Research On Symbol Flipping Based Non-binary LDPC Decoding Algorithms

With the rapid development of science and technology,people’s demand for efficient stable and reliable communication is getting higher and higher,and the support of advanced channel coding technology is needed.Low density parity-check code（LDPC）is an excellent channel coding scheme,which has the advantages of large decoding throughput and good performance.It has been selected as the coding standard of data channel in the fifth generation of mobile communication（5G）.LDPC code will still play an important role in future mobile communication systems in B5G and 6G.In this paper,the decoding algorithm of symbol flipping based non-binary LDPC is studied.The main research contents are as follows:1.The coding structure and decoding algorithm of non-binary LDPC are analyzed and studied.Firstly,this paper analyzes the construction method of non-binary LDPC code based on finite field,and completes the coding operation of non-binary LDPC code by lower triangulation matrix;Secondly,wtd-AlgB algorithm and P-SFDP algorithm are re-analyzed and described to lay a foundation for the subsequent algorithm proposed in this paper;Finally,a comprehensive simulation platform for coding and decoding under different channel environments is built,and the various algorithms involved in this paper are experimented and analyzed;2.A truncation mechanism based P-SFDP（TP-SFDP）is proposed.TP-SFDP algorithm truncates and divides the decoding nodes and symbols in the finite field by combining the frequency of external information and the characteristics of the flip function,so that only the variable nodes and symbols that meet the conditions can participate in the operation and the flip prediction.The simulation experiment shows that when T₁=4,T₂=1,and SNR=4.5d B,the number of variable nodes involved in calculation and flipping prediction is reduced from 225 to 165,and the number of symbols in the finite field is reduced from 16 to 2.The real number comparison times of TP-SFDP algorithm is about 48%of the original algorithm.The number of integer/real addition operations of TP-SFDP is about 40%of the original algorithm.At the same time,when BER=10^-5,the performance loss of TP-SFDP algorithm is about 0.1d B compared with the original algorithm.The improved decoding algorithm reduces the complexity of decoding through a slight loss of decoding performance and can effectively compromise between decoding performance and complexity.Various alternative decoding schemes can be obtained conveniently through different degrees of truncation;3.A comprehensive external information reliability algorithm B（CEIR-AlgB）is proposed.This algorithm is improved based on wtd-AlgB algorithm.The correlation reliability of the channel initial received information and the external information is added into the reliability calculation of wtd-AlgB algorithm,and the decision symbols of all variable nodes are updated in each iteration decoding.Experimental simulation shows that the proposed algorithm can improve the decoding performance and convergence speed,and has a performance gain of about 1.0～1.3 d B compared with wtd-AlgB algorithm;4.In view of the oscillation phenomenon in the decoding process of CEIR-AlgB algorithm,proposes to introduce the attenuation factor mechanism,which can effectively reduce the impact of the oscillation phenomenon.The simulation results show that the CEIR-AlgB algorithm can get a certain performance gain after introducing the attenuation factor.Compared with wtd-AlgB algorithm,the maximum performance gain can be 1.4 d B.