Symmetric two-user MIMO BC with evolving feedback

Abstract

Extending recent findings on the two-user MISO broadcast channel (BC) with imperfect and delayed channel state information at the transmitter (CSIT), the work here explores the performance of the two user MIMO BC, in the presence of feedback with evolving quality and timeliness. Under standard assumptions, and in the presence of M antennas at the transmitter and N antennas per receiver, the work derives the DoF region, which is optimal for a large range of current and delayed CSIT quality. This region concisely captures the effect of having predicted, current and delayed-CSIT, as well as concisely captures the effect of the quality of CSIT offered at any time, about any channel realization. In addition to the progress towards describing the limits of using such imperfect and delayed feedback in MIMO settings, the work offers different insights that include the fact that DoF optimality, in the presence of an increased number of receiving antennas, can be achieved with reduced quality feedback.