KR20070101192A - Transmitting system and method of processing data - Google Patents

Abstract

A transmitting system and a data processing method are provided to be suitable for transmission of supplementary data, be strong for noise and be compatible with an existing system. A transmitting system comprises the followings: a first parity adding unit which adds first parity data to first service data inputted with a first property; a multiplexing unit which multiplexes second service data inputted with a second property and the first service data where the first parity data are added; a second parity adding unit which adds second parity data to the service data multiplexed in the multiplexing unit; an interleaver which performs the interleaving of the service data where the second parity data is added; and a transmitting unit modulating and transmitting the interleaved service data. A length of the first parity data and a length of the second parity data are different.

Description

Transmitting system and method of processing data

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

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 registered in the U.S., may be exemplified in connection with 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, whereas in the case of additional data (eg program execution file, stock information, etc.), a bit error may occur. It can cause problems. therefore There is a need to develop a system that is more resistant to ghosting and noise in the channel.

The transmission of the 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.

Accordingly, an object of the present invention is to propose a new transmission system suitable for additional data transmission and resistant to noise.

Another object of the present invention is to propose a new transmission system compatible with the existing system.

It is another object of the present invention to provide a signal format that can be suitably used for transmission systems resistant to ghosts and noises.

A feature of the present invention for achieving the above object is a reed-solomon encoding means for encoding data to be sent through a first path, an interleaver for performing an interleaving process for the reed-solomon-coded data, and for the interleaved data. A null data insertion unit for inserting null data to generate data of a predefined sequence, and a header unit for adding header data to the data into which the null data is inserted, and inserting MPEG data input through a second path. Multiplexing unit for multiplexing, and a transmission system for modulating and transmitting the multiplexed data for the data input through the first and second paths by the VSB transmission method.

In the above, the interleaver may or may not perform an interleaving process on Reed Solomon-coded data. That is, it may be an unnecessary component in the transmission system.

In the above, the null sequence data constitutes a sequence by allocating a part of additional data. In addition, the data structure of the predefined sequence is characterized in that "1" and "0" are listed in a predefined order, the number of "1" and the number of "0" are the same.

The multiplexer multiplexes the additional data input in the first path and the MPEG data input in the second path in segment units. Also, the multiplexing ratio can be different depending on the amount of data.

In addition, a first feature of the additional data signal format of the present invention for achieving the above object consists of an MPEG header of 3 bytes, 92 bytes of additional data, and 92 bytes of null data in a total of 187 bytes. Some of the 184 bytes except the 3 bytes of the MPEG header data include Reed Solomon parity.

The digital communication system according to the present invention is advantageous in that it is 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.

Hereinafter, the features and advantages of the present invention will be described with reference to FIGS. 2 to 8.

2 is a block diagram of a transmission system for transmitting additional data and MPEG data according to the present invention. 3 is a diagram illustrating a data frame structure of a conventional transmission system. 4 is a diagram illustrating an embodiment of multiplexing MPEG data and additional data. FIG. 5 is a diagram illustrating a data configuration of a sequence inserter for generating a sequence, and FIG. 6 is a diagram illustrating data interleaving for additional data. 7 and 8 are diagrams illustrating a process illustrating an encoding process of additional data.

First, the additional data transmission system of the present invention will be described with reference to FIG. 2. As shown in FIG. 2, 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, the RD coder encodes the R-S encoder for error correction. An interleaving process is performed to improve the performance of burst noise on the encoded additional data. In this case, the interleaver may be omitted as necessary. The null sequence inserter inserts a null sequence in order to generate a sequence determined at an input terminal of a trellis encoder for the interleaved or Reed Solomon encoded additional data. The reason for inserting null sequence is to receive well even in poor channel environment. The data structure of the inserted sequence will be described later with reference to FIG. 5.

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 transmission system processes the data in the same manner as the conventional method and transmits the data to the receiver through the channel.

As an example of the Reed Solomon encoding method for the additional data, a code having a block size N = 184, payload K = 164, and an error correction capability T = 10 may be used. At this time, the generation polynomial of the Galois field and the encoder can be the same as that of the Reed-Solomon encoder of the VSB transmission system. The specifications N, K, and T of this Reed-Solomon encoder can be changed. For example, a sign with N = 184, K = 154, and T = 15 may be used, and a sign with N = 92, K = 82, and T = 5 may be used. Instead of the Reed-Solomon code, other codes with good performance may be used.

3 is a diagram illustrating a data frame and segment configuration of a conventional transmission system. Each segment or some segments include the additional data described above together with null data.

One data field consists of 312 data segments and one field sync segment, and each data segment consists of 187 bytes of data (including 3 MPEG headers) and 20 bytes of ATSC Reed-Solomon parity. . The three bytes representing the MPEG header are related to the MPEG decoder. In other words, ISO / IEC 13818-1 defines the header of MPEG transport packets. Except for the sync byte of 0x47, there is a 3 byte header that defines the PID (Program ID). In the transport section of the MPEG decoder, if the PID of the received packet is not the PID defined by the predetermined table, the packet is discarded. Therefore, the MPEG header inserter for additional data shown in FIG. 2 does not conflict with the PID selected by the MPEG decoder. Inserts a 3-byte header with an additional PID into the additional data packet. Therefore, it can be distinguished from MPEG data input through the second path.

FIG. 4 is a diagram illustrating an exemplary embodiment in which the multiplexer of FIG. 2 multiplexes additional data and MPEG data, and multiplexing of MPEG data and additional data may be performed in units of data segments. Multiplexing is performed by synchronizing with a field synchronization signal used for data frame synchronization in a VSB transmission system. The receiver can find and demultiplex MPEG data and additional data in synchronization with the field synchronization signal.

The rate and method of multiplexing can be varied, and the information can be informed to the receiver using 92 bits in a reserved area in the field sync signal. In order to enable the receiver to more reliably recover the multiplexed information, the receiver may insert and transmit additional data as well as the field synchronization signal.

FIG. 4 illustrates an example of multiplexing, in which additional data is multiplexed with 1/2 of a total of 312 segments. This multiplexing rate is determined depending on the broadcasting station.

FIG. 5 is a diagram showing the data structure of the sequence inserter. As a principle for receiving the data well, a predetermined sequence is inserted into a part of the additional data and sent together. The predetermined sequence is composed of 1 and 0 arranged in a predetermined order. The number of 1s and the number of 0s should be the same on average. One example of a predetermined sequence is the output of a pseudo random value generator with a predetermined initial value.

How much of the predetermined sequence is inserted into the data determines the reception performance of the additional data. The more the sequence is inserted into the certain additional data, the stronger the reception performance is obtained. That is, when one byte is input, the predetermined sequence generator inserts a null bit and outputs two bytes as shown in the figure. The null bits thus inserted are rendered by a randomizer (not shown) in the VSB transmission system shown in FIG. ).

Here, d0 is a bit corresponding to the lower bit of the two input bits of the trellis encoder. In addition, the basic operation of the trellis encoder outputs the number of output bits of three bits for two input bits. Since the VSB transmission process is the same as in the related art, description thereof is omitted. The receiver restores a sequence to be input to the input d0 of the trellis encoder, that is, a predetermined sequence, to improve the performance of the receiver. The null sequence is shown as a simple example, and any other sequence may be used instead of this null sequence. However, in order to be compatible with the conventional VSB system, the occurrence probability of 8 levels must be the same, and therefore, the existence probability of 0 and the existence probability of 1 of the sequence input to the input bit d0 of the trellis encoder must be the same.

6 illustrates an embodiment of an interleaver for additional data. The interleaver shown in the embodiment is a convolutional interleaver, and corresponds to the case where the number of branches B = 46 and the number of bytes M = 4 of the unit memory. The interleaver synchronization can be matched to the field synchronization signal of the VSB transmission system.

The values of B and M shown in the above embodiment may be changed, and another type of interleaver such as a block interleaver may be used instead of the convolutional interleaver. In addition, since the existing ATSC transmitter has a data interleaver, the interleaver for additional data may be omitted if there is no need to improve the performance of burst noise.

FIG. 7 illustrates a case where the block size of the additional data is 164. In the case of using the Reed-Solomon code, the data interleaver, and the null sequence inserter for the additional data shown in the previous embodiment, the packet until the additional data is processed and multiplexed It shows the transformation. 164 bytes of additional data are inserted into a 184 byte packet by inserting 20 bytes of parity bytes by the Reed-Solomon encoder. The number of additional parity bytes may vary depending on the number of additional data. That is, if the input additional data is 154, the parity is 30. In other words, the number of bytes of the additional data added with parity may be 184. After it is interleaved by the interleaver, 92 bytes each are inserted into the null sequence inserter to create two 184 byte packets. In addition, among the two packets divided above, the first packet has no parity and includes parity added in the second packet. Meanwhile, the MPEG header inserter inserts a 3-byte MPEG header at the beginning of the packets for compatibility with the ATSC 8T-VSB system. Finally, MUX multiplexes MPEG video / audio data and additional data packets and transmits them through encoding process of ATSC 8T-VSB system.

8 illustrates an example in which the block size of the additional data is 82 bytes. When using the Reed-Solomon code, the data interleaver, and the null sequence inserter for the additional data shown in the above-described embodiment, the additional data is processed and multiplexed. It shows the packet conversion. First, when 82 bytes of additional data are input, 10 bytes of parity are inserted by the ReedSolomon encoder and converted into 92 bytes of packets. As in FIG. 7, the parity number may vary. That is, if the number of additional data is 72, the parity may be 20. After the parity-added additional data is interleaved by the interleaver, it is input to the null sequence part and a null sequence of 92 bytes is inserted so that the total number of bytes becomes 184 bytes. As in the case of Fig. 7, the MPEG header inserter inserts a 3-byte MPEG header at the beginning of the packet for compatibility with the ATSC 8T-VSB system. Finally, MUX multiplexes MPEG video / audio data and additional data packets and transmits them through encoding process of ATSC 8T-VSB system.

7 and 8, the total number of bytes of the additional data inserted with the null sequence is 184 and the total number of bytes added with the MPEG header is equal to 187 bytes.

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.

1 is a block diagram showing the configuration of a conventional transmission system.

2 is a block diagram illustrating a transmission system for transmitting additional and MPEG data according to the present invention.

3 is a block diagram of a data frame of a transmission system according to the present invention;

4 is an explanatory diagram of multiplexing MPEG data and additional data;

5 is a data configuration diagram of a sequence inserter for generating a sequence.

6 is an explanatory diagram showing data interleaving for additional data;

7 and 8 are explanatory diagrams showing a process showing an encoding process of additional data;

Claims (8)

A first parity adding unit which adds first parity data to first service data input with a first attribute; A multiplexer which multiplexes second service data input with a second attribute and first service data to which the first parity data is added; A second parity adding unit which adds second parity data to service data multiplexed by the multiplexing unit; An interleaver for interleaving service data to which the second parity data is added; And A transmission unit for modulating and transmitting the interleaved service data, And a length of the first parity data and a length of the second parity data is different from each other. 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 a second parity data is added by performing Reed-Solomon encoding on the multiplexed service data. The method of claim 1, And the length of the first parity data is smaller than the length of the second parity data. Adding first parity data to the first service data input with the first attribute; Multiplexing second service data input with a second attribute and first service data to which the first parity data is added; Adding second parity data to the multiplexed service data; Performing interleaving on the service data to which the second parity data is added; And Modulating and transmitting the interleaved service data; And a length of the first parity data and a length of the second parity data are different from each other. The method of claim 5, wherein the first parity adding step And performing first reed-solomon coding on the first service data to add first parity data. The method of claim 5, wherein the second parity adding step And a second parity data by performing Reed-Solomon encoding on the multiplexed service data. The method of claim 5, The length of the first parity data is smaller than the length of the second parity data, the data processing method of the transmission system.

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