Exact Achievable Rate Analysis of Opportunistic NOMA-Based Cooperative Relaying over Rayleigh Fading Channels

Investigations have shown that cooperative communication systems using opportunistic non-orthogonal multiple access techniques which involve selection between direct and cooperative non-orthogonal multiple access transmissions provide improved performance with respect to the classical cooperative systems using NOMA. In this paper, a new relaying criterion is proposed for opportunistic non-orthogonal multiple access based cooperative relaying systems and an exact expression for the achievable average rate is derived under independent Rayleigh fading channels. Numerical results confirm that the derived analytical result matches well with the computer simulations and the proposed criterion provides improved performance compared to the existing opportunistic NOMA schemes in the literature.