Physical Layer Security Enhancement With Reconfigurable Intelligent Surface-Aided Networks

Reconfigurable intelligent surface (RIS)-assisted wireless communications have drawn significant attention recently. We study the physical layer security of the downlink RIS-assisted transmission framework for randomly located users in the presence of a multi-antenna eavesdropper. To show the advantages of RIS-assisted networks, we consider two practice scenarios: Communication with and without RIS. In both cases, we apply the stochastic geometry theory to derive the exact probability density function (PDF) and cumulative distribution function (CDF) of the received signal-to-interference-plus-noise ratio. Furthermore, the obtained PDF and CDF are exploited to evaluate important security performance of wireless communication including the secrecy outage probability, the probability of nonzero secrecy capacity, and the average secrecy rate. In order to validate the accuracy of our analytical results, extensive Monte-Carlo simulations are subsequently conducted which provide interesting insights on how the secrecy performance is influenced by various important network parameters. Our results show that compared with the communication scenario without an RIS, the deployment of RIS can improve the performance and enhance the communication security substantially. In particular, the security performance of the system can be significantly improved by increasing the number of reflecting elements equipped in an RIS.