Interference Alignment for the MIMO Interference Channel with Delayed Local CSIT

TL;DR

This paper investigates the impact of delayed local channel state information at transmitters on the degrees of freedom in MIMO interference channels, revealing scenarios where delayed CSIT matches perfect CSIT performance.

Contribution

It provides achievability results and tightness proofs for the DoF region in two-user MIMO channels with delayed local CSIT, and extends findings to the K-user MISO interference channel.

Findings

Achievable DoF regions are characterized for two-user MIMO channels.

In some configurations, delayed local CSIT achieves the same DoF as perfect CSIT.

The K-user MISO interference channel can have DoF greater than one with delayed local CSIT.

Abstract

We consider the MIMO (multiple-input multiple-output) Gaussian interference channel with i.i.d. fading across antennas and channel uses and with the delayed local channel state information at the transmitters (CSIT). For the two-user case, achievability results for the degrees of freedom (DoF) region of this channel are provided. We also prove the tightness of our achievable DoF region for some antenna configurations. Interestingly, there are some cases in which the DoF region with delayed local CSIT is identical to the DoF region with perfect CSIT and that is strictly larger than the DoF region with no CSIT. We then consider the $K$-user MISO (multiple-input single-output) IC and show that the degrees of freedom of this channel could be greater than one with delayed local CSIT.