Enhanced IDMA with Rate-Compatible Raptor-Like Quasi-Cyclic LDPC Code for 5G

Due to excellent performance and low implementation complexity, raptor-like quasi-cyclic low density parity check (RL-QC-LDPC) codes have been recently selected as the coding scheme of data channel for enhanced mobile broadband applications in the 5th generation (5G) cellular networks. However, for non-orthogonal multiple access (NOMA) schemes with turbo joint decoding, like interleave-division multiple access (IDMA), RL-QC-LDPC codes designed for single-user transmission face the problem of performance degradation. In this paper, the RL-QC- LDPC codes are designed for enhanced IDMA, where the conventional symbol-by-symbol elementary signal estimator is replaced by a symbol-by-symbol maximum a posteriori probability multi-user detector. Moreover, as recommended in 3GPP New Radio study item of channel coding, rate-compatibility is considered for enhanced IDMA, and rate-compatible RL-QC-LDPC code family is designed with the tool of extrinsic information transfer (EXIT) chart. According to EXIT analysis and simulation results, enhanced IDMA with the designed rate-compatible RL- QC-LDPC code family is capable of supporting multiple rates and different numbers of users with near-capacity performance.