Secrecy-Optimized Resource Allocation for UAV-Assisted Relaying Networks

Unmanned Aerial Vehicles (UAVs) communications have received increasing attention in both military and civilian applications due to low cost and ease of deployment. Security is an unavoidable yet challenging issue during the data transmission process of communication networks. In this paper, we concentrate on the resource allocation in secure relay network assisted by a UAV in the presence of multiple eavesdroppers. Our target is to maximize the secrecy rate by jointly designing the transmit beamformer and artificial noise subject to the transmit power constraint of UAV. The resulting optimization problem is highly intractable and the key observation is that the original optimization problem can be equivalently transformed into a two- level problem. In particular, the inner-level problem can be solved by exploiting Semi-Definite Relaxation (SDR) and Charnes-Cooper transformation techniques, and the outer-level problem is handled by performing one-dimensional algorithm. Also, the tightness of the rank-relaxation is analyzed. Finally, simulation results are provided to validate the performance of our proposed scheme.