Minimum transmit power NOMA beamforming for millimeter-wave communications

© 2017 IEEE. In order to improve the spectral efficiency of downlink in a multiuser system, nonorthogonal multiple access (NOMA) has been extensively studied for 5th generation (5G) systems. NOMA allows a group of users to share a given channel by exploiting the power difference. Since downlink multiuser beamforming can also be used to support multiple users for a given channel, in this paper, we combine NOMA and downlink beamforming for a millimeter (mm)-wave multiuser system. Since the performances of NOMA and downlink beamforming depend on the channel conditions, we consider a problem formulation that incorporates NOMA in multiuser beamforming selectively depending on the channel conditions. As a result, we can have NOMA beamforming that can outperform conventional beamforming for mm-wave channels.