Adaptive Cooperative NOMA with Energy Harvesting

In the two-user non-orthogonal multiple access (NOMA) networks, the transmission requirements of weak-user are sometimes not satisfied. To solve the issue, we propose a novel adaptive cooperative NOMA protocol to facilitate the information transfer of weak-user. In the protocol, base station (BS) can adaptively adjust the working mode of the networks according the requirement of the weak-user. Specifically, if the direct-link capacity can meet the transmission demand of weak-user, the networks operates in the traditional NOMA protocol. If the direct-link capacity cannot accomplish the information transfer of weak-user, strong-user, as a full-duplex (FD) relay, captures energy from the received signals to relay weak-user's messages guaranteeing its own transmission requirement. Under the protocol, the outage probabilities of two users are characterized and their closed-form expressions are derived to evaluate the reliability of the networks. Finally, numerical results are provided to validate the superiority of our proposed scheme.