Upper Bounds of Interference Alignment Degree of Freedom

TL;DR

This paper investigates the theoretical limits of interference alignment in wireless systems, analyzing existing bounds and proposing new approaches for practical finite-dimensional and MIMO-OFDM systems.

Contribution

It clarifies the applicability of existing DoF bounds to practical MIMO-OFDM systems and introduces new methods to estimate bounds in finite-dimension scenarios.

Findings

Existing MIMO DoF bounds do not apply to MIMO-OFDM.

Proposed approaches for finite-dimension and MIMO-OFDM DoF bounds.

Insight into the limitations of current interference alignment theories.

Abstract

Interference alignment allows multiple users to share the same frequency and time resource in a wireless communications system. At present, two performance bounds, in terms of degree of freedom, have been proposed. One is for infinite-dimension extension and the other is for MIMO systems. This paper provides an understanding of the MIMO bound by examining its proofs and shows that it does not apply to a more practical case: MIMO-OFDM. Several approaches are proposed in searching for DoF bounds for systems such as finite-dimension time extension and MIMO-OFDM systems.