Relay Selection for Bidirectional AF Relay Network with Outdated CSI

TL;DR

This paper investigates how outdated channel state information affects bidirectional amplify-and-forward relay networks, deriving analytical performance expressions and proposing a multiple relay scheme to mitigate diversity loss.

Contribution

It introduces a revised optimal relay selection scheme accounting for outdated CSI and proposes a multiple relay scheme to recover diversity loss.

Findings

Outdated CSI reduces diversity order to one.

Analytical expressions for SER and SNR are derived and verified.

Multiple relay scheme helps recover diversity loss.

Abstract

Most previous researches on bidirectional relay selection (RS) typically assume perfect channel state information (CSI). However, outdated CSI, caused by the the time-variation of channel, cannot be ignored in the practical system, and it will deteriorate the performance. In this paper, the effect of outdated CSI on the performance of bidirectional amplify-and-forward RS is investigated. The optimal single RS scheme in minimizing the symbol error rate (SER) is revised by incorporating the outdated channels. The analytical expressions of end-to-end signal to noise ratio (SNR) and symbol error rate (SER) are derived in a closed-form, along with the asymptotic SER expression in high SNR. All the analytical expressions are verified by the Monte-Carlo simulations. The analytical and the simulation results reveal that once CSI is outdated, the diversity order degrades to one from full diversity. Furthermore, a multiple RS scheme is proposed and verified that this scheme is a feasible solution to compensate the diversity loss caused by outdated CSI.