Secrecy Outage of Dual-hop Regenerative Multi-relay System with Relay Selection

TL;DR

This paper analyzes the secrecy outage probability in dual-hop regenerative multi-relay systems with relay selection, proposing schemes that improve secrecy performance without requiring full channel state information.

Contribution

It introduces a new relay selection scheme based on secrecy outage without needing instantaneous channel information, and provides closed-form expressions and asymptotic analysis.

Findings

Secrecy outage probability is derived in closed-form for various relay selection schemes.

Relay selection enhances secrecy performance, especially with more relays.

Asymptotic analysis reveals the impact of link qualities on secrecy outage.

Abstract

Relay selection is considered to enhance the secrecy of a dual-hop regenerative multi-relay system with an eavesdropper. Without assuming perfect decoding at the relays, the secrecy outage probability of a single relay system is obtained first. Secrecy outage of optimal, traditional and suboptimal relay selection schemes is then evaluated. To reduce the power consumption, partial relay selection schemes based only on either of the source-relay or relay-destination instantaneous channel state information (ICSI) are introduced. Its secrecy outage is evaluated and compared with the other schemes. Secrecy outage of all the selection schemes are obtained in closed-form. An optimal relay selection scheme is proposed using secrecy outage which does not require any ICSI. Asymptotic and diversity gain analysis of the secrecy outage is presented when source-relay and relay-destination average SNRs are same or different. We observe that the improvement in eavesdropper link quality affects the secrecy outage more when required secrecy rate is low as compared to the case when rate is high. We also observe that relay selection improves performance more when number of relays are more. It is important to note that either of the source-relay or the relay-destination link quality can equally limit the secrecy outage performance even if the other link quality is infinitely good.