CN1200564C - Data interweaving method in digital TV and broadcasting transmission - Google Patents

Abstract

The present invention discloses a data interweaving method in digital television broadcast transmission. In the method, randomized data enters an interweaving device after RS coding of T=10(207, 187), and the interweaving device interweaves data in a convolution interweaving mode. Segment synchronization takes part in the interweaving as a whole body, and frame / field synchronization and segment synchronization in the frame / field synchronization do not take part in the interweaving. The depth of interweaving serves as one frame, and data interweaving is carried out fully in the frame without overpassing the boundary of the frame. Different interweaving parameters M, B are selected in view of different transmission modes, so that the present invention has ideal interweaving effects and ensures the flexibility of a system for transmitting multiple services.

Description

Data Interleaving Method in Digital TV Broadcasting Transmission

Technical Field The present invention belongs to the field of digital signal transmission, in particular to a method for interleaving transmission data in digital television broadcast transmission.

Background Art A typical digital TV broadcasting transmission system (see Figure 1) includes a transmitter and a receiver. Digital modulation technology often encodes digital signals, and then adds necessary auxiliary information, such as: synchronization signals, pilot signals, etc. The coded digital signal forms a baseband signal after channel filtering. The baseband signal is modulated to a corresponding frequency band through an up-converter and then sent. At the receiving end, the tuner converts the high-frequency signal to the baseband to obtain a digital signal through an analog-to-digital converter. After the digital signal is processed, it is restored to the same information as the sending end.

The new digital TV broadcasting transmission system adopts offset quadrature amplitude modulation (Offset QAM, OQAM for short). Figure 2 shows the data composition of I channel and Q channel of OQAM modulation and other commonly used modulation methods [such as quadrature amplitude modulation (QAM), vestigial sideband modulation (VSB) mode]. In the OQAM modulation process, the input data is encoded and sent to the I channel and Q channel in turn; in the VSB modulation process, the input data is encoded and only sent to the I channel; Compared with OQAM and VSB, half the sampling rate is sent to I channel and Q channel at the same time. Compared with VSB and QAM, since the OQAM signal has the symmetrical characteristics of time domain and carrier phase at the same time, the two processes of carrier and clock recovery at the receiving end can be completed independently without crossing each other, which is beneficial to the receiver to achieve more stable reception and Reduce receiver cost.

The application fields of digital TV broadcasting transmission system include digital TV terrestrial broadcasting, digital TV cable broadcasting, digital TV microwave broadcasting (MMDS) and digital TV satellite broadcasting, etc. The content of the present invention mainly relates to digital TV terrestrial broadcasting, cable broadcasting and MMDS broadcasting system. In the new digital TV broadcasting system, there are three transmission modes for terrestrial broadcasting, namely: "2/3 inner code 64-OQAM" for fixed services, "1/2 inner code 16-OQAM" for mobile services OQAM" and "1/2 inner code 4-OQAM" for data services. There are four transmission modes for cable TV and MMDS broadcasting, which are high data mode 256-OQAM, high data mode 64-OQAM, normal data mode 16-OQAM and normal data mode 4-OQAM. According to business needs and actual application environment, the system is often required to contain mixed transmission modes. In different transmission modes, transmission signals can have different frame/field formats, that is, a frame signal consists of different numbers of field signals, and a field signal includes different data segments.

The digital TV terrestrial broadcasting system needs to carry out a series of channel coding processes on the input data during transmission, including data randomization, Reed-Solomon (RS) outer coding, data interleaving, and trellis coding TCM (2/3 code rate corresponds to 64 -OQAM, 1/2 code rate corresponds to 16-OQAM) or convolutional coding (1/2 code rate) or block coding (1/2 code rate) mode inner coding, adding synchronization signal, pilot signal, channel shaping filter , up-conversion, etc. Its processing module circuit and flow chart are shown in Figure 3. Compared with the digital TV terrestrial broadcasting system, the digital TV cable broadcasting and the MMDS broadcasting system are basically the same except that the internal coding module circuit is not included. That is to say, there is strong compatibility among terrestrial, cable, and MMDS broadcasting systems.

In order to deal with the impact noise (Impulse Noise) interference in the channel and cooperate with channel coding, the digital TV broadcasting transmission system needs to perform interleaving processing on the data. Although interleaving is beneficial to the inner code, it does not participate in the encoding process of the inner code. Usually, data interleaving adopts a convolutional interleaving algorithm. Convolutional interleaving disrupts continuous byte groups by effectively dispersing different numbers of bytes in the data structure, so that burst errors are dispersed, so that correct data can be recovered with error correction decoding, and deinterleaving performs corresponding reverse processing . Data interleaving involves three important parameters, namely the expected maximum impact noise length L _N , the number of errored bytes L that can be corrected by the RS decoder, and the size of the RS block L _RS . Accordingly, the designed interleaving depth L _M should at least reach L _M =L _N ×L _RS /L. If the interleaving depth is too small, the effect of avoiding impact noise is poor. However, the interleaving depth cannot be designed too large, otherwise the interleaving at the encoding end and the deinterleaving at the decoding end will cause a large system transmission delay, which will cause problems for broadcasting systems (especially cable broadcasting systems) with two-way interactive communication requirements. on the limit.

SUMMARY OF THE INVENTION The purpose of the present invention is to design a corresponding data interleaving mode for a digital TV broadcasting transmission system with a mixed transmission mode, so as to effectively avoid impact noise interference in the channel and simplify the structure of the realization circuit.

The data interleaving method designed by the present invention is as follows: in the digital television broadcasting transmission system, for various transmission modes, the data interleaving process is performed in the manner of convolution and interleaving. The input data enters the outer code encoder after being randomized, and the outer code adopts RS encoding of T=10(207,187). The size of the RS data is 187 bytes, carrying a check digit of 20 bytes, and each RS data block is 207 bytes. Thus, the number of erroneous bytes L that can be corrected by the RS decoder and the size L _RS of the RS block are determined. Because terrestrial broadcast channels contain much stronger impact noise interference than cable and MMDS broadcast channels, it is necessary to design a larger interweaving depth. On the other hand, the number of fields included in a frame of each transmission mode of terrestrial broadcasting is larger than that of each transmission mode of cable and MMDS broadcasting. Therefore, the interleaving depth designed by the present invention for each transmission mode of terrestrial broadcasting, cable broadcasting and MMDS broadcasting is the same as one frame of data. Let M be the number of bytes per unit delay of the interleaver, and B be the number of channels included in one cycle of the interleaver switch. By setting different combinations of B and M, three transmission services of terrestrial broadcasting can be realized have the same interleaving time length. In order to simplify the circuit structure, the four transmission modes of cable broadcasting and MMDS broadcasting adopt the same interleaving parameters. With proper parameter selection, this design can meet the relatively good impact noise environment requirements in cable and MMDS broadcast channels.

In the composition of the transmission signal, the interleaver acts on the randomized and RS outer coded data and the RS parity bit generated by the outer code. Segment synchronization as a whole participates in interleaving, frame/field synchronization and segment synchronization in frame/field do not participate in interleaving.

In the mixed transmission mode, each mode uses its own randomizer, its own RS encoder, its own interleaver and its own inner code encoder, and has no relationship with each other. The randomizer, interleaver, etc. of each pattern are reset by respective synchronous reset signals. The input and output of the convolutional interleaver are reset by the information bits in the frame/field sync signal. During normal operation, the interleaver repeats every frame and does not need to be reset again.

The present invention comprehensively considers the channel characteristics of terrestrial broadcasting, cable broadcasting and MMDS broadcasting and the difference of frame/field structure in each transmission mode, and sets the data interleaving depth to be consistent with the length of the data service frame. In this way, data interleaving is fully carried out within the frame without crossing the boundary of the frame, which ensures that various services can be flexibly combined in units of frames. The present invention sets corresponding interleaving parameters for each transmission mode according to actual application requirements, which not only achieves an ideal interleaving effect, but also ensures the flexibility of system transmission of various services.

The present invention will be further described below in conjunction with the accompanying drawings and examples.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a typical digital TV broadcasting transmission system.

Fig. 2 is I, Q channel signal composition of VSB, QAM and OQAM.

Fig. 3 is the circuit and process of each functional module of the transmitter in the digital terrestrial broadcasting system.

Figure 4 shows the circuit and flow of each functional module of the transmitter in the digital cable and MMDS broadcasting system.

FIG. 5 is a schematic diagram of a frame/field format of a digital television broadcasting system.

FIG. 6 is a schematic diagram of a 256-OQAM field format in a digital cable and MMDS broadcasting system.

FIG. 7 is a schematic diagram of a 64-OQAM field format in a digital cable and MMDS broadcasting system.

Fig. 8 is a schematic diagram of a 16-OQAM field format in a digital cable and MDS broadcasting system.

FIG. 9 is a schematic diagram of a 4-OQAM field format in a digital cable and MMDS broadcasting system.

Fig. 10 shows the principle and parameters of the convolutional interleaver in the terrestrial broadcast 64-OQAM transmission mode.

Fig. 11 shows the principle and parameters of the convolutional interleaver in the terrestrial broadcasting 16-OQAM transmission mode.

Fig. 12 shows the principle and parameters of the convolutional interleaver in the terrestrial broadcasting 4-OQAM transmission mode.

Fig. 13 shows the principles and parameters of the convolutional interleaver in 4-OQAM, 16-OQAM, 64-OQAM and 256-OQAM transmission modes of digital cable and MMDS broadcasting systems.

DETAILED DESCRIPTION In this embodiment, the three transmission modes of terrestrial broadcasting and the four transmission modes of cable and MMDS broadcasting have different segment and field structures. The frame/field format of digital TV terrestrial broadcasting system using 64-OQAM with 2/3 internal code, 16-OQAM with 1/2 internal code or 4-OQAM with 1/2 internal code is shown in Figure 9a. One frame consists of 16 fields, each field consists of 79 segments, the first segment is frame/field synchronization signal, and the last 78 segments are data signals; digital TV cable broadcasting and MMDS broadcasting systems use 256-OQAM, 64-OQAM The field formats of , 16-OQAM and 4-OQAM transmission modes are shown in Fig. 6, Fig. 7, Fig. 8 and Fig. 9 respectively. Each frame is composed of one field, and each field corresponds to four transmission modes, which are respectively composed of 79/ 105/157/313 sections, the first section is the field sync signal, and the following sections correspond to 78/104/156/312 sections as data signals. For various transmission modes, each segment has the same length and contains 836 symbols, of which the first 8 symbols are segment synchronization signals, which appear once in each segment, and the last 828 symbols are interleaved data signals or frame/field synchronization signals. The position of the segment sync after interleaving does not change.

The input data enters the outer code encoder after being randomized, and the outer code adopts RS encoding of T=10(207,187). The size of the RS data is 187 bytes, carrying a check digit of 20 bytes, and each RS data block is 207 bytes. After the outer coder is an interleaver, the present invention uses a convolutional interleaving method to interleave input data in units of bytes. The depth and mode of data interleaving are related to the transmission mode of the system and the frame/field format corresponding to each transmission mode. For the different transmission modes mentioned above, the principle and parameters of each convolutional interleaver are shown in Fig. 10, Fig. 11, Fig. 12 and Fig. 13 respectively. The grid in the figure represents an eight-bit parallel shift register, and the switch changes its position every byte cycle. M is the number of bytes per unit delay of the interleaver, and B is the number of paths included in one cycle of the interleaver switch.

The interleaver acts on the randomized and RS externally coded data and the RS parity bit generated by external coding. The segment synchronization participates in interleaving as a whole, and the frame/field synchronization and the segment synchronization in the frame/field do not participate in interleaving.

The parameters of each convolutional interleaver are selected as follows:

1) 64-OQAM of 2/3 inner code in digital terrestrial broadcasting system

The depth of the convolutional interleaver is selected as 16 fields, and each field contains 78 data segments, that is, the depth of the convolutional interleaver is 1248 segments. In Fig. 10, M=6, B=208, the segment synchronization participates in interleaving as a whole, and passes through from the first channel of the MUX. The interleaved data forms a frame after 2/3 inner code encoding and 8-level mapping, with a total of 16 fields and 1248 data segments.

2) 16-OQAM of 1/2 inner code in digital terrestrial broadcasting system

The depth of the convolutional interleaver is selected as 16 fields, and each field contains 78 data segments, that is, the depth of the convolutional interleaver is 1248 segments. In FIG. 11 , M=3, B=208, the segment synchronization participates in interleaving as a whole, and is passed through from the first channel of the MUX. The interleaved data forms a frame after 1/2 inner code encoding and 4-level mapping, with a total of 16 fields and 1248 data segments.

3) 4-OQAM of 1/2 inner code in digital terrestrial broadcasting system

The depth of the convolutional interleaver is selected as 16 fields, and each field contains 78 data segments, that is, the depth of the convolutional interleaver is 1248 segments. In Fig. 12, M=6, B=104, segment synchronization participates in interleaving as a whole, and passes through from the first channel of MUX. The interleaved data forms a frame after 1/2 inner code encoding and 2-level mapping, with a total of 16 fields and 1248 data segments.

4) 4-OQAM, 16-OQAM, 64-OQAM and 256-OQAM in digital cable, MMDS broadcasting system

The depth of the convolutional interleaver is selected as 1 field, and each field corresponds to 4-OQAM, 16-OQAM, 64-OQAM, and 256-OQAM, respectively containing 312, 156, 104, and 78 data segments, that is, the depth of the convolutional interleaver is 3 Paragraphs 12, 156, 104 and 78. In Fig. 13, M=3, B=104, segment synchronization participates in interleaving as a whole, and passes through from the first channel of MUX. The interleaved data are respectively mapped by 2-level, 4-level, 8-level, and 16-level to form a frame, a total of 1 field, respectively 312, 156, 104, and 78 data segments.

In the mixed transmission mode, each mode uses its own randomizer, its own RS encoder, its own interleaver and its own inner code encoder, and has no relationship with each other. The randomizer, interleaver, etc. of each pattern are reset by respective synchronous reset signals. The input and output of the convolutional interleaver are reset by the information bits in the frame/field sync signal. During normal operation, the interleaver repeats every frame and does not need to be reset again.

Claims (1)

1. the data interlacing method during a digital television broadcasting is transmitted, data after the randomization are through T=10 (207,187) enter interleaver behind the RS coding, interleaver adopts the mode of convolutional interleave to carry out data interlacing, each road unit delay amount of interleaver is the M byte, and interleaver change over switch one-period comprises the B road, and section is done as a whole participation synchronously and interweaved, section in frame/field synchronization and the frame/field does not participate in interweaving synchronously, it is characterized in that:

Described data interlacing method is applicable to that four kinds of transmission modes of three kinds of transmission modes of terrestrial broadcasting and wired and microwave broadcasting have the digital television broadcasting system of different sections, field structure, and segment sync signal is the 1 the tunnel straight-through from MUX's; In the 64-OQAM transmission mode of 2/3 ISN in terrestrial broadcast system, corresponding 16 an of frame, every contains 78 data segments, and M equals 6, and B equals 208; In the 16-OQAM transmission mode of 1/2 ISN in terrestrial broadcast system, corresponding 16 an of frame, every contains 78 data segments, and M equals 3, and B equals 208; In the 4-OQAM transmission mode of 1/2 ISN in terrestrial broadcast system, corresponding 16 an of frame, every contains 78 data segments, and M equals 6, and B equals 104; In 4-OQAM, 16-OQAM in wired and microwave broadcasting system, 64-OQAM and the 256-OQAM transmission mode, one frame is one, every corresponding 4-OQAM, 16-OQAM, 64-OQAM and 256-OQAM contain 312,156,104 and 78 data segments respectively, and M is equal to 3, and B is equal to 104.

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