Phase-Rotation-Aided Relay Selection in Two-Way Decode-and-Forward Relay Networks

TL;DR

This paper introduces a phase rotation aided relay selection scheme for two-way decode-and-forward relay networks, significantly enhancing symbol error rate performance by enlarging decision distances through phase adjustments based on channel state information.

Contribution

The paper proposes a novel phase rotation based relay selection method that improves SER performance and enables flexible relay configurations in two-way relay networks.

Findings

Achieves full diversity gain.

Improves array gain.

Enables flexible relay antenna configurations.

Abstract

This paper proposes a relay selection scheme that aims to improve the end-to-end symbol error rate (SER) performance of a two-way relay network (TWRN). The TWRN consists of two single-antenna sources and multiple relays employing decode-and-forward (DF) protocol. It is shown that the SER performance is determined by the minimum decision distance (DD) observed in the TWRN. However, the minimum DD is likely to be made arbitrarily small by channel fading. To tackle this problem, a phase rotation (PR) aided relay selection (RS) scheme is proposed to enlarge the minium DD, which in turn improves the SER performance. The proposed PR based scheme rotates the phases of the transmitted symbols of one source and of the selected relay according to the channel state information, aiming for increasing all DDs to be above a desired bound. The lower bound is further optimized by using a MaxMin-RS criterion associated with the channel gains. It is demonstrated that the PR aided MaxMin-RS approach achieves full diversity gain and an improved array gain. Furthermore, compared with the existing DF based schemes, the proposed scheme allows more flexible relay antenna configurations.