Securing UAV Communication with Mobile UAV Eavesdroppers: Joint Trajectory and Communication Design

This paper investigates an unmanned aerial vehicle (UAV)-enabled secure communication system, where ground users (GUs) send confidential information to a UAV by time division multiple access (TDMA) in the presence of a potential mobile UAV eavesdropper. The mobile UAV eavesdropper is performing other task periodically in the same area. Our goal is to maximize the minimum average secrecy rate among all GUs by jointly optimizing the UAV trajectory, transmit power control and user scheduling. To tackle the non-convex problem, we firstly transform it into a more tractable form. Then, we propose an efficient algorithm based on block coordinate descent and successive convex approximation techniques to solve the problem. Furthermore, considering the mobility of the eavesdropper, we propose a new and low-complexity method to design the initial trajectory. Numerical results validated the superior performance of our proposed design against other benchmark schemes based on hover-and-fly trajectory.