Joint robust 3D trajectory and communication design for dual-UAV enabled secure communications in probabilistic LoS channel

Abstract

This paper considers a dual-unmanned aerial vehicle (UAV) enabled secure communication system under the probabilistic line-of-sight (LoS) channel model. Specifically, one UAV transmits confidential information to multiple ground nodes while the other UAV cooperatively sends jamming signals to confuse a potential ground eavesdropper. We maximize the minimum worst-case average (expected) secrecy rate of the considered system, by jointly optimizing the communication scheduling, robust three-dimensional (3D) trajectories, transmit/jamming powers of both the UAVs for a given flight duration. However, the formulated problem is difficult to obtain a globally optimal solution due to the imperfect location information of the eavesdropper and its non-convex constraints. As such, we first derive an approximated (expected) secrecy rate with high accuracy, based on which we solve it by applying the block coordinate descent and successive convex approximation techniques to obtain its suboptimal solution. Simulation results show that the superiority of the proposed algorithm in urban environments, compared to other benchmarks.