Security and Reliability Trade-off in Device to Device Communications with Untrusted Relays

In this paper, we investigate the tradeoff between reliability and security in a device to device (D2D) network including a pair of D2D, an untrusted relay, and a jammer. The untrusted relay is used as aiding to D2D communications but due to untrusting the relay, data protection from eavesdropping by relay is very important. According to this, two protocols direct transmission (DT) and relay transmission (RT) are considered for transmission in network. In the DT protocol, D2D pair directly and without relay aid and in the RT protocol, D2D pair use from relay for communication. In this paper, first, secrecy outage probability (SOP) and intercept probability and then tradeoff between reliability and security presenting the closedform relations for two protocols are investigated. Simulation results show the reliability of analytic relationships and show that in a steady intercept probability, DT protocol into RT protocol has a higher reliability. Also, the simulation results show that in RT, intercept probability is lower into the DT protocol and consequently security increases in RT into the DT protocol. Also the results confirm that increasing security increases the likelihood of loss of communication, and increasing the likelihood of reliable communication reduces communications security.