Two-terminal Erasure Source-Broadcast with Feedback

TL;DR

This paper investigates how feedback channels influence the efficiency of transmitting a binary source over an erasure broadcast channel to two receivers with distortion constraints, proposing a hybrid coding scheme.

Contribution

It introduces a new coding scheme that combines random linear combinations and retransmissions, demonstrating that feedback can achieve the outer bound in two-user erasure broadcast channels.

Findings

Feedback enables achieving the point-to-point outer bound.

The coding scheme effectively minimizes transmission latency.

Feedback from only the stronger user suffices for optimality.

Abstract

We study the effects of introducing a feedback channel in the two-receiver erasure source-broadcast problem in which a binary equiprobable source is to be sent over an erasure broadcast channel to two receivers subject to erasure distortion constraints. The receivers each require a certain fraction of a source sequence, and we are interested in the minimum latency, or transmission time, required to serve them all. We first show that for a two-user broadcast channel, a point-to-point outer bound can always be achieved. We further show that the point-to-point outer bound can also be achieved if only one of the users, the stronger user, has a feedback channel. Our coding scheme relies on a hybrid approach that combines transmitting both random linear combinations of source symbols as well as a retransmission strategy.