Reliability and security performance analysis of non-regenerative untrusted relay networks

We investigate the physical layer security in non-regenerative untrusted relay networks, where the relay is a potential eavesdropper despite its cooperatively relaying the information. The current research and development of untrusted relay is often based on the assumption of perfect channel knowledge or the capability of variable-rate transmissions which is decided by instantaneous channel state information (CSI). In this paper, we investigate the secure transmission in a more practical scenario, where the source does not have or trust relay's feedback and uses fixed-rate transmissions. We first calculate the exact connection outage probability (COP) and secrecy outage probability (SOP) to describe the level of reliability and security of the communication system, respectively. Then, the closed-form of reliable-and-secure probability (RSP) is derived to character the trade-off between reliability and security. Finally, Monte-Carlo simulation results are presented to verify the validity of our theoretical analysis.