On the Capacity of Fading MIMO Broadcast Channels with Imperfect Transmitter Side-Information

TL;DR

This paper investigates how imperfect transmitter knowledge of fading impacts the capacity of MIMO broadcast channels, revealing significant throughput reductions at high SNR even with perfect receiver knowledge.

Contribution

It provides a general analysis of the capacity loss in fading MIMO broadcast channels due to only approximate transmitter side-information, extending beyond memoryless Gaussian models.

Findings

High SNR throughput is significantly reduced with imperfect transmitter knowledge.

Precise receiver knowledge does not prevent capacity loss caused by transmitter uncertainty.

Results are applicable to general fading models, not limited to Gaussian fading.

Abstract

A fading broadcast channel is considered where the transmitter employs two antennas and each of the two receivers employs a single receive antenna. It is demonstrated that even if the realization of the fading is precisely known to the receivers, the high signal-to-noise (SNR) throughput is greatly reduced if, rather than knowing the fading realization \emph{precisely}, the trasmitter only knows the fading realization \emph{approximately}. The results are general and are not limited to memoryless Gaussian fading.