Performance Analysis of Two-Step Bi-Directional Relaying with Multiple Antennas

TL;DR

This paper evaluates decode-and-forward multi-antenna relay systems for bi-directional communication, comparing different network coding schemes and proposing an antenna selection method to optimize performance with limited channel information.

Contribution

It introduces a performance comparison of binary and analog network coding in multi-antenna relays and proposes a Max-Min antenna selection scheme for partial channel knowledge.

Findings

Analog network coding with beamforming yields the best performance with full CSI.

The proposed Max-Min antenna selection scheme approaches optimal performance with partial CSI.

Performance depends on the availability of channel state information at the relay.

Abstract

In this paper we study decode-and-forward multi-antenna relay systems that achieve bi-directional communication in two time slots. We investigate different downlink broadcast schemes which employ binary or analog network coding at the relay. We also analyze and compare their performances in terms of diversity order and symbol error probability. It is shown that if exact downlink channel state information is available at the relay, using analog network coding in the form of multi-antenna maximal-ratio transmit beamforming to precode the information vectors at the relay gives the best performance. Then, we propose a Max-Min antenna selection with binary network coding scheme that can approach this performance with only partial channel state information.