Secrecy outage analysis of imperfect MRC in SWIPT systems with a random eavesdropper

Abstract

In this paper, we investigate the secrecy performance of simultaneous wireless information and power transfer (SWIPT) systems in terms of the secrecy outage probability (SOP), where multi-antenna diversity is employed to combat deep fading. In this investigated system, there are three nodes, namely, a source, a destination and an eavesdropper, and the destination and the eavesdropper are equipped with multiple antennas and adopt a maximal ratio combining (MRC) strategy. To reflect real-world conditions, MRC with Gaussian errors is also considered due to the imperfect channel state estimation. The eavesdropper, which is randomly distributed within a 2-dimensional disk area, harvests energy from the transmitted signals from the source to the destination and wiretaps the information from the received signals by using an energy-splitting strategy. Furthermore, we derive the closed-form expression of the SOP, along with the corresponding asymptotic SOP, to show the diversity order and array gain in the high signal-to-noise ratio region of the source−destination link. To obtain some valuable insights, we also perform some extensions in the case of perfect channel state estimation, including for large-scale antenna analysis, reliability–security tradeoff, multiple eavesdroppers and random locations modeled by a Gaussian distribution. Monte-Carlo simulations are presented to validate the correctness of our derived expressions.