Joint Optimization of User Scheduling, Flight Path and Power Allocation in a UAV Secure Communication System

In the future network, the data traffic increases rapidly and users’ communication service needs are diversified. The application of unmanned aerial vehicles (UAVs) in communication effectively relieves the pressure of ground communication equipment. However, the UAV-assisted communication also faces many challenges. Due to the broadcast and open characteristics of the UAV communication channel in the wireless network, it is easily subject to eavesdropping, so secure and efficient communication is hard to guarantee. In order to improve the security of the UAV communication system, this paper studies the secure communication system of a UAV as a base station to assist wireless network communication. In this system, the UAV, as an airborne mobile base station, transmits confidential information to multiple users on the ground, and there is an eavesdropper around the users. The optimization problem of joint user communication scheduling, UAV flight path, and power allocation is established to maximize the minimum secrecy rate of the system. Considering the constraints of user service quality, UAV flight path, and transmit power, the optimization problem is a nonconvex problem and the solution complexity is extremely high. Therefore, we propose an efficient iterative algorithm, jointly considering the block coordinate descent method and the successive convex approximation technique. Simulation results verify the correctness of the theoretical analysis, and further show that this scheme significantly improves the minimum secrecy rate of the system compared with other benchmark schemes.