Secure Decode-and-Forward Relay SWIPT Systems With Power Splitting Schemes

Simultaneous wireless information and power transfer (SWIPT) is a promising technology to mitigate the power constraint problem in wireless sensor networks by harvesting energy from received signals. A two-hop communication system is studied, where a relay node uses SWIPT to harvest energy and forward data. An eavesdropper exists and receives information both from the source and the relay. We considered two energy harvesting models, linear and nonlinear ones. The closed-form expression of the system's outage probability under information-theoretic physical layer security is derived for both models. We also analyze the optimal power splitting ratio and optimal relay distance with the aim to minimize the secrecy outage probability. For the nonlinear model, we derived the closed-form expression of the optimal power splitting ratio after the circuit becomes saturated.