KR100771631B1 - How to process data in broadcasting system and broadcasting system - Google Patents

Abstract

A broadcast system and a method for processing data in the broadcast system are proposed. The transmission system multiplexes the encoded MPEG data and the additional data encoded by inserting the null sequence in a generalized manner according to the number of packets of the additional data. Then, the multiplexed data is transmitted to the receiving system together with multiplexing information. The receiving system detects multiplexing information from the multiplexed data, generates a null sequence, and demultiplexes the MPEG data and the additional data from the multiplexed data using the null sequence and multiplexing information.

Multiplexing, transmission system, reception system, multiplexing information

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcasting system and a broadcasting system,

BRIEF DESCRIPTION OF DRAWINGS FIG. 1A is a block diagram showing a transmission system in a configuration of a VSB signal communication system according to the present invention; FIG.

1B is a block diagram illustrating a detailed configuration of an 8 VSB transmission system in FIG.

FIG. 2 is a diagram illustrating a configuration of a data field when decoding performance is poor in the VSB signal communication system according to the present invention. FIG.

3 is a diagram showing a configuration of a data field when the additional data and the MPEG data are multiplexed at a ratio of 1: 3 in the VSB signal communication system according to the present invention.

4 is a diagram showing a configuration of a data field when multiplexing additional data and MPEG data at a ratio of 1: 1 in the VSB signal communication system according to the present invention;

5A is a diagram showing a configuration of the multiplexed field data when the offset K1 is 0 and the additional data segment and the MPEG data segment are multiplexed at a ratio of 1:

5B is a diagram showing a configuration of the multiplexed field data when the offset K1 is 1 and the additional data segment and the MPEG data segment are multiplexed at a ratio of 1:

5C is a diagram showing a configuration of the multiplexed field data when the offset K1 is 2 and the additional data segment and the MPEG data segment are multiplexed at a ratio of 1:

5D is a diagram showing a configuration of the multiplexed field data when the offset K1 is set to 3 and the additional data segment and the MPEG data segment are multiplexed at a ratio of 1:

6A is a diagram showing a configuration of the multiplexed field data when the offset K1 is 0 and the offset K2 is 1 and the additional data segment and the MPEG data segment are multiplexed at a ratio of 1:

6B is a diagram showing a configuration of the multiplexed field data when the offset K1 is set to 0 and the offset K2 is set to 2 to multiplex the additional data segment and the MPEG data segment at a ratio of 1:

7 is a diagram showing a detailed configuration of a data interleaver when multiplexing the additional data and MPEG data at a ratio of 1: 3 in the VSB signal communication system according to the present invention.

8 is a diagram showing a detailed configuration of a trellis encoder when multiplexing the additional data and MPEG data at a ratio of 1: 3 in the VSB signal communication system according to the present invention.

FIG. 9 is a diagram showing a structure of segments existing in a field synchronization section of a data field according to the present invention.

10 is a block diagram showing the configuration of a receiving system for eight VSBs among the configurations of the VSB signal communication system according to the present invention

The present invention relates to an apparatus and a method for multiplexing MPEG data and additional data in a broadcasting system.

A VSB digital signal means a signal modulated by a VSB (Vestigial Side Band) method. Such a VSB digital signal is used in recent digital television broadcasting and the like.

In the United States, ATSC 8T-VSB transmission system was adopted as a standard for terrestrial digital broadcasting in 1995 and digital broadcasting was started in the second half of 1998 using the ATSC 8T-VSB transmission system.

On the other hand, the Republic of Korea has also adopted the ATSC 8T-VSB transmission method as the standard in the United States and started the experimental broadcasting in May 1995 using the ATSC 8T-VSB transmission method. Then, from August 31, 2000, The same experimental broadcast was converted into a test broadcast system.

According to the conventional ATSC 8T-VSB transmission system, a data randomizer randomizes input MPEG video data and audio data, a lead-solo processor encodes the random data into Reed-Solomon coding, The parity code of the byte is added to the data.

The data interleaver interleaves the encoded data, and the trellis encoder performs trellis encoding by converting the interleaved data from a byte format to a symbol format.

Meanwhile, the multiplexer multiplexes the symbol sequence from the trellis encoder and external synchronization signals, and the pilot inserter adds a pilot signal to the symbol sequence.

Meanwhile, in the VSB modulator, the symbol stream is modulated to an 8 VSB signal corresponding to the intermediate frequency band, and the RF converter converts the signal corresponding to the intermediate frequency band into a signal of a radio frequency (RF) band. The signal of this RF band is transmitted to the receiver through the antenna.

Conventional VSB related communication systems described above have been registered by US Zenith as United States Patent Numbers (USP) 5636251, 5629958, and 5600677 in the United States.

The 8T-VSB transmission scheme adopted as a standard for digital television broadcasting in North America and the Republic of Korea is developed for transmitting MPEG video data and MPEG audio data. Meanwhile, as the technology for processing digital signals has rapidly developed and the Internet has been widely used, digital home appliances, computers, and the Internet are being integrated into a single large frame.

Therefore, in order to meet various demands of users, it is necessary to develop a communication system capable of adding various additional data to image data and sound data through the digital broadcasting channel and transmitting the added data.

On the other hand, those who use the supplementary data broadcasting are predicted to use the supplementary data broadcasting by using a personal computer (PC) card or a portable device having a simple type indoor antenna for broadcasting the supplementary data.

However, in the room, the signal intensity is greatly reduced due to the blocking by the wall and the influence of the nearby moving body, and ghost and noise due to the reflected waves may occur. This greatly degrades the performance of receiving the additional data broadcast signal.

On the other hand, unlike general video data and sound data, when the additional data is transmitted, the error rate must be lower than that in transmission. In the case of the general image data and the sound data, an error of a degree that the human eyes and ears can not detect is not a problem.

On the other hand, in the case of the additional data (e.g., program execution file, stock information, etc.), even if only one bit of error occurs on the additional data, serious problems may occur. therefore It is absolutely necessary to develop a communication system that is more resistant to ghost and noise in the channel.

The additional data is usually transmitted in a time-division manner over the same channel as MPEG video data and MPEG audio data. However, since the start of digital broadcasting, ATSC VSB digital broadcasting receivers, which only receive MPEG video data and audio data, are widely available in the consumer electronics market.

Therefore, the additional data to be transmitted through the same channel as the MPEG video data and the MPEG audio data should have no effect on the ATSC VSB digital broadcasting receiver that has been prevalent in the market.

The above situation is defined as ATSC VSB compatible, and the additional data broadcasting system should be compatible with the system for the ATSC VSB.

On the other hand, in a poor channel environment, the reception performance of the conventional reception system for the ATSC VSB may be deteriorated, and furthermore, the viewing feeling of the viewer may be deteriorated.

When the existing receiving system for ATSC VSB multiplexes the additional data and the MPEG data on a segment basis, the multiplexing order greatly influences decoding performance of the additional data. In other words, the decoding performance of the additional data can be remarkably reduced according to the multiplexing order

It is an object of the present invention to provide a method of multiplexing MPEG data and additional data in a new VSB transmission system suitable for additional data transmission and resistant to noise.

It is another object of the present invention to provide a method for multiplexing MPEG data and additional data in a VSB transmission system capable of improving decoding performance when decoding symbols of additional data in a VSB receiving system.

It is still another object of the present invention to provide a method of efficiently multiplexing additional data and MPEG data in the VSB transmission system.

The features of the present invention for achieving the above objects are described below.

According to the above feature, a segment, which is input through one path of the VSB communication system and composed of a segment consisting of additional data packets and MPEG transport packets input through another path of the VSB communication system, .

Preferably, the number of packets of additional data to be multiplexed is variable from 0 to 156 in one data field.

Preferably, when multiplexing the additional data and the MPEG data in the data field, the multiplexing information that indicates the multiplexing position of the additional data may be included together.

Preferably, the multiplexing information is located in a reserved area of a segment corresponding to a field sync signal in the data field, the multiplexing information includes a current packet number of additional data to be multiplexed in a current data field, The number of fields until the number of packets is changed, and the number of packets to be changed in the additional data.

Preferably, the multiplexing information includes information inverted by 12 bits. Therefore, even when there is interference of an NTSC broadcast signal on the receiving side of the VSB communication system, the multiplexed information can be restored.

Hereinafter, the features and advantages of the present invention will be described in detail with reference to FIGS. 1 to 10.

The VSB communication system according to the present invention mainly comprises a transmission system and a reception system. First, a transmission system for additional data according to the present invention will be described with reference to Figs. 1a and 1b.

As shown in FIG. 1A, the additional data is input through a first path of the transmission system, and the encoded data is encoded before being transmitted to the reception system. Here, the transmission system means a broadcasting station, and the additional data is transmitted from the broadcasting station to the reception system through a channel (air or cable). In the encoding process for the additional data, a Reed-Solomon encoder is used to encode the encoded additional data, an MPEG header is added to the encoded additional data, and the encoded data is input to the multiplexer. That is, the encoding process is performed before the MPEG header is added, which can diversify the encoding method according to the designer.

In this patent, the encoding process will be described by taking as an example a Reed-Solomon encoder, an interleaver, and a null sequence inserter.

First, a Reed-Solomon encoder (or R-S encoder) 1 codes the additional data for error correction. The interleaver 2 performs an interleaving process on the encoded additional data to improve the performance of the burst noise. Here, the interleaver may be omitted as needed.

The null sequence inserting unit 3 inserts a null sequence into the interleaved or Reed-Solomon coded supplementary data. The null sequence is determined at an input end of a trellis encoder (not shown) before the interleaved or Reed-Solomon coded supplementary data.

Here, the reason why the null sequence is inserted is to allow the receiving system to receive the transmitted additional data even in a poor channel environment.

On the other hand, the MPEG header inserting unit 4 adds an MPEG header to the additional data inserted with the null sequence to have compatibility with the existing VSB receiving system. The additional data to which the MPEG header is added is input to the multiplexer 5.

On the other hand, the MPEG data input through the second path of the VSB transmission system, that is, data for a broadcast program (e.g., movie, sports, entertainment, drama, etc.) is input to the multiplexer 5 through the MPEG encoding process .

The multiplexer 5 multiplexes the additional data and the MPEG data input through the first path and the second path under the control of a control unit (not shown), and the multiplexed data is transmitted to the 8T VSB transmission system 6, .

For the multiplexed data, the 8T VSB transmission system 6 performs the same processing as the conventional method, and then transmits the processed data to the reception system through the channel.

To describe in more detail, the additional data packet of 164 bytes is encoded by the Reed-Solomon encoder 1 and converted into a packet of 184 bytes. These 184-byte packets are interleaved in the data interleaver 2, and the order of the data is changed at this time.

When the null sequence is inserted on the interleaved packet, two 184-byte packets are output. Then, a 3-byte MPEG transport header is added to each 184-byte packet, resulting in two 187-byte packets.

Each of the generated 187-byte packets is multiplexed with the MPEG transport packet on a segment basis in the 8T VSB transmission system 6, and then transmitted to the reception system.

In the multiplexer 5, the additional data packet and the MPEG transport packet are multiplexed in the VSB data field on a segment-by-segment basis. At this time, one segment is composed of 187 bytes, and the data field is composed of 312 segments.

Hereinafter, the operation of the 8T VSB transmission system 6 will be described with reference to FIG.

The packets multiplexed on a segment basis are processed by the 8T VSB transmission system 6. In FIG. 1B, the data randomizer 11 randomizes the multiplexed packets, and the Reed-Solomon encoder 12 reed-solomons the MPEG data and adds 20 bytes of parity code in the MPEG data packets.

The data interleaver 13 interleaves the MPEG data packets, and the trellis encoder 14 converts the MPEG data packets from bytes to symbols, and performs trellis coding. At this time, the packets are changed in order by the data interleaver.

Therefore, symbols of one packet are not continuously input to the trellis encoder 14, but symbols of different packets are mixed and input to the trellis encoder 14. [

Meanwhile, the multiplexer 15 multiplexes and multiplexes symbol streams and synchronization signals, and the pilot inserter 16 adds pilot signals to the symbol streams. The VSB modulator 17 modulates the symbol streams into 8T-VSB signals. Meanwhile, the RF converter 18 converts the baseband signals corresponding to the 8T-VSB signals into RF band signals, and the RF band signals are transmitted through the antenna 7 toward the receiving system.

Meanwhile, both the trellis decoder and the slicer predictor used in the receiving system for the digital VSB, which is a counterpart of the transmission system, use a Viterbi algorithm. This Viterbi algorithm is an algorithm for predicting a state transition of the trellis encoder of the transmission system over time, that is, a path with the highest probability.

In the ACS (Accumulate / Compare / Select) part of the Viterbi algorithm, the metrics corresponding to all possible paths are calculated for each state, and the path having the smallest value (highest probability) And stores the metric value.

At this time, the currently calculated path metric is a value obtained by adding the path metric of the previous time and the branch metric corresponding to the path. Therefore, the path metrics calculated up to the previous symbol affect subsequent symbols.

Meanwhile, in the transmission system, the predefined sequence is inserted into the symbol of the additional data, but the symbol of the MPEG transport data does not include the predefined sequence. Therefore, in the symbol interval of the MPEG transport data, the reliability of the accumulated path metric is lower than the symbol interval of the additional data.

Therefore, when the symbol of the MPEG transport data and the additional data symbol are mixed, the symbol of the MPEG transport data located at the front affects the symbol of the additional data located at the rear, and as a result, The decoding performance is degraded.

Since the range of influence is within a few symbols, there is a difference between the decoding performance for the symbol of the additional data in the vicinity of the boundary and the decoding performance (error rate) for the symbol of the additional data located to some extent.

In other words, among the symbols of the additional data, the error rate is high on the additional data symbols at the boundary between the symbol interval of the MPEG transport data and the symbol interval of the additional data.

Therefore, in order to maximize the decoding performance for the symbols of the additional data, it is preferable that the symbols of the additional data are transmitted as many as possible. In other words, the boundary between the symbol interval of the MPEG transport data and the symbol interval of the additional data must be small. This boundary is closely related to multiplexing, interleaver and trellis coder.

2 shows an example of multiplexing the additional data and the MPEG transport data in a two-to-six manner, and shows a case where the decoding performance for the symbol of the additional data is poor.

In FIG. 2, the left drawing shows a case where data fields are formed by multiplexing in the form of two additional data segments and six MPEG transport segments.

On the other hand, in the case of the data field as shown in the drawing on the right, the output of the first 52 bytes from the data interleaver and the output of the next 52 bytes are input to the 12 trellis coders.

In the right figure, each column shows the input of each trellis encoder. As can be seen from the drawing, it can be seen that the bytes of the additional data do not converge on the specific trellis encoder since the multiplexing pattern is not 12-byte period.

Figures 3-4 show the most preferred examples of multiplexing. FIG. 3 shows an example of multiplexing the additional data and the MPEG transport data one by one, and FIG. 4 is a diagram showing an example of multiplexing the additional data and the MPEG transport data one-to-one.

The basic principle of multiplexing the additional data and MPEG transport data according to the present invention will be described below. The multiplexing principle according to the present invention is based on the number of additional data packets (P value) as shown in the following equations.

When the period of the multiplexing pattern for constructing one data field is set to four segments, the decoding performance of the additional data is maximized . Since one additional data packet corresponds to two segments, additional data packets from 0 to 156 (= 312/2) can be multiplexed in the data field.

As described above, the additional data segments multiplexed with the MPEG data at the 4-segment cycle are input to the trellis encoder via the interleaver. Using this fact, we can make the following rules. A map is made by multiplexing the additional data segments in the MPEG field data by the following equations. From the equations below, the additional data segments are multiplexed in the MPEG field data in order from the smallest value of s.

     I = 0, 1, 2, ..., 2P-1} (1) " MAP = {s / s =

     (I = 0, 1, 2, ..., 77) U = 43 / mo>

                   i = 0, 1, 2, ..., 2P-79} (2)

     77? MAP = {s / s = ((4i + K1) mod 312) + 1, i = 0,1,2,

                     {s / s = ((4i + K2) mod 312) + 1, i = 0,1,2, ..., 77} U

                    i = 0, 1, 2, ..., 2P-157} (3)

     I = 0, 1, 2, ..., 77} Ui = P? 156: MAP = {s / s = ((4i + K1)

                      {s / s = ((4i + K2) mod 312) + 1, i = 0,1,2, ..., 77} U

                      {s / s = ((4i + K3) mod 312) + 1, i = 0,1,2, ..., 77} U

                    i = 0, 1, 2, ..., 2P-235} (4)

The above equations (1) to (4) have the same conditions as the following equations (5) to (8). 1? S? 312 (5)

                      0? K1, k2, k3, k4? 311 (6)

                      (Km mod 4)? (Kn mod 4) for m? N (7)

                      1? M, n? 4 ..... (8)

In the above equations (1) to (8), s following the field sync signal indicates the position of each segment constituting the field data, and has a value from 1 to 312. The k1, k2, k3, and k4 indicate the offset for adjusting the start position for multiplexing the additional data segment on the basis of the field sync signal, and have values ranging from 0 to 311. On the other hand, (Km mod 4) and (Kn mod 4) have different values for different m and n.

To summarize the above equations (1) to (8), when the number of the additional data segments multiplexed in one field data is smaller than 1/4 312 (0? P? 39) The position of the additional data segment is allocated at a rate of one for every four segments of data.

On the other hand, when the number of the additional data segments multiplexed in one field data is larger than 1/4 312 and smaller than 1/2 312 (40? P? 78), first, The position of the additional data segment is determined at a ratio of one for each segment. Then, for the remaining additional data segments, the position of the additional data segment is allocated at a rate of one for every four segments of the field data from another specific position.

On the other hand, if the number of the additional data segments to be multiplexed in one field data is greater than 1/2 and is smaller than 3/4 of 312 (79? P? 117) And determines positions of half of the additional data segments to be multiplexed at a rate of one for every four segments. Then, with respect to the remaining additional data segments, positions of the remaining additional data segments are allocated at different ratios from one specific position to another, that is, the multiplexing start position of the additional data segment is changed every four segments of the field data.

On the other hand, when the number of the additional data segments to be multiplexed in one field data is larger than 3/4 and smaller than 1 (118 ≤ P ≤ 156) Of the additional data segments to be multiplexed. Then, with respect to the remaining additional data segments, positions of the remaining additional data segments are allocated at different ratios from one specific position to another, that is, the multiplexing start position of the additional data segment is changed every four segments of the field data.

As described above, in the above equations (1) to (8), the offset values K1, K2, K3 and K4 are between 0 and 311 because the additional data segments are multiplexed in the field data To generalize the starting position. Meanwhile, the four offset values K1, K2, K3, and K4 are determined to be constant values in the VSB transmission system, and if used, they need not be included in the multiplexing information for transmission to the VSB receiving system.

Hereinafter, multiplexing examples of the MPEG data segment and the additional data segment according to the equations (1) to (8) will be described with reference to the accompanying drawings.

5A is a diagram showing a structure of the multiplexed field data when the offset K1 is 0 and the additional data segment and the MPEG data segment (or MPEG transport segment) are multiplexed at a ratio of 1: 3.

5B is a diagram showing the structure of the multiplexed field data when the offset K1 is 1 and the additional data segment and the MPEG data segment (or MPEG transport segment) are multiplexed at a ratio of 1: 3.

FIG. 5C is a diagram showing the structure of the multiplexed field data when the offset K1 is 2 and the additional data segment and the MPEG data segment (or MPEG transport segment) are multiplexed at a ratio of 1: 3.

5D is a diagram showing the structure of the multiplexed field data when the offset K1 is 3 and the additional data segment and the MPEG data segment (or MPEG transport segment) are multiplexed at a ratio of 1: 3.

5A to 5D correspond to a case where the number of packets (P) of the additional data is 39. FIG. 5A to 5D, the left-side diagrams show that the additional data segment and the MPEG data segment are multiplexed on the basis of the field sync signal, and the diagrams on the right side show the output signals of the interleaver 12 < th > trellis encoder.

More specifically, FIG. 5A shows that the additional data segments are multiplexed for the four field data segments from the first segment of the field data on the basis of the field sync signal. 5A, the additional data corresponding to the first 52 bytes and the additional data corresponding to the second 52 bytes, which are output from the interleaver after the field sync signal, are input to the twelve trellis coder Show the case.

That is, the additional data corresponding to the first 52 bytes are input to the twelve trellis encoders four times by 12 bytes. At this time, 4 bytes of the 52 bytes remain. Thus, the remaining 4 bytes are input to the 12 trellis encoders along with the first 8 bytes of the second 52 bytes. As described above, according to the multiplexing pattern of the additional data according to the equations (1) to (8), the remaining 4 bytes of the first 52 bytes are the first 8 bytes of the second 52 bytes And maintains a constant multiplexing pattern. This means that the bytes of the additional data are shifted to a specific encoder or coder among the twelve trellis encoders. As described above, when the additional data bytes are multiplexed with the specific encoder or specific encoders, the error can be greatly reduced when the VSB receiving system separates and decodes the additional data and the MPEG data.

On the other hand, FIG. 5B is a diagram showing a form of multiplexing the additional data segments from the second segment of the field data on the basis of the field sync signal.

On the other hand, FIG. 5C is a diagram showing a form of multiplexing the additional data segments from the third segment of the field data on the basis of the field sync signal.

On the other hand, FIG. 5D is a diagram showing a mode of multiplexing the additional data segments from the fourth segment of the field data based on the field sync signal. 5B through 5D illustrate that the additional data segments are multiplexed by one segment for every four segments of the field data, and the additional data bytes are input into the specific trellis encoder or the encoder as in the case of FIG. 5A .

Hereinafter, the case where the additional data segment and the MPEG data segment are multiplexed at a ratio of 1: 1 will be described using the above equations (1) to (8).

FIG. 6A shows a case where when the offset K1 is 0 and the offset K2 is 1, the additional data segment and the MPEG data segment (or MPEG transport segment) are multiplexed at a ratio of 1: This is a diagram showing the configuration of data.

6B shows a case where when the offset K1 is set to 0 and the offset K2 is set to 2 and the additional data segment and the MPEG data segment (or MPEG transport segment) are multiplexed at a ratio of 1: 1, This is a diagram showing the configuration of data.

6A and 6B, the following regularities can be obtained. As described above, FIGS. 5A to 5D show examples in which the MPEG data segment (or MPEG transport segment) is multiplexed at a ratio of 1: 3. Here, although the multiplexing start positions of the additional data segments are different from each other based on the field sync signal, the additional data bytes are inputted to the specific trellis encoder or the encoder. Therefore, even when the MPEG data segment (or MPEG transport segment) is multiplexed at a ratio of 1: 1 by combining any two of the cases of Figs. 5A to 5D, the same characteristics as in the case of the 1: 3 case . For example, when the case of FIG. 5A is combined with the case of FIG. 5B, the additional data bytes are inputted to one specific trellis encoder as shown in FIG. 6A. When the case of FIG. 5A and the case of FIG. 5C are combined, as shown in FIG. 6B, the additional data bytes are inputted to one specific trellis encoder.

7 is a diagram showing a configuration of a data interleaver of an 8T VSB transmission system.

8 is a diagram showing the configuration of the trellis encoder of the 8T VSB transmission system. At this time, the 8T VSB transmission system continuously transmits the multiplexed data so that the decoding performance for the symbol of the additional data can be maximized.

Hereinafter, the process of multiplexing the additional data and the MPEG transport data one to three will be described in detail with reference to FIGS. 7 to 10.

7 shows a data interleaver in the 8T VSB transmission system as described above, wherein the number of branches is 52 and the number M of bytes in the unit memory is 4.

In FIG. 7, the interleaver operates in synchronization with the first byte of a data field. When the first byte is input, the first byte is directly output through the first branch, the second byte is input through the second branch, and the value before 52 X 4 bytes is output.

As described above, the input order and the output order of the data interleaver shown in FIG. 7 are as follows. The data input is input from the top to the bottom of the data field on a segment basis, and the bytes in each segment are input from left to right.

The first byte of the data field following the field sync signal is input to the first branch of FIG. 7 and then output as it is. The next input byte is input to the second branch of the interleaver, and the interleaver outputs the byte input 52 x 4 (M) = 208 bytes before the input byte, as shown in FIG.

When the next byte is input to the interleaver, the interleaver outputs a byte input before 52 x 8 (2M) = 416 bytes, compared to the input byte.

In this manner, 52 bytes from the interleaver are sequentially output to the 12 trellis coder and precoder shown in Fig. As described above, the 53rd input byte is input to the first branch of the interleaver and then output immediately. Here, the interleaver operates with a 52-segment depth and is connected to the 12 trellis encoders and precoders. Therefore, the 52 bytes output from the interleaver are input to the trellis encoder and the precoders by 12 bytes, and this process is performed with four cycles.

At this time, if the above process is performed four times, only 48 bytes (12 bytes X4 period = 48) are output to the trellis coder and the precoder, and 4 bytes remain.

The remaining 4 bytes are input to the 12 trellis encoders and precoders together with the first 8 bytes of the next 52 bytes input.

8 shows a detailed block diagram of a trellis encoder used in an 8 VSB transmission system. Referring to FIG. 8, it can be seen that the inputs and outputs of twelve trellis coder and precoder are multiplexed and used.

In FIG. 8, the twelve bytes output from the interleaver are input to the twelve trellis encoders and precoders one byte at a time.

At this time, Trellis encoding is performed on each byte to convert into four symbols (one symbol is composed of two bits). Also, as shown in FIG. 8, the symbols output from each trellis encoder are multiplexed by one symbol and then output.

9 is a diagram showing a configuration of a segment corresponding to a field sync signal existing in a data field in an 8T VSB transmission system.

Referring to FIG. 9, the segment corresponding to the field sync signal is detected by the VSB receiving system in the segment corresponding to the field sync signal, and multiplexed so that correct decoding can be performed using the detected multiplex information Information is included.

As described above, when the packet number P (0 to 156) of the additional data is determined, the multiplexing position of the additional data is determined in the data field. Therefore, the VSB transmission system transmits only the P value to the VSB receiving system do.

Meanwhile, even if the VSB transmission system is transmitting data to the VSB receiving system, a reserved area of a segment corresponding to the field sync signal shown in FIG. 8, The current P value, the number of data fields until the current P value changes, and the P value to be changed are transmitted to the VSB receiving system.

Therefore, the receiving system can receive data from the VSB transmission system without error even if the P value is changed.

As described above, the multiplexing information uses a reserved area included in a segment corresponding to the field sync signal. As shown in FIG. 9, among the 832 symbols constituting the segment corresponding to the field sync signal, 92 symbols are allocated as reserved areas.

For example, the multiplexing information transmitted through the spare area is as follows. 8 bits can be assigned as the current P value, 8 bits are allocated as the P value to be changed, and 8 bits are allocated as the number of fields until the current P value is changed to the new P value. Therefore, the total of 24 bits of multiplexing information is transmitted to the VSB receiving system through the spare area. Here, if the number of fields until the change is 0, the value 0 means that the current P value will not be changed for a while.

Meanwhile, it is necessary to restore the multiplexed information even when comb filtering is performed in the VSB receiving system due to interference of an NTSC broadcast signal, which is an existing broadcast type. For this case, the total of 24 bits of multiplexing information is divided into two pieces of 12-bit information. At this time, one 12-bit information has an inverted form with respect to the other information. In other words, the one 12-bit information is transmitted toward the VSB receiving system with 12-bit information inverted therefor.

Referring to FIG. 10, a total of 24 bits of multiplexed information is divided into two pieces of 12-bit information, and each piece of 12-bit information constitutes the spare area together with its inverted 12 bits.

Here, the inversion means a bit-wise inverse. Wherein the multiplexing information includes a multiplexing information in a first additional data segment following the field sync signal to transmit the multiplexing information stably from the VSB transmission system to the receiving system in a poor channel condition, To the VSB receiving system.

In this case, the multiplexing information is also included and transmitted in the same manner as in the case of the segment corresponding to the field sync signal.

10 is a block diagram showing a configuration of an 8T VSB receiving system.

10, a VSB receiving system according to the present invention includes a sequence generator 21 for indicating a symbol of additional data and generating a predefined sequence included in the additional data, An MPEG data processing unit 32 for performing processing in a reverse order to the VSB transmission system using a sequence, multiplexing information from a field sync signal in field data received from the VSB transmission system and controlling the demultiplexing A demultiplexing information reconstructing unit 33 for generating a control signal for signaling and Reed-Solomon decoding, demultiplexing the output data of the MPEG data processing unit 32 according to the demultiplexing control signal, separating the data into MPEG data and additional data A demultiplexer 34 for demultiplexing the output of the demultiplexer 34, The addition data is processed in reverse order and the delivery system comprises an additional data processor 35 to obtain the additional data of the original.

10, the MPEG data processing unit 32 includes a demodulator 41, a comb filter 42, a channel equalizer 43, a slicer predictor 44, a phase reconstructor 45, a trellis decoder A second data deinterleaver 46, a first data deinterleaver 47, a first Reed-Solomon decoder 48, and a data derandomizer 49. The additional data processing unit 35 includes an MPEG header removing unit 51, a null sequence removing unit 52, a second data deinterleaver 53, and a second Reed Solomon decoder 54.

In the demodulator 41, the RF band signal is converted into a baseband signal, and then the synchronization and timing recovery unit recovers the segment sync signal, the field sync signal, and the symbol timing.

The comb filter 42 removes the NTSC interference signal, and the channel equalizer 43 corrects the distorted channel using the slicer predictor 44.

The phase reconstructor 45 restores the phase of the MPEG data, and the trellis decoder 46 performs Viterbi decoding using the generated sequence and the Viterbi algorithm.

Here, the channel equalizer 43, the slicer predictor 44, the phase reconstructor 45, and the trellis decoder 46 may use the sequence generated from the sequence generator 31, Decodes the MPEG data.

The first data deinterleaver 47 performs an inverse operation on the data interleaver of the ATSC 8T VSB transmission system and the first Reed Solomon decoder 48 converts the Reed-Solomon encoded signal in the ATSC 8T VSB transmission system Decrypt again. Meanwhile, the data derandomizer 49 performs a reverse operation with respect to the data renderer of the transmission system.

The sequence generator 31 indicates whether the symbol received from the VSB transmission system is a symbol corresponding to the supplementary data, and generates the predefined sequence transmitted in the supplementary data.

As described above, the channel equalizer 43, the slicer predictor 44, the phase recoverer 45, and the trellis decoder 46 use their pre-defined sequence information to determine their performance . At this time, the components using the predefined sequence delay the sequence information in consideration of data processing delays of the previous components.

The demultiplexer 34 demultiplexes the data input from the MPEG data processor 32 into an additional data segment and an MPEG data segment using the multiplexing information restored from the field sync signal.

The first Reed Solomon decoder 48 does not perform Reed-Solomon decoding on the additional data segment but removes only 20 bytes of parity bits added by the Reed-Solomon encoder of the VSB transmission system.

When the noise of the channel is severe, a lot of errors occur in parity bytes of the ATSC Reed Solomon code compared to the additional data. This is because there is no predefined sequence in the parity byte of the ATSC Reed Solomon code, and there is no gain in the trellis decoder 46. [

Solomon decoding is not performed on the segment of the additional data by the first RS decoder 48 because if an error exceeding 10 bytes occurs on the segment of the additional data, the first RS decoder 48 ) Is likely to perform erroneous error correction.

A segment of the additional data output through the demultiplexer 34 is first input to the MPEG header removing unit 51. The MPEG header removing unit 51 extracts a segment of the additional data from the segment corresponding to the additional data, Remove the MPEG header. The MPEG header is inserted when transmitting the additional data in the ATSC format in the VSB transmission system.

Subsequently, the null sequence eliminator 52 removes the null sequence inserted from the null sequence insertion unit of the VSB transmission system from the additional data segment. Then, the second deinterleaver 53 performs a reverse operation on the additional data segment for the interleaving process in the VSB transmission system.

If the interleaving operation is omitted in the VSB transmission system, the VSB reception system also does not include the second deinterleaver 53. On the other hand, the second Reed Solomon decoder 54 decodes the Reed-Solomon code for the additional data.

The VSB reception system shown in FIG. 10 improves its reception performance using the predefined sequence in the VSB transmission system as described above. In Fig. 10, the characteristic portion is the multiplexed information reconstruction unit 33. [ The multiplexing information reconstructing unit 33 detects the multiplexing information contained in the input bitstream and outputs a demultiplexer control signal for demultiplexing the bitstream into additional data and MPEG data packets in the demultiplexer using the multiplexing information do.

In other words, by decoding the additional data with the multiplexed information restored from the field sync signal, more stable decoding can be performed.

If the input data is additional data, the multiplexed information reconstructing unit may output a control signal for bypassing the first Reed Solomon decoder 48 without performing the first Reed Solomon decoding, And outputs it using the multiplexing information.

As described above, the digital broadcasting system according to the present invention has the following advantages.

First, it is resistant to errors by using predefined sequences and multiplexing information when transmitting MPEG data and additional data together through a channel.

Second, the communication system for digital VSB according to the present invention has compatibility with the existing VSB receiving system.

Third, by using the predefined sequence and multiplexing information, the additional data can be received without error even in a channel where ghost and noise are more intense than the conventional VSB communication system.

Fourth, by multiplexing the additional data and the MPEG data according to a predetermined rule, the decoding performance for the additional data can be improved in the VSB receiving system.

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 invention as defined in the appended claims. Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments but should be determined according to the claims.

Claims (8)

Encoding the first error-correction-coded data with the MPEG data, performing second error correction coding on the first error-correction-coded data, receiving the error-correction coded data, and performing demodulation; Correcting errors generated in the multiplexed data using the parity added to the demodulated data; Separating the first and second error correction-coded received data from the error-corrected data; And And correcting an error generated in the separated data using parity added to the separated data in the step, Wherein the data having the first attribute is data received by first and second error correction coding, and the data having the second attribute is data received after the second error correction coding. 2. The method of claim 1, wherein the error correction step And performing Reed-Solomon decoding to correct errors generated during transmission of the corresponding data. delete A demodulator for receiving the first error correction coded data after being multiplexed with the MPEG data and then performing a second error correction coding and demodulating the received first error correction coded data; A first Reed Solomon decoder for correcting errors generated in the multiplexed data using the parity added to the demodulated data in the demodulator; A demultiplexer for separating the first and second error correction-coded data received from the error-corrected data in the first Reed-Solomon decoder; And And a second Reed Solomon decoder for correcting an error generated in the separated data using parity added to the data separated by the demultiplexer. delete delete delete delete

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