On Joint Optimization of Trajectory and Phase Shift for IRS-UAV Assisted Covert Communication Systems

Abstract

In this paper, we propose an unmanned aerial vehicle carrying intelligent reflecting surface (IRS-UAV) as a relaying node to assist covert communication system (CCS). To ensure the security of the covert messages, we derive the minimum error detection probability for the eavesdropper when the locations of the UAV and BS are known. Under the assumption that the eavesdropper can minimize the detection error probability, we then formulate the maximization of the average rate of the proposed IRS-UAV assisted CCS as an optimization problem with respect to the UAVs trajectory and the IRSs phase shift. Furthermore, we use the Taylor's extension to approximate the optimization problem to be convex, and propose an iterative algorithm to solve the convex problem. Numerical results demonstrate that the developed optimization method significantly improves the data rate for IRS-UAV assisted covert communication in comparison with existing algorithms.