Near capacity LDPC coded MU-BICM-ID for 5G

In 5th generation (5G) wireless communication networks, non-orthogonal multiple access (NOMA) is a key technique for supporting massive connectivity and high spectral efficiency. In NOMA systems, the signals sent by multiple users are superimposed at the receiver, which is a multiple access channel (MAC) in information-theoretic perspective. In this paper, we propose near-capacity multi-user bit-interleaved coded modulation with iterative demapping (MU-BICM-ID) scheme for two-user Gaussian multiple-access channel (GMAC), especially for high spectral efficiency scenarios. To retrieve the shaping loss, we suggest to use amplitude phase shift keying (APSK) constellation instead of conventional quadrature amplitude modulation (QAM) constellation. Furthermore, we disclose the fact that the low-density parity-check (LDPC) code optimized for point-to-point is not suitable for GMAC, and therefore we propose and optimize Raptor-like LDPC code for GMAC. Via extrinsic information transfer (EXIT) chart analysis as well as bit-error rate (BER) simulation, we illustrate the near-capacity performance of the proposed scheme.