Physical Layer Security in the Untrusted EH Relay Networks with the Cooperative Jammer

For the untrusted relay wireless powered networks under the time switching relaying (TSR) protocols, a physical layer security transmission scheme based on the cooperative jammer is proposed. The main idea is that the untrusted relay may eavesdrop the secret information from the source node to the destination node. To protect the secret information from eavesdropping, the cooperative jammer transmits the jamming signal to the untrusted relay node with constant transmitting power. The expressions of the connection outage probability (COP) and the secrecy outage probability (SOP) are derived and the validity of the expressions are verified with the Monte Carlo simulations. The investigation results show that the security performance of the system can be improved, but also the reliability of the connection performance could be reduced when increasing the transmitting power of the cooperative jammer node. Increasing the transmitting power of untrusted relay node is beneficial to improve the connection reliability of the system.