Research On The SCL Decoding Algorithm Of Polar Codes Based On Bit-Flipping In 5G System

Since 2012,the 5th Generation Mobile Communication（5G）system and key technologies have gradually become research hotspots in the field of mobile communication.2019 is the first year of 5G commercialization in China and after 7 years of research and development,the 5G standardization work has been completed,and the control channel adopts the polar code as the channel coding scheme.With the large-scale popularization of 5G technology,so as to ensure the efficiency and accuracy of data transmission,high-efficiency decoding schemes of polar codes have become a research hotspot.Based on this,this thesis analyzes the existing decoding algorithm of polar code for achieving a good compromise between computational complexity and error correction performance.The main research work completed is as follows:1.In order to solve the problem of poor decoding performance of the Successive Cancellation（SC）decoding algorithm when the code lengths are short and medium,the path list and bit-flipping methods are added on the basis of the SC decoding algorithm and the Successive Cancellation List Flip（SCLF）decoding algorithm is proposed.The algorithm uses bit-flipping to build the most unreliable information bit collection called the flipping set（Flipping Set,FS）,and proposes a new metric to reduce the range of FS and improve the accuracy of FS.The simulation results show that with the increase of the signal-to-noise ratio,the proposed SCLF decoding algorithm has a greater improvement in the Block Error Rate（BLER）.The performance gain of the SCLF（N=256,L=8）decoding algorithm is 0.55d B higher than that the SC（N=256）decoding algorithm at BLER=10^-3;the performance gain of the SCLF（N=256,L=8）decoding algorithm is 0.22 d B higher than that the CA-SCL（N=256,L=8）decoding algorithm at BLER=10^-4;the performance gain of the SCLF（N=256,L=16）decoding algorithm is 0.17 d B higher than that the CA-SCL（N=256,L=16）decoding algorithm at BLER=10^-5.Therefore,the SCLF decoding algorithm has better error correction performance.2.In order to solve the problem of higher complexity of the SCLF decoding algorithm due to add path lists,four special nodes are added to the SCLF algorithm for and the Fast Successive Cancellation List Flip（FSCLF）decoding algorithm is proposed.The algorithm can directly obtain a decoding sequence by adding spceial nodes through fast decoding,which speeds up the decoding operation;In addition,the construction of FS no longer depends on the error propagation caused by previous decoding errors while calculating the judged LLR value of the special node to determine the positions that need to be flipped,which shrinks the search range and reduces the amount of calculation.The simulation results show that The performance gain of the proposed FSCLF（N=256,L=8）decoding algorithm is 0.10 d B higher than that the SCLF（N=256,L=8）decoding algorithm at BLER=10^-5;the performance gain of the FSCLF（N=256,L=16）decoding algorithm is 0.09d B higher than that the SCLF（N=256,L=16）decoding algorithm at BLER=10^-5;the performance gain of the proposed FSCLF（N=512,L=16）decoding algorithm is 0.10 d B higher than that the SCLF（N=512,L=16）decoding algorithm at BLER=10^-5.After analysis,the FSCLF algorithm can reduce complexity without performance loss and achieve the goal of both complexity and error correction performance are considered.