UAV-Mounted RIS-Assisted Legitimate Surveillance Over Maritime Low-Altitude Communication Networks

This paper considers a challenging maritime lowaltitude surveillance issue, in which, a legitimate monitor UAV intends to overhear a suspicious UAV-vessel link with the help of a jammer UAV.Both the suspicious receiver has the jamming detection ability and the jammer UAV is energy-constrained.To address these challenges, we propose a novel UAV-mounted reconfigurable intelligent surface (RIS) assisted approach, where the RIS is deployed on the jammer UAV to create an additional surveillance channel towards the legitimate UAV.Furthermore, the jammer UAV can also intelligently adjust its power allocation and flight trajectory to covertly disturb the suspicious transmission with the detection thresholds and the energy budgets.In such a setup, we consider a sum eavesdropping rate maximization problem of the legitimate UAV during all time slots.This formulated problem is solved by jointly optimizing the threedimensional (3D) trajectory of the legitimate UAV, the reflecting phase shifts of the RIS, as well as the 3D trajectory and jamming power of the jammer UAV under the mobility, covertness, and power limitation constraints.We decompose the non-convex design problem into three subproblems and propose an iterative algorithm to find its approximated optimal solution by using the block coordinate descent method.In each iteration, we utilize the successive convex approximation and phase alignment techniques to handle these subproblems.Numerical simulation results are provided to validate the effectiveness and tremendous potential of UAV-mounted RIS in the maritime low-altitude surveillance.