Joint Trajectory and Power Allocation Design for UAV-assisted Secure Wireless Communications and Energy Harvesting Networks

This paper investigates the joint trajectory and power allocation design for unmanned aerial vehicle (UAV)-aided secure wireless communication and energy harvesting (EH) networks. Specifically, the UAV transmits energy to EH users and confidential messages to one legitimate terrestrial user while mitigating the wiretapping threat posed by an eavesdropper. We aim to jointly design the UAV's trajectory and transmit power to maximize the average secrecy rate at the information user, considering the minimum harvested energy requirement for EH users and the UAV's power budget. The problem is inherently non-convex due to the coupling of design variables in the secrecy rate expression and harvested energy, making it challenging to solve directly. To address this, we provide various convex inner approximations and develop an iterative algorithm based on the sequential convex programming approach. Extensive numerical simulations are conducted to evaluate the system's performance and demonstrate the effectiveness of the proposed algorithm in enhancing the system's secrecy rate. In particular, we analyze the impact of varying time slots and required harvested energy on the UAV's trajectory and secrecy rate. Specifically, our results highlight the superior performance of our proposed algorithm compared to baseline methods such as line segment strategies.