RIS-Aided Physical Layer Security Improvement in Underlay Cognitive Radio Networks

Reconfigurable intelligent surface (RIS) technology is considered one of the leading technologies for sixth-generation wireless communication, and it has also been revealed to be effective in enhancing secure and reliable communications. This article investigates using RIS to improve physical layer security and data transmission in underlay cognitive radio networks (CRNs). Because of its capability to control the wireless environment, RIS can enhance the security of the primary network (PN) and increase the reliability of the secondary network (SN) data transmission. This approach is practical and beneficial for both the PN and SN in terms of reliability and security. The study focuses on a scenario where the eavesdropper is passive and uses either selection or maximal ratio combining to combine the signals from the PN. Analytical expressions for the secrecy outage probability and the probability of nonzero secrecy capacity of the PN are derived. Additionally, an expression for the SN outage probability is also provided. The results from simulations and the numerical analysis confirm the benefits of the proposed system model and validate the accuracy of the derived expressions. This work provides valuable insights into the integration of RIS with CRNs and highlights the potential role of RIS in the future of wireless communication systems.