UAV-Mounted Multi-Functional RIS for Combating Eavesdropping in Wireless Networks

In this letter, we propose an unmanned aerial vehicle (UAV)-mounted multi-functional reconfigurable intelligent surface (MF-RIS) to combat an eavesdropping attack. The proposed UAV-mounted MF-RIS is capable of reflecting and amplifying the desired signal, and emitting the friendly jamming (i.e., artificial noise) simultaneously. As such, the signal received at the legitimate user is significantly enhanced, while destructive interference is generated at the eavesdropper (Eve). In the presence of multiple Eves, we maximize the secrecy rate by jointly optimizing the transmit beamforming at the base station, the reflection matrix, and the deployment location of MF-RIS. Then, we propose an iterative algorithm to solve this non-convex problem efficiently. Simulation results show that, through the joint design of UAV and RIS architectures, the proposed MF-RIS can effectively combat eavesdropping and achieve more secure communications compared with existing passive or active RISs.