Joint Single- and Multi-Beam Angle-Domain NOMA for Hybrid MmWave MIMO Systems

In this paper, we propose a joint single-beam (SB) and multi-beam (MB) non-orthogonal multiple access (NOMA) scheme with limited feedback for the hybrid millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems. This scheme provides combined advantages with respect to the previous works: i) hybrid beamforming to restrain the number of radio-frequency chains, ii) joint SB- and MB-NOMA to benefit from NOMA multi-user diversity, whatever the load of the cell and the users’ position are, iii) limited feedback, with the only knowledge of users’ angle information. Specifically, we propose two schemes: the former gives a significant sumrate performance compared to digital beamforming, while the latter reduces the number of active radio-frequency chains, i.e., the energy consumption. Meanwhile, we develop a lowcomplex two-stage user grouping strategy by exploiting the joint potential of SB- and MB-NOMA schemes according to the users’ angle. Numerical results verify the performance of the proposed schemes using the stochastic mmWave channel model NYUSIM from New York University.