Secrecy Outage of Proactive Relay Selection by Eavesdropper

TL;DR

This paper analyzes the impact of an active eavesdropper using proactive relay selection on the secrecy outage probability in cooperative relay systems, revealing increased vulnerability with more relays.

Contribution

It introduces a proactive relay selection scheme by the eavesdropper and compares its performance with passive eavesdropping scenarios, providing closed-form SOP expressions.

Findings

Proactive eavesdropper relay selection significantly increases SOP.

The SOP worsens as the number of relays increases.

Proactive eavesdropping maintains the same diversity order.

Abstract

In this paper, we consider an active eavesdropping scenario in a cooperative system consisting of a source, a destination, and an active eavesdropper with multiple decode-and-forward relays. Considering an existing assumption in which an eavesdropper is also a part of network, a proactive relay selection by the eavesdropper is proposed. The best relay which maximizes the eavesdropping rate is selected by the eavesdropper. A relay selection scheme is also proposed to improve the secrecy of the system by minimizing the eavesdropping rate. Performances of these schemes are compared with two passive eavesdropping scenarios in which the eavesdropper performs selection and maximal ratio combining on the relayed links. A realistic channel model with independent non-identical links between nodes and direct links from the source to both the destination and eavesdropper are assumed. Closed-form expressions for the secrecy outage probability (SOP) of these schemes in Rayleigh fading channel are obtained. It is shown that the relay selection by the proactive eavesdropper is most detrimental to the system as not only the SOP increases with the increase in the number of relays, but its diversity also remains unchanged.