Research On The Performance Of Coded Modulation System Based On Polar Codes

It has been proved that the channel capacity of polarization codes could reach the Shannon limit when the code length tends to infinity.Nevertheless,the performance of their compiled code would suffers a loss and couldn't reach the ideal state if the code length is limited.Besides,the pure channel coding techniques often improve the system reliability at the cost of reducing the system effectiveness.This paper will be studied based on the compiled code principles and coding modulation techniques for polarised codes against to these limitations and challenges.In order to improve the accessibility of Shannon's channel capacity and the effectiveness of the decoding algorithm under the limited code length,the paper will study the coding by optimizing the polarization code decoding algorithm.The coding technique is also designed jointly with the higher-order modulation technique to improve the overall BER performance of the communication system.The main research includes the following three aspects:1.Research on the polarization coding construction method of the polarization code and the channel polarization phenomenon.The coding structure is mainly carried out by three reliability estimation methods of the polarization code,which are the Bach parameter method,the density evolution method and the Gaussian approximation method.After analyzing the channel polarization phenomenon,the result shows that when the code length of the polarization code is long enough,the channel capacity will show a trend of polarization.2.After studying and analyzing the polarization code decoding algorithm,the PB-SCL(Prune Branch,PB)decoding algorithm is proposed to optimize the pruning of SCL(Successive Cancellation List,SCL)decoding algorithm.The SCL decoding algorithm,the CA-SCL decoding algorithm and the BP(Belief Propagation,BP)decoding algorithm are studied based on the SC(Successive Cancellation,SC)decoding algorithm.The effects of different code lengths and rates on the performance of the polarisation code decoding algorithms are analysed by simulation,and the decoding performance of several different polarisation code decoding methods is compared.The simulation results show that the PB-SCL decoding algorithm with optimised pruning has comparable performance than the traditional SCL decoding algorithm,but reduces its decoding complexity.3.The polarisation code is designed in conjunction with Bit Interleaved Coded Modulation(BICM)technology and the polarisation code decoding algorithm is applied to the BICM coded modulation system of the polarisation code.The modulation method of BICM coding modulation system adopts the modulation method of QPSK and 16-QAM based on Gray mapping.The effect on the performance of the polarisation code is compared by simulation with and without the BICM coded modulation system scheme.The results show that the BICM modulation system based on polarisation codes has better BER performance than the polarisation codes without the BICM coding modulation system scheme.