The Arbitrarily Varying Multiple-Access Channel with Conferencing Encoders

TL;DR

This paper characterizes the capacity region of arbitrarily varying multiple-access channels with conferencing encoders, revealing a dichotomy in capacity outcomes and highlighting the significant benefits of encoder cooperation.

Contribution

It provides a complete capacity region characterization for AV-MACs with conferencing, including conditions for zero or full capacity, and discusses the impact of conferencing on capacity discontinuities.

Findings

Capacity region is either zero or equals the random coding region.

Conferencing can enable non-zero rates in otherwise zero-capacity channels.

Discontinuous capacity increase occurs with conferencing in AV-MACs.

Abstract

We derive the capacity region of arbitrarily varying multiple-access channels with conferencing encoders for both deterministic and random coding. For a complete description it is sufficient that one conferencing capacity is positive. We obtain a dichotomy: either the channel's deterministic capacity region is zero or it equals the two-dimensional random coding region. We determine exactly when either case holds. We also discuss the benefits of conferencing. We give the example of an AV-MAC which does not achieve any non-zero rate pair without encoder cooperation, but the two-dimensional random coding capacity region if conferencing is possible. Unlike compound multiple-access channels, arbitrarily varying multiple-access channels may exhibit a discontinuous increase of the capacity region when conferencing in at least one direction is enabled.