Link-State Based Decode-Forward Schemes for Two-way Relaying

TL;DR

This paper analyzes a composite decode-and-forward scheme for two-way relay channels, focusing on how link quality influences the choice of coding techniques to maximize transmission rates, with implications for 5G networks.

Contribution

It analytically characterizes link-state regimes and optimal relaying techniques, highlighting when to use independent coding versus block Markov coding based on link conditions.

Findings

Independent coding is optimal when user-to-relay links are marginally stronger than direct links.

Larger user-to-relay gains require combining block Markov and independent coding for optimal rates.

Link-state regimes guide relaying strategy choices in two-way relay channels.

Abstract

In this paper, we analyze a composite decode-and-forward scheme for the two-way relay channel with a direct link. During transmission, our scheme combines both block Markov coding and an independent coding scheme similar to network coding at the relay. The main contribution of this work is to examine how link state impacts the allocation of power between these two distinct techniques, which in turn governs the necessity of each technique in achieving the largest transmission rate region. We analytically determine the link-state regimes and associated relaying techniques. Our results illustrate an interesting trend: when the user-to-relay link is marginally stronger than the direct link, it is optimal to use only independent coding. In this case, the relay need not use full power. However, for larger user-to-relay link gains, the relay must supplement independent coding with block Markov coding to achieve the largest rate region. These link-state regimes are important for the application of two-way relaying in 5G networks, such as in D2D mode or relay-aided transmission.