CN101431501B - A Modulation Method for High Performance Digital TV Terrestrial Broadcasting Transmitter - Google Patents

Abstract

The invention discloses a modulation method for digital TV terrestrial broadcasting transmitter with time domain training sequence and cascade interleaved coded modulation comprising: 1) bit stream forming FFT data block on frequency domain after BCH coding, bit interleaving, LDPC coding, code element modulation, code element interleaving; 2) converting FFT data block to time domain discreet data sample value block via IFFT; 3) inserting cyclic prefix as protective interval to time domain discrete coding data sample block and forming time domain cyclic prefix discrete coding data sample block; 4) continuous four time domain cyclic prefix discrete coding data sample value block constituting a frame body; 5) training sequence serving as real part sequence of plural training sequence, service index sequence serving as imaginary part sequence to constitute discrete sample value block of plural training sequence; 6) inserting the discrete sample value block of plural training sequence in signal frame for forming frame body; 7) pulse shaping to signal frame using square root raised consine roll-off filter; 8) up-converting base band to carrier.

Description

A Modulation Method for High Performance Digital TV Terrestrial Broadcasting Transmitter

technical field

The invention belongs to the field of wireless communication, and more specifically relates to a modulation method of a digital TV terrestrial broadcasting transmitter with time-domain training sequence and cascade interleaving code modulation. the

Background technique

At present, terrestrial TV broadcasting has gradually developed from analog to digital. Digital TV terrestrial broadcasting transmission system, as an important part of digital TV terrestrial broadcasting, the development of its related technologies is closely related to people's quality of life, and therefore has received extensive attention from people. Digital TV terrestrial broadcasting related technologies and related industries are industries with rapid development and good market prospects in the field of communication and computer. In terms of technologies related to digital TV terrestrial broadcasting, countries are currently focusing on how to provide low-cost, reliable and high-speed mobile solutions for digital TV terrestrial broadcasting in a complex wave propagation environment. The digital TV terrestrial broadcasting transmitter modulation technology is the key technology of the digital TV terrestrial broadcasting system, which plays a decisive role in the performance of the whole system, and is the object of everyone's key research. the

Due to the rapid development of digital signal processing technology and integrated circuit technology, the system realization of Orthogonal Frequency Division Multiplexing (OFDM) technology becomes easier and easier. Because OFDM multi-carrier transmission technology has many advantages such as simple structure, high spectrum utilization rate, and anti-frequency selectivity and channel time variation, it has attracted much attention and has been deeply researched and applied in Xdsl, broadband mobile communication, broadband wireless local area network, It is widely used in many fields such as digital TV terrestrial broadcasting. the

Channel coding is an important part of digital communication systems. With the rapid development of modern information technology, channel coding technology has become an indispensable technology in the field of modern communication. Redundant code elements are embedded in the information sequence, and channel coding technology reduces signal errors during transmission through the role of redundant code elements, thereby improving the reliability of the communication system. the

Under multipath fading channels, the cascade optimization design of coding, interleaving and modulation schemes can achieve the largest possible signal diversity order, so as to obtain independent fading in symbol sequences equal to or exceeding the minimum free distance. Cascading different coding forms can make full use of the advantages of different coding techniques; inserting a bit interleaver between coding and symbol modulation can make the coding and modulation processes relatively independent and expand the diversity order from different multi-ary symbols To a different number of binary bits, so that the order of diversity is significantly improved and has good error characteristics in multipath fading channels. the

In the actual communication environment, the performance of digital TV terrestrial broadcasting communication system is affected by factors such as synchronization time, clock jitter, channel fading, and channel interference. Transmitter modulation method is the key technology to realize reliable digital TV terrestrial broadcasting. the

Using the digital TV terrestrial broadcasting transmission system to provide controllable multi-services such as gratuitous TV broadcasting, paid TV broadcasting, confidential information transmission, and multimedia value-added services is a reflection of the new generation of digital TV terrestrial broadcasting transmission system meeting social needs. the

Based on the above background, the present invention proposes a digital TV terrestrial broadcast transmitter modulation method with time-domain training sequence and concatenated interleaving code modulation for the actual communication environment, which can meet the requirements of high data rate controllable multi-service digital TV terrestrial broadcast transmission needs. the

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Contents of the invention

Aiming at high data rate controllable multi-service digital TV terrestrial broadcasting, the invention proposes a digital TV terrestrial broadcast transmitter modulation method with time-domain training sequence and cascaded interleaving code modulation. the

A kind of digital TV terrestrial broadcasting transmitter modulation method with time-domain training sequence and concatenated interleaving coding modulation that the present invention proposes is characterized in that it comprises the following steps:

1) The digital TV terrestrial broadcast transmitter passes its input data bit stream through BCH encoding (BoseChaudhuri Hocquenghem, BCH), bit interleaving, LDPC encoding (Low Density Parity Check, LDPC), symbol modulation, and symbol interleaving. Form FFT concatenated interleaving coded modulation data block on domain (the length (symbol number) of FFT concatenated interleaved coded modulated data block is K);

2) The digital TV terrestrial broadcasting transmitter adopts IFFT (Inverse Fast Discrete Fourier Transform) to transform the FFT concatenated interleaved coded modulation data block into a time domain discrete concatenated interleaved coded modulated data sample block;

3) The digital TV terrestrial broadcasting transmitter inserts the cyclic prefix (the length of the cyclic prefix is C) into the discrete concatenated interleaved coded modulation data sample block in the time domain as a guard interval to form the time domain cyclic prefix discrete concatenated interleaved coded modulated data Sample value block (time-domain cyclic prefix discrete concatenated interleaved code modulation data sample value block length is (K+C));

4) The digital TV terrestrial broadcasting transmitter forms a frame body (the length of the frame body is L, L=4×(K+C)) with four continuous time-domain cyclic prefix discrete concatenated interleaved coding modulated data sample blocks;

5) The digital TV terrestrial broadcasting transmitter uses the training sequence as the real part sequence of the complex training sequence, and uses the service index sequence as the imaginary part sequence of the complex training sequence, and constitutes discrete sample blocks of the complex training sequence (training sequence, The length of the discrete sample value block of the business index sequence and the complex training sequence is X);

6) The digital TV terrestrial broadcasting transmitter inserts the discrete sample blocks (as the frame header) of the complex training sequence formed in the time domain into the frame body to form a signal frame;

7) The digital TV terrestrial broadcast transmitter uses a square root raised cosine roll-off filter to shape the signal pulse of the signal frame;

8) The digital TV terrestrial broadcasting transmitter up-converts the baseband signal to the carrier. the

According to the above-mentioned digital TV terrestrial broadcasting transmitter modulation method with time-domain training sequence and concatenated interleaving code modulation, it is characterized in that: there are time-domain complex training sequence discrete sample blocks in the signal frame of the digital TV terrestrial broadcasting transmitter; The length (number of symbols) X of the training sequence of the TV terrestrial broadcast transmitter is 512, and the length (number of symbols) K (number of subcarriers) of the corresponding FFT concatenated interleaving coding modulation data block is 1024, and the corresponding subcarrier The frequency interval of the carrier is 8KHz, and the corresponding cyclic prefix length C is 1/16 of the length K of the FFT concatenated interleaving coding modulation data block; the training sequence and service index sequence of the digital TV terrestrial broadcasting transmitter consist of a series of 1 or -1 composition, with pseudo-random characteristics; the training sequence and service index sequence of the digital TV terrestrial broadcasting transmitter are orthogonal to each other; each different service index sequence of the digital TV terrestrial broadcasting transmitter contains and uniquely expresses Various system parameters and business mode information of the digital TV terrestrial broadcasting transmitter; LDPC coding rate is one of 1/4, 1/2, 5/8, 3/4 and 7/8; bit interleaving adopts random interleaving method ; The symbol modulation is one of QPSK, 16QAM, 32QAM and 64QAM, and the symbol constellation mapping method adopts Gray code mapping; the symbol interleaving adopts the random interleaving method. the

Features of the present invention:

The invention is a modulation scheme of mixing time domain and frequency domain. The signal frame of the digital TV terrestrial broadcasting transmitter has discrete sample blocks of time-domain complex training sequence, the training sequence and service index sequence of the digital TV terrestrial broadcasting transmitter have pseudo-random characteristics, the training sequence, business index sequence of the digital TV terrestrial broadcasting transmitter The index sequences are orthogonal to each other. The digital TV terrestrial broadcasting transmitter inserts the discrete sample blocks (as the frame header) of the complex training sequence formed in the time domain into the frame body to form a signal frame, which ensures the digital TV terrestrial Broadcast transmitters can achieve fast and accurate frame synchronization, frequency synchronization, time synchronization, estimation of channel transmission characteristics, and reliable tracking of phase noise and channel transmission characteristics. The cyclic prefix is inserted into the time-domain discrete concatenated interleaved coded modulation data sample block as a guard interval to form a time domain cyclic prefix discrete concatenated interleaved coded modulated data sample block, which can reduce the time domain complex training sequence discrete sample block, Interference effects between adjacent time-domain cyclic prefix discrete concatenated interleaved coded modulation data sample blocks. The efficiency of the digital TV terrestrial broadcasting system can be improved by forming four consecutive time-domain cyclic prefix discrete concatenated interleaved coded modulation data sample blocks into a frame body. The cascaded interleaving coding and modulation of the input data increases the diversity order, which makes the communication system have good bit error characteristics in the multipath fading channel. The different service index sequences of the digital TV terrestrial broadcasting transmitter contain and uniquely express the system parameters and business mode information of the digital TV terrestrial broadcasting transmitter, which can enable the digital TV terrestrial broadcasting transmission system to provide free TV broadcasting, paid TV Broadcasting, confidential information transmission, multimedia value-added services, etc. can control multiple services to meet social needs. The modulation method of the invention has many advantages such as short synchronization time, small clock jitter, anti-channel fading, anti-channel interference, high data rate and controllable multi-service digital TV terrestrial broadcast transmission.

Description of drawings

Fig. 1 is a schematic diagram of an embodiment of a digital TV terrestrial broadcast transmitter modulation method with time-domain training sequence and concatenated interleaving code modulation according to the present invention. the

Fig. 2 is a schematic diagram of an embodiment of a signal frame formed by a certain transmitter according to the modulation method of a digital TV terrestrial broadcasting transmitter with time-domain training sequence and concatenated interleaving code modulation of the present invention. the

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. the

According to the embodiment of a certain transmitter of the digital television terrestrial broadcasting transmitter modulation method proposed by the present invention with time-domain training sequence and concatenated interleaving code modulation, as shown in Figure 1, carry out according to the following steps:

1) The digital TV terrestrial broadcasting transmitter further forms an FFT concatenated interleaved coded modulation data block (FFT level The length (the number of symbols) of the interleaved coding modulation data block is K, and K is 1024, and the frequency interval of the corresponding subcarrier is 8KHz);

2) The digital TV terrestrial broadcasting transmitter adopts IFFT (Inverse Fast Discrete Fourier Transform) to transform the FFT concatenated interleaved coded modulation data block into a time domain discrete concatenated interleaved coded modulated data sample block;

3) The digital TV terrestrial broadcasting transmitter inserts the cyclic prefix (the length of the cyclic prefix is C) into the discrete concatenated interleaved coded modulation data sample block in the time domain as a guard interval to form the time domain cyclic prefix discrete concatenated interleaved coded modulated data Sample value block (the length of the time-domain cyclic prefix discrete concatenated interleaved coded modulation data sample block is (K+C), and C takes 1/16 of the length K of the FFT concatenated interleaved coded modulated data block);

4) The digital TV terrestrial broadcasting transmitter forms a frame body (the length of the frame body is L, L=4×(K+C)) with four continuous time-domain cyclic prefix discrete concatenated interleaved coded modulation data sample blocks;

5) The digital TV terrestrial broadcasting transmitter uses the training sequence as the real part sequence of the complex training sequence, and uses the service index sequence as the imaginary part sequence of the complex training sequence, and constitutes discrete sample blocks of the complex training sequence (training sequence, The length of the discrete sample block of the business index sequence and the complex training sequence is X, and X is 512);

6) The digital TV terrestrial broadcasting transmitter inserts the discrete sample blocks (as the frame header) of the complex training sequence formed in the time domain into the frame body to form a signal frame;

7) The digital TV terrestrial broadcast transmitter uses a square root raised cosine roll-off filter to shape the signal pulse of the signal frame;

8) The digital TV terrestrial broadcasting transmitter up-converts the baseband signal to the carrier. the

According to the embodiment of a signal frame formed by a certain transmitter of the digital TV terrestrial broadcasting transmitter modulation method with time-domain training sequence and concatenated interleaving code modulation of the present invention, as shown in Figure 2, the specific implementation is as follows:

The certain digital TV terrestrial broadcasting transmitter further forms an FFT concatenated interleaved coded modulation data block in the frequency domain after its input data bit stream undergoes BCH coding, bit interleaving, LDPC coding, symbol modulation and symbol interleaving, and then After IFFT, it is transformed into a discrete concatenated interleaved coded modulation data sample block in the time domain. the

The FFT cascaded interleaved coded modulation data block consists of subcarriers. The length (number of symbols) of the FFT concatenated interleaved coded modulation data block is K; the length K (number of subcarriers) of the FFT concatenated interleaved coded modulated data block is 1024, and the frequency interval of the corresponding subcarriers is 8KHz. the

The certain digital TV terrestrial broadcasting transmitter inserts the cyclic prefix (the length of the cyclic prefix is C) into the discrete concatenated interleaved coded modulation data sample block in the time domain as a guard interval to form a time domain cyclic prefix discrete concatenated interleaved coded modulation Data sample block (the length of the time-domain cyclic prefix discrete concatenated interleaved coded modulation data sample block is (K+C), and C is 1/16 of the length K of the FFT concatenated interleaved coded modulated data block). the

The certain digital TV terrestrial broadcasting transmitter forms a frame body (the length of the frame body is L, L=4×(K+C)) by forming four continuous time-domain cyclic prefix discrete concatenated interleaving coded modulation data sample blocks.

The certain digital TV terrestrial broadcasting transmitter uses the training sequence as the real part sequence of the complex training sequence and the service index sequence as the imaginary part sequence of the complex training sequence to form discrete sample blocks of the complex training sequence in the time domain. the

The lengths of the discrete sample blocks of the training sequence, the service index sequence, and the complex training sequence are all X, and X is 512. the

As a digital TV terrestrial broadcasting transmitter, the training sequence and service index sequence are composed of a series of 1 or -1, which have pseudo-random characteristics, and the training sequence and service index sequence are orthogonal to each other. The training sequence satisfying the above characteristics can be realized by a special type of shifted m-sequence as a pseudo-random number sequence and Walsh sequence, Hadamard sequence or orthogonal sequence generated by other methods as an orthogonal sequence. the

Each different service index sequence contains and uniquely expresses various system parameters and service mode information of the digital TV terrestrial broadcasting transmitter. the

The digital TV terrestrial broadcasting transmitter inserts discrete sample blocks (as frame headers) of the complex training sequence formed in the time domain into the frame body to form a signal frame. the

The certain digital television terrestrial broadcast transmitter employs a square root raised cosine roll-off filter to pulse shape the signal of the signal frame. The roll-off coefficient of the square-root raised cosine roll-off filter for pulse shaping the signal frame is 0.05. the

The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and those skilled in the art can make various modifications without departing from the spirit and scope of the claims of the application modify or remodel.

Claims (8)

1. one kind has time-domain training sequence and cascade interweaved code modulated digital television ground broadcast transmitter modulation method, it is characterized in that it comprises the following steps:

1) digital television ground broadcast transmitter is flowed through the input data bit of oneself and is further formed the cascade interweaved coding modulation data piece of FFT after Bose-Chaudhuri-Hocquenghem Code, Bit Interleave, LDPC coding, code element modulation, the symbol interleave on frequency domain, and the length of the cascade interweaved coding modulation data piece of FFT is K;

2) digital television ground broadcast transmitter adopts IFFT that the cascade interweaved coding modulation data piece of FFT is transformed to the discrete cascade interweaving encoding modulating data sample value piece of time domain, and IFFT represents the fast discrete Fourier inverse transformation;

3) digital television ground broadcast transmitter is inserted into Cyclic Prefix as protection the discrete cascade interweaving encoding modulating data sample value piece of time domain at interval, form the discrete cascade interweaving encoding modulating data sample value piece of time domain cyclic prefix, the length of Cyclic Prefix is C, and the length of the discrete cascade interweaving encoding modulating data sample value piece of time domain cyclic prefix is K+C;

4) digital television ground broadcast transmitter forms frame with the discrete cascade interweaving encoding modulating data sample value piece of 4 continuous time domain cyclic prefix, and the length of frame is L, L=4 * (K+C);

5) digital television ground broadcast transmitter with training sequence as the real part sequence of sequence of plural training, with the imaginary part sequence of operational indicator sequence as sequence of plural training, constitute the discrete sample block of sequence of plural training on time domain, the length of the discrete sample block of training sequence, operational indicator sequence, sequence of plural training all is X;

6) digital television ground broadcast transmitter is inserted into frame with the discrete sample block of the sequence of plural training that constitutes on the time domain as frame head, to form signal frame;

7) digital television ground broadcast transmitter adopts square root raised cosine filter that the signal pulse of signal frame is shaped;

8) digital television ground broadcast transmitter with the baseband signal up-conversion to carrier wave.

By claim 1 have time-domain training sequence and a cascade interweaved code modulated digital television ground broadcast transmitter modulation method, it is characterized in that: the length X of the discrete sample block of the training sequence of described digital television ground broadcast transmitter, operational indicator sequence, sequence of plural training is 512.

By claim 2 have time-domain training sequence and a cascade interweaved code modulated digital television ground broadcast transmitter modulation method, it is characterized in that: described training sequence, operational indicator sequence have pseudo-random characteristics.

By claim 2 have time-domain training sequence and a cascade interweaved code modulated digital television ground broadcast transmitter modulation method, it is characterized in that: described training sequence, operational indicator sequence have orthogonality each other.

5. have time-domain training sequence and a cascade interweaved code modulated digital television ground broadcast transmitter modulation method by claim 1, it is characterized in that: the cascade interweaved coding modulation data piece of described FFT is made up of subcarrier, the length K of the cascade interweaved coding modulation data piece of FFT is 1024, and the frequency interval of subcarrier is 8KHz.

6. have time-domain training sequence and a cascade interweaved code modulated digital television ground broadcast transmitter modulation method by claim 1, it is characterized in that: described to the input data carry out Bose-Chaudhuri-Hocquenghem Code, Bit Interleave, the LDPC coding, the code element modulation, the encoding rate of the LDPC coding that symbol interleave is handled is 1/4,1/2,5/8, in 3/4 and 7/8 one, Bit Interleave adopts the random interleaving mode, code element is modulated to QPSK, 16 QAM, a kind of among 32 QAM and 64 QAM, symbol constellations figure mapping mode adopts the Gray code mapping, and symbol interleave adopts the random interleaving mode.

7. have time-domain training sequence and a cascade interweaved code modulated digital television ground broadcast transmitter modulation method by claim 1; it is characterized in that: described length as the Cyclic Prefix of protecting the discrete cascade interweaving encoding modulating data sample value piece that is inserted into time domain at interval is C, and C gets 1/16 of K size.

By claim 1 have time-domain training sequence and a cascade interweaved code modulated digital television ground broadcast transmitter modulation method, it is characterized in that: described signal frame is inserted into the discrete cascade interweaving encoding modulating data sample value piece of 4 continuous time domain cyclic prefix by the discrete sample block of the sequence of plural training that constitutes on the time domain as frame head and forms as frame.

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