基于解調(diào)軟判決的信道編碼參數(shù)識別技術(shù)研究
發(fā)布時間：2019-05-25 03:22
【摘要】：在編碼參數(shù)未知的情況下,接收方常常利用信道編碼分析技術(shù)對接收到的編碼序列進行處理,根據(jù)識別出的編碼參數(shù)對接收序列進行譯碼,最終完成對信息序列的提取。該技術(shù)在信號截獲、智能通信等領(lǐng)域具有重要的應(yīng)用價值。傳統(tǒng)編碼分析方法的研究對象通常是解調(diào)硬判決序列,硬判決序列所能提供的信息量十分有限,隨著新型通信技術(shù)和編碼體制的廣泛應(yīng)用,這些方法容錯性差、適用面窄的缺點日益凸顯。同硬判決序列相比,軟判決序列往往可以為接收方提供更加豐富的先驗信息,因此,為克服硬判決方法所遇到的困難,本文研究解調(diào)軟判決條件下的編碼分析技術(shù)。通過求解由接收序列構(gòu)造的含錯方程組來尋找編碼約束關(guān)系,是一種常用的編碼分析思路�；诮庹{(diào)硬判決的Walsh-Hadamard變換法在求解含錯方程組時存在容錯性能不足的問題。為此,本文提出將Chase2譯碼算法中構(gòu)造候選碼字集的思想與Walsh-Hadamard變換相結(jié)合,通過對系數(shù)向量依概率加權(quán),定義了軟判決條件下Walsh-Hadamard變換譜系數(shù)的含義;同時,推導(dǎo)了適用于分組碼監(jiān)督向量的判決門限。仿真結(jié)果表明,在不明顯增加運算量的前提下,本文算法的容錯性能優(yōu)于傳統(tǒng)硬判決算法,且信噪比越低,優(yōu)勢越明顯。已有方法在處理中短碼長LDPC碼開集識別問題時,通常采用矩陣初等變換的方法來搜索監(jiān)督向量,在有誤碼的條件下,復(fù)雜的矩陣變換過程將引起嚴重的錯誤傳播問題,進而導(dǎo)致算法失效。為解決這一問題,本文利用軟判決序列所提供的概率信息,給出了一種基于可靠監(jiān)督關(guān)系的預(yù)判決方法,并對相關(guān)參數(shù)的選取進行了推導(dǎo),使得向量搜索空間在構(gòu)造過程中具有更強的容錯能力;在此基礎(chǔ)之上,利用廣義對數(shù)似然比檢驗對搜索空間中的向量進行判決,得到監(jiān)督向量;最后,提出一種基于多組數(shù)據(jù)和軟輸入軟輸出譯碼的迭代識別方案。仿真結(jié)果表明,低信噪比條件下,本文算法可以有效應(yīng)對中短碼長LDPC碼的開集識別問題。現(xiàn)有軟判決算法在對高碼率LDPC碼進行閉集識別時容錯性能有限。為此,本文首先對不同碼率下監(jiān)督關(guān)系對數(shù)似然比的分布特征進行了分析,指出了已有算法性能不足的原因;在此分析之上,提出了一種可以全面體現(xiàn)隨機變量分布特征的新判決參數(shù)——偏差比,進而給出一種利用最大偏差比判決器的LDPC碼識別算法。仿真結(jié)果表明,本文算法可以有效地完成低信噪比環(huán)境下的LDPC碼閉集識別問題,特別地,對于高碼率LDPC碼,新算法具有較為明顯的優(yōu)勢。
[Abstract]:In the case of unknown coding parameters, the receiver often uses channel coding analysis technology to process the received coding sequence, decode the received sequence according to the identified coding parameters, and finally complete the extraction of the information sequence. This technology has important application value in signal interception, intelligent communication and other fields. The research object of traditional coding analysis method is usually demodulation hard decision sequence, and the information provided by hard decision sequence is very limited. With the wide application of new communication technology and coding system, these methods have poor fault tolerance. The shortcomings of narrow applicable surface are becoming more and more prominent. Compared with the hard decision sequence, the soft decision sequence can often provide the receiver with more prior information. Therefore, in order to overcome the difficulties encountered by the hard decision method, this paper studies the coding analysis technology under the condition of demodulation soft decision. It is a common coding analysis idea to find the coding constraint relation by solving the error-containing equations constructed by the receiving sequence. The Walsh-Hadamard transform method based on demodulation hard decision has the problem of insufficient fault-tolerant performance in solving error-containing equations. In this paper, the idea of constructing candidate code word set in Chase2 decoding algorithm is combined with Walsh-Hadamard transform, and the meaning of Walsh-Hadamard transform spectral coefficient under soft decision condition is defined by weighted coefficient vector according to probability. At the same time, the decision threshold suitable for block code supervision vector is derived. The simulation results show that the fault-tolerant performance of the proposed algorithm is better than that of the traditional hard decision algorithm without obviously increasing the amount of computation, and the lower the signal-to-noise ratio (SNR), the more obvious the advantage. When dealing with the problem of open set recognition of LDPC codes with medium and short code length, the existing methods usually use the method of matrix elementary transformation to search the supervised vector. Under the condition of error code, the complex matrix transformation process will cause serious error propagation problem. This leads to the failure of the algorithm. In order to solve this problem, this paper presents a pre-decision method based on reliable supervision relationship by using the probability information provided by soft decision sequence, and deduces the selection of related parameters. The vector search space has stronger fault-tolerant ability in the construction process. On this basis, the generalized logarithmic likelihood ratio test is used to determine the vectors in the search space, and the supervised vectors are obtained. finally, an iterative recognition scheme based on multiple sets of data and soft input and soft output decoding is proposed. The simulation results show that the proposed algorithm can effectively solve the problem of open set recognition of LDPC codes with medium and short code length under the condition of low SNR. The fault-tolerant performance of the existing soft decision algorithms for closed set recognition of high bit rate LDPC codes is limited. Therefore, this paper first analyzes the distribution characteristics of logarithmic likelihood ratio of supervisory relationship at different bit rates, and points out the reasons for the lack of performance of the existing algorithms. On the basis of this analysis, a new decision parameter, deviation ratio, which can fully reflect the distribution characteristics of random variables, is proposed, and then a LDPC code recognition algorithm based on the maximum deviation ratio discriminator is proposed. The simulation results show that the proposed algorithm can effectively complete the problem of LDPC code closed set recognition in low SNR environment, especially for high bit rate LDPC codes, the new algorithm has obvious advantages.
【學(xué)位授予單位】：解放軍信息工程大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN911.22
本文編號：2485446
[Abstract]:In the case of unknown coding parameters, the receiver often uses channel coding analysis technology to process the received coding sequence, decode the received sequence according to the identified coding parameters, and finally complete the extraction of the information sequence. This technology has important application value in signal interception, intelligent communication and other fields. The research object of traditional coding analysis method is usually demodulation hard decision sequence, and the information provided by hard decision sequence is very limited. With the wide application of new communication technology and coding system, these methods have poor fault tolerance. The shortcomings of narrow applicable surface are becoming more and more prominent. Compared with the hard decision sequence, the soft decision sequence can often provide the receiver with more prior information. Therefore, in order to overcome the difficulties encountered by the hard decision method, this paper studies the coding analysis technology under the condition of demodulation soft decision. It is a common coding analysis idea to find the coding constraint relation by solving the error-containing equations constructed by the receiving sequence. The Walsh-Hadamard transform method based on demodulation hard decision has the problem of insufficient fault-tolerant performance in solving error-containing equations. In this paper, the idea of constructing candidate code word set in Chase2 decoding algorithm is combined with Walsh-Hadamard transform, and the meaning of Walsh-Hadamard transform spectral coefficient under soft decision condition is defined by weighted coefficient vector according to probability. At the same time, the decision threshold suitable for block code supervision vector is derived. The simulation results show that the fault-tolerant performance of the proposed algorithm is better than that of the traditional hard decision algorithm without obviously increasing the amount of computation, and the lower the signal-to-noise ratio (SNR), the more obvious the advantage. When dealing with the problem of open set recognition of LDPC codes with medium and short code length, the existing methods usually use the method of matrix elementary transformation to search the supervised vector. Under the condition of error code, the complex matrix transformation process will cause serious error propagation problem. This leads to the failure of the algorithm. In order to solve this problem, this paper presents a pre-decision method based on reliable supervision relationship by using the probability information provided by soft decision sequence, and deduces the selection of related parameters. The vector search space has stronger fault-tolerant ability in the construction process. On this basis, the generalized logarithmic likelihood ratio test is used to determine the vectors in the search space, and the supervised vectors are obtained. finally, an iterative recognition scheme based on multiple sets of data and soft input and soft output decoding is proposed. The simulation results show that the proposed algorithm can effectively solve the problem of open set recognition of LDPC codes with medium and short code length under the condition of low SNR. The fault-tolerant performance of the existing soft decision algorithms for closed set recognition of high bit rate LDPC codes is limited. Therefore, this paper first analyzes the distribution characteristics of logarithmic likelihood ratio of supervisory relationship at different bit rates, and points out the reasons for the lack of performance of the existing algorithms. On the basis of this analysis, a new decision parameter, deviation ratio, which can fully reflect the distribution characteristics of random variables, is proposed, and then a LDPC code recognition algorithm based on the maximum deviation ratio discriminator is proposed. The simulation results show that the proposed algorithm can effectively complete the problem of LDPC code closed set recognition in low SNR environment, especially for high bit rate LDPC codes, the new algorithm has obvious advantages.
【學(xué)位授予單位】：解放軍信息工程大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN911.22
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