Two-Way Interference Channel Capacity: How to Have the Cake and Eat it Too

TL;DR

This paper characterizes the capacity region of a deterministic two-way interference channel, revealing conditions where interaction enhances capacity and where it does not, using new schemes and bounds.

Contribution

It provides a complete capacity region characterization for the two-way interference channel with novel achievable schemes and outer bounds.

Findings

Interaction can improve capacity beyond one-way limits.

Simultaneous perfect feedback capacities are achievable.

Outer bounds identify regimes where interaction is ineffective.

Abstract

Two-way communication is prevalent and its fundamental limits are first studied in the point-to-point setting by Shannon [1]. One natural extension is a two-way interference channel (IC) with four independent messages: two associated with each direction of communication. In this work, we explore a deterministic two-way IC which captures key properties of the wireless Gaussian channel. Our main contribution lies in the complete capacity region characterization of the two-way IC (w.r.t. the forward and backward sum-rate pair) via a new achievable scheme and a new converse. One surprising consequence of this result is that not only we can get an interaction gain over the one-way non-feedback capacities, we can sometimes get all the way to perfect feedback capacities in both directions simultaneously. In addition, our novel outer bound characterizes channel regimes in which interaction has no bearing on capacity.