Receive Diversity and Ergodic Performance of Interference Alignment on the MIMO Gaussian Interference Channel

TL;DR

This paper explores interference alignment in MIMO Gaussian interference channels at finite SNR, introducing receive diversity, establishing a DMT, and deriving a tight ergodic mutual information bound, with performance comparisons to game-theoretic methods.

Contribution

It generalizes IA to include receive diversity, extends existence criteria, and provides a closed-form ergodic mutual information bound at arbitrary SNR.

Findings

Established a multi-user diversity-multiplexing trade-off for IA.

Derived a tight lower-bound for ergodic mutual information with IA.

Compared IA performance with game-theoretic distributed methods.

Abstract

We consider interference alignment (IA) over K-user Gaussian MIMO interference channel (MIMO-IC) when the SNR is not asymptotically high. We introduce a generalization of IA which enables receive diversity inside the interference-free subspace. We generalize the existence criterion of an IA solution proposed by Yetis et al. to this case, thereby establishing a multi-user diversity-multiplexing trade-off (DMT) for the interference channel. Furthermore, we derive a closed-form tight lower-bound for the ergodic mutual information achievable using IA over a Gaussian MIMO-IC with Gaussian i.i.d. channel coefficients at arbitrary SNR, when the transmitted signals are white inside the subspace defined by IA. Finally, as an application of the previous results, we compare the performance achievable by IA at various operating points allowed by the DMT, to a recently introduced distributed method based on game theory.