Hybrid Demodulate-Forward Relay Protocol for Two-Way Relay Channels

TL;DR

This paper introduces a Hybrid Demodulate-Forward protocol for Two-Way Relay Channels that improves error rates and spectrum efficiency by combining direct and differential demodulation techniques and employing a novel scheduling scheme.

Contribution

The paper proposes a new HDMF protocol with a decision criterion based on log-likelihood ratios, applicable across various modulation schemes, and demonstrates its superior performance over existing methods.

Findings

Lower error rate compared to existing protocols

Enhanced spectrum efficiency in unbalanced traffic scenarios

Reduced scheduling overhead

Abstract

Two-Way Relay Channel (TWRC) plays an important role in relay networks, and efficient relaying protocols are particularly important for this model. {\color{black} However, existing protocols may not be able to realize the potential of TWRC if the two independent fading channels are not carefully handled}. In this paper, a Hybrid DeModulate-Forward (HDMF) protocol is proposed to address such a problem. {\color{black} We first introduce the two basic components of HDMF - direct and differential DMF, and then propose the key decision criterion for HDMF based on the corresponding log-likelihood ratios. We further enhance the protocol so that it can be applied independently from the modulation schemes. Through extensive mathematical analysis, theoretical performance of the proposed protocol is investigated. By comparing with existing protocols, the proposed HDMF has lower error rate. A novel scheduling scheme for the proposed protocol is introduced, which has lower length than the benchmark method. The results also reveal the protocol's potential to improve spectrum efficiency of relay channels with unbalanced bilateral traffic.}