Patent Publication Number: US-8989319-B2

Title: Method and apparatus for transmitting/receiving broadcasting-communication data

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of application Ser. No. 12/994,827 filed on Nov. 26, 2010, now issued as U.S. Pat. No. 8,654,886, and claims priority under 35 U.S.C. §119 of Korean Patent Application Nos. 10-2008-0050044 filed on May 29, 2008 and 10-2009-0046540 filed on May 27, 2009, the disclosures of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a method and apparatus for transmitting/receiving broadcasting-communication data. 
     BACKGROUND ART 
     Communication technology has made a progress by being divided into a cable transmission technology mainly providing a data service and a wireless transmission technology focusing on a speech service. Recent progress in high-speed wireless transmission technology and cable network infrastructure contributes to the continuous development of cable and wireless integrated technologies that can provide a data service while securing mobility. The cable-wireless integrated technology can provide users with a variety of services with no regional restriction. 
     Meanwhile, broadcasting technology is undergoing a dramatic change from analog scheme to digital scheme. The change in the broadcasting technology has made it possible to provide users with even more abundant sorts of services such as bi-directional broadcasting service and additional services as well as typical real-time broadcasting services. A broadcasting system occupies one axis of information infrastructure in combination with a communication system, such as cable and wireless internet. A broadcasting system and a communication system, which used to be separate systems independent from each other, are organically combined with each other and make advances. 
     Generally, broadcasting-communication system exists in the form of diverse systems developed to provide diverse services. The data transmission rate of the broadcasting-communication system is determined according to the standard of a corresponding technological area. For example, the standard data transmission rate of the Advanced Terrestrial Systems Committee (ATSC) 8-Vestigial Sideband (VSB) is 19.39 Mbps at 6 MHz band, whereas the standard data transmission rate of Digital Video Broadcasting-Terrestrial (DVB-T) ranges from at least 4.354 Mbps up to 27.710 Mbps at 7 MHz band. Also, the standard data transmission rate of the Terrestrial-Digital Multimedia Broadcasting (T-DMB) is 1.125 Mbps at 1.536 MHz band. 
     Meanwhile, development of diverse services and contents produces services of a new concept such as a data broadcasting service, a non-real time (NRT) service, a disaster alert service and so forth. This calls for technical schemes that can support and transmit the additional services. Conventional broadcasting-communication system uses a method of reducing the data transmission rates of an original service and allocating a new service to the reserved data transmission rate. In other words, some of the bandwidth to be allocated to the original service is allocated to an additional service. As a result, the bandwidth to be allocated to the original service is reduced. In an ATSC 8-VSB system, among 19.39 Mbps allocated to a High-Definition (HD) broadcasting, about 2 Mbps is allocated to a new additional service such as a data broadcasting, and the remaining 17.4 Mbps is allocated to the original HD broadcasting service. Since this method reduces the data transmission rate of the original service to transmit the new additional service, there is a drawback in that the quality of the original service is deteriorated. Therefore, it is required to develop a data transmission method that can transmit additional data without affecting the transmission of original data. 
     DISCLOSURE 
     Technical Problem 
     An embodiment of the present invention is directed to providing a method and apparatus that can improve the overall transmission efficiency of a system by transmitting new additional data while maintaining the data transmission rate of original data. 
     Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it is obvious to those skilled in the art of the present invention that the objects and advantages of the present invention can be realized by the means as claimed and combinations thereof. 
     Technical Solution 
     In accordance with an aspect of the present invention, there is provided an apparatus for transmitting broadcasting-communication data including original data and additional data, which includes: an original signal generator configured to receive the original data and generate baseband original signals; a first modulator configured to receive the baseband additional signals and generate original signals of a predetermined band; an additional signal generator configured to receive the additional data and generate baseband additional signals; a second modulator configured to receive the baseband additional signals and generate additional signals of a predetermined band; an average power controller configured to control an average power of the additional signals of the predetermined band; an inserter configured to insert the additional signals of the predetermined band with a controlled average power to the original signals of the predetermined band to thereby generate mixed signals of a predetermined band; and a transmitter configured to transmit the mixed signals of the predetermined band. 
     In accordance with another aspect of the present invention, there is provided an apparatus for transmitting broadcasting-communication data including original data and additional data, which includes: an original signal generator configured to receive the original data and generate baseband original signals; an additional signal generator configured to receive the additional data and generate baseband additional signals; an average power controller configured to control an average power of the baseband additional signals; an inserter configured to insert the baseband additional signals with a controlled average power to the baseband original signals to thereby generate baseband mixed signals; a modulator configured to receive the baseband mixed signals and generate mixed signals of a predetermined band; and a transmitter configured to transmit the mixed signals of the predetermined band. 
     In accordance with another aspect of the present invention, there is provided a method for transmitting broadcasting-communication data including original data and additional data, which includes: receiving the original data and generating baseband original signals; receiving the baseband original signals and generating original signals of a predetermined band; receiving the additional data and generating baseband additional signals; receiving the baseband additional signals and generating additional signals of a predetermined band; controlling an average power of the additional signals of the predetermined band; inserting the additional signals of the predetermined band with a controlled average power to the original signals of the predetermined band to thereby generate mixed signals of a predetermined band; and transmitting the mixed signals of the predetermined band. 
     In accordance with another aspect of the present invention, there is provided a method for transmitting broadcasting-communication data including original data and additional data, which includes: receiving the original data and generating baseband original signals; receiving the additional data and generating baseband additional signals; controlling an average power of the baseband additional signals; inserting the baseband additional signals with a controlled average power to the baseband original signals to thereby generate baseband mixed signals; receiving the baseband mixed signals and generating mixed signals of a predetermined band; and transmitting the mixed signals of the predetermined band. 
     In accordance with another aspect of the present invention, there is provided a broadcasting-communication data receiving apparatus for receiving mixed signals including original signals and additional signals, which includes: a receiver configured to receive the mixed signals and output mixed signals of a predetermined band; a first demodulator configured to receive the mixed signals of the predetermined band and generate baseband mixed signals; an original data generator configured to receive the baseband mixed signals and generate original data; an original signal generator configured to receive the original data and generate baseband original signals; a modulator configured to receive the baseband original signals and generate original signals of a predetermined band; a subtractor configured to subtract the original signals of the predetermined band from the mixed signals of the predetermined band to thereby generate additional signals of a predetermined band; a second demodulator configured to receive the additional signals of the predetermined band and generate baseband additional signals; and an additional data generator configured to receive the baseband additional signals and generate additional data. 
     In accordance with another aspect of the present invention, there is provided a broadcasting-communication data receiving apparatus for receiving mixed signals including original signals and additional signals, which includes: a receiver configured to receive the mixed signals and output mixed signals of a predetermined band; a demodulator configured to receive the mixed signals of the predetermined band and generate baseband mixed signals; an original data generator configured to receive the baseband mixed signals and generate original data; an original signal generator configured to receive the original data and generate baseband original signals; a subtractor configured to subtract the baseband original signals from the baseband mixed signals to thereby generate baseband additional signals; and an additional data generator configured to receive the baseband additional signals and generate additional data. 
     In accordance with another aspect of the present invention, there is provided a broadcasting-communication data receiving method for receiving mixed signals including original signals and additional signals, which includes: receiving the mixed signals and outputting mixed signals of a predetermined band; receiving the mixed signals of the predetermined band and generating baseband mixed signals; receiving the baseband mixed signals and generating original data; receiving the original data and generating baseband original signals; receiving the baseband original signals and generating original signals of a predetermined band; subtracting the original signals of the predetermined band from the mixed signals of the predetermined band to thereby generate additional signals of a predetermined band; receiving the additional signals of the predetermined band and generating baseband additional signals; and receiving the baseband additional signals and generating additional data. 
     In accordance with another aspect of the present invention, there is provided a broadcasting-communication data receiving method for receiving mixed signals including original signals and additional signals, which includes: receiving the mixed signals and outputting mixed signals of a predetermined band; receiving the mixed signals of the predetermined band and generating baseband mixed signals; receiving the baseband mixed signals and generating original data; receiving the original data and generating baseband original signals; subtracting the baseband original signals from the baseband mixed signals to thereby generate baseband additional signals; and receiving the baseband additional signals and generating additional data. 
     Advantageous Effects 
     The technology of the present invention described above can improve the overall transmission efficiency of a system by transmitting new additional data while maintaining the data transmission rate of original data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block view of a broadcasting-communication data transmitting apparatus in accordance with an embodiment of the present invention. 
         FIG. 2  is a block view of a broadcasting-communication data transmitting apparatus in accordance with another embodiment of the present invention. 
         FIG. 3  is a block view of an original signal generator shown in  FIGS. 1 and 2 . 
         FIG. 4  is a block view of an additional signal generator shown in  FIGS. 1 and 2 . 
         FIG. 5  is a block view of a Forward Error Correction (FEC) encoder shown in  FIG. 4 . 
         FIG. 6  shows an orthogonal sequence generated in a spreading sequence generator shown in  FIG. 4 . 
         FIG. 7  is a block view of an average power controller shown in  FIG. 1 . 
         FIG. 8  is a block view of an average power controller shown in  FIG. 2 . 
         FIG. 9  is a block view illustrating a broadcasting-communication data transmitting apparatus based on the Advanced Terrestrial Systems Committee (ATSC) 8-Vestigial Sideband (VSB) in accordance with yet another embodiment of the present invention. 
         FIG. 10  is a block view describing a broadcasting-communication data receiving apparatus in accordance with a first embodiment of the present invention. 
         FIG. 11  is a block view describing a broadcasting-communication data receiving apparatus in accordance with a second of the present invention. 
         FIG. 12  is a block view describing a broadcasting-communication data receiving apparatus in accordance with a third embodiment of the present invention. 
         FIG. 13  is a block view describing a broadcasting-communication data receiving apparatus in accordance with a fourth embodiment of the present invention. 
         FIG. 14  is a block view describing an original data generator shown in  FIGS. 10 to 13 . 
         FIG. 15  is a block view describing an additional data generator shown in  FIGS. 10 to 13 . 
         FIG. 16  shows an orthogonal sequence generated in a despreading sequence generator shown in  FIG. 15 . 
         FIG. 17  is a block view of a correlator shown in  FIG. 15 . 
         FIG. 18  is a block view of an FEC decoder shown in  FIG. 15 . 
         FIG. 19  is a block view illustrating a broadcasting-communication receiving apparatus based on the ATSC 8-VSB standard in accordance with a fifth embodiment of the present invention. 
     
    
    
     BEST MODE FOR THE INVENTION 
     The advantages, features and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter. When it is considered that detailed description on a prior art may obscure a point of the present invention, the description will not be provided. Hereafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are given to the same constituent elements, although they appear in different drawings. 
     Hereafter, broadcasting or communication data that used to be provided to users will be referred to as original data, and data to be provided additionally to the users other than the original data will be referred to as additional data. 
       FIG. 1  is a block view of a broadcasting-communication data transmitting apparatus in accordance with an embodiment of the present invention. Referring to  FIG. 1 , the broadcasting-communication data transmitting apparatus includes an original signal generator  102 , a first modulator  104 , an additional signal generator  106 , a second modulator  108 , an average power controller  110 , an additional data inserter  112 , and a transmitter  114 . 
     The original signal generator  102  receives original data and generates baseband original signals in conformity with the transmission standard of a broadcasting-communication system. The first modulator  104  receives the baseband original signals generated in the original signal generator  102  and modulates them into original signals of a predetermined band. 
     The additional signal generator  106  receives additional data and generates baseband additional signals in conformity with the transmission standard of the broadcasting-communication system. The second modulator  108  receives the baseband additional signals generated in the additional signal generator  106  and modulates them into additional signals of a predetermined band. 
     The average power controller  110  controls the average power of the additional signals of the predetermined band generated in the second modulator  108 . Herein, the reason why the average power of the additional signals of the predetermined band is controlled is that the additional signals of the predetermined band are band-spread and inserted in the form of noise, which scarcely affects the original signals of the predetermined band. Therefore, the average power controller  110  controls the average power of the additional signals of the predetermined band as long as the original signals are not affected. 
     The additional data inserter  112  inserts the additional signals of the predetermined band whose average power is controlled by the average power controller  110  into the original signals of the predetermined band generated in the first modulator  104  to thereby generate mixed signals of a predetermined band including the original signals and the additional signals mixed with each other. 
     The transmitter  114  transmits the mixed signals of the predetermined band generated in the additional data inserter  112 . If necessary, the transmitter  114  may convert the mixed signals of the predetermined band into radio frequency (RF) band, which is appropriate for wireless transmission. 
       FIG. 2  is a block view of a broadcasting-communication data transmitting apparatus in accordance with another embodiment of the present invention. Referring to  FIG. 2 , the broadcasting-communication data transmitting apparatus includes an original signal generator  202 , an additional signal generator  204 , an average power controller  206 , an inserter  208 , a modulator  210 , and a transmitter  212 . 
     The original signal generator  202  receives original data and generates baseband original signals in conformity with the transmission standard of a broadcasting-communication system. The additional signal generator  204  receives the additional signals and generates baseband additional signals in conformity with the transmission standard of the broadcasting-communication system. 
     The average power controller  206  controls the average power of the baseband additional signals generated in the additional signal generator  204 . 
     The inserter  208  inserts the additional signals of the predetermined band whose average power is controlled by the average power controller  206  into the original signals of the predetermined band generated in the original signal generator  202  to thereby produce baseband mixed signals. 
     The modulator  210  receives the baseband mixed signals generated in the inserter  208  and modulates them into mixed signals of a predetermined band. 
     The transmitter  212  transmits the mixed signals of the predetermined band generated in the modulator  210 . If necessary, the transmitter  212  may convert the mixed signals of the predetermined band into RF band, which is appropriate for wireless transmission. 
     Since the broadcasting-communication data transmitting apparatus of  FIG. 2  uses one modulator, it has lower hardware complexity than the structure of  FIG. 1 . Also, since the insertion of the additional signals into the original signals is performed at baseband, it can be easily realized. 
       FIG. 3  is a block view of an original signal generator  102  or  202  shown in  FIGS. 1 and 2 . 
     The original signal generator  102  of  FIG. 1  or the original signal generator  202  of  FIG. 2  may be formed in various forms.  FIG. 3  presents an example. The drawings shows a block view of an original signal generator according to the Advanced Terrestrial Systems Committee (ATSC) 8-Vestigial SideBand (VSB) transmission standard, where Moving Picture Experts Group (MPEG) 2 Transport Stream (TS) is used as original data. 
     As illustrated in  FIG. 3 , the original signal generator includes a data randomizer  302 , a Reed Solomon (RS) encoder  304 , an interleaver  306 , a Trellis Coded Modulation (TCM) encoder  308 , and a multiplexer (MUX)  310 . 
     The data randomizer  302  receives original data, e.g., MPEG-2 transport stream, and spreads the spectrum of the received original data throughout the entire band. This is to prevent energy from being concentrated on a specific frequency. 
     The RS encoder  304 , which has excellent burst error correction capability, decreases errors occurring in the randomized original data outputted from the data randomizer  302  by performing outer encoding. The interleaver  306  regularly rearranges the RS-encoded original data to prevent burst error. 
     The interleaved original data outputted from the interleaver  306  undergo inner encoding in the TCM encoder  308 , which is a sort of convolutional encoder. The inner-encoded original data obtained in the TCM encoder  308  are multiplexed with a field synchronization signal and a segment synchronization signal in the multiplexer  310  to be converted into baseband ATSC broadcasting signal. 
     The additional signal generator of the broadcasting-communication data transmitting apparatus suggested in the embodiment of the present invention is not limited to the ATSC 8-VSB system shown in  FIG. 3 , and diverse broadcasting-communication standards may be applied thereto. 
       FIG. 4  is a block view of an additional signal generator  106  and  204  shown in  FIGS. 1 and 2 . Referring to  FIG. 4 , the additional signal generator includes a Forward Error Correction (FEC) encoder  402 , a spreading sequence generator  404 , and a spreader  406 . 
     The FEC encoder  402  receives additional data and performs error correction encoding onto the additional data. Herein, the additional data inputted to the FEC encoder  402  may be compressed through diverse methods, e.g., H.264 and MPEG-4, the compression method of the additional data may be different according to the system standard and requirements. Also, diverse error correction codes, such as turbo code, Low Density Parity Check (LDPC) code, and a concatenate code, may be used in the FEC encoder  402 . The error correction code to be used in the FEC encoder  402  may become different as well according to the system standard and requirements. 
     The spreading sequence generator  404  generates orthogonal or quasi-orthogonal sequence for spreading the error correction-encoded data obtained in the FEC encoder  402 . The spreading sequence generator  404  may generate an orthogonal sequence, such as Walsh sequence, or a quasi-orthogonal sequence, such as Gold sequence, Kasami sequence, Bose-Chadhuri-Hocquenghem (BCH) sequence. Whether to select the orthogonal sequence or the quasi-orthogonal sequence may be determined based on the system standard and requirements. 
     The spreader  406  maps the error correction-encoded additional data obtained in the FEC encoder  402  to a spreading sequence generated in the spreading sequence generator  404 . This process is referred to as spreading. The sampling frequency of the spreading sequence is N times the sampling frequency of the error correction-encoded additional data inputted to the spreader  406 , where N is an integer. Therefore, the baseband additional signals outputted from the spreader  406  have a spreading gain as much as dB. Herein, N denotes the length of the spreading sequence. 
     The FEC encoder  402 , the spreading sequence generator  404 , and the spreader  406  shown in  FIG. 4  may be formed diversely according to the system standard and requirements. 
     The spreader  406  maps error correction-encoded additional data obtained in the FEC encoder  402  to the spreading sequence generated in the spreading sequence generator  404 . This process is referred to as spreading. The sampling frequency of the spreading sequence is N times the sampling frequency of the error correction-encoded additional data inputted to the spreader  406 , N being an integer. Thus, the baseband additional signals outputted from the spreader  406  come to have a spreading gain of 10·log 10  N dB, where N denotes the length of the spreading sequence. 
     The FEC encoder  402 , the spreading sequence generator  404 , and the spreader  406  shown in  FIG. 4  may be formed diversely according to the system standard and requirements. 
       FIG. 5  is a block view of the FEC encoder shown in  FIG. 4 . As illustrated in  FIG. 5 , the FEC encoder  402  includes a BCH encoder  502 , a first interleaver  504 , an LDPC encoder  506 , and a second interleaver  508 . 
     The BCH encoder  502 , which is a linear block encoder with excellent random error correction capability, receives the additional data and performs outer encoding. The outer-encoded additional data obtained in the BCH encoder  502  are interleaved in the first interleaver  504 . 
     The LDPC encoder  506 , which has excellent error correction capability, receives the interleaved additional data obtained in the first interleaver  504  and performs inner encoding. The inner-encoded additional data obtained in the LDPC encoder  506  are interleaved again in the second interleaver  508  to thereby produce error correction-encoded additional data. 
       FIG. 6  shows an orthogonal sequence generated in a spreading sequence generator  404  shown in  FIG. 4 . 
     The sequence shown in  FIG. 6  is a Walsh sequence having a length of 8 and generated in the spreading sequence generator  404  shown in  FIG. 4 . The Walsh sequence having a length of 8 includes 8 components W 0 , W 1 , W 2 , W 3 , W 4 , W 5 , W 6 , W 7 , as shown in  FIG. 6 , and the sequences are orthogonal to each other. The Walsh sequence satisfies the following Equation 1. 
     
       
         
           
             
               
                 
                   
                     &lt; 
                     
                       W 
                       i 
                     
                   
                   , 
                   
                     
                       
                         W 
                         j 
                       
                       &gt;= 
                       
                         
                           ∑ 
                           
                             k 
                             = 
                             0 
                           
                           7 
                         
                         ⁢ 
                         
                           
                             
                               W 
                               i 
                             
                             ⁡ 
                             
                               ( 
                               k 
                               ) 
                             
                           
                           · 
                           
                             
                               W 
                               j 
                             
                             ⁡ 
                             
                               ( 
                               k 
                               ) 
                             
                           
                         
                       
                     
                     = 
                     
                       { 
                       
                         
                           
                             8 
                           
                           
                             
                               i 
                               = 
                               j 
                             
                           
                         
                         
                           
                             0 
                           
                           
                             
                               i 
                               ≠ 
                               j 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   Eq 
                   . 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
             
           
         
       
     
     where W i (k) denotes the k th  value of the i th  Walsh code W i . 
     A Walsh sequence having a length of N may be easily generated from Walsh-Hadamard transformation of a Walsh sequence having a length of 2. 
     The following Tables 1 and 2 describe a spreading process performed in the spreader  406  by using the Walsh sequence having a length of 8, that is, the mapping of the error correction-encoded additional data into a spreading sequence. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 C(i) c(i + 1) 
                 Mapping Sequence 
               
               
                   
               
             
            
               
                 00 
                 W 0   
               
               
                 01 
                 W 1   
               
               
                 10 
                 −W 0   
               
               
                 11 
                 −W 1   
               
               
                   
               
            
           
         
       
     
     The Table 1 describes a process of grouping the error correction-encoded additional data obtained in the FEC encoder  402  by two bits (c(i), c(i+1)) and mapping the 2-bit groups to two Walsh sequences W 0  and W 1 . Herein, c(i) denotes the Most Significant Bit (MSB), and c(i+1) denotes the Least Significant Bit (LSB). 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 C(i) c(i + 1) c(i + 2) c(i + 3) 
                 Mapping Sequence 
               
               
                   
               
             
            
               
                 0000 
                 W 0   
               
               
                 0001 
                 W 1   
               
               
                 0010 
                 W 2   
               
               
                 0011 
                 W 3   
               
               
                 0100 
                 W 4   
               
               
                 0101 
                 W 5   
               
               
                 0110 
                 W 6   
               
               
                 0111 
                 W 7   
               
               
                 1000 
                 −W 7   
               
               
                 1001 
                 −W 6   
               
               
                 1010 
                 −W 5   
               
               
                 1011 
                 −W 4   
               
               
                 1100 
                 −W 3   
               
               
                 1101 
                 −W 2   
               
               
                 1110 
                 −W 1   
               
               
                 1111 
                 −W 0   
               
               
                   
               
            
           
         
       
     
     The Table 2 describes a process of grouping the error correction-encoded additional data obtained in the FEC encoder  402  by four bits (c(i), c(i+1), c(i+2), c(i+3)) and mapping the 4-bit groups to 8 Walsh sequences W 0 , W 1 , W 2 , W 3 , W 4 , W 5 , W 6 , W 7 . Herein, c(i) denotes the Most Significant Bit (MSB), and c(i+3) denotes the Least Significant Bit (LSB). 
       FIG. 7  is a block view of the average power controller  110  shown in  FIG. 1 . The average power controller  110  includes a first average power calculator  702 , a second average power calculator  704 , an insertion level decider  706 , and a multiplier  708 . 
     The first average power calculator  702  receives original signals of a predetermined band outputted from the first modulator  104  and calculates the average power of the original signals. The second average power calculator  704  receives additional signals of a predetermined band outputted from the second modulator  108  and calculates the average power of the additional signals. 
     The insertion level decider  706  compares the average power of the original signals of the predetermined band, which is obtained in the first average power calculator  702 , with the average power of the additional signals of the predetermined band, which is obtained in the second average power calculator  704 , and decides an insertion level α. Herein, α is a constant used to make the average power of the additional signals of the predetermined band far lower than the average power of the original signals of the predetermined band. 
     The multiplier  708  multiples the additional signals of the predetermined band outputted from the second modulator  108  by the insertion level α decided in the insertion level decider  706 . As a result, the additional signals of the predetermined band come to have an average power far lower than that of the original signals of the predetermined band. 
       FIG. 8  is a block view of the average power controller  206  shown in  FIG. 2 . The average power controller  206  includes a first average power calculator  802 , a second average power calculator  804 , an insertion level decider  806 , and a multiplier  808 . 
     The first average power calculator  802  receives baseband original signals outputted from the original signal generator  202  and calculates the average power of the baseband original signals. The second average power calculator  804  receives baseband additional signals outputted from the additional signal generator  204  and calculates the average power of the baseband additional signals. 
     The insertion level decider  806  compares the average power of the original signals of the baseband, which is obtained in the first average power calculator  802 , with the average power of the additional signals of the baseband, which is obtained in the second average power calculator  804 , and decides an insertion level α. 
     The multiplier  808  multiples the baseband additional signals outputted from the additional signal generator  204  by the insertion level α decided in the insertion level decider  806 . As a result, the baseband additional signals come to have an average power far lower than that of the baseband original signals. 
     The average power controller appearing in the embodiments of  FIGS. 7 and 8  decides the insertion level by comparing the average power of the signals with each other. This is no more than an embodiment and the insertion levels may be decided through other methods. For example, the average power controller may decides an appropriate insertion level for the average power of a corresponding signal based on a table including records on the insertion levels suitable for each average power of original signals and additional signals. 
       FIG. 9  is a block view illustrating a broadcasting-communication data transmitting apparatus based on the ATSC 8-VSB standard in accordance with yet another embodiment of the present invention. 
     Referring to  FIG. 9 , the broadcasting-communication data transmitting apparatus includes an original signal generator  902 , an additional signal generator  914 , an average power controller  930 , an inserter  940 , a modulator  942 , and a transmitter  948 . 
     The original signal generator  902  includes a data randomizer  904 , a Reed Solomon (RS) encoder  906 , an interleaver  908 , a TCM encoder  910 , and a multiplexer  912 . 
     The additional signal generator  914  includes an FEC encoder  916 , a spreader  926 , and a Walsh sequence generator  928 . Herein, the FEC encoder  916  includes a BCH encoder  918 , a first interleaver  920 , an LDPC encoder  922 , and a second interleaver  924 . 
     The average power controller  930  includes a first average power calculator  932 , a second average power calculator  934 , an insertion level decider  936 , and a multiplier  938 . 
     The modulator  942  includes a VSB modulator  944  and a pilot adder  946 . 
     The transmitter  948  includes an RF up-converter  950 , a high-power amplifier  952 , and a transmission antenna  954 . 
     Hereafter, a data transmitting process of the broadcasting-communication data transmitting apparatus of  FIG. 9  will be described. First, the data randomizer  904  receives original data, e.g., MPEG-2 transport stream, and outputs randomized original data. The randomized original data undergo error correction encoding in the RS encoder and then go through interleaving in the interleaver  908 . The TCM encoder  910  receives the interleaved original data and performs TCM inner encoding. The multiplexer  912  multiplexes the inner-encoded original data together with a field synchronization signal and a segment synchronization signal and converts them into baseband ATSC original signals. 
     Meanwhile, additional data compressed based on such a compression scheme as H.264 are outer-encoded in the BCH encoder  918  and interleaved in the first interleaver  920 . The interleaved additional data obtained in the first interleaver  920  are inner-encoded in the LDPC encoder  922 , and then interleaved again in the second interleaver  924  to be transformed into error correction-encoded additional data. 
     The Walsh sequence generator  928  included in the additional signal generator  914  generates a Walsh sequence having orthogonal property to spread the error correction-encoded additional data. The spreader  926  maps the error correction-encoded additional data, which are outputted from the FEC encoder  916 , to the Walsh sequence generated in the Walsh sequence generator  928 . 
     The first average power calculator  932  included in the average power controller  930  calculates the average power of baseband ATSC original signals outputted from the multiplexer  912  of the original signal generator  902 . The second average power calculator  934  calculates the average power of the baseband additional data outputted from the spreader  926 . 
     The insertion level decider  936  compares the average powers outputted from the first average power calculator  932  and the second average power calculator  934  with each other and determines an insertion level α. The insertion level α is a constant that makes the average power of the baseband additional signals far lower than the average power of the baseband original signals. 
     The multiplier  938  controls the average power by multiplying the baseband additional signals outputted from the spreader  926  by the insertion level α decided in the insertion level decider  936 . 
     The inserter  940  inserts the baseband additional signals with a controlled average power into the baseband ATSC original signals, which is expressed as the following Equation 2.
 
 s ( n )= d ( n )+α· d′ ( n )  Eq. 2
 
     where d(n) denotes a baseband ATSC original signal and may have a value among −7, −5, −3, −1, +1, +3, +5, and +7; d′(n) denotes a baseband additional signal; a denotes the insertion level of the baseband additional signal; and s(n) denotes a baseband mixed signal including an additional signal inserted to an original signal. 
     The mixed signals generated in the inserter  940  are inputted to a pilot adder  946  included in the modulator  942 . The pilot adder  946  adds a pilot signal to a baseband mixed signal outputted from the inserter  940 , which is expressed as the following Equation 3.
 
 t ( n )= s ( n )+1.25  Eq. 3
 
     where the number 1.25 denotes a pilot signal added to a mixed signal s(n); and t(n) denotes a baseband mixed signal with a pilot signal added thereto. 
     The VSB modulator  944  modulates the baseband mixed signals with a pilot signal added thereto into VSB signals of a predetermined band. 
     The RF up-converter  950  included in the transmitter  948  up-converts the VSB-modulated mixed signals of the predetermined band into RF signals. The RF signals obtained in the RF up-converter  950  are amplified by the high-power amplifier  952  and wirelessly transmitted through the transmission antenna  954 . 
     In the above, the broadcasting-communication data transmitting apparatus and method according to the present invention have been described. Hereafter, a broadcasting-communication data receiving apparatus and method will be described. 
       FIG. 10  is a block view describing a broadcasting-communication data receiving apparatus in accordance with a first embodiment of the present invention. 
     Referring to  FIG. 10 , the broadcasting-communication data receiving apparatus includes a receiver  1002 , a first demodulator  1004 , an original data generator  1006 , an original signal generator  1008 , a modulator  1010 , a subtractor  1012 , a second demodulator  1014 , and an additional data generator  1016 . 
     The receiver  1002  receives mixed signals including original signals and additional signals mixed with each other, which are transmitted from a broadcasting-communication data transmitting apparatus. If necessary, the receiver  1002  may convert the mixed signals into mixed signals of a predetermined band. 
     The first demodulator  1004  receives mixed signals of a predetermined band and generates baseband mixed signals. The original data generator  1006  receives the baseband mixed signals outputted from the first demodulator  1004  and restores original data. 
     The original signal generator  1008  receives error correction-decoded original data outputted from the original data generator  1006  and generates the baseband original signals without an additional signal again. The modulator  1010  receives the baseband original signals generated through the original signal generator  1008  and converts them into the same band as the predetermined band of the mixed signals outputted from the receiver  1002 . 
     The subtractor  1012  generates additional signals of a predetermined band by subtracting the additional signals of the predetermined band outputted from the modulator  1010  from the mixed signals of the predetermined band outputted from the receiver  1002 . 
     The second demodulator  1014  receives the additional signals of the predetermined band outputted from the subtractor  1012  and generates baseband additional signals. The additional data generator  1016  receives the baseband additional signals and restores the additional data. 
       FIG. 11  is a block view describing a broadcasting-communication data receiving apparatus in accordance with a second of the present invention. Referring to  FIG. 11 , the broadcasting-communication data receiving apparatus includes a receiver  1022 , a first demodulator  1024 , an original data generator  1026 , a decider  1028 , a modulator  1030 , a subtractor  1032 , a second demodulator  1034 , and an additional data generator  1036 . 
     The receiver  1022  receives mixed signals including original signals and additional signals mixed with each other from a broadcasting-communication data transmitting apparatus. If necessary, the receiver  1022  may convert the mixed signals into mixed signals of a predetermined band. 
     The first demodulator  1024  receives the mixed signals of the predetermined band and generates baseband mixed signals. The original data generator  1026  receives the baseband mixed signals outputted from the first demodulator  1024  and restores original data. 
     The decider  1028  receives the baseband mixed signals outputted from the first demodulator  1024  and makes a decision to have only baseband original signals without additional signals. In other words, the decider  1028  removes the components including the additional signals, other than the baseband original signals, and leaves only the baseband original signals of the baseband mixed signals outputted from the first demodulator  1024 . For example, when an original signal component to be transmitted from a transmitting apparatus is an integer number ‘7’ and an additional signal is ‘0.2’ and noise occurring during the transmission is ‘0.3,’ the mixed signal inputted to the decider  1028  becomes 7.5. The decider  1028  removes ‘0.5’ from ‘7.5,’ leaving only the original signal component ‘7.’ 
     The modulator  1030  receives the baseband original signals of the predetermined band decided in the decider  1028  and converts the baseband original signals into the same band as the predetermined band of the mixed signals outputted from the receiver  1022 . 
     The subtractor  1032  generates additional signals of a predetermined band by subtracting the original signals of the predetermined band outputted from the modulator  1030  from the mixed signals of the predetermined band outputted from the receiver  1022 . 
     The second demodulator  1034  receives the additional signals of the predetermined band outputted from the subtractor  1032  and generates baseband additional signals. The additional data generator  1036  receives the baseband additional signals and restores additional signals. 
     The broadcasting-communication data receiving apparatus shown in  FIGS. 10 and 11  is appropriate for receiving mixed signals transmitted from a transmitting apparatus including a first modulator and a second modulator separately, like the broadcasting-communication data transmitting apparatus shown in  FIG. 1 . 
       FIG. 12  is a block view describing a broadcasting-communication data receiving apparatus in accordance with a third embodiment of the present invention. Referring to  FIG. 12 , the broadcasting-communication data receiving apparatus includes a receiver  1102 , a demodulator  1104 , an original data generator  1106 , an original signal generator  1108 , a subtractor  1110 , and an additional data generator  1112 . 
     The receiver  1102  receives mixed signals including original signals and additional signals mixed with each other from a broadcasting-communication data transmitting apparatus. If necessary, the receiver  1102  may convert the mixed signals into mixed signals of a predetermined band. 
     The demodulator  1104  receives the mixed signals of the predetermined band and generates baseband mixed signals. 
     The original data generator  1106  receives the baseband mixed signals outputted from the demodulator  1104  and restores original data. 
     The original signal generator  1108  receives error correction-decoded original data outputted from the original data generator  1106  and generates baseband original signals without additional signals therein again. 
     The subtractor  1110  generates baseband additional signals by subtracting the baseband original signals outputted from the original signal generator  1108  out of the baseband mixed signals outputted from the demodulator  1104 . 
     The additional data generator  1112  receives the baseband additional signals and restores additional signals. 
       FIG. 13  is a block view describing a broadcasting-communication data receiving apparatus in accordance with a fourth embodiment of the present invention. Referring to  FIG. 13 , the broadcasting-communication data receiving apparatus includes a receiver  1122 , a demodulator  1124 , an original data generator  1126 , a decider  1128 , a subtractor  1130 , and an additional data generator  1132 . 
     The receiver  1122  receives mixed signals including original signals and additional signals mixed with each other from a broadcasting-communication data transmitting apparatus. If necessary, the receiver  1122  may convert the mixed signals into mixed signals of a predetermined band. 
     The demodulator  1124  receives the mixed signals of the predetermined band and generates baseband mixed signals. 
     The original data generator  1126  receives the baseband mixed signals outputted from the demodulator  1124  and restores original data. 
     The decider  1128  receives the baseband mixed signals outputted from the demodulator  1124  and makes a decision to have only baseband original signals without additional signals. In other words, the decider  1128  removes the components including the additional signals, other than the baseband original signals, of the baseband mixed signals outputted from the demodulator  1124 , and leaves only the baseband original signals. 
     The subtractor  1130  generates baseband additional signals by subtracting the baseband original signals outputted from the decider  1128  out of the baseband mixed signals outputted from the demodulator  1124 . 
     The additional data generator  1132  receives the baseband additional signals and restores additional signals. 
     The broadcasting-communication data receiving apparatus shown in  FIGS. 12 and 13  is appropriate for receiving mixed signals transmitted from a transmitting apparatus including a single modulator  210 , like the broadcasting-communication data transmitting apparatus shown in  FIG. 2 . 
       FIG. 14  is a block view describing the original data generator shown in  FIGS. 10 to 13 . Referring to  FIG. 14 , the original data generator includes a TCM decoder  1202 , a deinterleaver  1204 , an RS decoder  1206 , and a data derandomizer  1208 . 
     The TCM decoder  1202  receives baseband original signals, e.g., baseband ATSC broadcasting signals, and performs inner decoding on the baseband original signals to thereby primarily remove noise included therein. 
     The deinterleaver  1204  receives the baseband original signals without noise outputted from the TCM decoder  1202  and outputs deinterleaved baseband original signals. 
     The RS decoder  1206  receives the deinterleaved baseband original signals and performs outer decoding to thereby secondarily remove noise. 
     The data derandomizer  1208  receives the baseband original signals outputted from the RS decoder  1206  and derandomizes the baseband original signal to thereby generate original data, e.g., MPEG-2 transport stream. 
     The original data generator of the broadcasting-communication data receiving apparatus of the present invention is not limited to the ATSC 8-VSB system as shown in  FIG. 14 , and it may adopt diverse kinds of broadcasting-communication standards. 
     Particularly, according to the ATSC 8-VSB transmission standard, the original signal generator of  FIGS. 10 to 13  may transmit symbol-level output signals outputted from the TCM decoder  1202  to the modulator  1010  or the subtractor  1110 . This is performed to prevent an ambiguity problem of a TCM code. The ambiguity problem of a TCM code is a phenomenon that different outputs are acquired according to the state of a memory although the same inputs are made. This occurs because the initial state of a memory of a TCM encoder is not uniform. 
       FIG. 15  is a block view describing the additional data generator shown in  FIGS. 10 to 13 . Referring to  FIG. 15 , the additional data generator includes a correlator  1302 , an FEC decoder  1304 , and a despreading sequence generator  1306 . 
     The despreading sequence generator  1306  generates an orthogonal or quasi-orthogonal sequence for despreading baseband additional signals inputted to the correlator  1302 . The despreading sequence generator  1306  may generate an orthogonal sequence, e.g., Walsh sequence, or a quasi-orthogonal sequence, e.g., Gold sequence, Kasami sequence, and Bose-Chadhuri-Hocquenghem (BCH) sequence, which corresponds to the spreading sequence generator of the broadcasting-communication data transmitting apparatus of the present invention. Whether to select an orthogonal sequence or a quasi-orthogonal sequence may depend on the system standard and requirements. 
     The correlator  1302  calculates correlation values by correlating the inputted baseband additional signals with the despreading sequence generated in the despreading sequence generator  1306  and selects the largest correlation value among the correlation values. Therefore, the additional signals outputted from the correlator  1302  come to have a spreading gain as much as 10·log 10  N dB due to the correlation, where N denotes the length of the despreading sequence. 
     The FEC decoder  1304  removes noise caused during the signal transmission from the baseband additional signals having the spreading gain as much as 10·log 10  N dB and outputted from the correlator  1302 . Herein, the FEC decoder  1304  may use diverse error correction codes, such as a turbo code, an LDPC code, a concatenate code and so forth. The error correction code may be selected according to the system standard and requirements. 
     The correlator  1302 , the FEC decoder  1304 , and the despreading sequence generator  1306  may be formed diversely according to the system standard and requirements. 
       FIG. 16  shows an orthogonal sequence generated in the despreading sequence generator  1306  shown in  FIG. 15 . 
     The spreading sequence shown in  FIG. 16  is a Walsh sequence having a length of 8. The Walsh sequence having a length of 8 includes 8 components W 0 , W 1 , W 2 , W 3 , W 4 , W 5 , W 6 , W 7 , and the sequences are orthogonal to each other. The Walsh sequence satisfies the following Equation 4. 
     
       
         
           
             
               
                 
                   
                     &lt; 
                     
                       W 
                       i 
                     
                   
                   , 
                   
                     
                       
                         W 
                         j 
                       
                       &gt;= 
                       
                         
                           ∑ 
                           
                             k 
                             = 
                             0 
                           
                           7 
                         
                         ⁢ 
                         
                           
                             
                               W 
                               i 
                             
                             ⁡ 
                             
                               ( 
                               k 
                               ) 
                             
                           
                           · 
                           
                             
                               W 
                               j 
                               * 
                             
                             ⁡ 
                             
                               ( 
                               k 
                               ) 
                             
                           
                         
                       
                     
                     = 
                     
                       { 
                       
                         
                           
                             8 
                           
                           
                             
                               i 
                               = 
                               j 
                             
                           
                         
                         
                           
                             0 
                           
                           
                             
                               i 
                               ≠ 
                               j 
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   Eq 
                   . 
                   
                       
                   
                   ⁢ 
                   4 
                 
               
             
           
         
       
     
     where W i (k) denotes the k th  value of the i th  Walsh code; and * denotes a conjugate. 
     A Walsh sequence having a length of N may be easily generated from Walsh-Hadamard transformation of a Walsh sequence having a length of 2. 
       FIG. 17  is a block view of the correlator  1302  shown in  FIG. 15 . Referring to  FIG. 17 , the correlator  1302  includes a correlation value calculator  1502  and a correlation value selector  1504 . 
     The correlation value calculator  1502  multiples the baseband additional signals by conjugates of the sequences W 0 , W 1 , W 2 , W 3 , W 4 , W 5 , W 6 , W 7  generated in the despreading sequence generator  1306 , which is a despreading process, and calculates correlation values R 0 , R 1 , R 2 , R 3 , R 4 , R 5 , R 6  and R 7  through a sum-and-dump process. 
     The correlation value selector  1504  selects one whose absolute value is the largest among the correlation values R 0 , R 1 , R 2 , R 3 , R 4 , R 5 , R 6  and R 7  obtained in the correlation value calculator  1502 , and the sign for the value follows the sign of the value before the value takes on the absolute mark. The output of the correlation value selector  1504  is expressed as the following Equation 5.
 
Output of correlator= sgn ( R   i     max   )·| R   i     max     |=R   i     MAX     Eq. 5
 
     Herein, sgn( ) and ∥ denote a sign and an absolute value, respectively, and i max  denotes the index of the largest value among the absolute values of the correlation values. The i max  is expressed as the following Equation 6.
 
 i   max   =arg   i   max|R   i   Eq. 6
 
       FIG. 18  is a block view of the FEC decoder  1304  shown in  FIG. 15 . Referring to  FIG. 18 , the FEC decoder  1304  includes a second deinterleaver  1602 , an LDPC decoder  1604 , a first deinterleaver  1606 , and a BCH decoder  1608 . 
     The second deinterleaver  1602  receives the baseband additional signals having a spreading gain, which are outputted from the correlator  1302  and outputs deinterleaved baseband additional signals. The LDPC decoder  1604  receives the deinterleaved baseband additional signals obtained in the second deinterleaver  1602  and primarily removes noise caused during a transmission process. 
     The first deinterleaver  1606  receives the additional signals without noise, which are obtained in the LDPC decoder  1604  and outputs deinterleaved additional signals. The BCH decoder  1608  receives the deinterleaved additional signals obtained in the first deinterleaver  1606 , secondarily removes the noise caused in the transmission process, and generates error correction-decoded additional data. 
       FIG. 19  is a block view illustrating a broadcasting-communication receiving apparatus based on the ATSC 8-VSB standard in accordance with a fifth embodiment of the present invention. Referring to  FIG. 19 , the broadcasting-communication receiving apparatus includes a receiver  1702 , a demodulator  1708 , an original data generator  1714 , a subtractor  1724 , and an additional data generator  1726 . 
     The receiver  1702  includes a reception antenna  1704  and a tuner  1706 . Also, the demodulator  1708  includes a VSB demodulator  1710  and an equalizer  1712 . 
     The original data generator  1714  includes a TCM decoder  1716 , a deinterleaver  1718 , an RS decoder  1720 , and a data derandomizer  1722 . 
     The additional data generator  1726  includes a correlator  1728 , a despreading sequence generator  1730 , and an FEC decoder  1732 . 
     The FEC decoder  1732  includes a second deinterleaver  1734 , an LDPC decoder  1736 , a first deinterleaver  1738 , and a BCH decoder  1740 . 
     Hereafter, a data receiving method of the broadcasting-communication data receiving apparatus shown in  FIG. 19  will be described in detail. First, the reception antenna  1704  receives mixed signals including original signals and additional signals mixed with each other from a broadcasting-communication data transmitting apparatus. The mixed signals are converted into mixed signals of a predetermined band through the tuner  1706  included in the receiver  1702 . 
     The VSB demodulator  1710  receives the mixed signals of the predetermined band outputted from the tuner  1706  and converts them into baseband mixed signals. The equalizer  1712  receives the baseband mixed signals and removes multi-path signals generated during a transmission process. 
     The TCM decoder  1716  primarily removes the noise caused during the transmission process out of the baseband mixed signals without the multi-path signals, which are obtained in the equalizer  1712 . The deinterleaver  1718  deinterleaves the baseband mixed signals with noise primarily removed. 
     The RS decoder  1720  secondarily removes noise caused during the transmission process out of the deinterleaved mixed signals. The data derandomizer  1722  derandomizes the baseband mixed signals without noise obtained from the RS decoder  1720  and generates original data, e.g., MPEG-2 transport stream. 
     Meanwhile, the subtractor  1724  subtracts symbol-level output signals of the TCM decoder  1716 , which correspond to the original signals, from the baseband mixed signals outputted from the equalizer  1712  to thereby leave only baseband additional signals. 
     The despreading sequence generator  1730  generates an orthogonal or quasi-orthogonal sequence for despreading the baseband additional signals outputted from the subtractor  1724 . The correlator  1728  calculates correlation values by correlating the despreading sequence generated in the despreading sequence generator  1730  with the baseband additional signals outputted from the subtractor  1724 , and selects the largest correlation value among the correlation values. 
     The baseband additional signals having a spreading gain outputted from the correlator  1728  are deinterleaved in the second deinterleaver  1734 . The LDPC decoder  1736  decodes the deinterleaved additional signals to thereby primarily remove noise caused during the transmission process. 
     The first deinterleaver  1738  deinterleaves the output signals of the LDPC decoder  1736 . The BCH decoder  1740  secondarily removes noise from the deinterleaved baseband additional signals outputted from the first deinterleaver  1738  to thereby generate error correction-decoded additional data. 
     The apparatus and method of the present invention described above is advantageous in that it can improve the overall transmission efficiency of a system by transmitting new additional data while maintaining the data transmission rate of original data. In short, the apparatus and method of the present invention can transmit/receive additional data while maintaining the bandwidth for transmitting original data and compatibility with conventional data transmission/reception systems. 
     Particularly, when data are transmitted, the apparatus and method of the present invention can easily separate original signals and additional signals from each other in the receiving part, compared to the prior art, because additional signals are inserted to original data by controlling the average power of the additional data. Also, the data transmission/reception method of the present invention can transmit more additional data than the prior art, which is advantageous as well. 
     The broadcasting-communication data transmitting/receiving method and apparatus of the present invention described above is appropriate for broadcasting systems, e.g., ATSC, DVB, DMB, ISDB-T, and communication systems, e.g., WiBro, but it is not limited to them and it can be applied to any environments requiring general additional data transmission. 
     While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.