Average Power Analysis and User Clustering Design for MISO-NOMA Systems

This paper investigates the power consumption and user-clustering of a multi-cluster multi-input single-output non-orthogonal multiple access (MISO-NOMA) systems. First, we derive the average transmit power of a two-user cluster, given constraints on the signal-to-interference-plus-noise-ratios (SINRs) of users and a threshold on the alignment of channel directions. Then the asymptotic behavior of the average transmit power under several scenarios are studied to show the scaling of the transmit power with respect to the base station (BS) antenna number and the alignment threshold. After that, a two-layer user clustering algorithm is proposed to improve the power efficiency by selecting the head and tail users in each cluster sequentially. Simulation results validate the correctness of our theoretical results. Further, the proposed user-cluster algorithm is shown to achieve significant saving on the transmit power.