RIS-Assisted Secure UAV Communication Scheme Against Active Jamming and Passive Eavesdropping

Unmanned aerial vehicles (UAVs) could acquire strong line-of-sight (LoS) channels for terrestrial nodes, which means UAV communications are more vulnerable to jammers and eavesdroppers. Thanks to the reconfigurable intelligent surface (RIS), it is capable of reconfiguring the propagation environment and has good prospects for forthcoming secure transmission in combination with UAV wireless network. In this paper, we facilitate RIS to aid the uplink communication between the ground user and the UAV in the existence of a malevolent jammer and an eavesdropper by maximizing the average secrecy rate (ASR) of the proposed scheme. In order to achieve this goal, we jointly optimize the transmission power of the ground user, the RIS phase shift, and the trajectory of the UAV. Nevertheless, the proposed problem cannot be solved directly because of the coupled optimization variables and the non-convexity. Consequently, we tackle it by decomposing the original problem into three achievable sub-problems, in which formulated problem could be handled by using alternative optimization, the successive convex approximation, and semidefinite relaxation. Finally, we continuously optimize three variables and iterate over three sub-problems until the ASR converges to a stationary value. Simulation results show that the proposed scheme effectively boost the ASR compared with other baselines.