Lattice Coding and the Generalized Degrees of Freedom of the Interference Channel with Relay

TL;DR

This paper investigates the generalized degrees of freedom (GDoF) in a symmetric two-user Gaussian interference relay channel, demonstrating that relays can enhance GDoF using a novel functional decode-and-forward scheme.

Contribution

It introduces new bounds and a functional decode-and-forward scheme to characterize GDoF, showing relays can improve GDoF in certain regimes.

Findings

Relay can increase GDoF in the interference relay channel.

Functional decode-and-forward achieves the GDoF gains.

GDoF is characterized for the regime where source-relay link is weaker than interference.

Abstract

The generalized degrees of freedom (GDoF) of the symmetric two-user Gaussian interference relay channel (IRC) is studied. While it is known that the relay does not increase the DoF of the IC, this is not known for the more general GDoF. For the characterization of the GDoF, new sum-capacity upper bounds and lower bounds are derived. The lower bounds are obtained by a new scheme, which is based on functional decode-and-forward (FDF). The GDoF is characterized for the regime in which the source-relay link is weaker than the interference link, which constitutes half the overall space of channel parameters. It is shown that the relay can indeed increase the GDoF of the IRC and that it is achieved by FDF.