the Total_Length field, and may check a GSE packet located between the first GSE packet including start information of the PDU and the last GSE packet including end information of the encapsulated PDU in the GSE packet based on the Frag_ID field. 
       FIG. 29  is a conceptual diagram illustrating a method for constructing the GSE packet according to the present invention. 
     Referring to  FIG. 29 , a Real-time Transport Protocol (RTP) packet is encapsulated into a User Datagram Protocol (UDP) packet in order to construct one GSE packet. The UDP packet is encapsulated into the IP packet. The IP packet is encapsulated into the GSE packet. The BB frame is formed by the GSE packet. In this case, the RTP packet may include a header of 12 bytes and a payload, and this payload may include mobile service data. 
     The GSE packet may include the PDU header having a total length of 40 bytes, for example, the RTP packet&#39;s header of 12 bytes, the UDP packet&#39;s header of 8 bytes, and the IP packet&#39;s header of 20 bytes. Therefore, a bandwidth occupied by a network for transmitting actual broadcast contents is reduced. 
     In accordance with this embodiment of the present invention, header information contained in the PDU contained in the GSE packet is compressed, and the compressed header information is stored. For example, a Robust Header Compression (ROHC) may be used to compress the above PDU header information. The ROHC may include a variety of exemplary header compression methods, for example, a Unidirectional Mode, a Bidirectional Optimistic Mode, and a Bidirectional Reliable Mode. The Bidirectional Optimistic Mode and the Bidirectional Reliable Mode may transmit a feedback message for indicating whether or not reception data is correctly received to a compression part for performing the data compression. Otherwise, the Unidirectional Mode may not transmit the feedback message to the compression part. Therefore, the Bidirectional Optimistic Mode and the Bidirectional Reliable Mode may transmit the feedback information to the compression part, such that they may compress the header more effectively and reliably than the Unidirectional Mode. 
     The PDU header of 40 bytes contained in the GSE packet may be compressed to 3 bytes or 4 bytes on the basis of the ROHC algorithm. 
     If the header of the PDU contained in the GSE packet is compressed, the GSE handler  2513  may extract the header of the compressed PDU from the GSE packet, and may recover the extracted header of the compressed PDU, such that it may calculate the PDU. 
       FIG. 30  is a flow chart illustrating a data processing method according to the present invention. 
     Referring to  FIG. 30 , one physical channel is selected or changed at step S 3000 . The selected physical channel is tuned at step S 3010 . A broadcast signal in which main service data and mobile service data are multiplexed is demodulated at step S 3020 . In this case, a digital broadcasting system for use in the above-mentioned data processing method may acquire high-speed data channel information indicating a relationship between the ensemble of the mobile service data and a virtual channel from the demodulated broadcast signal. 
     The digital broadcasting system may detect a mobile service data frame from the demodulated broadcast signal using the high-speed data channel information at step S 3030 . In this case, the RS frame may be detected as the mobile service data frame as an example. 
     The detected mobile service data frame may be scanned in row units at step S 3040 . In this case, the detected mobile service data frame may be stored in a buffer, and the stored mobile service data frame may be read in row units. 
     The digital broadcasting system may extract the GSE packet from the mobile service data frame at step S 3050 . In this case, the BB frame may construct one row of the mobile service data frame. In this case, the digital broadcasting system may extract at least one GSE packet contained in one BB frame from one row of the mobile service data frame. 
     The digital broadcasting system may calculate the IP datagram from the extracted GSE packet at step S 3060 . In this case, if data contained in the PDU header in total data contained in the above GSE packet is compressed data, the compressed data is recovered such that the IP datagram can be calculated. The digital broadcasting system may calculate the IP datagram from one or two GSE packets. If the IP datagram is calculated from at least two GSE packets, IP datagram fragments contained in each GSE packet are reassembled such that the IP datagram is calculated. 
     As apparent from the above description, the digital broadcasting system and the data processing method according to the present invention have strong resistance to any errors encountered when mobile service data is transmitted over a channel, and can be easily compatible with the conventional receiver. The digital broadcasting system and the data processing method according to the present invention can normally receive mobile service data without any errors over a poor channel which has lots of ghosts and noises. The digital broadcasting system and the data processing method according to the present invention insert known data at a specific location of a data zone, and perform signal transmission, thereby increasing the reception (Rx) performance under a high-variation channel environment. Specifically, the digital broadcasting system and the data processing method according to the present invention can be more effectively used for mobile phones or mobile receivers, channel conditions of which are excessively changed and have weak resistances to noise. 
     Also, the digital broadcasting system and the data processing method can quickly access services provided to mobile service data, when the mobile service data is multiplexed with main service data and the multiplexed resultant data is transmitted. 
     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.