| Polar code is an error correction code that has been proven to achieve channel capacity and has been selected as the coding scheme for the control channel of the 5th generation（5G）mobile communication system.To further improve the decoding performance,this thesis proposes the Post-Processing for CRC Aided Successive Cancellation List Decoding of Polar Codes（PCA-SCL）based on the Segmented-CRC Adaptive SCL（SCAD-SCL）polar decoding algorithm and the Post-Processing for CRC Aided Successive Cancellation List Decoding of Polar Codes（PCA-SCL）decoding algorithm.Processing Adaptive Polar Decoding Assisted by Segmented Cyclic Redundancy Bit（PSCAD-SCL）algorithm,then build the Tapped Delay Lines（TDL）model in the 5G protocol and perform performance analysis on the 5G physical layer simulation platform,the specific work is as follows.1.The basic principles of Polar code are summarised.Firstly,the channel coding principles adopted in 4G and 5G protocols are introduced,and then the coding principles,implementation process and coding evaluation index of Polar code are described in detail.Finally,the working principle and implementation process of several basic decoding algorithms of Polar code are described in detail,and performance analysis and comparison are carried out.2.A post-processing decoding algorithm for SCAD-SCL（PSCAD-SCL decoding algorithm）is proposed.The original SCAD-SCL decoding algorithm achieves decoding early stop and reduces useless decoding calculations,but does not further improve performance.Inspired by the post-processing decoding algorithm of CA-SCL（PCA-SCL decoding algorithm）,this thesis proposes the PSCAD-SCL algorithm by considering the optimization of the log-likelihood ratio of decoding under different signal-to-noise ratios.When the original SCAD-SCL algorithm fails to decode,it improves the bit error rate performance by flipping and appropriately scaling up the unreliable log-likelihood ratio values for re-decoding at different signal-to-noise ratios.The simulation results show that the BER performance of PSCAD-SCL is better than the original SCAD-SCL decoding algorithm in the range of 0.5 to 2 d B SNR,and the coding gain of PSCAD-SCL decoding algorithm is improved by about 0.2 d B at BER of 10-4.3.Build a 5G physical layer simulation platform.Based on the 5G physical layer protocol,the display module,parameter configuration module and channel simulation module are designed to complete the development of the mobile communication link simulation platform.Taking the physical downlink control channel as an example,the TDL model is built,and two decoding algorithms,the original SCAD-SCL and the improved PSCAD-SCL,are used for polar decoding.The simulation results show that the bit error rate of PSCAD-SCL is better than the original SCAD-SCL decoding algorithm at signal-to-noise ratios of 1 to 3 d B in the 5G physical layer simulation platform built in this thesis,and the coding gain of PSCAD-SCL algorithm is improved by about 0.3 d B at BER of 10-4. |
