Throughput Optimization for Downlink 5G NOMA Systems with Cooperative Relaying

For fifth generation (5G) wireless communication, the non-orthogonal multiple access (NOMA) protocol is one of the most effective medium access control (MAC) protocols to increase cell capacity. NOMA system assigns two-dimensional time-frequency resources for multiple users with very large channel gain differences. This paper uses optimization methods to enhance the performance two-user NOMA systems in downlink scenario. Here, an ON/OFF-full-duplex (ON/OFF -FDR) cooperative relaying scheme is considered. To enhance the performance of the far user, the near user is considered a relay, where full-duplex relaying (FDR) is employed for transmission using NOMA from the base station to a far user. An ON/OFF approach is presented to determine if cooperative relaying is required or not. The scheme's performance is evaluated using the parameters outage probability and sum throughput. Then the sum throughput is optimized using particle swarm optimization (PSO) and real-coded genetic algorithm (RGA) where better results for sum throughput are achieved.