Power Allocation and Initial Access Using PSO for Uplink NOMA mmWave Communications

Abstract

This paper investigates the performance of non-orthogonal multiple access (NOMA) in a 2-user uplink millimeter-wave (mmWave) network. In particular, we consider a scenario where the Base Station (BS) is equipped with an analog beamformer with a single radio-frequency chain and serves two single-antenna NOMA users, without knowledge of the channel state information (CSI) at the BS. As the power allocation inherently intertwines with Initial Access (IA), in this paper, a joint IA and power allocation problem is considered to optimize the achievable sum rate with minimum rate constraint for each user. To solve this non-convex problem, we first solve the IA problem to obtain a sub-optimal beamforming. Then, we achieve the sub-optimal power allocation for a 2-user uplink NOMA network. These optimization problems are solved using Particle Swarm Optimization (PSO). Extensive performance evaluations are conducted to compare the achievable sum rates of the NOMA and OMA systems. Results show that the performance of the NOMA system with the proposed sub-optimal solution is better than the OMA system and achieves near-ideal sum rate performance.