Secrecy performance of dual-hop threshold relaying system with diversity reception

TL;DR

This paper analyzes the secrecy performance of a dual-hop cooperative relay system with diversity reception, deriving closed-form expressions for secrecy outage probability and ergodic secrecy rate under various channel information scenarios.

Contribution

It provides new analytical expressions for secrecy metrics in a threshold-based decode-and-forward relay system with diversity reception, considering different CSI conditions.

Findings

CSI knowledge benefits low-rate scenarios more.

Increasing relay threshold SNR can raise SOP if relayed link is stronger.

SOP plateaus with fixed link SNRs, but ergodic rate can be improved.

Abstract

In this paper, the secrecy of a cooperative system consisting of a single source, relay, destination and eavesdropper is analyzed. The threshold-selection decode-and-forward relay is considered, where the relay can correctly decode and forward only if it satisfies a threshold signal-to-noise ratio (SNR). Both destination and eavesdropper take advantage of the direct and relayed transmissions through maximal ratio diversity combining. The secrecy outage probability (SOP) and ergodic secrecy rate are derived in closed-form for different channel state information (CSI) availability. It was observed that when the required rate is low, having CSI knowledge is more advantageous than in the case of higher rate. An increase in the required threshold SNR at the relay can increase the SOP if the relayed link SNR is relatively higher than the direct link SNR. It was also shown that SOP cannot be improved beyond a certain value when keeping either dual-hop link average SNR fixed and increasing the other link SNR, whereas the ergodic secrecy rate can be increased by keeping the source to destination average SNR fixed.