Secure Beamforming for Full-Duplex Wireless Powered Communication Systems With Self-Energy Recycling

In this letter, we study a novel multi-antenna wireless powered communication (WPC) system consisting of an energy source (ES), a full-duplex self-energy recycling information source (IS), an information receiver (IR), and an energy receiver (ER) (potential eavesdropper). The energy-constrained IS, powered by ES, sends the confidential information to IR over the wiretap channel. Our goal is to maximize the secrecy rate for IR by jointly optimizing the energy and information beamforming vectors, under the constraints of the transmit power at ES and IS and the harvested energy at ER. To solve the formulated non-convex problem, a partial Lagrange dual method coupled with two-stage optimization method is proposed, which derives the optimal solution in semi-closed form. Numerical results show the superiority of our proposed design compared with the existing schemes.