Aerial Reconfigurable Intelligent Surfaces-Enabled Secured Wireless Communications: Performance Analysis and Optimization

Integrating aerial reconfigurable intelligent surfaces (ARIS) with unmanned aerial vehicles (UAVs) presents a significant opportunity to enhance the performance of wireless networks. This integration allows ARIS to be mounted on UAVs, providing greater configuration flexibility, establishing reliable air-ground connections, and enabling three-dimensional signal reflections. However, this integration also introduces unique challenges related to physical layer security (PLS). Addressing these security considerations is essential, given the significance of secure and reliable communication. In this paper, we investigate the PLS for ARIS to assist wireless communication systems. Our objective is to select the ARIS that maximizes the secrecy capacity of the proposed system model. Two selection approaches are considered, namely, optimal and sub-optimal ARIS selection, and analytical expressions for the secrecy outage probability and probability of non-zero secrecy capacity over Nakagami-m fading channels are derived. Additionally, we examine the impact of varying the number of UAVs and the locations of the eavesdropper in practical scenarios. Moreover, the collaborative scenario is investigated, where all UAVs cooperate to improve secrecy transmission. Each ARIS reflects identical copies of the transmitted signal on the same time-frequency channel without mutual interference. The optimization problem of UAV locations and RIS phase shifts to maximize the secrecy capacity under specific constraints is formulated and addressed using an improved particle swarm optimization technique. These scenarios highlight the potential of ARIS in achieving secure and efficient wireless communications. Simulation results verify the analytical derivations, highlighting the critical role of selecting the ARIS in enhancing secrecy performance. As revealed by simulations, doubling the number of UAVs leads to a notable improvement in the average secrecy rate by approximately 77.78%. The obtained results highlight the significance of the proposed ARIS-assisted system in enhancing the PLS for wireless communications.