Joint Trajectory and Power Control for Secure Dual-UAV Communications Against Air and Ground Eavesdropping

With the maturity of unmanned aerial vehicle (UAV) technology, UAV plays an important role in communication due to its high mobility. In this paper, we study a dual-UAVs assisted communication system to combat both UAV eavesdropper and multiple eavesdroppers on the ground. Our goal is to maximize the minimum average secrecy rate among all ground users by jointly optimizing the UAV basestation trajectory, auxiliary interference UAV trajectory, transmit power control and user scheduling. To tackle this problem, we propose an efficient algorithm based on successive convex approximation (SCA) and block coordinate descent (BCD) to make the problem approximate convex. Specifically, we consider a more complex scene with eavesdroppers on the ground and in the air, and we adapt the Rician fading channel model with small scale fading and large scale fading for air-to-ground communication, and the free space fading model for air-to-air communication. Compared with the single fading channel model, a more realistic situation is presented. The simulation results show joint design of dual-UAVs can significantly improve the average secrecy rate compared with the single UAV-Aided scheme, and when only ideal line of sight (LoS) fading is considered, the secrecy rate is slightly higher than our proposed scheme. However, if the trajectory of the UAVs considering only LoS is put into our proposed model, the result will be slightly lower than our proposed algorithm.