Physical layer security in RIS-aided communication systems: Secrecy performance analyses

In this work, the secrecy performance of a novel reconfigurable intelligent surface (RIS)-assisted wireless communication system is investigated in the presence of an eavesdropper. This study is realized to characterize the privacy performance for the case where a single antenna base station (BS) sends confidential information to a single antenna legitimate user via RIS with the existence of a single antenna eavesdropper in urban wireless networks. In particular, new average secrecy capacity and approximate secrecy capacity expressions are derived. The secrecy outage probability (SOP) scenario for a legitimate user receiver and single antenna eavesdropper is further examined. Finally, the asymptotic SOP analysis is also conducted to obtain insights for the considered system model. Additionally, the impact of imperfect channel state information, a crucial factor in practical RISaided systems, on the achievable secrecy performance is also considered. It is verified that the analytical results are consistent with the simulations, which confirm the accuracy of the derived closed-form equations. It can be observed from the extensive simulation results that increasing the number of RIS elements improves both the average secrecy capacity and the SOP performance.