Degrees of Freedom Region of the MIMO Interference Channel with Output Feedback and Delayed CSIT

TL;DR

This paper characterizes the degrees of freedom region for a two-user MIMO interference channel with output feedback and delayed CSIT, showing that these resources can significantly enhance communication capacity.

Contribution

It introduces new coding schemes utilizing feedback and delayed CSIT, proving their combined benefit and equivalence of local and global feedback in the DoF region.

Findings

Feedback and delayed CSIT enlarge the DoF region.

Coding schemes effectively combine feedback and delayed CSIT.

Local feedback is equivalent to global feedback for DoF.

Abstract

The two-user multiple-input multiple-output (MIMO) interference channel (IC) with arbitrary number of antennas at each terminal is considered and the degrees of freedom (DoF) region is characterized in the presence of noiseless channel output feedback from each receiver to its respective transmitter and availability of delayed channel state information at the transmitters (CSIT). It is shown that having output feedback and delayed CSIT can strictly enlarge the DoF region of the MIMO IC when compared to the case in which only delayed CSIT is present. The proposed coding schemes that achieve the corresponding DoF region with feedback and delayed CSIT utilize both resources, i.e., feedback and delayed CSIT in a non-trivial manner. It is also shown that the DoF region with local feedback and delayed CSIT is equal to the DoF region with global feedback and delayed CSIT, i.e., local feedback and delayed CSIT is equivalent to global feedback and delayed CSIT from the perspective of the degrees of freedom region. The converse is proved for a stronger setting in which the channels to the two receivers need not be statistically equivalent.