Physical Layer Security Methods For Simultaneous Wireless Information And Power Transfer Systems

Recently,the exponential growth in the demand for high data rates in wireless communication networks has led to a tremendous need for energy.The rapidly escalated energy consumption not only increases the operating cost of communication systems,but also raises serious environmental concerns.As a result,green radio communications have received much attention in both academia and industry.However,mobile communication devices are typically powered by batteries with limited capacity.Hence,the lifetime of mobile communication devices has become the bottleneck in the development of wireless communication services.Simultaneous wireless information and power transfer based on radio frequency signals provides an alternative to traditional battery powered technologies.It is an effective way to solve or prolong the network survival time.Meanwhile,because of the broadcast nature of radio propagation and the inherent randomness of wireless channel,the legal signals transmitted in simultaneous wireless information and power transfer systems are vulnerable to be wiretapped by malicious receivers.Therefore,physical layer security methods for simultaneous wireless information and power transfer systems are considered in this paper.Specifically,this paper mainly proposes the following two schemes:Firstly,considering the problem of physical layer secure communication for multiple-input multiple-output multi-antenna-eavesdropper downlink channel in simultaneous wireless information and power transfer systems,an artificial noise-aided beamforming design scheme is proposed in this paper.After giving the system model for the proposed scheme,the optimization problem aiming at maximizing the transmission rate of the receiver is established under the conditions that power constraint at the transmitter,energy collection threshold at the receiver and the information leakage control requirement at the eavesdropper are satisfied.By using minimum mean squared error method and successive convex approximation method,the nonconvex problem is transformed into two convex subproblems which could be solved by second order cone programming.Then an iterative algorithm is proposed to solve the original problem.The secure communication effectiveness of the proposed scheme is verified by simulation results.Secondly,considering a secure simultaneous wireless information and power transfer system with multiple intermediate nodes and an eavesdropper,this paper presents a power allocation scheme based on joint cooperative relaying and cooperative jamming.The details of the scheme are as follows: the intermediate nodes which can successfully decode the source signals act as the relays,and forward the decoded information to the intended receiver after beamforming;meanwhile,the remaining nodes act as the friendly jammers,and send artificial noise to confuse the eavesdropper after converting the received signals into available energy.The system's security rate can be maximized by jointly optimizing the transmit power of the transmitter,the relays and the jammers with the constraints that the total power constraint,the received signals to interference plus noise ratio threshold at the relays and energy threshold at the jammers are satisfied.The closed-form optimal transmit power of the proposed scheme is deduced by mathematical methods.Finally,the simulation results and performance analyses of this scheme are given.