Optimal secure transmit design for wireless information and power transfer in V2X vehicular communication systems

Simultaneous wireless information and power transfer (SWIPT) in vehicle to everything networks is a perspective technology which helps prolong the lifetime of sensors installed on roadside devices and vehicles. In this study, we consider a secure vehicular communication system with SWIPT under a non-linear EH model where the energy vehicular receivers 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 energy vehicular users. In addition, the considered optimization problem also considers different quality of service requirements: a maximum tolerable capacity at energy vehicular receivers and a minimum needed signal-to-interference-ratio at information vehicular 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. To decrease calculational complexity, we also propose a suboptimal secure beamforming scheme for facilitating wireless energy transfer and providing physical layer security. Simulation results indicate that the developed secure transmit signal algorithm can obtain better performance gains than other algorithms.