Design of Unequal Error Protection LDPC Code in PPM and LDPC Optical Communication System
Jingsong Xiang, Yimiao Wu, Xiaohui Lu, Gaomeng Cha · 2019
In the space optical communication system, the link power loss is large, and the unequal error protection (UEP) scheme can effectively protect more important data in the transmission process and save transmission power. However, the performance of existing unequal error protection LDPC codes used directly in space optical communication systems is not ideal. In this paper, a design scheme of LDPC codes with multilevel unequal error protection performance is proposed for pulse position modulation (PPM) and Low-density parity-check (LDPC) codes iterative demodulation system. The scheme is aimed at maximizing the average variable node degree of each protection level to improve the unequal error protection characteristics of LDPC codes while combining the improved external information in the BICM-ID system extrinsic information transfer(EXIT) method to analyze the convergence threshold of degree distribution and optimize the degree distribution of UEP-LDPC code by iterative linear programming to obtain the minimum threshold and satisfy the unequal error protection characteristics. The simulation results show that the UEP-LDPC code constructed in this paper has improved performance compared with the existing UEP-LDPC code.