Cooperative NOMA with Joint User and Relay Selection

A Non Orthogonal Multiple Access (NOMA) system with cooperative user relaying is an effective way to improve the spectral efficiency and reliability of the network. This paper considers a multiuser downlink scenario, where users are supported on the basis of power domain NOMA and can alternatively act as relays to provide cooperation in the network. Joint user and relay selection has been considered to identify the two destinations to be served as a NOMA pair, and a probable relay node from among the available users or nodes in the network. The outage performance of the system under two different relay selection schemes viz. Partial Relay Selection (PRS) and Optimal Relay Selection (ORS) have been considered along with the proposed user selection scheme and the same have been verified by Monte Carlo simulations.