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Design of Nested QC-LDPC Codes for Compute-Forward Multiple Access

Compute-forward multiple access (CFMA) is a new-type multiple-access technique in recent years, whose most significant advantage is that it can achieve the whole capacity region of the multiple-access channel (MAC) without time sharing or rate splitting. In this work, we propose a modified protograph-based extrinsic information transfer (P- EXIT) technique to analyse and optimize the iterative decoding performances of quasi-cyclic low density parity check (QC-LDPC) codes in CFMA. In addition, a kind of extending technique is designed to construct nested QC-LDPC codes for CFMA. The simulation results show that the nested QC-LDPC codes constructed by our method work efficiently in CFMA system and have a gap of 1.186dB from Shannon Bound at bit error rate of 10-6.