Secrecy Outage Probability of Reconfigurable Intelligent Surface-Aided Cooperative Underlay Cognitive Radio Network Communications

With the introduction of wireless communications in a diverse range of security-sensitive scenarios such as healthcare, Smart Cities, internet-of-things (IoT) infrastructure, nuclear power plants, so forth, it has become necessary to protect the wireless network against malicious eavesdroppers via physical layer security (PLS). We analyze and study the impact of an eavesdropper located in an underlay cooperative cognitive radio network (CRN). A reconfigurable intelligent surface is used to improve the secrecy outage probability of the proposed system. CRs resolve spectrum scarcity by enabling spectrum sharing. On the other hand, RIS is a planar surface device equipped with signal enhancing reflecting elements that enhance signals at desired users and suppress signal power at undesired eavesdroppers in PLS networks. Therefore, the integration of RIS in cooperative underlay CR networks can enable secure wireless communications. To this end, we derive closed-form secrecy outage probability (SOP) expressions for a network that consists of a primary destination, secondary source, secondary user and a passive eavesdropper. The obtained equations are verified via simulation.