Physical Layer Security Analysis of Cognitive NOMA Internet of Things Networks

—The implementation of advanced communication technologies such as non-orthogonal multiple access technologies (NOMA) and cognitive radio technology (CR) in the Internet of Things (IoT) networks facilitates wide bandwidth, massive access and low latency. However, the development and deployment of IoT systems are hampered by network security issues. Physical layer security (PLS) is an emerging technique to complement and signiﬁcantly improve communication security in wireless networks. This paper analyses the PLS performance of cooperative NOMA cognitive wireless networks. Furthermore, a cognitive collaboration method is proposed, combining legitimate links and eavesdropping links. More speciﬁcally, new closed expressions of the outage probability (OP) of the primary user (PU) and secondary users (SUs), as well as the intercept probability (IP) of an eavesdropper (E), are derived to evaluate the proposed scheme’s PLS transmission performance. Monte Carlo simu-lations verify the analysis. The results show the SU selection scheme incorporated with the eavesdropping link can slightly improve the security performance compared with the legitimate link. It can also be obtained that increasing the transmit power and increasing the number of SUs could enhance the security performance of PU and SUs.