Particle Swarm Optimization-Based Power Allocation Scheme for Secrecy Sum Rate Maximization in NOMA with Cooperative Relaying

Abstract

In this paper, we study a particle swarm optimization (PSO)-based power allocation scheme for physical-layer security under downlink non-orthogonal multiple-access (NOMA) with cooperative relaying where a source node communicates directly with a nearby user and with a distant user via decode-and-forward relay. First, we formulate the optimization problem to maximize the secrecy sum rate (SSR) under the constraints of a minimum rate at each user and maximum transmission power at the source and the relay. Then, we stablish the lower and upper boundaries of the variables that need to be optimized, and we derive a solution via the proposed low computational-complexity scheme based on PSO algorithm. Next, we compare the SSR performance of the proposed scheme with two baseline schemes: orthogonal multiple access (OMA) and NOMA without cooperative relaying. Finally, simulation results show that NOMA with cooperative relaying can increase the SSR, compared to OMA and NOMA without cooperative relaying.