Channel Aided Interference Alignment

TL;DR

This paper investigates the conditions under which perfect interference alignment is feasible in time-varying interference channels with limited channel extensions, proposing a method based on channel structure to achieve it.

Contribution

It derives necessary and sufficient channel structure conditions for perfect IA feasibility and introduces a method leveraging these conditions, especially for the 3-user interference channel.

Findings

Only one channel coefficient condition is needed for perfect IA in 3-user channels.

Derived channel structure conditions serve as feasibility criteria for perfect IA.

The method enables practical IA implementation with limited channel extensions.

Abstract

Interference alignment (IA) techniques mostly attain their degrees of freedom (DoF) benefits as the number of channel extensions tends to infinity. Intuitively, the more interfering signals that need to be aligned, the larger the number of dimensions needed to align them. This requirement poses a major challenge for IA in practical systems. This work evaluates the necessary and sufficient conditions on channel structure of a fully connected interference network with time-varying fading to make perfect IA feasible within limited number of channel extensions. We propose a method based on the obtained conditions on the channel structure to achieve perfect IA. For the case of $3$ user interference channel, it is shown that only one condition on channel coefficients is required to make perfect IA feasible at all receivers. IA feasibility literature have mainly focused on network topology so far. In contrast, derived channel aiding conditions in this work can be considered as the perfect IA feasibility conditions on channel structure.