Resources optimization for secure transmission in wireless powered communication networks

This paper studies the secrecy communication on wireless powered communication network (WPCN) in an orthogonal frequency division multiplexing (OFDM) system, where an energy harvest (EH) user sends confidential information to the hybrid access point (HAP) in the presence of a potential eavesdropper. We introduce a wireless powered cooperative jammer to improve the secrecy performance of this system. For the user and the jammer, we both consider the linear energy harvesting model and the nonlinear energy harvesting model. More specifically, the half-duplex WPCN is considered first. We study secrecy rate maximization problem by jointly optimizing the time allocation and the transmit power allocation for the HAP, the jammer and the user over sub-carriers. The nested form algorithm is proposed to solve the original non-convex problem, where one-dimension search method is used at the outer layer and a convex approximation algorithm by leveraging DC-based optimization is adopted at the inner layer. Then, the full-duplex WPCN is considered. We formulated the secrecy rate maximization problem and optimized the transmit power by using the DC algorithm and convex optimization. Simulation results demonstrate that the proposed scheme dramatically enhances the secrecy rate compared to the benchmark schemes.