Beam Design and User Scheduling for Nonorthogonal Multiple Access With Multiple Antennas Based on Pareto Optimality

Abstract

In this paper, the problem of transmit beam design and user scheduling is investigated for multiuser (MU) multiple-input single-output (MISO) nonorthogonal multiple access (NOMA) downlink. First, Pareto-optimal beam design is solved for two-user MISO broadcast channels (BCs) with successive interference cancelation (SIC), and certain properties of Pareto-optimal beam vectors are obtained. Based on this result, a beam design and user scheduling method is proposed for MUMISO NOMA. In the proposed method, simultaneously served users are grouped into multiple clusters with two users in each cluster, and a hierarchical beam structure composed of zero forcing intercluster beamforming and two-user Pareto-optimal intracluster beamforming is applied. The proposed method has the ability to control the rates of strong and weak users and hence provides great flexibility to MU-MISO NOMA operation. In addition, the problem of Pareto-optimal beam design for general M-user MISO BCs with SIC is solved.