Secure communication in untrusted relay selection networks with wireless energy harvesting

In this paper, we consider the secrecy performance of an energy-harvesting relaying system with Kth best partial relay selection where the communication of a multi-antenna source-destination pair is assisted via single-antenna untrusted relays. To protect confidential source messages from untrusted relays, transmit beamforming and destination jamming signals are used. The relays are energy-constrained nodes that use the power-splitting policy to harvest energy through the wireless signals from both the source and destination. For performance evaluation, closed-form expressions of the secrecy outage probability and average secrecy capacity (ASC) are derived for Nakagami-m fading channels. The analytical results are confirmed via Monte Carlo simulations. Numerical results provide valuable insights into the effect of various system parameters, such as relay location, number of relays, and power splitting ratio, on the secrecy performance. Specifically, the maximum ASC is achieved when the relay is located between the source and destination.