User-pairing in NOMA Uplink networks under Secrecy Constraints

To enhance the sum secrecy rate of uplink networks, we propose the use of full-duplex transmission and wiretap coding in conjunction with NOMA. In further detail, in this paper we investigate the secrecy rates and provide closed-form expressions for the secrecy outage probability in a full-duplex two-user NOMA uplink network. We derive the optimal power allocation that maximizes the sum secrecy rate while guaranteeing to each user a target secrecy rate. Numerical results show that the proposed power allocation guarantees zero secrecy outage probability to both users, provided that the two users are paired so that the distance between the users exceeds a certain threshold.