Harvested Energy Maximization for Secure Full-Duplex Multi-User MIMO Networks with Non-linear Energy Harvesting

This paper is concerned with secure communication in multiuser full-duplex (FD) communication systems with simultaneous wireless information and power transfer (SWIPT). In the considered system, an FD base station (BS) equipped with multiple antennas communicate with both uplink users (ULUs) and downlink users (DLUs) at the same time and in the same frequency while the set of energy harvesters can scavenge energy from ambient radio frequency signals. To keep the uplink and downlink information signals confidential from the energy harvesters which can be potential eavesdroppers and to optimize the harvested energy, we aim at designing the precoders and the transmit artificial noise covariance at the BS and the transmit precoders at ULUs to maximize the harvested energy subject to the constraints of the required minimum quality of service (QoS) and transmit power at the transmitters. Due to high nonconvexity and nonlinearity of the formulated design problem, we develop an iterative algorithm based on successive convex programming (SCP) by seeking appropriate surrogate functions to recast the original optimization problems into convex optimization ones. Then, the simulation results are conducted to evaluate the system performance in terms of the sum harvested energy for different system setups.