Beam Selection Method Based on Angle-Domain Adaptive Beam Grouping for Massive MIMO Analog Beamforming Using NOMA in Cellular Downlink

This paper investigates a beam selection method for the downlink massive multiple-input multiple-output (mMIMO) analog beamforming (BF) with non-orthogonal multiple access (NOMA) based on intra-beam superposition coding. The purpose of this study is to select a set of beams that have low mutual inter-beam interference and high NOMA gain by non-orthogonal multiplexing multiple users within each of the beams based only on the limited signal-to-noise power ratio (SNR) feedback of the best beam from each user which is assumed in 5G NR. The proposed method is based on our previously reported beam selection method using the angle-domain beam grouping (ADG), which utilizes a beam group that contains multiple neighboring-angle beams. The proposed ADG adaptively controls the configuration of beam groups so that the number of users reported the SNR for the edge beam of the beam group is minimized. This brings about a further reduction of inter-beam interference and an increase in the NOMA effect. Computer simulation results show that the proposed adaptive ADG improves the system-level throughput compared to the conventional methods.