Physical layer security in NOMA-enabled cognitive radio networks

This paper investigates physical layer security (PLS) in nonorthogonal multiple access-enabled (NOMA-enabled) cognitive radio networks (CRNs). Considering an existing eavesdropper, the NOMA-enabled CRNs transfer data with the decode-and-forward (DF) collaborative mode over Nakagami-m channels. To analyze the advantages of NOMA-enabled CRNs in PLS perspective, the secrecy performance is evaluated by the closed-form expressions for connection outage probability (COP), secrecy outage probability (SOP) and effective secrecy throughput (EST). In addition, Monte Carlo simulations are provided to verify the derived analytical results and provide insights into the impact of the parameters on the system performance. We analyze the effect of channel parameter m on the secrecy performance and find that at low SNR, the performance in Nakagami-m channels as channel parameter m = 2 is better than that in Rayleigh channels (m = 1). In the end, we demonstrate that secondary users with NOMA scheme can achieve a higher EST than that with orthogonal multiple access (OMA) scheme.