When Does Spatial Correlation Add Value to Delayed Channel State Information?

TL;DR

This paper investigates how spatial correlation in wireless channels influences the value of delayed channel state information, revealing conditions where correlation either nullifies or enhances the benefits of delayed knowledge.

Contribution

It characterizes the capacity region of two-user erasure interference channels with delayed and spatially correlated channels, introducing an extremal entropy inequality for analysis.

Findings

Spatial correlation can negate the benefits of delayed CSI in some cases.

In other cases, spatial correlation allows delayed CSI to match the performance of instantaneous CSI.

Transmitter only needs delayed knowledge of connected channels to achieve capacity.

Abstract

Fast fading wireless networks with delayed knowledge of the channel state information have received significant attention in recent years. An exception is networks where channels are spatially correlated. This paper characterizes the capacity region of two-user erasure interference channels with delayed knowledge of the channel state information and spatially correlated channels. There are instances where spatial correlation eliminates any potential gain from delayed channel state information and instances where it enables the same performance that is possible with instantaneous knowledge of channel state. The key is an extremal entropy inequality for spatially correlated channels that separates the two types of instances. It is also shown that to achieve the capacity region, each transmitter only needs to rely on the delayed knowledge of the channels to which it is connected.