Joint relay-and-antenna selection in NOMA relaying networks over Nakagami-m fading channels

In this paper, we design non-orthogonal multiple access (NOMA) for multiple-antenna multiple-relay decode-and-forward (DF) cooperation network. A joint relay-and-antenna selection (JRAS) scheme, which determines the best relay and the best antennas at the source and the users, is proposed to minimize the outage probability. The outage performance of the proposed JRAS scheme is analyzed, and the exact closed-form expression for the outage probability is derived. Furthermore, we also obtain the asymptotic expression for the outage probability in high signal-to-noise ratio (SNR) regime. Finally, the correctness of theoretical analysis and the superiority of the proposed JRAS scheme over conventional max-min-max scheme are verified by simulation results. Meanwhile, compared to orthogonal multiple access (OMA), it is shown that NOMA with the proposed JRAS scheme can achieve a better outage performance.