KR20060063867A - Broadcasting system and method of processing data in a broadcasting system - Google Patents

Abstract

A broadcast system and a method of processing data in the broadcast system are proposed. The transmission system multiplexes the encoded MPEG data and the null sequence by inserting the encoded additional data in a generalized manner according to the number of packets of the additional data. The multiplexed data is then sent to the receiving system along with the multiplexed information. On the other hand, the receiving system detects multiplexed information from the multiplexed data, generates a null sequence, and demultiplexes MPEG data and additional data from the multiplexed data using the null sequence and the multiplexed information.

Multiplexing, transmitting system, receiving system, multiplexing information

Description

Broadcasting system and method of processing data in a Broadcasting system

Figure 1a is a block diagram showing a transmission system of the configuration of the communication system for VSB signals of the present invention

FIG. 1B is a block diagram showing a detailed configuration of 8 VSB transmission systems in FIG. 1A

Figure 2 is a diagram showing the configuration of the data field when the decoding performance is not good in the communication system for VSB signals of the present invention

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

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

5A is a diagram showing the configuration of the multiplexed field data when multiplexing the additional data segment and the MPEG data segment at a ratio of 1: 3 with the offset K1 set to 0;

5B is a diagram showing the configuration of the multiplexed field data when multiplexing the additional data segment and the MPEG data segment at a ratio of 1: 3 with the offset K1 as 1;

5C is a diagram showing the configuration of the multiplexed field data when multiplexing the additional data segment and the MPEG data segment at a ratio of 1: 3 with the offset K1 as 2;

FIG. 5D is a diagram showing the configuration of the multiplexed field data when multiplexing the additional data segment and the MPEG data segment at a ratio of 1: 3 with the offset K1 as 3;

FIG. 6A is a diagram showing the configuration of the multiplexed field data when multiplexing the additional data segment and the MPEG data segment at a ratio of 1: 1 by using the offset K1 as 0 and the offset K2 as 1; FIG.

FIG. 6B is a diagram showing the configuration of the multiplexed field data when multiplexing the additional data segment and the MPEG data segment at a ratio of 1: 1 by setting the offset K1 to 0 and the offset K2 to 2;

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

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

9 is a diagram showing a configuration of a segment existing in a field sync interval among data fields according to the present invention.

10 is a block diagram showing the configuration of a receiving system for 8 VSBs among the components of a communication system for VSB signals according to the present invention;

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

The VSB digital signal refers to a signal modulated by VSB (Vestigial Side Band). Such VSB digital signals are used in recent digital television broadcasting and the like.

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

Meanwhile, the Republic of Korea also adopted the ATSC 8T-VSB transmission method as a standard in the United States, and began experiment broadcasting in May 1995 using this ATSC 8T-VSB transmission method, and from August 31, 2000, The same experimental broadcast was converted to a test broadcast system.

According to the existing ATSC 8T-VSB transmission system, a data randomizer randomly inputs the MPEG video data and the acoustic data, and the Reed-Soloron encoder encodes the randomized data by Reed-Solomon encoding. A parity code of bytes is added to the data.

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

On the other hand, the multiplexer multiplexes the symbol string from the trellis encoder and the synchronization signals from the outside, and the pilot inserter adds a pilot signal to the symbol string.

On the other hand, the VSB modulator modulates the symbol string into 8 VSB signals 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. Signals in this RF band are transmitted to the receiver through the antenna.

The aforementioned VSB related communication system has been registered in the United States by United States Patent Numbers (USP) 5636251, 5629958, and 5600677 in the United States.

The 8T-VSB transmission scheme, which has been adopted as the standard for digital television broadcasting in North America and the Republic of Korea, has been developed for transmitting MPEG image data and MPEG acoustic data. Meanwhile, as the technology for processing digital signals is rapidly developed and the Internet is widely used in recent years, digital home appliances, computers, and the Internet are being integrated into one big framework.

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 broadcast channel and transmitting the added data.

Meanwhile, those who use the additional data broadcast are expected to use the additional data broadcast by using a personal computer (PC) card or a portable device having a simple indoor antenna for broadcasting the additional data.

However, in the room, the signal strength can be greatly reduced and ghosts and noise due to the reflected wave can be caused by the wall blocking and the influence of the proximity moving body. This, in turn, greatly reduces the performance of receiving the additional data broadcast signal.

On the other hand, unlike the general image data and audio data, when transmitting the additional data should have a lower error rate than when transmitting. In the case of the general image data and sound data, an error of a degree that the human eye and the ear cannot detect is not a problem.

On the other hand, in the case of the additional data (eg program execution file, stock information, etc.), even a single bit error on the additional data can cause serious problems. therefore It is absolutely necessary to develop a communication system that is more resistant to ghosts and noise occurring in the channel.

The additional data is usually transmitted in a time division manner through the same channel as MPEG video data and MPEG sound data. However, since the digital broadcasting began, ATSC VSB digital broadcasting receivers that receive only MPEG image data and sound data have been widely used in the home appliance market.

Therefore, the additional data to be transmitted through the same channel as the MPEG video data and the MPEG sound data should not have any effect on the ATSC VSB digital broadcasting receiver that has been prevalent in the rotating market.

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

On the other hand, in a poor channel environment, the reception performance of the conventional ATSC VSB receiving system may be degraded, and further, the viewer's viewing may be degraded.

When the conventional ATSC VSB receiving system multiplexes the additional data and the MPEG data in segments, the multiplexing order may greatly influence the decoding performance of the additional data. In other words, the decoding performance of the additional data can be significantly reduced in the multiplexing order.

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

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

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

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

According to the above feature, a segment composed of additional data packets inputted through one path of a VSB communication system and a segment composed of MPEG transport packets inputted through another path of the VSB communication system are defined according to a predetermined rule in a data field. Multiplexed by

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, multiplexing information for identifying the multiplexed 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 synchronization signal in the data field, wherein the multiplexing information is a current packet number of additional data to be multiplexed in a current data field, the current 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, the multiplexing information can be restored even when there is interference of the NTSC broadcast signal at the receiving side of the VSB communication system.

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 is largely composed of 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 is subjected to an encoding process on the additional data 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 receiving system through a channel (air or cable). In the encoding process of the additional data, an encoding is performed using a Reed Solomon encoder, an MPEG header is added to the encoded additional data, and then input to the multiplexer. That is, the encoding process is performed before the MPEG header is added, which can vary the encoding method according to the designer.

In the present patent, the encoding process will be described using Reed Solomon encoder, interleaver and null sequence insertion unit as an example.

First, the Reed Solomon encoder (or R-S encoder) 1 encodes the additional data for error correction. The interleaver 2 performs an interleaving process to increase the performance of burst noise on the encoded additional data. In this case, the interleaver may be omitted as necessary.

The null sequence inserter 3 inserts a null sequence into the interleaved or Reed Solomon encoded side data. The null sequence is previously determined at an input of a trellis encoder (not shown) for the interleaved or Reed Solomon encoded side data.

The reason for inserting the null sequence is to receive the transmitted additional data well in the receiving system even in a poor channel environment.

Meanwhile, the MPEG header inserter 4 adds an MPEG header on the additional data into which the null sequence is inserted in order to be compatible with the existing VSB receiving system. Additional data to which this MPEG header is added is input to the multiplexer 5.

Meanwhile, MPEG data input through the second path of the VSB transmission system, that is, data for broadcast programs (eg, movies, sports, entertainment, and dramas) 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 and second paths under the control of a control unit (not shown), and the multiplexed data is an 8T VSB transmission system 6. Is output.

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

In more detail, the above-described additional data packet of 164 bytes is encoded by the Reed-Solomon encoder 1 and converted into a packet of 184 bytes. This 184 byte packet is interleaved in the data interleaver 2, at which time the order of the data is reversed.

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

Each of the two generated 187 byte packets is transmitted to the receiving system after being multiplexed with the MPEG transport packet on a segment basis in the transmission system 6 for 8T VSB.

The additional data packet and the MPEG transport packet in the multiplexer 5 are multiplexed in a time division manner in units of segments in the VSB data field. At this time, one segment is composed of 187 bytes, and the data field is composed of 312 segments.

The operation of the 8T VSB transmission system 6 will now be described with reference to FIG. 1B.

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 adds 20 bytes of parity code to the MPEG data packets by reed- Solomon encoding the MPEG data.

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

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

On the other hand, the multiplexer 15 multiplexes (multiplexes) symbol strings and synchronization signals, and the pilot inserter 16 adds a pilot signal to the symbol strings. VSB modulator 17 modulates the symbol strings 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.

On the other hand, both the trellis decoder and slicer predictor used in the reception system for the digital VSB, which is the other side of the transmission system, use the Viterbi algorithm. This Viterbi algorithm is a state transition over time of the trellis encoder of the transmission system, that is, an algorithm for predicting a path having the highest probability.

In the Viterbi algorithm, the ACS (Accumulate / Compare / Select) section calculates metrics corresponding to all possible routes for each state, selects the path with the smallest value (highest probability), and then selects the corresponding path. Stores the metric value.

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

Meanwhile, in the transmission system, a predefined sequence is inserted into a symbol of the additional data, whereas a symbol of the MPEG transport data does not include the predefined sequence. Therefore, in the symbol period of the MPEG transport data, the reliability of the accumulated path metric is lower than that of the symbol data 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 in front affects the symbol of the additional data located in the rear, and eventually, the symbol of the additional data. Decoding performance for is lowered.

At this time, since the range of influence is within a few symbols, there is a difference between the decoding performance of the symbol of the additional data near the boundary and the decoding performance (error rate) of the symbol of the additional data located behind some extent.

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

Therefore, in order to maximize the decoding performance of the symbol of the additional data, it is preferable that the symbols of the additional data are transmitted continuously as much as possible. In other words, the boundary between the symbol period of the MPEG transport data and the symbol period of the additional data should be small. This boundary is closely related to the multiplexing, interleaver, and trellis coders.

FIG. 2 is an example of multiplexing additional data and MPEG transport data 2 to 6, and illustrates a case in which decoding performance of symbols of the additional data is not good.

In FIG. 2, the left figure shows a case where a data field is configured 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 figure on the left, the first 52 bytes of output and the next 52 bytes of output from the data interleaver are input to 12 trellis encoders.

In the figure on the right, each column represents the input of each trellis encoder. As can be seen from the figure, first, since the multiplexing pattern does not have a 12-byte period, it can be seen that the bytes of the additional data are not driven to a specific trellis encoder.

3-4 show the most preferred examples of multiplexing. 3 shows an example of multiplexing additional data and MPEG transport data in a one-to-three manner, and FIG. 4 is a diagram illustrating an example of multiplexing additional data and MPEG transport data in a one-to-one manner.

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 in the following equations.

The decoding performance of the additional data is maximized when the period of the multiplexing pattern for configuring one data field is 4 segments . Since one additional data packet corresponds to two segments, it is possible to multiplex from 0 to 156 (= 312/2) additional data packets in one data field.

As described above, the additional data segment multiplexed with the MPEG data in four segment periods is input to the trellis encoder via the interleaver. You can use this fact to create rules like the following equations. The following formula produces a map for multiplexing the additional data segments in the MPEG field data. From the following equations, the additional data segments are multiplexed into the MPEG field data in order from the value of s being small.

     0≤P≤39: MAP = {s / s = ((4i + K1) mod 312) + 1, i = 0,1,2, ..., 2P-1} ..... (1)

     40≤P≤78: MAP = {s / s = ((4i + K1) mod 312) + 1, i = 0,1,2, ..., 77} U

                   {s / s = ((4i + K2) mod 312) + 1, i = 0,1,2, ..., 2P-79} ..... (2)

     79≤P≤117: MAP = {s / s = ((4i + K1) mod 312) + 1, i = 0,1,2, ..., 77} U

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

                    {s / s = ((4i + K3) mod 312) + 1, i = 0,1,2, ..., 2P-157} ..... (3)

     118≤P≤156: MAP = {s / s = ((4i + K1) mod 312) + 1, i = 0,1,2, ..., 77} U

                      {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

                    {s / s = ((4i + K4) mod 312) + 1, 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 Equations (1) to (8), s following the field synchronization signal indicates a position of each segment constituting the field data, and has a value from 1 to 312. Meanwhile, k1, k2, k3, and k4 indicate an offset for adjusting a start position for multiplexing the additional data segment on the basis of the field sync signal, and have a value from 0 to 311. Meanwhile, for different m and n, (Km mod 4) and (Kn mod 4) have different values.

Summarizing the equations (1) to (8), if the number of additional data segments multiplexed in one field data is less than 312 1/4 (0≤P≤39), the field from the specific position of the field data The positions of the additional data segments are allocated at one ratio for every four segments of data.

On the other hand, if the number of additional data segments multiplexed in one field data is larger than 312 1/4 and smaller than 1/2 of 312 (40 ≦ P ≦ 78), first of the field data is determined from the specific position of the field data. The location of the additional data segment is determined at one ratio per segment. Then, for the remaining additional data segments, the positions of the additional data segments are allocated at one ratio for every four segments of the field data from other specific positions.

On the other hand, when the number of additional data segments to be multiplexed in one field data is larger than 312 1/2 and smaller than 3/4 of 312 (79 ≦ P ≦ 117), first of all the field data is determined from a specific position of the field data. The positions of 1/2 of the additional data segments to be multiplexed are determined at one ratio every four segments. Then, for the remaining additional data segments, the positions of the remaining additional data segments are allocated in one ratio for every four segments of the field data by differentiating the multiplexing start position of the additional data segment from another specific position.

On the other hand, when the number of additional data segments to be multiplexed in one field data is greater than 312 3/4 and less than 1 (118? P? 156), one every four segments of the field data is first specified from the specific position of the field data. Determine multiplexing positions of three quarters of the additional data segments to be multiplexed at the rate of. Then, for the remaining additional data segments, the positions of the remaining additional data segments are allocated in one ratio for every four segments of the field data by differentiating the multiplexing start position of the additional data segment from another specific position.

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

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

FIG. 5A is a diagram showing the configuration of the multiplexed field data when multiplexing the additional data segment and the MPEG data segment (or MPEG transport segment) at a ratio of 1: 3 with the offset K1 set to zero.

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

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

FIG. 5D is a diagram showing the configuration of the multiplexed field data when multiplexing the additional data segment and the MPEG data segment (or MPEG transport segment) at a ratio of 1: 3 with the offset K1 set to 3. FIG.

5A to 5D correspond to the case where the packet number P of the additional data is 39. FIG. 5A to 5D, diagrams on the left side show multiplexing of the additional data segment and the MPEG data segment on the basis of the field synchronization signal, and diagrams on the right side show that the output signal of the interleaver The input form of the trellis encoder consisting of 12 is shown.

In more detail, FIG. 5A shows the multiplexing of the additional data segment every four field data segments from the first segment of the field data based on the field sync signal. 5A shows that after the field sync signal, additional data corresponding to first 52 bytes and additional data corresponding to second 52 bytes are input to the 12 trellis encoders. Show the case.

That is, the additional data corresponding to the first 52 bytes is input to the 12 trellis encoders four times for 12 bytes. At this time, 4 bytes of the 52 bytes remain. As such, the remaining four bytes are input to the twelve trellis encoders along with the first eight bytes of the second 52 bytes. As described above, according to the multiplexing pattern of the additional data according to the above formulas (1) to (8), the remaining 4 bytes of the first 52 bytes are the first 8 bytes of the second 52 bytes. In addition, a constant multiplexing pattern is maintained. This means that the bytes of the additional data are driven to a specific encoder or coders of the 12 trellis encoders. As such, when the additional data bytes are clustered into the specific encoder or the specific encoders and multiplexed, it is possible to greatly reduce an occurrence of an error when separating and decoding the additional data and the MPEG data in the VSB receiving system.

FIG. 5B is a diagram illustrating a method of multiplexing the additional data segment from the second segment of the field data based on the field sync signal.

5C is a diagram illustrating a method of multiplexing the additional data segment from the third segment of the field data based on the field sync signal.

5D is a diagram illustrating a form of multiplexing the additional data segment from the fourth segment of the field data based on the field sync signal. 5B to 5D show that the additional data segment is multiplexed by one segment for every four segments of the field data, as in the case of FIG. 5A, and the additional data bytes are input to the specific trellis encoder or encoders. .

Hereinafter, a case of multiplexing the additional data segment and the MPEG data segment in a ratio of 1: 1 by using Equations (1) to (8) will be described.

FIG. 6A shows the multiplexed field when multiplexing the additional data segment and the MPEG data segment (or MPEG transport segment) in a ratio of 1: 1 with the offset K1 as 0 and the offset K2 as 1; FIG. Diagram showing the organization of data.

FIG. 6B shows the multiplexed field when multiplexing the additional data segment and the MPEG data segment (or MPEG transport segment) at a ratio of 1: 1 by setting the offset K1 to 0 and the offset K2 to 2. FIG. Diagram showing the organization of data.

According to Figs. 6A and 6B, the following regularity can be seen. As described above, FIGS. 5A to 5D show examples when the MPEG data segment (or MPEG transport segment) is multiplexed at a ratio of 1: 3. Here, even if the multiplexing start position of the additional data segment is different based on the field synchronization signal, the additional data bytes are input to the specific trellis encoder or coders. Accordingly, even when the MPEG data segment (or MPEG transport segment) is multiplexed at a ratio of 1: 1 by combining any two cases of FIGS. 5A to 5D, the same characteristic as that of the 1: 3 case is maintained. It becomes possible. For example, combining the case of FIG. 5A and the case of FIG. 5B, as shown in FIG. 6A, the additional data bytes are crowded into one specific trellis encoder and input. In combination with the case of FIG. 5A and the case of FIG. 5C, as shown in FIG. 6B, the additional data bytes are gathered into one specific trellis encoder and input.

7 is a diagram showing the 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. In this case, the 8T VSB transmission system continuously transmits the multiplexed data so that decoding performance of symbols of the additional data may be maximized.

Hereinafter, a process of multiplexing additional data and MPEG transport data 1 to 3 will be described in detail with reference to FIGS. 7 to 10.

Fig. 7 shows the data interleaver in the 8T VSB transmission system as described above, wherein the branch number B is 52 and the number of bytes M of the unit memory is four convolutional interleavers.

In Fig. 7, the interleaver operates in synchronization with the first byte of one data field. First, when the first byte is input, the first byte is directly output through the second branch, and the second byte is input through the second branch, and a value 52 x 4 bytes before is output.

As described above, the input order and output order of the data interleaver shown in FIG. 7 are as follows. Data input is input from the upper side to the lower side of the data field in segments, and bytes in each segment are input from the left to the right.

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

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

In this way, 52 bytes from the interleaver are output in order to the 12 trellis encoders and precoders shown in FIG. As described above, the 53 th input byte is immediately output after being input to the first branch of the interleaver. Here, the interleaver operates with a 52 segment depth and is connected to the 12 trellis encoders and precoders. Therefore, 52 bytes output from the interleaver are input to the trellis encoder and precoder by 12 bytes, and this process is performed with four cycles.

At this time, if the process is performed four times, only 48 bytes (12 bytes X 4 cycles = 48) are outputted to the trellis encoder and precoder, and still 4 bytes remain.

The remaining four bytes are then input to the twelve trellis encoder and precoder together with the first eight of the 52 bytes to be 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 inputs and outputs of twelve trellis encoders and precoders are multiplexed.

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

At this time, trellis coding is performed on each byte and converted into four symbols (one symbol consists of two bits). 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 synchronization signal existing in a data field in an 8T VSB transmission system.

According to FIG. 9, the segment corresponding to the field synchronization signal is multiplexed so that a VSB receiving system can detect the multiplexing information present in the segment corresponding to the field synchronization signal and perform correct decoding using the detected multiplexing information. Information is included.

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

Meanwhile, even when the VSB transmission system is transmitting data to the VSB receiving system, a reserved area of a segment corresponding to the field synchronization signal shown in FIG. 8 can be changed so that the amount of additional data to be multiplexed can be changed. The current P value, the number of data fields until the current P value is changed, and the P value to be changed are transmitted to the VSB receiving system.

Therefore, the receiving system can receive data from the VSB transmitting system without error even if the P value changes.

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

For example, the multiplexing information transmitted through the spare area is as follows. Eight bits may be allocated as the current P value, eight bits are allocated as the P value to be changed, and eight bits are allocated as the number of fields until the current P value is changed to the new P value. Thus, the total 24 bits of multiplexing information is transmitted toward the VSB receiving system through the spare area. Here, if the number of fields up to the change is 0, 0 means that the current P value will not change for the time being.

Meanwhile, even when comb filtering is performed in the VSB receiving system due to interference of an existing broadcast type NTSC broadcast signal, it is necessary to restore the multiplexed information. For this case, the total 24-bit multiplexing information is divided into two 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 sent towards the VSB receiving system along with the 12 bit information inverted about it.

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

Here, the inversion means bit-wise inverse. In order to more reliably transmit the multiplexing information from the VSB transmitting system to the receiving system in a poor channel situation, the multiplexing information has a form including the multiplexing information in the first additional data segment following the field synchronization signal. It may also transmit toward the VSB receiving system.

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

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

In FIG. 10, the VSB receiving system according to the present invention indicates a sequence generator 21 for indicating a symbol of additional data and generating a predefined sequence included in the additional data, and generating the data received from the VSB transmission system. MPEG data processing unit 32 which processes in reverse order with the VSB transmission system using a sequence, detects multiplexing information from field synchronization signals in field data received from the VSB transmission system, and controls the demultiplexing using this multiplexing information. A multiplexed information recovery unit 33 generating a signal and a Reed Solomon decoding control signal, and demultiplexing the output data of the MPEG data processing unit 32 according to the demultiplexing control signal to separate the data into MPEG data and additional data. A demultiplexer 34 and an output from 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.

As shown in Fig. 10, the MPEG data processor 32 includes a demodulator 41, a comb filter 42, a channel equalizer 43, a slicer predictor 44, a phase decompressor 45, and a trellis decoder. 46, a first data deinterleaver 47, a first Reed Solomon decoder 48, and a data derandomizer 49. The additional data processor 35 includes an MPEG header remover 51, a null sequence remover 52, a second data deinterleaver 53, and a second Reed Solomon decoder 54.

The demodulator 41 converts the RF band signal into a baseband signal, and then the sync and timing recoverer 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 recoverer 45 recovers the phase of the MPEG data, and the trellis decoder 46 performs Viterbi decoding by using the generated sequence and the Viterbi algorithm.

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

The first data deinterleaver 47 performs a reverse operation on the data interleaver of the ATSC 8T VSB transmission system, and the first Reed Solomon decoder 48 receives a Reed Solomon-coded signal from the ATSC 8T VSB transmission system. Decrypt again. On the other hand, the data derandomizer 49 performs a reverse operation on the data randomizer of the transmission system.

On the other hand, the sequence generator 31 indicates whether or not a symbol received from the VSB transmission system is a symbol corresponding to the additional data, and generates the same predefined sequence to be inserted and transmitted in the additional data.

As described above, the channel equalizer 43, the slicer predictor 44, the phase decompressor 45, and the trellis decoder 46 each have their own performance using the predefined sequence information. Improves. In this case, the components using the predefined sequence may delay and use the sequence information in consideration of data processing delays of 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 recovered from the field synchronization signal.

The first Reed Solomon decoder 48 removes only 20 bytes of parity bits added by the Reed Solomon encoder of the VSB transmission system without performing Reed Solomon decoding on the additional data segment.

If the noise of the channel is severe, more error occurs in the parity byte of the ATSC Reed Solomon code than the additional data. The reason is that there is no predefined sequence in the parity byte of the ATSC Reed Solomon code, so there is no gain in the trellis decoder 46.

The reason why the first Reed Solomon decoder 48 does not perform Reed Solomon decoding on the segment of the additional data is that when an error exceeding 10 bytes occurs on the segment of the additional data, the first Reed Solomon decoder 48 Is likely to perform incorrect error correction.

On the other hand, the 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 is 3 bytes from the segment corresponding to the additional data. Remove the MPEG header. The MPEG header was inserted when the additional data was transmitted in the ATSC format in the VSB transmission system.

Subsequently, the null sequence remover 52 removes the null sequence that was inserted in the null sequence inserter of the VSB transmission system from the additional data segment. Then, the second deinterleaver 53 performs a reverse operation on the interleaving process in the VSB transmission system on the additional data segment.

If the interleaving operation is omitted in the VSB transmitting system, the VSB receiving system also does not include the second deinterleaver 53. Meanwhile, the second Reed Solomon decoder 54 decodes the Reed Solomon code for the additional data.

The VSB receiving system shown in Fig. 10 improves its receiving performance by using the sequence predefined in the VSB transmitting system as described above. On Fig. 10, the feature portion is the multiplexed information reconstruction unit 33. The multiplexing information recovery unit 33 detects the multiplexing information included in the input bitstream and outputs a control signal for the demultiplexer for separating 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 synchronization signal, more stable decoding can be performed.

The multiplexing information reconstruction unit may further include a control signal from the field synchronization signal to bypass the first Reed Solomon decoder 48 without performing a first Reed Solomon decoding when the input data is additional data. Output using 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 sequence and multiplexing information when transmitting MPEG data and additional data together through a channel.

Second, the digital VSB communication system according to the present invention is compatible with the existing VSB receiving system.

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

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

As described above, those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (8)

If the first data having the first attribute and the second data having the second attribute are multiplexed and transmitted, receiving and demodulating the received data; Correcting an error generated during transmission of the multiplexed first and second data using parity added to the demodulated data; Demultiplexing first data and second data from the error corrected data; And And correcting an error generated during transmission of the data to which the parity is added by using parity added to any one of the first and second data separated by the demultiplexing. The method of claim 1, wherein the error correction step is Receiving method characterized in that for performing the Reed-Solomon decryption to correct the error occurred during the transmission of the data. The method of claim 1, wherein the demultiplexing step And receiving first and second data from the error corrected data according to a data attribute. A demodulator configured to receive and demodulate the first data having the first attribute and the second data having the second attribute after being multiplexed; A first Reed Solomon decoder configured to perform Reed Solomon decoding on the data demodulated by the demodulator; A demultiplexer for separating first data and second data from the data decoded by the first Reed Solomon decoder; And And a second Reed Solomon decoder configured to perform Reed Solomon decoding on any one of the first and second data separated by the demultiplexer. The method of claim 4, wherein the first Reed Solomon decoder And an error generated during transmission of the multiplexed first and second data using parity added to the demodulated data. The method of claim 4, wherein the second Reed Solomon decoder And receiving an error of the data to which the parity is added by using parity added to any one of the first and second data separated by the demultiplexer. The method of claim 4, wherein the demultiplexer And receiving first data and second data from the data decoded by the first Reed Solomon decoder according to data attributes. The method of claim 4, wherein The data which is not decoded in the second Reed Solomon decoder is MPEG data.

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