Secrecy outage analysis of a NOMA EH network with backhaul connections

In this paper, we investigate the secrecy performance of a non-orthogonal multiple access system (NOMA) using imperfect successive interference cancellation (SIC) in a multiple untrusted energy harvesting (EH) relaying network with unreliable backhaul links. The best transmitter (Tx) and untrusted relay are selected to assist communication between the base station (BS) and destination users. Moreover, the best untrusted relay using the amplify-and-forward (AF) protocol and the power-splitting (PS) architecture works as both a helper that assists in forwarding the received signals from the Tx to destination users and as an eavesdropper that tries to overhear the confidential information. To enhance the secrecy capacity and protect the confidential source data from overhearing of an untrusted relay, the BS sends artificial noise (AN) or jamming signals. Furthermore, in this paper, we consider the imperfect cancelation of the jamming signal at the destination users. To evaluate the secrecy outage performance of users and the overall system, we derive closed-form expressions of the secrecy outage probability (SOP) under Rayleigh fading channels. We also use Monte Carlo simulations to verify the accuracy of the analytical results. The SOP comparison between NOMA and OFDM systems and the influence of various system parameters are analyzed to obtain valuable insights about both systems. (C) 2020 Elsevier B.V. All rights reserved.