Secure Precoding Scheme for Full-Duplex MIMO Untrusted Relay Network with Energy Harvesting

In this paper, we propose a novel secure precoding scheme for the full-duplex multiple-input multiple-output (MIMO) untrusted relay network. To ensure security, the source uses a fraction of power to send artificial noise and the destination collaboratively transmits jamming signal with the harvested energy to the relay. Aiming at improving the power efficiency and keeping security simultaneously, we jointly maximize the achievable secrecy rate by optimizing the precoders of the information signal, jamming signal, artificial noise, amplification matrix, and power splitting ratio subject to the power constraints. Furthermore, to make the optimization problem solvable, we propose an iterative algorithm and deal with the non-convex constraints through concave convex procedure (CCCP). Simulation results show that the proposed precoding scheme has significantly improved the secrecy performance and power efficiency compared with the typical direct link (DL) scheme and non-cooperative jamming (No-CJ) scheme.