Incremental Relaying with Partial Relay Selection for Enhancing the Performance of Underlay Cognitive NOMA Networks

In this paper, we consider an underlay cognitive non-orthogonal multiple access (CNOMA) network, where incremental relaying with partial relay selection (PRS) scheme (i.e., IRP scheme) is proposed for the secondary network. We derive analytical expressions for the outage probabilities of the secondary users (SUs) and the system throughput of the IRP-CNOMA network. The proposed approach is compared to conventional cooperative relaying-based CNOMA (CR-CNOMA) networks with PRS scheme (i.e., CRP-CNOMA) and random relay selection (RRS) scheme. The results show that the proposed scheme significantly lowers the outage probability of the SUs while improving the system throughput.