CN1521965A - Signal Transmission Method in Digital Terrestrial Broadcasting Transmission System - Google Patents

Abstract

The invention discloses a signal transmission method in digital ground surface broadcast transmission system, wherein the transmission signal data is delivered by field unit, each field data includes a plurality of data signals and a field synchronizing signal, a plurality of field data and a frame synchronizing signal form a frame signal, the number of fields forming a frame and the data symbols contained in each field varies with the modulation mode. The transmission mode for each frame is fixed, the transmission mode for each frame can be the same or different. The invention can be applied to optimize the transmission system performance with respect to different transmission conditions.

Description

Signal Transmission Method in Digital Terrestrial Broadcasting Transmission System

Technical Field The present invention belongs to the field of signal transmission, and in particular relates to a data arrangement method for transmission signals in digital terrestrial broadcast transmission.

Background Art As shown in Figure 1, a typical wireless transmission system includes a transmitter and a receiver. In a receiver, if there is a tuner, there is no need for down conversion. 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.

New digital terrestrial broadcasting systems use offset quadrature amplitude modulation (OQAM). In the OQAM modulation process, the input data is sent to the I channel and Q channel in turn after encoding, as shown in Figure 2.

The digital terrestrial broadcasting system performs a series of channel coding processes on the input data during transmission, including Reed-Solomon (RS) outer coding, data randomization, data interleaving, and trellis coding (TCM) inner coding (or none), Add synchronization signal, pilot signal, channel shaping filter, up-conversion, etc. Its processing modules and flow chart are shown in Figure 3.

In the new digital terrestrial broadcasting system, due to the diversified requirements of broadcasting applications, such as fixed reception of TV signals, mobile reception of TV signals and mobile reception of data signals, the system often requires a mixed transmission mode. In order to solve the problem of mixed transmission of various transmission modes in the same transmission system, the American ATSC system and the ADTB-T system proposed by the applicant arrange the transmission signals into frame, field, and segment structures, and at the same time insert frames, fields , segment synchronization signal to indicate the transmission mode and a series of other information, such as system parameters, randomizer and interleaved reset indication information. In the American ATSC system, each frame contains two fields, and each field contains 1 field sync segment and 312 data segments. In the ADTB-T system previously proposed by the applicant, under different modulation modes, the number of fields contained in each frame is different, but each field contains 1 field synchronization segment and 52 data segments.

Although the above two system designs can basically meet the requirements of hybrid transmission, there are still some defects. As we all know, fixed reception and mobile reception have different requirements on the transmission system due to different reception conditions. Higher data rates are desired for fixed reception, while fast tracking of the channel is required for mobile reception. Existing designs do not adequately account for these differences, which is not conducive to optimizing system performance. On the other hand, the cycle of the frame synchronization signal, field synchronization signal and segment synchronization signal of the ATSC system is fixed, which is easy to cause periodic interference.

SUMMARY OF THE INVENTION The purpose of the present invention is to provide a new signal transmission method in the digital terrestrial broadcasting transmission system. By using the data arrangement of the signal transmission method, it can meet the mixed transmission requirements of various transmission modes in the digital terrestrial broadcasting transmission, and at the same time, it can Optimize system performance.

The signal transmission method designed by the present invention is as follows: the transmission scheme transmits three kinds of services, which are respectively fixed reception of television signals (fixed service), mobile reception of television signals (mobile service) and mobile reception of data signals (data service). Among them, the fixed service can choose two modulation modes of 16-OQAM and trellis coding 64-OQAM; the mobile service can choose two modulation modes of 4-OQAM and trellis coding 16-OQAM; the data service can choose convolution coding 4-OQAM modulation mode.

Fixed service data, mobile service data and data service data use independent input buffer circuits, RS coding circuits, scrambling circuits, interleaving circuits and lattice coding circuits. With the close cooperation of the multiplexer, the code rate of the fixed service, mobile service and data service will be mixed by the transmission system according to the needs, and the coordination work of each unit circuit of the transmission system will be controlled by the control unit. The control unit crosses the frame field structure in a certain order and interval according to the buffer status of the fixed service code stream, the mobile service code stream and the data service code stream.

The respective modulation modes of the three services have similar frame and field structures, and can be mixed and transmitted in units of frames according to application requirements. The frame synchronization signal at the beginning of each frame clearly indicates the modulation mode of the frame, and at the same time provides the channel coding reset information of the respective modulation modes of the three services. The field synchronization signal at the start of each field indicates the start of the field in the respective transmission modes of the three services of terrestrial broadcasting, and indicates the reset of the trellis coding.

In trellis coding 64-OQAM modulation mode, each frame contains 1 frame synchronization signal and 16 field data, and each field data contains 43056 (ie 52×828) data symbols and 1 field synchronization signal. Each data symbol is a 3-bit, 8-level symbol. Each frame transmits 832 (ie 16*52*1) effective MPEG-II packets.

In 16-OQAM modulation mode, each frame contains 1 frame synchronization signal and 16 field data, and each field data contains 43056 (ie 52×828) data symbols and 1 field synchronization signal. Each data symbol is a 2-bit, 4-level symbol. Each frame transmits 832 (ie 16*52*1) effective MPEG-II packets.

In trellis coding 16-OQAM modulation mode, each frame contains 1 frame synchronization signal and 64 field data, and each field data contains 21528 (ie 26×828) data symbols and 1 field synchronization signal. Each data symbol is a 2-bit, 4-level symbol. Each frame transmits 832 (ie 64*26*1/2) valid MPEG-II packets.

In 4-OQAM modulation mode, each frame contains 1 frame synchronization signal and 64 field data, and each field data contains 21528 (ie 26×828) data symbols and 1 field synchronization signal. Each data symbol is a 1-bit, 2-level symbol. Each frame transmits 832 (ie 64*26*1/2) valid MPEG-II packets.

In the convolutional coding 4-OQAM modulation mode, each frame contains 1 frame synchronization signal and 256 field data, and each field data contains 10764 (ie 13×828) data symbols and 1 field synchronization signal. Each data symbol is a 1-bit, 2-level symbol. Each frame transmits 832 (ie 256*13*1/4) effective MPEG-II packets.

The frame synchronization signal is used to indicate the start of the frame in the respective transmission modes of the three services of terrestrial broadcasting, and to indicate the reset of trellis coding, interleaving, and scrambling. The frame synchronization signal can be used for system synchronization and channel estimation.

The frame sync signal is transmitted every frame. The frame synchronization signal has a total of 4968 symbols, including 4 preamble symbols, 64 2-level system information symbols, 4514 3-level symbols and 386 3-level reserved symbols. In trellis coding 64-OQAM modulation mode, trellis coding 16-OQAM modulation mode and convolutional coding 4-OQAM modulation mode, the 4 pre-symbols are trailing symbols of trellis coding; in 16-OQAM modulation mode and In the 4-OQAM modulation mode, the 4 pre-symbols are fixed 2-level symbols "1010".

Some frame sync signals contain 4 trellis-coded trailing symbols. However, the frame synchronization signal itself does not participate in channel coding. The trailing signal of trellis encoding is the output of continuous encoding with 0 as input after the end of trellis encoding. The trailing signal of trellis encoding is used to completely end the decoding of a frame of data when the receiving end decodes.

Each system information is expressed by a 64-bit two-level sequence. There are 64 of these two-level sequences, derived from the 64-bit long Walsh lattice. Inverting 64 64-bit long Walsh vectors yields 128 vectors. These 128 vectors are multiplied by a random sequence with a length of 64 to obtain 128 system information vectors. Each transmission mode corresponds to one of the 128 system information vectors, and the other vectors are reserved modes. When the receiver receives the reserved mode, it does not process the signal and skips the frame.

The frame sync signal contains a pseudo-random sequence of 4514 3-level symbols. The 3-level pseudo-random sequence is generated by GF(47) in binary system.

The frame sync signal contains 386 3-level reserved symbols. This reserved symbol is used for future business expansion. The 386 3-level reserved symbols are the 1130th symbol to the 1515th symbol of the above-mentioned GF(47).

The field synchronization signal is used to indicate the start of the field in the respective transmission modes of the three services of terrestrial broadcasting, and to indicate the reset of the trellis coding. Field synchronization signals can be used to assist in system synchronization and channel estimation.

The field sync signal is transmitted once per field. The field synchronization signal has a total of 516 symbols, including 4 preamble symbols, a 9-order maximum length sequence PN511 containing 511 2-level symbols, and a 2-level symbol+1. In the trellis coding 64-OQAM modulation mode, trellis coding 16-OQAM modulation mode and convolutional coding 4-OQAM modulation mode, the 4 leading symbols of the field synchronization signal in the first field of each frame are fixed 2 Flat signal "1010", except for the first field of each frame, the 4 leading symbols of the field synchronization signals of each field are trailing symbols of lattice coding; in the 16-OQAM modulation mode and 4-OQAM modulation mode, each The 4 leading symbols of a field sync signal are fixed 2-level signals "1010".

Some field synchronization signals contain 4 trellis-coded trailing symbols, but the field synchronization signal itself does not participate in channel coding. The trailing symbol of trellis encoding is the output of continuous encoding with 0 as input after the end of a trellis encoding. The trailing signal of the trellis code is used to completely end the decoding of a field of data when the receiving end decodes.

In digital terrestrial broadcasting transmission, adopting the data arrangement method of the frame field format structure designed by the present invention, the transmission system can set the system information bit, take the field as the minimum constituent unit of transmission data, and use the frame as the minimum independent transmission unit of different transmission services The mode supports mixed transmission of multiple transmission modes of the system, increases the flexibility of the system in selecting different services, and expands the application range of the system.

The present invention uses the frame synchronization signal to identify different services. The length of the frame synchronization signal is 4968 symbols, and the length of the random sequence is 4514 three-level symbols. The present invention does not use the segment synchronization signal, and the field synchronization signal uses 516 symbols, but different transmission modes use different field lengths, that is, the number of symbols contained in different transmission modes is different. This design is conducive to improving the transmission data rate of the system during fixed reception. Because of the known information of more field synchronization signals during mobile reception, it can facilitate the fast tracking of the channel, so that the system can not only realize the flexible combination of different services transmission, and can optimize system performance for different transmission conditions.

In the present invention, there is no fixed and equal integer relationship between the frame synchronization signal and the field synchronization signal, and the frame synchronization signal and the field synchronization signal themselves, and no periodic interference will be formed.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Figure 1 is a typical system block diagram of digital transmission.

Fig. 2 is a schematic diagram of I and Q channel signal composition of OQAM.

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

FIG. 4 is a schematic diagram of a frame field structure in 16-OQAM and trellis coding 64-OQAM modulation modes.

FIG. 5 is a schematic diagram of a frame field structure in 4-OQAM and trellis coding 16-OQAM modulation modes.

FIG. 6 is a schematic diagram of a frame field structure in a convolutional coding 4-OQAM modulation mode.

FIG. 7 is a schematic diagram of a composition structure of a frame synchronization signal.

Figure 8 shows the generation method and preset value of PN63.

FIG. 9 is a pseudo-random sequence including 4514 3-level symbols in the frame synchronization signal.

FIG. 10 is a schematic diagram of a composition structure of a field synchronization signal.

Figure 11 shows the generation method and preset value of PN511.

Specific implementation methods According to business needs and actual application environments, terrestrial broadcasting has five transmission modes, namely 16-OQAM and trellis coding 64-OQAM for fixed services, 4-OQAM and trellis coding 16 for mobile services -OQAM, and convolutional coding 4-OQAM for data services.

In Fig. 3, the input data first enters the outer code encoder, the outer code is usually RS code, in this digital terrestrial broadcasting system, the outer code adopts RS code of T=10(207,187). That is, the data size is 187 bytes, and it carries a check digit of 20 bytes. Each RS data block is 207 bytes.

For various OQAM modulation modes, the unit symbol sampling frequency is 14.28MHz, the real part (I channel) appears on odd points, and the imaginary part (Q channel) appears on even points.

The system's fixed service data, mobile service data and data service data use independent input buffer circuits, RS coding circuits, scrambling circuits, interleaving circuits and lattice coding circuits. With the close cooperation of the multiplexer, the code rate of the fixed service, mobile service and data service will be mixed by the transmission system according to the needs, and the coordination work of each unit circuit of the transmission system will be controlled by the control unit. The control unit crosses the frame field structure in a certain order and interval according to the buffer status of the fixed service code stream, the mobile service code stream and the data service code stream.

The respective modulation modes of the three services have similar frame and field structures, and can be mixed and transmitted in units of frames according to application requirements. The frame synchronization signal at the beginning of each frame clearly indicates the modulation mode of the frame, and at the same time provides the channel coding reset information of the respective modulation modes of the three services. The field synchronization signal at the start of each field indicates the start of the field in the respective transmission modes of the three services of terrestrial broadcasting, and indicates the reset of the trellis coding.

As shown in FIG. 7, the frame synchronization signal is transmitted every frame. The frame synchronization signal has a total of 4968 symbols, including 4 preamble symbols, 64 2-level system information symbols, 4514 3-level symbols and 386 3-level reserved symbols. In trellis coding 64-OQAM modulation mode, trellis coding 16-OQAM modulation mode and convolutional coding 4-OQAM modulation mode, the four pre-symbols are trellis coding with 8 levels, 4 levels and 2 levels respectively Trailing symbol; in 16-OQAM modulation mode and 4-OQAM modulation mode, the 4 pre-symbols are fixed 2-level symbols "1010".

Some frame sync signals contain 4 trellis-coded trailing symbols. However, the frame synchronization signal itself does not participate in channel coding. The trailing signal of trellis encoding is the output of continuous encoding with 0 as input after the end of trellis encoding. The trailing signal of trellis encoding is used to completely end the decoding of a frame of data when the receiving end decodes.

Each system information is expressed by a 64-bit two-level sequence. There are 64 of these two-level sequences, derived from the 64-bit long Walsh lattice. See formula 1-1 for the basic Walsh lattice, and formula 1-2 for the systematic generation method of the Walsh lattice.

$\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]$

Formula 1-1 Basic Walsh grid

$\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}\mathrm{<span\; class="notranslate">\; h</span>}& \mathrm{<span\; class="notranslate">\; h</span>}\\ \mathrm{<span\; class="notranslate">\; h</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}\end{array}\right]$

Formula 1-2 The systematic generation method of Walsh lattice type, where H is the Walsh lattice type of the previous order

Inverting 64 64-bit long Walsh vectors yields 128 vectors. These 128 vectors are multiplied by a random sequence with a length of 64 to obtain 128 system information vectors. The random sequence is generated by a 6-bit shift register to generate a 6-order maximum length sequence with a length of 63 and then add a 0 to generate it. The method for generating the 63-bit maximum length sequence is shown in FIG. 8 . The generating formula is, X ⁶ +X+1, and the default value is 000001. Its complete sequence is as follows:

100000100001100010100111101000111001001011011101100110101011111

Map 1 to 1 and 0 to -1 in the above sequence, and add -1 at the 64th bit to get a 64-bit random sequence value. Its complete sequence is as follows:

1-1-1-1-1-11-1-1-1-111-1-1-11-11-1-11111-11-1-1-1111-1-11-1-11-111- 1111-111-1-111-11-11-111111-1

Each transmission mode corresponds to one of the 128 system information vectors, and the other vectors are reserved modes. The following are examples of definitions for each mode:

1st vector reserved

2nd vector reserved

3rd vector reserved

The 4th vector lattice coding 64-OQAM

5th vector reserved

6th vector reserved

The seventh vector lattice coding 16-OQAM

8th vector 16-OQAM

9th Vector Convolutional Coding 4-OQAM

10th vector 4-OQAM

Other vectors reserved

When the receiver receives the reserved mode, it does not process the signal and skips the frame.

The frame sync signal contains a pseudo-random sequence of 4514 3-level symbols. The 3-level pseudo-random sequence is generated by GF(47) in binary system.

GF(47) under the 3-ary system has 2257 3-level symbols. The sequence is a function of order 47 in the 3-level Galois field. g(x)=x ³ +g ₂ x ² +g ₁ x+g ₀ , g _i ∈GF(q), i=0, 1, 2. Its generation method is as follows:

A 2257-bit 3-level sequence is generated from the original polynomial (4,1,0,1) of the 3-level GF(47). It can be obtained by the following MATLAB function,

           
p = gfprimck(3, 47), where

m=3

pol=[4101]
        <!-- SIPO <DP n="7"> -->
        <dp n="d7"/>
p=47

function[out]=build_gf_sequence(m, pol, p)

L=p^3-1;

N=L/(p-1);

mpol = mod(-pol, p);

d(1)=0;

d(2)=0;

d(3)=1;

for k＝4:L

s=0;

for q＝1:m

s=mod(s-d(k-q)*pol(m+1-q), p);

end

d(k)=s;

end

%Create all of the non-zero elements of the prime 6eld GF(p).

%G(k)is A^k

G = gftuple([0:p^1-2]', [1], p);

%Build a table of the psi() mapping

exponent=zeros(p-1, 1);

psi=zeros(p-1,1);

for v=1:p-1

exponent(v)=find(G==v)-1;

psi(v)=(-1)^exponent(v);

end

theta = zeros(p, 1);

theta(1)=0;

for k＝1:p-0
        <!-- SIPO <DP n="8"> -->
        <dp n="d8"/>
theta(k+1)=psi(k);

end

out = zeros(N, 1);

for k＝1:N

out(k)＝-1*((-1)^k)*theta(d(k)+1);

end

        

Add the last 1128 symbols of the 2257 symbols of GF(47) in the 3-ary system to the 2257 symbols of GF(47) in the 3-ary system, plus the GF(47) in the 3-ary system The first 1129 symbols in the 2257 symbols are combined into a pseudo-random sequence with a length of 4514 3-level symbols, as shown in FIG. 9 .

The frame sync signal contains 386 3-level reserved symbols. This reserved symbol is used for future business expansion. The 386 3-level reserved symbols are the 1130th symbol to the 1515th symbol of the above-mentioned GF(47).

In the frame synchronization signal, the 8-level, 4-level and 2-level values of the 4 trellis-coded trailing signals are consistent with the signal levels in the corresponding modulation mode, the 2-level symbols of the system information and 4514 3-level symbols The normalized values of the two non-zero levels in the level symbols are shown in Table 1. The value of the other level of the 4514 3-level symbols and 386 reserved symbols is 0.

Table 1 Frame synchronization signal level for each modulation mode of terrestrial broadcasting Modulation mode and signal level Frame sync signal level 64-OQAM, ±1, ±3, ±5, ±7 ±4.50 16-OQAM, ±1, ±3 ±2.25 4-OQAM, ±1 ±1.00

The field synchronization signal is used to indicate the start of the field in the respective transmission modes of the three services of terrestrial broadcasting, and to indicate the reset of the trellis coding. Field synchronization signals can be used to assist in system synchronization and channel estimation.

As shown in FIG. 10, the field sync signal is transmitted once every field. The field synchronization signal has a total of 516 symbols, including 4 preamble symbols, a 9-order maximum length sequence PN511 containing 511 2-level symbols, and a 2-level symbol+1. In the trellis coding 64-OQAM modulation mode, trellis coding 16-OQAM modulation mode and convolutional coding 4-OQAM modulation mode, the 4 leading symbols of the field synchronization signal in the first field of each frame are fixed 2 Flat signal "1010", except for the first field of each frame, the 4 leading symbols of the field synchronization signals of each field are respectively 8-level, 4-level and 2-level lattice-coded trailing symbols; in 16-OQAM In the modulation mode and the 4-OQAM modulation mode, the 4 leading symbols of each field synchronization signal are fixed 2-level signals "1010".

The field sync signal itself does not participate in channel coding. The trailing signal of trellis coding is the output of continuing coding with 0 as input after a field of trellis coding ends. The trailing signal of the trellis code is used to completely end the decoding of a field of data when the receiving end decodes.

The generation method of PN511 is shown in Figure 11. The generating formula of PN511 is X ⁹ +X ⁷ +X ⁶ +X ⁴ +X ³ +X+1, and the default value is 010000000. Its complete sequence is shown in Table 2.

                Table 2 PN511 sequence, in the table 1 is mapped to 1, and 0 is mapped to -1

0000 0001 0111 1111 1100 1010 1010 1110 0110 0110 1000 1000 1001 1110 0001 1101

0111 1101 0011 0101 0011 1011 0011 1010 0100 0101 1000 1111 0010 0001 0100 0111

1100 1111 0101 0001 0100 1100 0011 0001 0000 0100 0011 1111 0000 0101 0100 0000

1100 1111 1110 1110 1010 1001 0110 0110 0011 0111 0111 1011 0100 1010 0100 1110

0111 0001 0111 0100 0011 0100 1111 1011 0001 0101 1011 1100 1101 1010 1110 1101

1001 0110 1101 1100 1001 0010 1110 0011 1001 0111 1010 0011 0101 1000 0100 1101

1111 0001 0010 1011 1100 0110 0101 0000 1000 1100 0001 1110 1111 1101 0110 1010

1100 1001 1001 0001 1101 1100 0010 1101 0000 0110 1100 0000 1001 0000 0001 110

In the field synchronous signal, the 8-level, 4-level and 2-level values of the 4 trellis-coded trailing symbols are consistent with the signal levels in the corresponding modulation mode, and the normalization of PN511 and the last 2-level symbol See Table 3 for unitized values.

Table 3 Field synchronization signal level of each modulation mode of terrestrial broadcasting Modulation mode and signal level Vertical sync signal level 64-OQAM, ±1, ±3, ±5, ±7 ±4.50 16-OQAM, ±1, ±3 ±2.25 4-OQAM, ±1 ±1.00

As shown in Figure 4, in the trellis coding 64-OQAM modulation mode, each frame contains 1 frame synchronization signal and 16 field data, and each field data contains 43056 (ie 52×828) data symbols and 1 field synchronization signal. Each data symbol is a 3-bit, 8-level symbol. Each frame transmits 832 (ie 16×52×1) effective MPEG-II packets, including 702120 (4968+516×16+43056×16) symbols.

As shown in Figure 4, in the 16-0QAM modulation mode, each frame contains 1 frame synchronization signal and 16 field data, and each field data contains 43056 (ie 52×828) data symbols and 1 field synchronization signal. Each data symbol is a 2-bit, 4-level symbol. Each frame transmits 832 (ie 16×52×1) effective MPEG-II packets, including 702120 (4968+516×16+43056×16) symbols.

As shown in Figure 5, in the trellis coding 16-OQAM modulation mode, each frame contains 1 frame synchronization signal and 64 field data, and each field data contains 21528 (ie 26×828) data symbols and 1 field synchronization signal. Each data symbol is a 2-bit, 4-level symbol. Each frame transmits 832 (ie 64×26×1/2) effective MPEG-II packets, including 1415784 (4968+516×64+21528×64) symbols.

As shown in Figure 5, in 4-OQAM modulation mode, each frame contains 1 frame synchronization signal and 64 field data, and each field data contains 21528 (ie 26×828) data symbols and 1 field synchronization signal. Each data symbol is a 1-bit, 2-level symbol. Each frame transmits 832 (ie 64×26×1/2) effective MPEG-II packets, including 1415784 (4968+516×64+21528×64) symbols.

As shown in Figure 6, in the convolutional coding 4-OQAM modulation mode, each frame contains 1 frame synchronization signal and 256 field data, and each field data contains 10764 (ie 13×828) data symbols and 1 field synchronization signal. Each data symbol is a 1-bit, 2-level symbol. Each frame transmits 832 (ie 256×13×1/4) effective MPEG-II packets, including 2892648 (4968+516×256+10764×256) symbols.

In digital terrestrial broadcasting transmission, adopting the data arrangement method of the frame field format structure designed by the present invention, the transmission system can set the system information bit, take the field as the minimum constituent unit of transmission data, and use the frame as the minimum independent transmission unit of different transmission services The mode supports mixed transmission of multiple transmission modes of the system, increases the flexibility of the system in selecting different services, and expands the application range of the system.

Claims (2)

1. The signal transmission method in the digital terrestrial broadcasting transmission system, the transmission system transmits three kinds of services such as fixed service, mobile service and data service, it is characterized in that: The transmission signal data is sent in units of fields. Each field of data includes M data symbols and a field synchronization signal. N field data and a frame synchronization signal constitute a frame signal. Each frame is transmitted according to a modulation mode. The modulation modes of the frames are independent of each other; Fixed service data, mobile service data and data service data use independent input buffer circuits, RS coding circuits, scrambling circuits, interleaving circuits and lattice coding circuits. Under the action of multiplexers, fixed service, mobile service and data service The code rate is mixed by the transmission system according to the needs, and the control unit crosses the frame field structure according to a certain order and interval according to the buffer status of the fixed service code stream, mobile service code stream and data service code stream. 2. The signal transmission method according to claim 1, characterized in that: In lattice coded 64-OQAM modulation mode, M is equal to 43056, N is equal to 16, and each data symbol is a 3-bit, 8-level symbol; In 16-OQAM modulation mode, M is equal to 43056, N is equal to 16, and each data symbol is a 2-bit, 4-level symbol; In the trellis coding 16-OQAM modulation mode, M is equal to 21528, N is equal to 64, and each data symbol is a 2-bit, 4-level symbol; In 4-OQAM modulation mode, M is equal to 21528, N is equal to 64, and each data symbol is a 1-bit, 2-level symbol; In the convolutional coding 4-OQAM modulation mode, M is equal to 10764, N is equal to 256, and each data symbol is a 1-bit, 2-level symbol.

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