Low complexity multi-level NB-QC-LDPC coded modulation scheme for optical communication systems
Dongdong Wang, Chenhua Sun, Liqian Wang, Xue Chen, Yantao Guo, Guannan Jia, Yong Li, Yan Wang ยท 2019
In this paper, we propose a multi-level non-binary quasi-cyclic low density parity check (NB-QC-LDPC) coded modulation (CM) scheme to reduce the decoding complexity while maintaining and/or exceeding the super BER performance of the traditional NB-QC-LDPC CM scheme. Firstly, local optimal searching combined with the classical superposition construction is proposed to construct the required NB-QC-LDPC codes with possibly enlarged girth and less number of the shortest cycles. Secondly, by analyzing the changing trend of the BER performance and decoding complexity of the NB-QC-LDPC code defined over ๐บ๐น(๐) incident to ๐. We find that the decoding complexity increases proportionally with the increase of ๐, but the best BER performance usually corresponds to a smaller ๐. Finally, by replacing the high-order NB-QC-LDPC code based CM scheme to the multi-level low-order NB-QC-LDPC code based CM scheme, the decoding complexity can be effectively reduced. Simulation results show that the designed two-level ๐บ๐น(4)/๐บ๐น(8) QC-LDPC code based 16QAM/64QAM CM system can perform almost the same or even better BER performance with/than the corresponding traditional ๐บ๐น(16) / ๐บ๐น(64) QC-LDPC code based 16QAM/64QAM CM system.