Secrecy performance of an uplink-downlink cooperative PD-NOMA DF network in PLS

Abstract

In this paper, we investigate the secrecy performance of an uplink-downlink power domain non-orthogonal multiple access (PD-NOMA) system with imperfect successive interference cancellation (SIC) in physical layer security (PLS). In the proposed system, two source users (SUs) communicate with two destination users (DUs) with the help of a cluster of multi-relay nodes using the decode-and-forward (DF) protocol in the presence of multi-eavesdroppers. These eavesdroppers try to overhear the wireless signal around the DUs. In our system, the selected DF-relay node also works as a jammer to improve security and protect confidential information from multi-eavesdroppers. In this role, the DF-relay node generates a jamming signal, creating artificial interference to reduce the quality of the eavesdropping channels. To evaluate the secrecy performance of the system, we derived the analytical expressions of the secrecy outage probability (SOP) for both DUs using three relay selection strategies over Rayleigh fading channels and used Monte Carlo simulations to confirm the accuracy of our calculations. Furthermore, we examined the effects of system parameters such as the number of eavesdroppers and DF relaying nodes, the power allocation, SIC performance, the position of eavesdropper on the SOP of the two DUs. We compared the performance of our proposed NOMA system with those of conventional orthogonal multiple access (OMA) schemes.