Reflections in the Sky: Joint Trajectory and Passive Beamforming Design for Secure UAV Networks with Reconfigurable Intelligent Surface

TL;DR

This paper proposes a joint optimization framework for UAV trajectory, RIS phase shifts, and power control to maximize secure energy efficiency in RIS-assisted UAV communication systems, demonstrating significant performance gains.

Contribution

It introduces an iterative algorithm combining SCA and simplified schemes for joint optimization, advancing secure UAV network design with RIS technology.

Findings

Secure energy efficiency improved by up to 38%

Proposed algorithm converges rapidly

Significant gains over traditional schemes without RIS

Abstract

This paper investigates the problem of secure energy efficiency maximization for a reconfigurable intelligent surface (RIS) assisted uplink wireless communication system, where an unmanned aerial vehicle (UAV) equipped with an RIS works as a mobile relay between the base station (BS) and a group of users. We focus on maximizing the secure energy efficiency of the system via jointly optimizing the UAV's trajectory, the RIS's phase shift, users' association and transmit power. To tackle this problem, we divide the original problem into three sub-problems, and propose an efficient iterative algorithm. In particular, the successive convex approximation method (SCA) is applied to solve the nonconvex UAV trajectory, the RIS's phase shift, and transmit power optimization sub-problems. We further provide two schemes to simplify the solution of phase and trajectory sub-problem. Simulation results demonstrate that the proposed algorithm converges fast, and the proposed design can enhance the secure energy efficiency by up to 38\% gains, as compared to the traditional schemes without any RIS.