Research On Low Complexity Encoding And Decoding Algorithm Of Polar Codes

Polar codes is the first coding method that can reach the Shannon limit in theory.It has low coding and decoding complexity.It is an excellent channel coding solution.Now it is one of the channel coding solutions in 5G communication.However,there are still many problems to be solved in practical applications,among which the problem of finding low complexity encoding and decoding algorithms and realize variable code length Polar codes is particularly important.Firstly,this paper studies the decoding algorithms of Successive Cancellation(SC),fast-SC and Successive Cancellation List(SCL).Based on these algorithms,a new decoding method is proposed to reduce the decoding complexity.Then the punctured Polar codes is studied,and based on the puncturing scheme,a construction method of variable code length with lower complexity is proposed.The main work is as follows:(1)A Prefast-SCL decoding algorithm for adaptive channel is proposed.The algorithm uses the idea of cascade,combines efficient fast decoding and highly reliable Cyclic Redundancy Check-aided SCL(CA-SCL)decoding algorithm,judges the channel conditions through the verification information,and selects the decoding scheme adaptively.In order to further improve the performance of the decoding algorithm,this paper adjusts the fast SC decoding scheme,and reduces the splitting times of the SCL algorithm according to the distribution of log likelihood ratio(LLR)of the research channel,so as to improve the time performance of the algorithm;In addition,the channel location filtering and the number of SCL reserved paths are experimentally explored to improve the error correction performance.Theoretical analysis and simulation experiments show that compared with CA-SCL and adaptive-SCL decoding algorithms,prefast SCL algorithm effectively reduces the decoding complexity while the reliability remains basically unchanged.(2)Based on the idea of puncturing and segmentation,a construction method of closest segment puncture(CSP)is proposed.In this method,Polar codes of a target length is decomposed into a punctured Polar codes and several standard Polar codes.After decomposition,the sum of the code length of each sub Polar codes is as close as possible to the target code length,so that its encoding and decoding can obtain the time performance gain from the reduction of the number of holes.At the same time,this construction method reduces the number of holes and can effectively improve the accuracy when the number of holes is large.In addition,this paper also gives the decoding scheme corresponding to the construction method.By combining each segment decoding path,a new alternative path is obtained and then checked in turn to improve the reliability of the new method.The simulation results show that the CSP construction method can obtain the time performance gain from the number of holes,and the complexity is lower than that of the hole drilling polarization code.When the number of holes is greater than 1 / 5 of the mother code,the accuracy performance is higher than that of the hole punctured Polar codes,and the performance gain is more obvious with the increase of the number of holes.When the code length is 1360,the CSP construction method has about 0.5d B performance improvement compared with the perforated polarization code,while the coding complexity is reduced by about 30%.