On Channel Output Feedback in Deterministic Interference Channels

TL;DR

This paper investigates how different configurations of channel output feedback influence the sum capacity in a symmetric deterministic interference channel, revealing that additional feedback links do not always improve capacity.

Contribution

It demonstrates that a single feedback link achieves the same sum capacity as multiple links, and shows no capacity gain in a half-duplex feedback model under certain conditions.

Findings

Single feedback link suffices for maximum sum capacity

Additional feedback links do not increase sum capacity

No capacity gain in half-duplex feedback when interference exceeds direct links

Abstract

In this paper, we study the effect of channel output feedback on the sum capacity in a two-user symmetric deterministic interference channel. We find that having a single feedback link from one of the receivers to its own transmitter results in the same sum capacity as having a total of 4 feedback links from both the receivers to both the transmitters. Hence, from the sum capacity point of view, the three additional feedback links are not helpful. We also consider a half-duplex feedback model where the forward and the feedback resources are symmetric and timeshared. Surprisingly, we find that there is no gain in sum-capacity with feedback in a half-duplex feedback model when interference links have more capacity than direct links.