Utilization of Max-Min User Relay in Cooperative NOMA Systems

Abstract

Non-orthogonal multiple access (NOMA) has been focused to increase system capacity and spectral efficiency for the fifth generation (5G) mobile networks. In order to improve the performance of the NOMA systems with successive interference cancellation (SIC), a max-min user relay assisted cooperative NOMA scheme is investigated in this paper. The derived closed-form expression for outage probability is verified through Monte Carlo simulation results. We found that the performance with max-min relay outperforms the random relay. It is also shown that the performance of the destination user (DU) improves with the power allocation coefficient of DU. However, we noticed that there is an optimal value to minimize the outage probability of the relay-user (RU).