A General Framework and Novel Transceiver Architecture Based on Hybrid Beamforming for NOMA in Massive MIMO Channels

Abstract

In this paper, a generic user-grouping based hybrid beamforming framework for mm-wave massive MIMO systems with code domain non-orthogonal multiple access (NOMA), which is considered as an intra-group process, is proposed. It is shown that message passing algorithm (MPA) for decoding sparse code multiple access (SCMA) can be directly applied in this framework without additional complexity. While classical multi-user shared access (MUSA) receiver is adapted for downlink, a novel receiver architecture which is an improvement over classical one is proposed for uplink MUSA. This receiver makes MUSA preferable over SCMA for uplink transmission with lower complexity. In addition, simulation results showed that code domain NOMA methods outperform conventional methods where users are spatially close to each other and number of radio frequency (RF) chains at the base station (BS) is very limited.