Secure Transmission Design for UAV-Based SWIPT Networks

Due to the higher probability of the existence of LoS links between the transmitter and the UAVs and the broadcast nature of simultaneous wireless and information power transfer. To overcome it, we consider a secure UAV-enabled communication system with SWIPT under a non-linear EH model where the UAVs are able to collect energy from the radio frequency signals as they are idle. We formulate the secure transmit signal design as an optimization problem which aims to maximize the minimum fairness energy power at the UAVs. In addition, the considered optimization problem also considers different quality of service requirements: a maximum tolerable capacity at UAVs and a minimum needed signal-to-interference-ratio at ground information receivers. To obtain a manageable solution, we reexpress the referred problem by variable substitutions and replacing a non-convex constraint with a convex form. Then, we adopt the semidefinite relaxation (SDR) technique to obtain the optimal solution of the original problem. Simulation results indicate that the developed secure transmit signal algorithm can obtain better performance gains than other algorithms.