On the Cost and Benefit of Cooperation (Extended Version)

TL;DR

This paper analyzes a cooperative coding scheme with a cooperation facilitator, demonstrating significant capacity gains in most channels, especially Gaussian multiple access channels, and highlighting the impact on network properties.

Contribution

It introduces a model with a cooperation facilitator that generalizes existing models and quantifies the sum-capacity gain from cooperation.

Findings

Cooperation can significantly increase sum-capacity in most channels.

Adding a cooperation facilitator alters the network's edge removal property.

Explicit sum-rate gain characterization for Gaussian multiple access channels.

Abstract

In a cooperative coding scheme, network nodes work together to achieve higher transmission rates. To obtain a better understanding of cooperation, we consider a model in which two transmitters send rate-limited descriptions of their messages to a "cooperation facilitator", a node that sends back rate-limited descriptions of the pair to each transmitter. This model includes the conferencing encoders model and a prior model from the current authors as special cases. We show that except for a special class of multiple access channels, the gain in sum-capacity resulting from cooperation under this model is quite large. Adding a cooperation facilitator to any such channel results in a network that does not satisfy the edge removal property. An important special case is the Gaussian multiple access channel, for which we explicitly characterize the sum-rate cooperation gain.