CN115296777A - Code word feedback compensation anti-interference method based on LDPC channel coding - Google Patents
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Abstract
The invention discloses a code word feedback compensation anti-interference method based on LDPC channel coding, and belongs to the field of communication signal processing. The invention selects LDPC code as channel coding code word scheme based on original frequency hopping communication system; before diversity combining is carried out at a receiving end, aiming at a symbol at a bit level, firstly, the position of an interfered bit is determined through interference detection, soft information carried by the bit is erased and set to zero, and the anti-interference capability of a system is effectively improved; secondly, the receiving end restores an initial receiving signal through coherent combination to be used as the input of a decoder, and the decoding result is combined with the undisturbed bit information to carry out correction compensation feedback of the zero setting bit; and finally, the receiving end continuously optimizes the value through iteration, so that the initial posterior probability information of the interfered bit is reasonably compensated, and the original coherent combination result is replaced to be input by a decoder. The invention is suitable for the communication field and is used for improving the decoding reliability.
Description
Technical Field
The invention relates to a code word feedback compensation anti-interference method based on LDPC channel coding, belonging to the field of communication signal processing.
Background
Diversity combining (Diversity combining), a common anti-interference technique, is based on the principle that multiple copies of the same transmitted information are transmitted through multiple channels, and the receiver increases the probability of correctly recovering the original information by receiving multiple copies containing the same original information. The key of the diversity combining technology is in which way the receiving end combines, and different diversity combining algorithms have a large influence on the system performance. In a conventional frequency hopping communication system, a common diversity combining algorithm includes: maximum Likelihood (ML) combining, adaptive Gain Control (AGC) combining, equal Gain Control (EGC) combining, self Normalization (SNORM) combining, truncated linear (CL), product (PD) combining, and the like. The diversity combining algorithm has different requirements on channel Side Information (SI), and the complete channel Side Information includes whether a frequency hopping point is disturbed, an interference type, a Signal-to-noise ratio (SNR) and a Signal-to-interference-and-noise ratio (SJR), and Signal energy. For example, ML combining, which is an optimal diversity combining algorithm, relies on complete side information including signal, interference, and noise power; in the sub-optimal combining algorithm, such as the AGC combining algorithm, only part of the side information is needed to include interference and noise power information, and the part of the sub-optimal combining algorithm does not need the side information, such as CL combining and PD combining. Such merging algorithms that do not require side information only require the signal level as a reference value to complete the merging process. The suboptimal merging algorithm is widely used by virtue of low dependency on information integrity side information and simpler implementation steps.
In the field of communication signal processing, such as: direct Sequence Spread Spectrum (Direct Hopping) Frequency Hopping (FH) technology, channel Coding (Channel Coding), diversity combining (Diversity combining), adaptive antenna (Adaptive antenna), interleaving (Interleaving) and other technologies are mainstream anti-interference technologies at present. Among the numerous channel-coded codewords, in particular, LDPC (low density parity check) codes, which are excellent channel codes in recent years, have been widely used in various commercial standards such as 802.11, 802.16, DVB-S2, CCSDS, 5G, etc., by virtue of their performance approaching the shannon limit, good error correction and detection capabilities, parallel processing capabilities, and simple structure.
In order to obtain better anti-interference capability and greater link signal-to-noise ratio, a composite communication system of channel coding, diversity combining and frequency hopping is widely adopted. However, signal level or amplitude information necessary for implementing the sub-optimal combining algorithm at the receiving end is easily affected by interference to generate distortion under a bad transmission channel with complex interference, so that the diversity combining process is affected, and the influence of the interference cannot be effectively suppressed. The received information restored by diversity combination is wrapped by excessive interference influence, so that the reliability of subsequent decoding output is reduced, and the overall bit error rate performance of the system is reduced.
Disclosure of Invention
The method aims at the problems that in the traditional frequency hopping communication system based on channel coding and diversity combining, the suboptimal combining algorithm cannot inhibit interference influence, so that the combined result is distorted, the decoding process is influenced, and the overall error rate performance of the system is reduced. The invention mainly aims to provide a code word Feedback compensation Anti-interference method (CFC-AJ) based on LDPC channel coding, which comprehensively utilizes hard decision bit information output by a decoder and undisturbed bits in a received signal to compensate bit prior information of the received signal, optimizes the input of the decoder through an iterative Feedback loop and improves the decoding reliability.
The purpose of the invention is realized by the following technical scheme:
the invention discloses a code word feedback compensation anti-interference method based on LDPC channel coding, which selects LDPC codes as a code word scheme of channel coding on the basis of an original frequency hopping communication system; before diversity combining is carried out at a receiving end, aiming at a symbol at a bit level, firstly, the position of an interfered bit is determined through interference detection, soft information carried by the bit is erased and set to zero, and the anti-interference capability of a system is effectively improved; secondly, the receiving end restores an initial receiving signal through coherent combination to be used as the input of a decoder, and the decoding result is combined with undisturbed bit information to carry out correction compensation feedback of a zero setting bit; and finally, the receiving end carries out iteration continuous optimization value taking to ensure that the initial posterior probability information of the interfered bit is reasonably compensated, and the original coherent combination result is replaced to be input by a decoder, so that the decoding reliability is improved.
The invention discloses a code word feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding, which comprises the following steps:
step one, the originating terminal carries out LDPC channel coding, diversity and frequency hopping processing on the original information sequence.
Multiplying an original information sequence X with the length of K symbols by a generating matrix G to obtain a coding result C = X.G, wherein the length of the coding result C is N; the coding result C is copied through diversity to obtain a set C with the diversity set number Z and containing completely same original information sequences div ＝{C 1 ,C 2 ,…,C Z In which C is i As in the collectionA group of information sequences, i is more than or equal to 1 and less than or equal to Z; by means of multi-ary frequency shift keying, a set of information sequences C div Modulated as a set of frequency-hopping signals F div ＝{F 1 ,F 2 ,...,F Z In which F i I is more than or equal to 1 and less than or equal to Z in a series of frequency hopping information sequences in the frequency hopping signal set.
And step two, receiving the signal sent in the step one, determining an interfered frequency point through interference detection, determining the position of an interfered bit after debounce, and carrying out erasing zero setting on the bit to inhibit the influence of interference.
With R div ＝{R 1 ,R 2 ,...,R Z Denotes a reception signal set, where R i For a string of information sequences in the received signal set, i is greater than or equal to 1 and less than or equal to Z. T is c Representing a set of undisturbed bits, T representing a set of disturbed bits, E div ＝{E 1 ,E 2 ,...,E Z Denotes the set of received signals after erasure nulling, where E i Representing a string of information sequences in the signal set after the erasure zero setting, wherein i is more than or equal to 1 and less than or equal to Z. The bits in the received signal may be represented as,
calculating the absolute value of the posterior probability information of the undisturbed bit in the received signal to obtain the mean value
And step three, carrying out coherent combination on the signal sets.
In a received signal set E after interference suppression, bit amplitude information of the same position in different signal sequences is coherently combined to finally obtain a string of information sequences G = [ G = [ G ] 1 ,g 2 ,...,g N ]G bits of the sequence j Is shown as
The decoder adopts a minimum sum decoding algorithm, so that the amplitude information of each bit in the information sequence G represents the prior probability soft information thereof and serves as the input of the decoder.
And step four, finishing the minimum sum decoding process.
With information sequence G = [ G = 1 ,g 2 ,...,g N ]The amplitude information of each bit is used as the input of a decoder, and the decoder adopts a minimum sum decoding algorithm to complete the decoding process of preset times of iteration. The decoder outputs a set L of posterior probability information of each bit judge And a decoding decision result D. The decoding judgment result D is obtained by judging posterior probability information, and the relationship between the decoding judgment result D and the posterior probability information is as follows:
wherein n represents L judge N is more than or equal to 1 and less than or equal to N in the nth bit. After all iterative decoding is completed, the receiving end extracts all variable node posterior probability information L judge Is expressed as a set of polarities of the respective bits
L sign ＝sign(L judge ) (5)
And step five, compensating the prior probability information of the interference bits and feeding back results.
According to the mean value Q in the step two and the polarity set L of each bit in the step four sign The receiving end compensates the prior probability information lost by the interfered bit to obtain a new corrected receiving signal bit set
Wherein
And representing a string of corrected information sequences in the set, wherein i is more than or equal to 1 and less than or equal to Z. The superscript v represents the v th compensation feedback iteration.
The specific compensation method is shown in the following formula,
wherein alpha is more than 0 and less than 1, and alpha is a correction scale factor. Due to the influence of interference, the prior probability information carried by the received signal cannot provide higher reliability for the decoding process, and the polarity judgment of each bit in the decoding result of the decoder is not absolutely correct. Therefore, the module introduces a correction scale factor alpha in the compensation process, slows down the influence of interference defects, slowly compensates the amplitude information of the interfered bits, and improves the reliability of the whole method. The value of α was obtained by monte carlo simulation.
Collecting the modified bits in the above steps
Feeding back to step two to replace the original received signal set E div 。
And step six, judging the stop of compensation.
Repeating the third step to the fifth step, and before each compensation feedback, calculating whether the judgment result D meets the check equation H.D or not in the step T And =0. Before the maximum number of times of compensation iteration is reached, if a check equation is established, a receiving end is regarded as obtaining effective code words, immediately finishing compensation feedback, and taking a decoding judgment result D in the current iteration feedback as a final decoder output y; otherwise, counting check equations H.D in each feedback iteration of the receiving end T The number of check nodes which are true in the number of =0 is recorded as a set I check ＝{b 1 ,b 2 ,...,b v In which b is k And k is more than or equal to 1 and less than or equal to v for the number of check nodes enabling the check equation to be established in the kth compensation feedback iteration. After completing all compensation iterations, the receiving end selects I check Maximum value b of k And taking the corresponding kth decoding judgment result D as the final decoder output Y.
The final decoding judgment result is gradually accurate by the correction result of each compensation iteration, an optimal solution is obtained under the conditions of a given correction scale factor alpha and the maximum compensation iteration number v, and the decoding reliability is improved.
Has the advantages that:
1. the invention discloses a code word feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding, which replaces the traditional suboptimum merging algorithm to restore received information through interference detection and coherent merging, reduces the dependence on channel side information and reduces the complexity of system realization;
2. the invention discloses a code word feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding.A receiving end comprehensively utilizes the good error correction and detection capability of an LDPC code and good bits not affected by interference, corrects erasure zero bits, introduces a compensation feedback loop at the receiving end, and continuously optimizes a compensation value through iterative feedback so that the initial prior probability information of the affected bits is reasonably compensated, and replaces an original coherent combination result as the input of a decoder, thereby further improving the decoding reliability.
Drawings
FIG. 1 is a schematic flow chart of a codeword feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding according to the present invention;
FIG. 2 is a block diagram of the system architecture of the codeword feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding according to the present invention;
fig. 3 is a graph comparing BER performance curves of a codeword feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding with reference to (512, 256) code patterns in the CCSDS 131.1-0-1 standard according to an embodiment of the present invention and a conventional frequency hopping anti-interference method based on LDPC channel coding.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples. The technical problems and the advantages solved by the technical solutions of the present invention are also described, and it should be noted that the described embodiments are only intended to facilitate the understanding of the present invention, and do not have any limiting effect.
In order to make the objects, technical solutions and advantages of the present invention easier to understand, the present invention is further described in detail below with reference to the accompanying drawings and the detailed description. The present embodiment is a codeword feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding for an LDPC code pattern in the U.S. deep space communication CCSDS 131.1-0-1 standard (512, 256), wherein system parameters in the present embodiment are shown in the following table:
| parameter(s) | Details of |
| Number of symbols per frame | 512 |
| |
1/2 |
| Punching mode | 128 bits at the end of the check bit |
| Modulation system | BPSK |
| Channel model | Mixed channel (background noise + interference) |
| Maximum number of iterations of decoder | 20 |
| Number of diversity sets | 2 |
| Compensating for feedback iteration times | 10 |
| Modifying a scale factor | 0.5 |
As shown in fig. 2, this embodiment further discloses a block diagram of a codeword feedback compensation anti-interference (CFC-AJ) system based on LDPC channel coding, which is used to implement a codeword feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding. The code word feedback compensation anti-interference system based on the LDPC channel coding mainly comprises a coding module, a diversity module, a frequency hopping module, an interference detection module, a debounce module, a merging module, an LDPC decoding module, a compensation feedback module and a judgment module. The coding module completes the LDPC channel coding process of an original information sequence to obtain coded information, the diversity module performs diversity retransmission and frequency hopping processing on an original signal of a transmitting end, signal loss caused by channel non-ideal characteristics is reduced, interference tolerance of a system is improved, and the frequency hopping module brings larger spread spectrum gain and stronger anti-interference performance to the system. And the interference detection module relates to the step two, and obtains the information such as the type, the energy, the frequency band and the like of the interference signal in real time through interference detection, thereby laying a foundation for subsequent interference suppression. The frequency hopping module is corresponding to the frequency hopping module of the transmitting end, and restores the carrier frequency of the received signal to the intermediate frequency or the baseband. And a combining module relates to a third step, and performs equal-gain coherent combining on the interference-suppressed received signals, so that not only can self amplitude information carried by each bit be accumulated, the prior probability be increased, and the influence of the non-ideal characteristics of the channel be reduced, but also bit soft information lost due to interference suppression can be compensated to a certain extent, and the convergence speed of iterative decoding is accelerated. And the LDPC decoding module adopts a common minimum sum decoding algorithm, extracts the bit sequence amplitude value obtained in the merging module to represent the initial prior probability value as the input of the decoder. The decoder fully utilizes the error correction and detection capabilities of the LDPC channel coding and decoding, so that the bit soft information with zero amplitude due to interference suppression is continuously close to the optimal solution of the bit soft information from zero value, and the anti-interference performance of the system is enhanced. And a compensation feedback module relates to a fifth step, and integrates the error correction capability of the LDPC decoder and information carried by undisturbed bits in an original receiving signal to provide information compensation for disturbed bits, reduces the influence of insufficient reliability caused by interference by correcting a scale factor and an iterative process, gradually improves the reliability and accuracy of compensation information, and ensures that the missing bit information tends to judge a correct result.
As shown in fig. 1, in this embodiment, the code word feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding includes the following specific steps:
step one, sending the signal which is processed by LDPC channel coding, diversity and frequency hopping.
Multiplying an original information sequence X with the length of 256 symbols by a generating matrix G to obtain a coding result C = X.G, and after punching, the length of the coding result C is 512; the coding result C is copied by diversity to obtain a set C containing 2 completely identical coded information sequences div ＝{C 1 ,C 2 In which C is 1 ,C 2 Two groups of completely same coded information sequences; by means of multi-ary frequency shift keying, a set of information sequences C div Modulated as a set F of frequency-hopping signals div ＝{F 1 ,F 2 In which F 1 ,F 2 Are identical hopping information sequences.
And step two, receiving the signal sent in the step one, determining the interfered frequency point through interference detection, determining the corresponding interfered bit position after debounce, and carrying out erasure zero setting on the interfered bit position to inhibit the influence of interference.
With R div ＝{R 1 ,R 2 Denotes a set of received signals, where R 1 ,R 2 Is the information sequence in the received signal set. T is c Representing a set of undisturbed bits, T representing a set of disturbed bits, E div ＝{E 1 ,E 2 Denotes the received signal after erasure zeroing, where E 1 ,E 2 Is the information sequence in the received signal set. Then each bit in the received signal may be represented as,
calculating the absolute value of the posterior probability information of the undisturbed bit in the received signal to obtain the mean value
And step three, carrying out coherent combination on the signal sets.
Carrying out coherent combination on bit amplitude information of the same position in different signal sequences in a receiving signal set E after interference suppression, and finally obtaining an information sequence g = [ g ] 1 ,g 2 ]Each bit g in the sequence j Can be expressed as
The decoder adopts a minimum sum decoding algorithm, so that the amplitude information of each bit in the information sequence g represents the soft information of the posterior probability and serves as the input of the decoder.
And step four, finishing the minimum sum decoding process.
With information sequence G = [ G = 1 ,g 2 ,...,g N ]The amplitude information of each bit is used as the input of a decoder, and the decoder adopts a minimum sum decoding algorithm to complete the decoding process of preset times of iteration. The decoder outputs a set L of posterior probability information of each bit judge And a decoding decision result D. The decoding judgment result D is obtained by judging the posterior probability information, and the relationship between the two is as follows:
wherein n represents L judge N is more than or equal to 1 and less than or equal to 512. After all iterative decoding is completed, the receiving end extracts all variable node posterior probability information L judge Is expressed as a set of polarities of the respective bits
L sign ＝sign(L judge ) (11)
And step five, compensating the interference bit posterior probability information and feeding back a result.
Extracting the polarity of each bit of the variable node hard decision result D in the iterative decoding result of the step six to form a set L sign According to the mean value Q in the second step, the compensation of the posterior probability information missing from the interfered bit is completed to obtain a new corrected receiving signal bit set
Wherein
Is a modified information sequence. The superscript v represents the v-th compensation feedback iteration, with a maximum of 10.
The specific compensation method is shown in the following formula,
because the received signal is affected by interference, the posterior probability information carried by the received signal cannot ensure the accuracy of the decoding result. Therefore, the judgment of the bit polarity in the iterative decoding result is not absolutely correct. Therefore, by introducing the correction scale factor, the influence of the interference defect is relieved, the amplitude information of the interfered bit is slowly compensated and fed back, and the reliability of the whole method is improved.
The corrected bit set obtained in the above step
Feeding back to step two to replace the original received signal set E div 。
And step six, judging the stop of compensation.
Repeating the third step to the fifth step, wherein before each compensation feedback, the receiving end calculates whether the judgment result D meets the check equation H.D T And =0. In the achievement ofBefore the maximum times of the compensation iteration, if the check equation is established, the receiving end is regarded as obtaining an effective code word, immediately finishing the compensation feedback, and taking a decoding judgment result D in the current iteration feedback as a final decoder output y; otherwise, counting check equations H.D in each feedback iteration of the receiving end T The number of check nodes which are true in the number of =0 is recorded as a set I check ＝{b 1 ,b 2 ,...,b 10 In which b is k And k is more than or equal to 1 and less than or equal to 10 for the number of check nodes for enabling the check equation to be established in the kth compensation feedback iteration. After completing all compensation iterations, the receiving end selects I check Maximum value b of k And taking the corresponding kth decoding judgment result D as the final decoder output Y.
Fig. 2 dashed arrows represent the iteration flow. With the increase of the iteration times, the bit soft information fed back by compensation gradually converges to the performance of correct initial prior probability information. The BER is used as a measurement standard, in order to embody the performance advantage of the CFC-AJ method, the diversity combining processing with the same diversity set number is introduced on the basis of the traditional frequency hopping anti-interference method based on LDPC channel coding, and the equal gain combining algorithm in the suboptimal combining algorithm is adopted, and the performance is analyzed as the comparison. As shown in fig. 3, different interference proportionality coefficients p represent the proportion of the interfered frequency band to the total frequency hopping spectrum during channel transmission. As can be seen from the figure, the introduction of the code word feedback compensation anti-interference (CFC-AJ) method based on LDPC channel coding can bring considerable system performance improvement. With 10e-6 as the performance index of the bit error rate, under the environment of an interference scale factor p =0.1 channel, the CFC-AJ method which does not combine diversity combining can obtain about 1dB performance gain, and the gain is increased along with the increase of the interference scale and the number of diversity sets, so that the decoding reliability of the system is improved. Meanwhile, under the non-ideal channel environment with a large interference proportionality coefficient such as p =0.3 or p =0.4, the system can effectively cope with the influence of interference and signal attenuation under the condition of a low diversity set number Z = 2.
The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (6)
1. A code word feedback compensation anti-interference method based on LDPC channel coding is characterized in that: comprises the following steps of (a) carrying out,
firstly, a transmitting end performs LDPC channel coding, diversity and frequency hopping processing on an original information sequence;
step two, receiving the signal sent in the step one, determining an interfered frequency point through interference detection, determining an interfered bit position after debounce, and erasing and zeroing the interfered bit position to inhibit the influence of interference;
step three, carrying out coherent combination on the signal sets;
step four, finishing the minimum sum decoding process;
fifthly, compensating the prior probability information of the interference bits and feeding back a result;
step six, judging the stop of compensation;
repeating the third step to the fifth step, and before each compensation feedback, calculating whether the judgment result D meets the check equation H.D T =0; before the maximum number of times of compensation iteration is reached, if a check equation is established, a receiving end is regarded as obtaining an effective code word, the compensation feedback is immediately finished, and a decoding judgment result D in the current iteration feedback is used as a final decoder output y; otherwise, counting check equations H.D in each feedback iteration of the receiving end T The number of check nodes which are true in the number of =0 is recorded as a set I check ＝{b 1 ,b 2 ,...,b v In which b is k K is more than or equal to 1 and less than or equal to v for the number of check nodes for enabling a check equation to be established in the kth compensation feedback iteration; after completing all compensation iterations, the receiving end selects I check Maximum value b of k The corresponding kth decoding judgment result D is used as the final decoder output Y;
the final decoding judgment result is gradually accurate by the correction result of each compensation iteration, an optimal solution is obtained under the conditions of a given correction scale factor alpha and the maximum compensation iteration number v, and the decoding reliability is improved.
2. The LDPC channel coding based codeword feedback compensation anti-interference method as claimed in claim 1, wherein: the implementation method of the first step is that,
multiplying an original information sequence X with the length of K symbols by a generating matrix G to obtain a coding result C = X.G, wherein the length of the coding result C is N; the coding result C is copied through diversity to obtain a set C with the diversity set number Z and containing completely same original information sequences div ＝{C 1 ,C 2 ,...,C Z In which C is i I is more than or equal to 1 and less than or equal to Z for a group of information sequences in the set; by means of multi-ary frequency shift keying, a set of information sequences C div Modulated as a set of frequency-hopping signals F div ＝{F 1 ,F 2 ,...,F Z In which F i I is more than or equal to 1 and less than or equal to Z in a series of frequency hopping information sequences in the frequency hopping signal set.
3. The LDPC channel coding based codeword feedback compensation anti-interference method as claimed in claim 1, wherein: the implementation method of the second step is that,
with R div ＝{R 1 ,R 2 ,...,R Z Denotes a set of received signals, where R i For a string of information sequences in a received signal set, i is more than or equal to 1 and less than or equal to Z; t is c Representing the set of undisturbed bits, T representing the set of disturbed bits, E div ＝{E 1 ,E 2 ,...,E Z Denotes the set of received signals after erasure nulling, where E i Representing a string of information sequences in the signal set after the erasure zero setting, wherein i is more than or equal to 1 and less than or equal to Z; the bits in the received signal are represented as,
calculating the absolute value of the posterior probability information of the undisturbed bit in the received signal to obtain the mean value
4. The method of claim 1, wherein the code word feedback compensation anti-interference method based on LDPC channel coding is characterized in that: the implementation method of the third step is that,
in a receiving signal set E after interference suppression, bit amplitude information at the same position in different signal sequences is coherently combined to finally obtain a string of information sequences G = [ G = 1 ,g 2 ,...,g N ]G bits of the sequence j Is shown as
The decoder adopts a minimum sum decoding algorithm, so that the amplitude information of each bit in the information sequence G represents the prior probability soft information thereof and serves as the input of the decoder.
5. The LDPC channel coding based codeword feedback compensation anti-interference method as claimed in claim 1, wherein: the implementation method of the fourth step is that,
with the information sequence G = [ G ] 1 ,g 2 ,...,g N ]The amplitude information of each bit is used as the input of a decoder, and the decoder adopts a minimum sum decoding algorithm to finish the decoding process of the preset times of iteration; the decoder outputs a set L of posterior probability information of each bit judge And a decoding decision result D; the decoding judgment result D is obtained by judging posterior probability information, and the relationship between the decoding judgment result D and the posterior probability information is as follows:
wherein n represents L judge N is more than or equal to 1 and less than or equal to N in the nth bit; after all iterative decoding is completed, the receiving end extracts all variable node posterior probability information L judge Is expressed as a set of polarities of the respective bits
L sign ＝sign(L judge ) (5)。
6. The LDPC channel coding based codeword feedback compensation anti-interference method as claimed in claim 1, wherein: the implementation method of the fifth step is that,
according to the mean value Q in the step two and the polarity set L of each bit in the step four sign The receiving end compensates the prior probability information lost by the interfered bit to obtain a new corrected receiving signal bit set
Wherein
Representing a string of corrected information sequences in the set, wherein i is more than or equal to 1 and less than or equal to Z; superscript v represents the vth compensation feedback iteration process;
the specific compensation method is shown in the following formula,
wherein alpha is more than 0 and less than 1, and alpha is a correction scale factor; due to the influence of interference, prior probability information carried by a received signal cannot provide higher reliability for a decoding process, and polarity judgment of each bit in a decoding result of a decoder is not absolutely correct; therefore, the module introduces a correction scale factor alpha in the compensation process, slows down the influence of interference defects, slowly compensates the amplitude information of the interfered bits, and improves the reliability of the whole method; the value of alpha is obtained by Monte Carlo simulation;
collecting the modified bits in the above steps
Feeding back to step two to replace the original received signal set E div 。
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