Joint design of relay precoding and artificial noise with presence of an eavesdropper

Wireless devices have experienced great development in the past decade. During this period, secrecy studies have drawn heated attention. Traditionally, there mainly exist two methods to optimize secrecy transmissions, precoding scheme and artificial-noise-aided scheme. In this paper, we propose a joint design of precoding and artificial noise in a relay-aided network with the channel state information (CSI) already known. Besides, based on wiretapping knowledge known or not, defined by whether we have known which user is wiretapped, we proposed two different schemes. Simulation results are given to verify the effectiveness of our proposed schemes.