Research On Joint Coding And Modulation Technology Based On NB-LDPC Code

Joint coding and modulation technology can exchange the complexity of the equipment for higher coding gain without reducing the spectrum efficiency and power efficiency of the communication system,so as to improve the performance of the system.This paper focuses on three research points:low error level and low complexity binary LDPC coding modulation scheme,low complexity multi-level LDPC coding modulation scheme and low complexity probability shaping coding modulation scheme.The specific research contents are as follows.1、Aiming at the problem that the multi-level coding modulation structure using non ideal binary LDPC code as component code is prone to error leveling,this paper proposes a scheme to adjust the component code rate according to the error rate of each subchannel based on the channel capacity criterion.Simulation results show that the proposed scheme can significantly reduce the error level of multi-level coded modulation system,and the coding gain is increased by 0.15dB@BER=1e-6 under 16QAM modulation format.Aiming at the problem that the subchannel interleaving is too complex in the bit interleaving coding modulation structure of highorder modulation format,a simplified interleaving scheme of IQ two-way packet interleaving is proposed in this paper.The simulation results show that the interleaving scale of the proposed scheme in 16QAM modulation format is 17%of that of the traditional scheme,and the coding gain is the same.2、Compared with binary LDPC codes,M-ary LDPC codes have higher coding gain,but also bring higher decoding complexity.In order to reduce the implementation complexity of M-ary LDPC code,a multi-level coding and modulation scheme based on low-order M-ary LDPC code is designed in this paper.The simulation results show that the decoding complexity of the schemes designed in 16QAM and 64QAM modulation formats is 30%and 14%of that of the traditional M-ary LDPC code and modulation order matching schemes respectively,and the coding gain is the same.3、For the 32QAM modulation format,the standard gray mapping cannot be carried out,resulting in the loss of subchannel mutual information in the coded modulation system.The introduction of probability shaping can improve the system capacity.In view of the high decoding complexity of the system in which 32QAM probability shaping module is directly cascaded with GF(32)LDPC code,this paper designs a scheme in which probability shaping is added to the modulation symbol amplitude and the redundant bits of binary LDPC code are added to the symbol bits.The simulation results show that the decoding complexity of the designed scheme is 25%of that of the traditional scheme,and the coding gain is the same.