Optimal Beamforming Design for Information and Power Transmission in the Presence of Eavesdroppers

Abstract

This paper considers a MISO simultaneous wireless information and power transfer system in which a transmitter sends information and power simultaneously to a legitimate receiver in the presence of many eavesdroppers. The receiver adopts power splitting scheme so that it decodes information and harvests energy at the same time. We formulate the two equivalent optimization problems—the transmit power minimization problem under SINR and required harvested energy constraints and the secrecy rate maximization problem under total transmit power and harvested energy constraints. We apply the semidefinite relaxation technique to obtain the optimal beamforming vectors and prove that the relaxation is tight. We show that optimizing the eavesdropper SINR threshold is necessary to minimize the total power consumption. We also present the optimal robust beamforming design based on the S-Procedure in uncertain channel cases.