The Degrees of Freedom of MIMO Interference Channels without State Information at Transmitters

TL;DR

This paper characterizes the degrees of freedom region for two-user MIMO interference channels with no channel state information at the transmitters, revealing the loss of beamforming and interference alignment gains in high-SNR regimes.

Contribution

It provides a complete characterization of the DoF region for MIMO interference channels without CSIT, extending previous results to arbitrary antenna configurations.

Findings

The DoF region is fully characterized for the given channel model.

Beamforming and interference alignment do not provide DoF gains without CSIT.

The capacity region is characterized to the first order of the logarithm of SNR.

Abstract

This paper fully determines the degree-of-freedom (DoF) region of two-user interference channels with arbitrary number of transmit and receive antennas and isotropic fading, where the channel state information is available to the receivers but not to the transmitters. The result characterizes the capacity region to the first order of the logarithm of the signal-to-noise ratio (SNR) in the high-SNR regime. The DoF region is achieved using random Gaussian codebooks independent of the channel states. Hence the DoF gain due to beamforming and interference alignment is completely lost in absence of channel state information at the transmitters (CSIT).