Cognitive Radio-Inspired NOMA Relaying Networks with Imperfect CSI over Nakagami-m Fading

This paper investigates a cognitive radio-inspired NOMA (CR-NOMA) decode-and-forward (DF) relaying network with imperfect channel state information, and a joint relay and antenna selection strategy is designed to improve the transmission reliability. Exact expression for the outage probability is derived in closed-form. Moreover, the asymptotic outage expression and the existence of error floor (EF) which is caused by channel estimation error are also obtained in high SNR region. Finally, simulation results demonstrate the superiority of CR-NOMA in outage performance over that of NOMA with fixed power allocation (F-NOMA). Compared with orthogonal multiple access, NOMA can achieve a lower outage probability and user fairness.