Cooperative NOMA with full-duplex amplify-and-forward relaying

In this paper, we study the performance of a cooperative non-orthogonal multiple access (NOMA) system with a dedicated relay. This relay is full duplex (FD) and works in an amplify-and-forward (AF) mode. Our NOMA system consists of two users where one of them is near to the base station and the other one is assumed to be far from the base station. We derive exact expressions for outage probability and ergodic achievable rate of two NOMA users. The simulations demonstrate that in the case of imperfect self-interference cancelation, our proposed FD-AF relaying scheme has better performance rather than FD decode-and-forward NOMA scheme. In addition, we calculate the outage probability of users in high signal-to-noise ratio (SNR) regime and derive diversity order of unity for each of NOMA users. We show that in high SNRs, the ergodic achievable rate of near user increases with transmit SNR, but the rate of far user tends to a fixed value. Ergodic sum rate expression in high SNR regime shows that it is independent of NOMA power allocation coefficient and increases log-linearly with transmit SNR. Finally, we verify our analytical formulas for outage probability and ergodic achievable rate by Monte Carlo simulations.