Secrecy Performance of Cooperative NOMA System with Multiple Full-Duplex Relays against Non-Colluding/Colluding Eavesdroppers

In 5G and beyond wireless communication networks, non-orthogonal multiple access (NOMA) and Full-Duplex (FD) techniques are considered as promising key techniques. However, the secrecy in NOMA systems has proven to be quite challenging, especially in the presence of multiple eavesdroppers. For this purpose and using the potential of cooperative and FD communication, we investigate the secrecy performance of dual-hop FD Amplify-and-Forward NOMA system. Based on the channel state information of the first hop, partial relay selection (PRS) is performed to determine the best relay. The secrecy outage behaviour of the considered system is studied through deriving closed-form expressions of the secrecy outage probability (SOP) metric for both strong and weak NOMA users under the presence of multiple eavesdroppers in colluding and non-colluding wiretapping scenarios. Numerical results are also provided to verify the derived analytical results.