Outage probability of energy harvesting cooperative NOMA network with direct link

Abstract

Abstract In this study, we examine the dependability of a cooperative non-orthogonal multiple access (NOMA) network, where the source and relay nodes harvest energy from a power beacon. The source node transmits information directly to the near user via a direct link and to the far user via either a direct or relay-assisted link. The relay node forwards the signal to the far user and simultaneously transmits the signal it generates as a reward to the destination node using NOMA. When the direct connection between the source and the far user fails to be formed, the far user can only receive the signal transmitted via the relay-assisted link, otherwise, the far user merges the two replicas received from the direct and relay-assisted links by selecting combining (SC) or maximal ratio combining (MRC). An incremental cooperative NOMA scheme is proposed to further enhance the performance of the far user. In this approach, the far user adaptively switches between NOMA and orthogonal multiple access (OMA) based on the quality of its direct channel to the source. Explicit expressions for the outage probabilities of the near user, far user, and destination node are derived under Rayleigh fading channel conditions. Simulation results validate the theoretical analysis, demonstrating that the proposed incremental cooperative NOMA scheme achieves superior performance. Moreover, the performance of direct transmission schemes employing SC or MRC is significantly improved, thereby ensuring the overall system performance.