Outage Probability Analysis of Wireless-powered Full-duplex Cognitive Non-Orthogonal Multiple Access Relaying Systems

In this paper, we consider a non-orthogonal multiple access (NOMA) cognitive relaying system, where a full-duplex (FD) dual-antenna relay assists transmission from an access point (AP) to a cognitive far user, while at the same time, the AP transmits to a cognitive near user. Relay is wirelessly powered from the AP via time switching protocol and then forwards AP's information to the far user. We develop new exact outage probability expressions corresponding to the near and far users. Simulation results demonstrate that the choice of the time-split plays a critical role in determining the FD gains. With higher time-split factor, the outage performance of the far user is improved at low signal-to-noise ratio (SNR) regime, while at the high SNR regime the lower time-split factor yields better outage performance, which is due to the impact of the residual self-interference at the relay.