On Achievable Schemes of Interference Alignment in Constant Channels via Finite Amplify-and-Forward Relays

TL;DR

This paper investigates how to achieve interference alignment in constant channels using finite amplify-and-forward relays, focusing on channel properties and subspace management to optimize degrees of freedom.

Contribution

It introduces two strategies—edge coding and middle coding—for interference alignment, emphasizing the roles of channel relativity and subspace dimension control.

Findings

Interference alignment can be achieved with finite AF relays in constant channels.

Channel relativity and subspace dimension suppression are critical for alignment.

The proposed schemes enable half of the interference-free degrees of freedom.

Abstract

This paper elaborates on the achievable schemes of interference alignment in constant channels via finite amplify-and-forward (AF) relays. Consider $K$ sources communicating with $K$ destinations without direct links besides the relay connections. The total number of relays is finite. The objective is to achieve interference alignment for all user pairs to obtain half of their interference-free degrees of freedom. In general, two strategies are employed: coding at the edge and coding in the middle, in which relays show different roles. The contributions are that two fundamental and critical elements are captured to enable interference alignment in this network: channel randomness or relativity; subspace dimension suppression.