Research On Coded Modulation Technology Of Polar Codes

As a new type of coding scheme that can theoretically realize the capacity of binary-input discrete memoryless channels(B-DMC),polar codes have attracted wide attention due to their low complexity encoding and decoding algorithm and excellent error correction performance.In 2016,polar codes were determined as the coding scheme for the control channel in the 5G enhanced mobile broadband scenario.Studies have shown that the combination of polar codes and high-order modulation techniques can effectively improve the band utilization of the system.T herefore,improving the performance of high-order modulation system based on polar codes and enhancing the communication system capacity are the current research hotspots.This thesis uses the high-order modulation modes in 5G communication to carry out related research and improvement on the bit-interleaved polar coded modulation system.At the same time,the probability shaping scheme is introduced to optimize the symbol probability distribution of the channel.The main research work of the thesis include s the following aspects:(1)The basic principles of polar codes are systematically described,including the channel polarization and construction methods of polar codes.At the same time,the encoding algorithm and three common decoding algorithms are introduced in detail.(2)This thesis simulates the bit error rate of the polar code s in high-order modulation system under different modulation order,and an improved interleaving algorithm is proposed to optimize the interleaver.The interleaver is proposed based on the parameters of the reliability of sub-channels,and the high-reliability sub-channels are interleaved with the low-reliability subchannels to assist decoding.Therefore,the error correction performance of polar codes is improved.Simulation proves that,compared with other interleaving algorithms,the proposed interleaving has better bit error rate in bit-interleavd polar coded modulation system.(3)Research on the principle of probability shaping,which can realize the Gaussian or Gauss-like distribution of the probability of modulation symbols.In this thesis,the probabilistic shaping adopts bit weighted distribution matching(BWDM)algorithm,which effectively realizes the target distribution of symbol probability by using the bit marking and bit inversion process to increase the probability of bit ’0’ in binary sequence.In addition,the encoder in high-order modulation system adopts systematic polar coding algorithm,which can compensate for the influence of bit mixing on the probability distribution of modulation symbols.Simulation results show that the polar codes high-order modulation system has better performance under the joint design of BWDM algorithm and systematic polar encoder.