Secure Wireless Powered Cooperative Communication Networks With Finite Energy Storage

This paper investigates secure transmission in a wireless powered cooperative communication network (WPCCN) over Nakagami-mfading channels, where multiple intermediate energy harvesting (EH) nodes with finite energy storage are deployed to assist the secure transmission between source and destination in the presence of an eavesdropper. Specifically, the intermediate EH nodes first harvest and accumulate energy from the source's signal and then forward the confidential signal or emit jamming signal to interfere the eavesdropper according to actual requirements. In order to exploit the intermediate EH nodes for secure improvement, considering both energy storage status and channel gains, three relay-and-jammer selection schemes at the intermediate nodes are proposed, namely: energy threshold based best-relay and random-jammer (ETBR), energy threshold based random-relay and best-jammer (ETRB), and energy threshold based best-relay and best-jammer (ETBB). For understanding the impact of critical parameters on the secrecy performance, we first capture the evolution of the EH nodes' storages using finite-state Markov chain (FSMC) and then derive the analytical expressions for hybrid outage probability (HOP) and secrecy throughput (ST). Furthermore, numerical results demonstrate that our proposed selection schemes outperform the existing schemes (bR-rJ, rR-bJ, bR-bJ) due to the consideration of energy accumulation and storage status. In addition, there is a suitable value of the energy threshold for each proposed scheme to achieve the optimal secrecy performance.