Effects of CSI Knowledge on Secrecy of Threshold-Selection Decode-and-Forward Relaying

Abstract

This paper considers secrecy of a three node cooperative wireless system in the presence of a passive eavesdropper. The threshold-selection decode-and-forward (DF) relay is considered, which can decode the source message correctly only if a predefined signal-to-noise ratio (SNR) is achieved. The effects of channel state information (CSI) availability on secrecy outage probability (SOP) and ergodic secrecy rate (ESR) are investigated, and closed-form expressions are derived. Diversity is achieved from the direct and relaying paths both at the destination and at the eavesdropper by combinations of maximalratio combining (MRC) and selection combining (SC) schemes. An asymptotic analysis is provided when each hop SNR is the same in the balanced case and when it is different in the unbalanced case. The analysis shows that both hops can be a bottleneck for secure communication; however, they do not affect the secrecy identically. While it is observed that CSI knowledge can improve secrecy, the amount of improvement for SOP is more when the required rate is low and for ESR when the operating SNR is also low. It is also shown that the source to eavesdropper link SNR is more crucial for secure communication.Index Terms-Channel state information, cooperative diversity, decode-and-forward relay, ergodic secrecy rate, secrecy outage probability, threshold-selection relay.This work was presented in part at the 2016 IEEE 84th Vehicular Technology Conference, Montreal, Canada.Chinmoy Kundu and Trung Q. Duong are with the

Secrecy Performance of Multi-Antenna Wiretap Channels With Diversity Combining Over Correlated Rayleigh Fading Channels

“…When the eavesdropper's CSI is available to the transmitter, the transmit antenna having the largest secrecy capacity is selected, and it can be expressed as [36], [37] n * = arg max…”