Degrees of Freedom of Multi-Source Relay Networks

TL;DR

This paper analyzes the degrees of freedom in multi-source Gaussian relay networks with multiple relay layers, proposing interference alignment and opportunistic cancellation schemes to achieve optimal or near-optimal capacity scaling.

Contribution

It introduces new achievable degrees of freedom results for multi-hop relay networks using interference alignment and symbol extension techniques.

Findings

Achieves min{K,K/2+L/(2(K-1))} degrees of freedom in 2-hop networks with L relays.

Full K degrees of freedom are achievable in K-hop networks with K relays per layer if K is even.

Proposes interference alignment and opportunistic interference cancellation schemes.

Abstract

We study a multi-source Gaussian relay network consisting of $K$ source--destination pairs having $K$ unicast sessions. We assume $M$ layers of relays between the sources and the destinations. We find achievable degrees of freedom of the network. Our schemes are based on interference alignment at the transmitters and symbol extension and opportunistic interference cancellation at the relays. For $K$-$L$-$K$ networks, i.e., 2-hop network with $L$ relays, we show $\min\{K,K/2+L/(2(K-1))\}$ degrees of freedom are achievable. For $K$-hop networks with $K$ relays in each layer, we show the full $K$ degrees of freedom are achievable provided that $K$ is even and the channel distribution satisfies a certain symmetry.