Anotace:
In this paper, we consider an unmanned aerial vehicle (UAV)-enabled mobile relaying system consists of a ground control station (GCS), a high-mobility UAV for relaying, a destination, and an eavesdropper. To improve the security of the three-dimension (3D) mobile relaying system with delayed channel state information (CSI), we propose a destination-specific (DS) 3D beamforming scheme and an eavesdropper-null (EN) 3D beamforming scheme, in both the horizontal angle and the vertical angle of antenna pattern are adapted instantaneously. In particular, we study the secrecy rate maximization problem via trajectory planning. However, this problem with mobility constraint and location constraint is a non-convex optimization problem. To solve it, we propose a successive trajectory planning algorithm by optimizing the incremental in each time-slot. Simulation results verify that the 3D beamforming schemes can greatly improve the security of UAV-enabled mobile relaying system and the proposed trajectory planning algorithm is also proven become effective.