KR20070004472A - Transmitting/receiving system and method of data processing in the transmitting/receiving system - Google Patents

Abstract

A transmission/reception system and a data processing method are provided to be suitable for transmitting additional data and be strong in a noise. The first parity adding unit adds the first parity data to the first service data inputted through the first path. A multiplexing unit adds an MPEG(Moving Picture Experts Group) header to the first service data to which the first parity data are added, and multiplexes the first service data and the second service data inputted through the second path. The second parity adding unit adds the second parity data to the service data multiplexed in the multiplexing unit. A transmitting unit modulates the service data to which the second parity data are added, and transmits the modulated data.

Description

Transmitting / receiving system and method of data processing in the transmitting / receiving system}

Figure 1a is an 8VSB transmission system for additional data transmission

Figure 1b is an 8VSB transmission system

2 is a block diagram of a data field when decoding performance is not good

3 is a diagram illustrating a data field in the case of 1: 3 multiplexing according to the present invention.

4 is a configuration diagram of data fields in the case of 1: 1 multiplexing according to the present invention.

5 is a block diagram of a data interleaver in case of 1: 3 multiplexing according to the present invention

6 is a data input / output diagram of the data interleaver of FIG.

7 is a block diagram of a trellis encoder in case of 1: 3 multiplexing of the present invention

Fig. 8 is a diagram showing the segment structure between field moving mechanisms existing in the data field of the present invention.

9 is an 8VSB receiving system of the present invention.

The present invention relates to a digital communication system, and more particularly, to a transmission system for modulating and transmitting digital data, a receiving system for receiving the same, and a data processing method.

In the United States, ATSC 8T-VSB transmission system was adopted as a standard in 1995 for terrestrial digital broadcasting, and broadcasted since the second half of 1998.In Korea, ATSC 8T-VSB transmission system, which is identical to the US method, was adopted as a standard in May 1995. Experimental broadcasting was started, and on August 31, 2000, the test broadcasting system was switched.

1 shows a conventional ATSC 8T-VSB transmission system. The data randomizer randomizes the input MPEG video / audio data, and the Reed-Soloron encoder adds 20 bytes of parity code by Reed-Solomon encoding the data, and the data interleaver interleaves the data, and the trellis encoder Converts the data from bytes into symbols and then trellis-codes them. The mux muxes the symbol strings and sync signals, the pilot inserter adds the pilot signal to the symbol strings, the VSB modulator modulates the symbol strings into an 8 VSB signal of the intermediate frequency band, and the RF converter converts the intermediate frequency signal into an RF band signal. Transmit and transmit through the antenna. For example, USP5636251, USP5629958, and USP5600677, which are filed in the US by Zenith in the US, may be exemplified in relation to the existing VSB.

The 8T-VSB transmission system, adopted as a digital broadcasting standard in North America and Korea, is a system developed for transmission of MPEG video / audio data. However, with the rapid development of digital signal processing technology and the widespread use of the Internet, digital home appliances, computers, and the Internet are being integrated into one big framework. Therefore, in order to meet various needs of users, it is necessary to develop a system capable of transmitting various additional data in addition to video / audio data through a digital broadcasting channel.

Some users of supplementary data broadcasting are expected to use supplementary data broadcasting by using PC card or portable device equipped with simple indoor antenna. In the room, signal strength is greatly reduced by wall blocking and influence of proximity moving body. Due to the effects of ghosts and noise caused by reflected waves, broadcast reception performance may deteriorate. However, unlike general video / audio data, the additional data transmission should have a lower error rate. In the case of video / audio data, errors that the human eye and ears cannot detect are not a problem, while in the case of additional data (e.g., program executable files, stock information, etc.), a bit error may occur. It may cause a problem. therefore There is a need to develop a system that is more resistant to ghosting and noise in the channel.

The transmission of additional data will usually be done in a time division manner over the same channel as the MPEG video / sound. Since the beginning of digital broadcasting, however, ATSC VSB digital broadcasting receivers that receive only MPEG video / audio have been widely used in the market. Therefore, additional data transmitted on the same channel as MPEG video / audio should not affect the existing ATSC VSB-only receivers that have been used in the market. Such a situation is defined as ATSC VSB compatible, and the additional data broadcasting system should be compatible with the ATSC VSB system.

In addition, in a poor channel environment, the reception performance of the conventional ATSC VSB receiving system may be degraded. That is, the viewer's feeling can be reduced. In order to solve this problem, the applicant has filed a related patent (application number: P00-83533 application date: December 28, 2000, application number: P01-3304, application date: 2001, 1.19).

In such a system, when multiplexing additional data and MPEG data in units of segments, the multiplexing order may determine decoding performance in decoding additional data. In other words, the decoding performance can be significantly reduced depending on the multiplexing procedure.

Accordingly, the present invention has been made to solve the above problems, and proposes a new transmission system suitable for additional data transmission and resistant to noise.

Another object of the present invention is to improve decoding performance of additional data symbols.

Another object of the present invention is to provide a transmission system and a reception system for improving decoding performance of additional data symbols.

It is still another object of the present invention to provide a method and apparatus for multiplexing additional data and MPEG data in a receiver with excellent decoding performance, which can be applied in a transmission system described in the presently filed patent application (P00-83533, December 29, 2000). To provide.

A feature of the present invention for achieving the above object is that a segment consisting of additional data packets inputted through a first path and a segment consisting of MPEG transport packets inputted through a second path are defined in a data field. Multiplexed by The number of packets of the additional data multiplexed above varies from 0 to 156. In addition, when multiplexing the additional data and the MPEG data in the data field, the information field may also include multiplexing information for identifying the multiplexing position of the additional data. The multiplexing information is located in a reserved area of a segment having a field synchronization signal in a data field, and the number of additional data packets multiplexed in the current data field, the number of fields until the number is changed, and the number of additional data packets to be changed. It consists of numbers. In addition, the multiplexed information includes information inverted by 12 bits so that the multiplexed information can be recovered even if there is NTSC signal interference at the receiver.

Hereinafter, the features and advantages of the present invention will be described with reference to FIGS. 1 to 9. First, the additional data transmission system of the present invention will be described with reference to FIGS. 1A and 1B. 1A and 1B have the same configuration as the patent P00-83533, 2000.12.29 previously filed by the present applicant. That is, as shown in FIG. 1A, some encoding processes are performed to transmit additional data to a receiver through a channel (public or cable) at a broadcast station through a first path. First, it is encoded by the Reed Solomon encoder (R-S encoder) for error correction. An interleaving process is performed on the encoded additional data to improve burst noise performance. In this case, the interleaver may be omitted as necessary. The null sequence insertion unit inserts a null sequence in order to generate a predetermined sequence at an input terminal of a trellis coder for the interleaved or Reed Solomon coded additional data. The reason for inserting null sequences is to ensure good reception even in poor channel environments. The additional data inserted with the null sequence is input to the multiplexer after the MPEG header is added for compatibility with the existing VSB receiver. In addition, broadcast program data (eg, movies, sports, entertainment, dramas, etc.) in the second path is input to the multiplexer through MPEG encoding. The multiplexer (eg, a mux) outputs data to the VSB transmission system based on a control operation of a controller (not shown) and additional data and MPEG data input through the first and second paths. With respect to the multiplexed data, the VSB transmission system processes the data in the same manner as the conventional method and transmits the data to the receiver through the channel.

In addition, 164 bytes of additional data packets are Reed-Solomon encoded and converted into 184 bytes of packets, which are interleaved and reordered, and a null sequence is inserted to output two 184 bytes of packets, each of which has three bytes of The MPEG transport header is added to output two 187 byte packets. The two packets thus generated are multiplexed with MPEG transport packets in segments of VSB systems and transmitted.

Multiplexing of the additional data packet and the MPEG transport packet is performed by time division by segment within the VSB data field. One segment consists of 187 bytes and the data field consists of 312 segments.

Packets multiplexed on a segment basis are processed by the VSB transmission system, and the order is changed by the data interleaver. This reordered byte of data is converted into a trellis encoder after byte-symbol conversion. Therefore, the symbols of one packet are not continuously input to the trellis encoder, but the symbols of different packets are mixed and input to the trellis encoder. Both the trellis decoder and slicer predictor used in the digital VSB receiver system use the Viterbi algorithm, which predicts the state transition over time of the trellis encoder, that is, the path with the highest probability. It is an algorithm.

The ACS (Accumulate / Compare / Select) section of the Viterbi algorithm calculates the metric of all possible routes for each state, selects the path with the lowest value (highest probability), and stores the metric value. do. The calculated route metric is the sum of the route metric and the branch metric of the previous time corresponding to the route. Thus, the path metric calculated to the previous symbol affects subsequent symbols.

The foregoing is described in detail in the patent application P00-83533,2000,12,29 filed by the present applicant. Therefore, the above patent will reveal the details of the transmission system.

In addition, in the patent application (P00-83533, 2000.12.29) filed by the applicant, the contents of inserting a predefined sequence in the additional data symbol and transmitting to the receiver side are described. However, since the MPEG transmission data symbol does not include a predefined sequence, the reliability of the accumulated path metric is inferior to the additional data symbol in the MPEG transport symbol interval. Therefore, when the MPEG transport symbol and the additional data symbol are mixed, the decoding performance of the additional data symbol is degraded because the preceding MPEG transport symbol affects the subsequent additional data symbol. At this time, since the influence range is within a few symbols, there is a difference between the decoding performance of the additional data symbol near the boundary and the decoding performance (error rate) of the additional data symbol after a certain degree. In other words, among the additional data symbols, the error rate of the additional data symbol at the boundary between the MPEG transport symbol section and the additional data symbol section is high. Therefore, in order to maximize the decoding performance of the additional data symbols, it is desirable that the additional data symbols be continuously transmitted as much as possible. In other words, the boundary between the MPEG transport symbol interval and the additional data symbol interval should be small. This is related to multiplexing, interleaver and trellis coder.

 2 shows a case where the decoding performance of a symbol of additional data is not good as an example of multiplexing. 2 shows a case where the field of data is multiplexed in the form of two additional data segments and six MPEG transport segments. On the other hand, the right figure of Fig. 2 shows that in this case, the output of the first 52 bytes and the next 52 bytes in the data interleaver is input to the 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 no additional data bytes are driven to a specific trellis encoder.

3 to 4 show the case of 1: 3 and the case of 1: 1 multiplexing as the most preferable examples of multiplexing. The basic principle of such multiplexing provides a multiplexing method based on the number of additional data packets (P value) as shown in the following equations.

In other words, it is a method of maximizing the decoding performance of additional data by making the period of the multiplexing pattern four 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 the data field. The following summarizes the multiplexing method according to the number of additional data packets. In Equation, P denotes the number of additional data packets multiplexed in one data field, and MAP is a set indicating a location where additional data is multiplexed in the field. The value of P is divided into four ranges and multiplexed as follows. The element s in the set indicates the segment position in the field after the field synchronization signal. Once the P value is determined, the MAP is determined, and the additional data segments are multiplexed in the order of s in the MAP.

  0 <= P <= 39: MAP = {s | s = 4i + 1, i = 0,1, ..., 2P-1}, (1 <= s <= 312)

 40 <= P <= 78: MAP = {s | s = 4i + 1, i = 0,1, ..., 77} U

                        {s | s = 4i + 3, i = 0,1, ..., 2P-79}

 79 <= P <= 117: MAP = {s | s = 4i + 1, i = 0,1, ..., 77} U

                        {s | s = 4i + 3, i = 0,1, ..., 77} U

                        {s | s = 4i + 2, i = 0,1, ..., 2P-157}

118 <= P <= 156: MAP = {s | s = 4i + 1, i = 0,1, ..., 77} U

                        {s | s = 4i + 3, i = 0,1, ..., 77} U

                        {s | s = 4i + 2, i = 0,1, ..., 77} U

                        {s | s = 4i + 4, i = 0,1, ..., 2P-235}

3 shows a multiplexing method in 1: 3 multiplexing, where P is 0 <= P <= 39. FIG. In addition, Figure 4 shows a multiplexing method when 1: 1 multiplexing is applied in the case where P is 40 <= P <= 78.

Data multiplexed on the basis of this method are processed by the data interleaver shown in FIG. 5 and the trellis encoder shown in FIG. 6, which are successively gathered and transmitted to maximize the decoding performance of the above-mentioned additional data symbols. Becomes

Hereinafter, the case of 1: 3 multiplexing will be described in detail with reference to FIGS. 5 to 7. Fig. 5 shows a data interleaver in an 8VSB system, which is a convolutional interleaver with the number of branches B = 52 and the unit memory bytes M = 4. The interleaver operates in synchronization with the first byte of the data field. First, when the first byte is input, it is directly output through the first branch, and the second byte is input through the second branch, and a value 52X4 bytes before is output.

FIG. 6 illustrates an input and output sequence of the data interleaver shown in FIG. Data input is entered from top to bottom in segment units, and bytes within a segment are entered first temporally from left to right. The numbers on the figure show the output order of the interleaver. The first byte of the data field after the field sync signal is inputted to the first branch and immediately output. That corresponds to the number 1 in FIG. The next input byte is input to the second branch, and the output is the byte 52 x 4 = 208 bytes before the input byte. Therefore, the byte corresponding to the number 2 is output in FIG. If the next byte is entered, the byte 52 x 8 = 416 bytes before the input byte is output. Therefore, the byte corresponding to the number 3 is output. In this way, 52 bytes are output in the order shown in the trellis encoder shown in Fig. 7, and the 53th input byte is inputted to the first branch and immediately output. The interleaver operates at 52 segment depths. The 52-byte output of the interleaver is input to the trellis encoder by 12 bytes, and after 4 cycles (12 bytes X 4 cycles = 48), 4 bytes remain. It is then input to 12 trellis encoders with the first 8 bytes of the 52-byte output.

7 shows a detailed view of the trellis encoder used in the 8VSB system. 7 shows that 12 trellis encoders are used by multiplexing. When 12 bytes output from the interleaver are input, 12 trellis encoders are inputted to 12 trellis encoders one by one. At this time, each byte is converted into four symbols (2 bits) to perform trellis encoding, and the output of each trellis encoder is multiplexed by one symbol and output.

FIG. 8 illustrates a segment configuration of a field synchronization signal existing in a field in an 8VSB system, and includes multiplexing information for a receiver to detect multiplexing information present in a field synchronization segment so that correct decoding can be performed. As described above, when the value of the number of additional data packets P (0 to 156) is determined, the multiplexing position is determined. Therefore, the transmitter only needs to transmit the P value. On the other hand, in order to allow the sender to change the amount of additional data multiplexed even during transmission, the number of data fields until the P value is changed and the P value to be changed are transmitted. In this way, the receiver can receive without error even if the P value changes.

As a method of transmitting the multiplexing information, a reserved area within the field synchronization signal is used. As shown in the figure, it can be seen that 92 symbols are reserved among the total 832 symbols. An example of transmitting multiplexed information may be as follows. It is to transmit a total of 24 bits of 8 bits of current P value, 8 bits of P value to be changed and 8 bits of field to be changed. If the number of fields until the change is 0, this means that it will not change for the time being.

However, even when the receiver performs a comb filter due to the interference of the existing NTSC, the inverted information is transmitted by dividing 12 bits in order to recover the multiplexed information. For example, as shown in FIG. 8, a total of 24 bits are divided into two by 12 bits and each inverted 12 bits are transmitted together. Inversion here means bit-wise inverse. In order to transmit the multiplexing information more stably even in a poor channel situation, the above-described multiplexing information may be included in the first additional data segment following the field synchronization signal. In this case, of course, as described above with respect to the field synchronization signal, multiplexing information is transmitted.

9 is a diagram showing the configuration of a receiver of 8VSB. The feature of FIG. 9 detects the multiplexing information included in the bitstream input as the multiplex recovery unit and outputs a control signal which allows the demux to separate the additional data and the MPEG packet. On the other hand, the additional data is decoded using the multiplexed information reconstructed from the field synchronization signal, and the multiplexed information included therein is compared to make more stable multiplexed information. In the case of additional data, a control signal for bypassing Reed Solomon decoding is also output. The process of processing the data according to this control signal is the same as the patent (application number: P01-3304, 2001.1.19) filed by the applicant.

As described above, the digital communication system according to the present invention has the advantage of being resistant to errors and compatible with existing receivers when transmitting additional data through a channel. The advantage is that additional data can be received without error even in ghost and noisy channels. In addition, by decoding the additional data and MPEG data according to a certain rule, the decoding performance of the additional data in the receiver is improved.

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 (20)

A first parity adding unit which adds first parity data to first service data input through a first path; A multiplexer which adds an MPEG header to the first service data to which the first parity data is added, and multiplexes the second service data input through a second path; A second parity adding unit which adds second parity data to service data multiplexed by the multiplexing unit; And And a transmission unit for modulating and transmitting the service data to which the second parity data is added. The method of claim 1, And an interleaver for interleaving the first and second service data to which the second parity data is added. The method of claim 1, And a trellis encoding unit configured to perform trellis encoding on the first and second service data to which the second parity data is added. The method of claim 1, wherein the first parity adder And a first parity data is added by performing Reed Solomon encoding on the first service data. The method of claim 1, wherein the second parity adder And transmitting second parity data by performing Reed Solomon encoding on the multiplexed first and second service data. Adding first parity data to first service data input through the first path; Adding an MPEG header to the first service data to which the first parity data is added; Multiplexing first service data appended with the MPEG header and second service data input through a second path; Adding second parity data to the service data multiplexed in the step; And And modulating and transmitting the service data to which the second parity data is added. The method of claim 6, And performing interleaving on the first and second service data to which the second parity data is added. The method of claim 6, And performing trellis coding on the first and second service data to which the second parity data has been added. 7. The method of claim 6, wherein the first parity adding step is And resolving Solomon encoding on the first service data to add first parity data. The method of claim 6, wherein the second parity adding step And resolving the multiplexed first and second service data to add second parity data. A demodulator for demodulating input data multiplexed with the first service data and the second service data; A first error correction unit correcting an error generated in the demodulated data by using first parity data added to the demodulated data; A demultiplexer demultiplexing the first error corrected data into a first service data and a second service data; A header removing unit to remove an MPEG header added to the first service data input separately from the demultiplexer; And And a second error correction unit for additionally correcting an error generated in the first service data by using second parity data added to the first service data from which the MPEG header is removed. The method of claim 11, And a trellis decoder for performing trellis decoding on the demodulated data. The method of claim 11, And a deinterleaver for performing deinterleaving on the demodulated data. 12. The method of claim 11, wherein the first error correction unit And a Reed-Solomon decoding on the demodulated data to perform error correction. The method of claim 11, wherein the second error correction unit And a Reed-Solomon decoding on the first service data from which the MPEG header has been removed to perform error correction. Demodulating first input data multiplexed with first service data and second service data; A first error correction step of correcting an error generated in the demodulated data by using first parity data added to the demodulated data; Demultiplexing the first error corrected data into a first service data and a second service data; Removing the MPEG header added to the first service data separated and output in the step; And And a second error correction step of additionally correcting an error generated in the first service data by using second parity data added to the first service data from which the MPEG header has been removed. Way. The method of claim 16, And performing trellis decoding on the demodulated data. The method of claim 16, And performing deinterleaving on the demodulated data. 17. The method of claim 16, wherein the first error correction step is And relying Reed Solomon on the demodulated data to perform error correction. 17. The method of claim 16 wherein the second error correction step is And relying Reed Solomon on the first service data from which the MPEG header has been removed to perform error correction.

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