Joint Design of User Clustering, Beamforming, and Power Allocation for NOMA

Abstract

This paper investigates the application of downlink beamforming along with non-orthogonal multiple access (NOMA) in a multiple-input multiple-output (MIMO) system. The joint design of user clustering, downlink beamforming and power allocation is formulated as a mixed-integer non-linear programming (MINLP) model, aiming to minimize the total transmission power while satisfying quality-of-service (QoS) and power constraints. To tackle this challenging problem, we reformulate it into a more tractable form and conceive a low complexity algorithm based on the penalty dual decomposition technique for its solution. The performance of the proposed NOMA scheme with joint design of user clustering, beamforming and power allocation is validated by means of simulations over millimeter-wave (mmWave) channels. The results show the advantages of the proposed scheme in terms of total transmit power and spectral efficiency over competing multiple access schemes.