Security-Reliability Tradeoff for Cooperative Relay Networks

This chapter investigates the security-reliability tradeoff (SRT) for wireless communications in the face of multiple eavesdroppers, where the security and reliability are measured by using the intercept probability encountered at the eavesdroppers and the outage probability experienced by the legitimate destination, respectively. We consider a cooperative relay network consisting of a source and a destination with the aid of multiple relay nodes and present two relay selection schemes, namely the single-relay selection (SRS) and multi-relay selection (MRS), to protect the security of source-destination transmissions against eavesdropping. To be specific, in the SRS scheme, only the single “best” relay is selected to assist the source-destination transmissions, whereas in the MRS scheme, multiple relays are enabled to participate in forwarding the source signal to the destination. For comparison purposes, we also consider the traditional direct transmission as a benchmark. We carry out the SRT analysis for the direct transmission as well as the SRS and MRS schemes in terms of deriving their closed-form intercept and outage probability expressions over Rayleigh fading channels. Numerical results demonstrate that both the SRS and MRS schemes perform better than the conventional direct transmission in terms of their SRTs, showing the security and reliability benefits of exploiting the relay selection against eavesdropping. Additionally, with an increasing number of eavesdroppers, the SRTs of the SRS and MRS schemes degrade. By contrast, as the number of relay nodes increases, the SRTs of both the SRS and MRS schemes improve significantly and the MRS consistently outperforms the SRS in terms of their SRTs.