Average Transmit Power Analysis and User Clustering Design of Downlink Multi-Antenna NOMA with Matched Filter Beamforming

Abstract

Non-orthogonal multiple access (NOMA) in power domain is considered as a candidate technique in the next generation mobile networks as it can improve the spectral efficiency, the number of connected devices and user fairness compared to traditional orthogonal multiple access (OMA) techniques. In this thesis we analyze the average transmit power in downlink multi-antenna NOMA systems with two-user clusters where the signal-to-interference-plus-noise-ratios (SINRs) for all users are guaranteed. For systems with a single cluster, a modified NOMA scheme based on the threshold on the alignment of channel directions is proposed to save the transmit power and theoretical analysis in terms of the average transmit power is conducted to demonstrate the superiority of our proposed scheme compared to the original NOMA scheme. To further improve the alignment-based NOMA scheme, a hybrid of NOMA and multi-user beamforming is also proposed. In addition, for systems with more than two users, user clustering algorithms are developed to group the users into multiple two-user clusters with respect to the minimization of the total transmit power. Simulation results validate the correctness of our theoretical results and demonstrate the performance improvement brought by the clustering algorithms.