Secrecy Energy Efficiency Optimization in AN-Aided MISO System with Energy Harvesting

This paper investigates secrecy energy efficiency (SEE) optimization problem for simultaneous wireless information and power transfer (SWIPT) in a multiple-input singleoutput (MISO) downlink system, in which the legitimate user (LU) exploits power splitting (PS) scheme for information decoding (ID) and energy harvesting (EH) simultaneously. In order to prevent eavesdroppers from disturbing the reception of the legitimate user, BS also emits artificial noise (AN). The objective is to maximize SEE by jointly optimizing the confidential signal power, AN power and PS ratio while guaranteeing the secrecy rate, maximum transmitted power and minimum harvested energy constraints. The problem is nonconvex and hard to solve, we first convert it into an easier subtractive form, and then propose an effective two-stage algorithm. Numerical results illustrate the efficiency of the algorithm and the benefits of AN in enhancing the SEE performance.