CN101567744B - Method for analyzing system information symbols in DTMB system - Google Patents
Method for analyzing system information symbols in DTMB system Download PDFInfo
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- CN101567744B CN101567744B CN200810043307A CN200810043307A CN101567744B CN 101567744 B CN101567744 B CN 101567744B CN 200810043307 A CN200810043307 A CN 200810043307A CN 200810043307 A CN200810043307 A CN 200810043307A CN 101567744 B CN101567744 B CN 101567744B
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Abstract
The invention discloses a method for analyzing system information symbols in a DTMB system, comprising the following steps: 32 system information indication symbols are separated at a receiving end; descrambling is carried out to the 32 system information indication symbols; the real part and the imaginary part of a sequence after being descrambled are added together, and multi-frame average is carried out; the symbol bit of each value is taken from the sequence after the multi-frame average; dispreading operation is carried out, and rapid Hadamard transform is carried out for the symbol bit sequence to obtain a transformed sequence which is Y(n), wherein n is equal to 32; a maximum value is found out in the Y(n) and set as Y (index), and the index value is remembered; and finally the system information is determined, and a table is searched to obtain the system information corresponding to s4s3s2s1s0. The invention can obtain reliable system information with simple operation, and is suitable for a DTMB digital terrestrial television receiving system.
Description
Technical field
The present invention relates to the transmission of wireless signals field, particularly relate to the analytic method of system information symbol in a kind of DTMB system.
Background technology
Terrestrial DTV transmission standard (GB20600-2006 in China; Be the DTMB standard) in; Stipulated a series of system information; These system informations are for each signal frame provides necessary demodulation sign indicating number information, comprise the code check, interlace mode information, frame information pattern of symbol constellation mapped mode, LDPC coding etc.For receiving terminal, must at first resolve these system information symbol, could select correct pattern for next step received signal.
Preset 64 kinds of different system information patterns in the DTMB standard, and adopted the spread spectrum transmission.Described 64 kinds of system informations can be used 6 bit (s before spread spectrum
5s
4s
3s
2s
1s
0) represent.Wherein, s
3s
2s
1s
0The presentation code modulating mode, s
4The expression interweaving information, s
5Keep.The information implication that each bit is represented is shown in table one, table two.
Table one
| s 3s 2s 1s 0(presentation code modulating mode) | The expression implication |
| 0000 | The first frame designated symbol of the superframe of odd-numbered |
| 0001 | 4QAM, |
| 0010 | 4QAM, LDPC code check 2 |
| 0011 | 4QAM, LDPC code check 3 |
| 0100 | Keep |
| 0101 | Keep |
| 0110 | Keep |
| 0111 | 4QAM-NR, LDPC code check 3 |
| 1000 | Keep |
| 1001 | 16QAM, |
| 1010 | 16QAM, LDPC code check 2 |
| 1011 | 16QAM, LDPC code check 3 |
| 1100 | 32QAM, LDPC code check 3 |
| 1101 | 64QAM, |
| 1110 | 64QAM, LDPC code check 2 |
| 1111 | 64QAM, LDPC code check 3 |
Table two
| s 4 | The expression implication |
| 0 | |
| 1 | Interlace mode 2 |
The system information that employing 6 bits recited above are represented will be transformed to the system information vector of 32 bit long through spread spectrum, and promptly using length is that 32 Walsh (Walsh) sequence and length are that 32 random sequence is shone upon protection.Concrete steps are following:
1, produce 32 32 long Walsh vectors, they are respectively each row vectors of 32 * 32 Walsh piece.
2, with above-mentioned 32 32 long Walsh vector negates, together with original 32 Walsh vectors, can obtain 64 vectors altogether, each vector length is 32 bits.
3, described 64 vectors and a length be 32 random sequence step-by-step mutually XOR obtain 64 system information vectors.After said random sequence is produced a length and is 31 5 rank maximal-length sequences by the LFSR of one 5 bit, one 0 of follow-up again benefit and producing.The theory diagram that produces random sequence is referring to shown in Figure 1.The length of system information vector also is 32 bits.
4, use information bits s
5s
4s
3s
2s
1s
0Corresponding each 64 the system information vector of 64 probable values, select corresponding vector wherein, adopt I, 4QAM modulation that Q is identical to become 32 complex symbols the system information vector of this 32 bit.
5, like this after overprotection, each system information vector length is 32 complex symbols, adds 4 complex symbols again in its front, as the indication of Frame bulk-mode.The data symbol of these 36 system information symbol after through Multiplexing module and chnnel coding is combined into the frame data, and its multiplexing structure is as shown in Figure 2.
Will obtain the system information transmissions symbol at receiving terminal, need at first isolate the system information designated symbol of 32 bits usually, then it carried out descrambling and despreader, last correspondence goes out real system information parameters.Wherein,, also must there be good method to eliminate, to obtain real system information reliably for the error code that produces in the Channel Transmission.
Summary of the invention
The technical problem that the present invention will solve provides the analytic method of system information symbol in a kind of DTMB system, and that this method is implemented is simple, can access reliable system information.
For solving the problems of the technologies described above, the analytic method of system information symbol comprises the steps: in the DTMB of the present invention system
The first step, isolate 32 system information designated symbols at receiving terminal;
Second the step, said 32 system information designated symbols are carried out descrambling;
In the 3rd step,,, the result is carried out multi-frame mean except that the 0th of superframe carries out real part and imaginary part addition the signal frame to the sequence behind the descrambling;
The 4th the step, get sign bit, with the sequence behind the multi-frame mean, get the sign bit of each value;
The 5th step, carry out de-spreading operation, the sign bit sequence is carried out fast hadamard transform, the sequence that obtains after the conversion is Y (n); N=32 wherein, maximizing in Y (n) is made as Y (index); Write down this index value, the scope of this index value is 0～31, representes with 5 bits.
The 6th the step, confirm system information, continuous detecting multiframe system information is same value, if the index value of continuous multiple frames all the unanimity; Think that then this value is credible; Otherwise continue to detect, till finding the identical index value of continuous multiple frames, this 5 bit index value is corresponding s
4s
3s
2s
1s
0Value; Table look-up, obtain s
4s
3s
2s
1s
0Pairing system information.
Adopt system information symbol analytic method of the present invention, can obtain system information result quite reliably, implementation method also can adopt comparatively simple hardware construction simultaneously, under the prerequisite of guaranteed performance, reaches the lower purpose of implementation complexity.
Description of drawings
Below in conjunction with accompanying drawing and embodiment the present invention is done further detailed explanation:
Fig. 1 is the theory diagram that produces random sequence;
Fig. 2 is a frame data multiplexing structural representation;
Fig. 3 is the analytic method sketch map of system information symbol in the DTMB of the present invention system;
Fig. 4 is the αLv Boqi structural representation that carries out multi-frame mean.
Embodiment
As shown in Figure 3, the analytic method of system information symbol in the DTMB of the present invention system, the concrete process that realizes is:
The first step, need isolate 32 system information designated symbols at receiving terminal, the position of these 32 system information designated symbols is as shown in Figure 2.
Second step, said 32 system information designated symbols are carried out descrambling, promptly remove the superincumbent scrambler of stack.Specifically the method for realization is, produces a same pseudo random sequence in this locality, and the producing method of this pseudo random sequence is as shown in Figure 1; It is 32 pseudo random sequence that said 32 system information designated symbols multiply by length respectively, and each value that wherein produces need be through 1 to "+1 " value and 0 mapping to " 1 " value, obtains the sequence behind the descrambling, and length also is 32.
The 3rd step, in order to let the system information designated symbol that receives more stable, and eliminate the error code influence that produces at random, need carry out multi-frame mean (except the 0th signal frame of superframe) to the sequence behind the descrambling that obtains in second step.
Each the worth real part and the imaginary part addition of the sequence during at first we go on foot second behind the descrambling, the sequence that obtains note is S (n), carries out multi-frame mean then.
Concrete grammar is to realize through αLv Boqi.
The realization principle of α filtering realizes according to following formula:
S(n)’＝α*S(n)+(1-α)*S(n)
last，
Wherein, and S (n)
LastSequence for the previous frame of buffer memory.
Referring to shown in Figure 4, the system information designated symbol that this frame is received multiply by weight, and the system information designated symbol of previous frame multiply by weight (1-α), and summation is afterwards as real system information designated symbol.Because the system information designated symbol is except the 0th signal frame of superframe, the system information designated symbol will remain unchanged.Therefore can improve the received signal to noise ratio of system information designated symbol part through such filtering operation effectively, receive correctness thereby better improve.
The 4th goes on foot, gets sign bit.With resulting result of the 3rd step, promptly the sequence S behind the multi-frame mean (n) ' gets its sign bit, and the sign bit sequence of establishing the result is:
x(n)＝sign{S(n)’}
Do despreader to next step.The purpose of doing like this is in order to obtain more stable sequence, and has also reduced follow-up amount of calculation.Because for multi-carrier OFDM systems; System information symbol is arranged in frequency domain; Be distributed on the subcarrier in frequency domain of each 18 symbol on both sides, owing to the reasons such as frequency selectivity of root raised cosine filter and channel can cause on each carrier wave capacity volume variance very big, promptly carrier wave has lost the characteristic of equal weight; This introduces bigger distortion can for the Hadamard transform result, gets sign bit and does next step despreading and then can remedy this distortion to a certain extent.And for single-carrier system; System information symbol is positioned on the time domain, does not have these problems, and the impaired part of frequency domain will be shared on the whole frequency domain; So also can not get sign bit here, directly the sequence S (n) ' after average passed to next step and do Hadamard transform.
The 5th goes on foot, carries out de-spreading operation.Rely on 10log10 (32)=15dB despreading gain, further improve the stability of system information designated symbol.The concrete method that adopts is a fast hadamard transform.X (n) sequence is carried out fast hadamard transform, and the sequence that obtains after the conversion is Y (n), n=32 here, and maximizing in Y (n) is made as Y (index), writes down this index value.The scope of this index value should be between 0～31, representes with 5 bits.
The purpose in this step is the raw information that the system information designated symbol behind the spread spectrum of 32 bits is reverted to 5 bits.Adopt fast hadamard transform can save amount of calculation, the related operation of amount of calculation by 32 * 32 times become 32 * 5 times, reduced complexity.About the implementation of fast hadamard transform, existing various kinds of document is described, and repeats no more here.
The 6th step, definite system information of being represented by 6 bits because system information is concerning the mode of operation of whole receiving system, therefore when confirming system information, need be done repeatedly and confirm.Concrete grammar is: continuous detecting multiframe system information is same value, if exist the index value of continuous multiple frames all consistent, thinks that then this value is credible, otherwise continues to detect, till finding the identical index value of continuous multiple frames.This 5 bit index value is corresponding s
4s
3s
2s
1s
0Value.Table look-up, obtain s
4s
3s
2s
1s
0Pairing system information.
More than through embodiment the present invention has been carried out detailed explanation, but these are not to be construed as limiting the invention.Protection scope of the present invention should comprise those conspicuous for a person skilled in the art conversion or substitute and improve.
Claims (1)
1. the analytic method of system information symbol in the DTMB system is characterized in that, comprises the steps:
The first step, isolate 32 system information designated symbols at receiving terminal;
Second the step, said 32 system information designated symbols are carried out descrambling;
In the 3rd step,,, carry out multi-frame mean except that the 0th of superframe the signal frame to the sequence behind the descrambling;
The 4th the step, get sign bit, with the sequence behind the multi-frame mean, get the sign bit of each value;
The 5th step, carry out de-spreading operation, the sign bit sequence is carried out fast hadamard transform, the sequence that obtains after the conversion is Y (n); N=32 wherein, maximizing in Y (n) is made as Y (index); Write down this index value, the scope of this index value is 0～31, representes with 5 bits;
The 6th the step, confirm system information, continuous detecting multiframe system information is same value, if the index value of continuous multiple frames all the unanimity; Think that then this value is credible; Otherwise continue to detect, till finding the identical index value of continuous multiple frames, the corresponding s of this 5 bit index value
4s
3s
2s
1s
0Value; Table look-up, obtain s
4s
3s
2s
1s
0Pairing system information;
Wherein, The concrete method that realizes of described multi-frame mean of the 3rd step is: the system information designated symbol that this frame is received multiply by weight; And the system information designated symbol of previous frame multiply by weight (1-α), summation is afterwards as real system information designated symbol;
The described sign bit of getting of the 4th step, the concrete method that realizes is:
With resulting result of the 3rd step, the sequence S behind the multi-frame mean (n) ' gets its sign bit, and the sign bit sequence of establishing the result is:
x(n)＝sign{S(n)’}
Do despreader to next step.
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| CN1684399A (en) * | 2004-04-13 | 2005-10-19 | 上海明波通信技术有限公司 | Quick decoding method and its device for transmission format combined instruction |
| CN1728818A (en) * | 2005-07-29 | 2006-02-01 | 上海广电通讯网络有限公司 | Wireless distribution association mode of digital TV contents for multiple receiving terminals shared in same account |
| CN1984326A (en) * | 2006-04-25 | 2007-06-20 | 华为技术有限公司 | Method, apparatus and system for transmitting wireless digital TV-set and broadcast |
| CN101022597A (en) * | 2007-03-19 | 2007-08-22 | 中兴通讯股份有限公司 | Channel quality identification decoding device for high-speed special physical control channel |
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2008
- 2008-04-25 CN CN200810043307A patent/CN101567744B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1605171A (en) * | 2001-10-17 | 2005-04-06 | 北方电讯网络有限公司 | Method and apparatus for channel quality measurements |
| CN1437342A (en) * | 2002-02-04 | 2003-08-20 | 华为技术有限公司 | Decoding method and device for transmission format combination indicating data |
| CN1684399A (en) * | 2004-04-13 | 2005-10-19 | 上海明波通信技术有限公司 | Quick decoding method and its device for transmission format combined instruction |
| CN1728818A (en) * | 2005-07-29 | 2006-02-01 | 上海广电通讯网络有限公司 | Wireless distribution association mode of digital TV contents for multiple receiving terminals shared in same account |
| CN1984326A (en) * | 2006-04-25 | 2007-06-20 | 华为技术有限公司 | Method, apparatus and system for transmitting wireless digital TV-set and broadcast |
| CN101022597A (en) * | 2007-03-19 | 2007-08-22 | 中兴通讯股份有限公司 | Channel quality identification decoding device for high-speed special physical control channel |
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Owner name: MAIKESHENG TECHNOLOGY (HONGKONG) CO., LTD. Free format text: FORMER OWNER: MAXSCEND TECHNOLOGIES (SHANGHAI) INC. Effective date: 20141115 |
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Effective date of registration: 20141115 Address after: Room 16, building 2-16, good view commercial centre, No. Garden Street, Kowloon Mong, Hongkong, China Patentee after: Mike Sheng Technology (Hongkong) Co., Ltd. Address before: 201203, room 3000, building 5, Zhangjiang port, Zhangjiang East Road, Pudong New Area,, Shanghai Patentee before: Maxscend Technologies Inc. |