Physical Layer Security Analysis of Cognitive NOMA Internet of Things Networks

The implementation of advanced communication technologies such as nonorthogonal multiple access technologies (NOMA) and cognitive radio (CR) technology 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 article 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 simulations 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.