Non-orthogonal multiple access in full-duplex relaying system with Nakagami-m fading

This study presents a full-duplex (FD) relaying non-orthogonal multiple access (NOMA) scheme with self-interference at relay taken into account, where a sender communicates with multiple terminals simultaneously with the help of an FD amplify-and-forward relay. The relay is equipped with two antennas, one for transmission and the other for reception. Moreover, with a direct link as a useful information transmission link, selection combining is applied to merge the information from the sender and the relay. General closed-form expressions of the outage probability are deduced and the upper bound of the ergodic sum rate is derived, including half-duplex (HD) mode relay as a special case. Compared with the HD relaying scheme, the authors can observe that the FD relaying scheme can achieve higher ergodic sum rate in the moderate- and high-SNR regions and that the outage behaviour can be improved in most cases (if the self-interference is not extremely severe). More importantly, the use of NOMA in FD relaying system is shown to outperform conventional orthogonal multiple access (OMA) network in terms of terminal fairness. Extensive simulation results are presented to confirm their conclusions and provide a significant reference for the system design.