Ergodic Secrecy Capacity Performance in RIS-Enabled Wireless Communications

In this paper, we investigate the secrecy performance of a secure wireless communication system configured with reconfigurable intelligent surfaces (RIS). In particular, a legitimate source sends its private message to a legitimate destination with the aid of an RIS, while a passive eavesdropper intercepts this private information from both source and RIS. Considering this system setup, we first study the statistical analysis of the instantaneous signal-to-noise ratios (SNRs) at the destination and eavesdropper by exploiting the method of moments. Then, we deduce the closed-form expression of the ergodic secrecy capacity (ESC) over independent and identically distributed Rayleigh fading channels. Further, we provide the asymptotic ESC analysis in the high SNR regime to reveal some insightful information. Using the asymptotic ESC analysis, we also analytically present the impact of number of RIS elements on the ESC performance. Lastly, the analytical findings are corroborated via numerical and simulation studies, and show the impact of various involved parameters on the ESC performance.