Joint source-channel coding with feedback

TL;DR

This paper explores how variable-length coding with feedback improves the fundamental delay-distortion tradeoff in transmitting sources over channels, and analyzes energy efficiency in Gaussian channels with feedback.

Contribution

It quantifies the benefits of feedback and variable-length coding on delay-distortion limits and energy requirements in source-channel transmission.

Findings

Feedback and variable-length coding significantly improve delay-distortion tradeoff.

Feedback reduces the minimum energy needed for source reproduction.

Allowing average power constraints further decreases energy requirements.

Abstract

This paper quantifies the fundamental limits of variable-length transmission of a general (possibly analog) source over a memoryless channel with noiseless feedback, under a distortion constraint. We consider excess distortion, average distortion and guaranteed distortion ($d$-semifaithful codes). In contrast to the asymptotic fundamental limit, a general conclusion is that allowing variable-length codes and feedback leads to a sizable improvement in the fundamental delay-distortion tradeoff. In addition, we investigate the minimum energy required to reproduce $k$ source samples with a given fidelity after transmission over a memoryless Gaussian channel, and we show that the required minimum energy is reduced with feedback and an average (rather than maximal) power constraint.