Secure transmission scheme based on dual- thresholds for simultaneous wireless information and power transfer

This paper studies a simultaneous wireless information and power transfer system with multiple external eavesdroppers and internal curious users. We model the random network by Poisson cluster process in consideration of the case where eavesdroppers hide around certain targets. Focusing on the users that work in harvesting-transmitting mode with time switching receivers, we establish communication model via time division multiple access. On this basis, we propose a lightweight secure transmission scheme based on dual-thresholds for physical-layer security enhancement, which consists of two protocols applied to the downlink (DL) and uplink (UL) transmission respectively. In the DL, we design a dynamic information-power switching transmission protocol based on signal-to-noise ratio threshold, which provides an opportunistic approach to reform the fixed period allocation of information and power transfer; in the UL, an energy threshold is proposed for users to control the transmission, which is called a user-led on-off transmission protocol. Furthermore, we give a comprehensive performance analysis for the proposed scheme in terms of delay, reliability, security and secrecy throughput. Based on the analysis results, we optimize the two thresholds and the DL-UL allocation coefficient to maximize the secrecy throughput. Simulation results show the proposed scheme can bring about a substantial secrecy gain.