Research On Successive Cancellation Bit-Flipping Decoding Algorithms Of Polar Codes

Polar codes,as a channel coding technology which can theoretically reach the symmetrical capacity of binary-input discrete memoryless channel(B-DMC),have become a research hotspot.Compared with the typical SCF decoding algorithm,the performance of SCF decoding algorithm has been greatly improved,but compared with the ideal SCF decoding algorithm,it is still insufficient.In order to improve the performance of SCF decoding algorithm,this thesis mainly optimizes the measurement formula and segmentation method of SCF decoding algorithm.This thesis proposes a SCF decoding algorithm based on log likelihood ratio(LLR)and polarization channel reliability.In traditional SCF decoding algorithm,the absolute value of LLR is used to measure the reliability of information bit decoding results.Because this decoding algorithm fails to take into account other factors that cause the error decoding of SC decoding algorithm,the performance of block error rate(BLER)is deficiency.Therefore,the distribution of the absolute value of LLR and the polarization channel reliability of an information bit is analyzed when it is the first decision error of information bit(TFDEIB).By analyzing the distribution of these factors,a measurement formula is designed.The simulation results show that,compared with the traditional SCF decoding algorithm,the BLER performance of SCF decoding algorithm based on LLR and polarization channel reliability can achieve a maximum decoding gain of 0.12d B,and the number of flip attempts is reduced by 21.6%.The thesis proposes a segmented SCF decoding algorithm based on critical sets(CS).The SCF decoding algorithm with one bit flipped can only correct one error of induced-channel,while the SCF decoding algorithm with multi-bit flipped has very high computational complexity compared with segmented SCF decoding algorithm.Therefore,this algorithm uses rate-1 node and the number of segments to create CS,then nonuniform segments the information bits in CS based on error probability P_e~i.The simulation results show that,the proposed algorithm can obtain about 0.2d B gain and reduces the number of flipping attempts by 36.7%compared with the traditional SCF decoding algorithm.The segmented method also enables the decoding algorithm to achieve early termination and reduce the computational complexity.