A New Coding Scheme for Discrete Memoryless MACs with Common Rate-Limited Feedback

TL;DR

This paper introduces a novel coding scheme for the two-user discrete memoryless MAC with rate-limited feedback, outperforming previous schemes and achieving larger sum-rates in certain Gaussian channel scenarios.

Contribution

It combines existing feedback schemes into a new approach that surpasses prior achievable regions, especially for large feedback rates and specific Gaussian channels.

Findings

Achieves the same rate region as perfect feedback schemes for large feedback rates.

Includes the Shaviv-Steinberg region, with strict improvements in some cases.

Numerical results show larger sum-rate in Gaussian MACs for certain parameters.

Abstract

We propose a new coding scheme for the discrete memoryless two-user multi-access channel (MAC) with rate-limited feedback. Our scheme combines ideas from the Venkataramanan-Pradhan scheme for perfect feedback with ideas from the Shaviv-Steinberg scheme for rate-limited feedback. Our achievable region includes the Shaviv-Steinberg achievable region and this inclusion can be strict. For general MACs and for sufficiently large feedback rates, our scheme outperforms the Shaviv-Steinberg scheme as it achieves the same rate region as the Venkataramanan-Pradhan scheme for perfect feedback (which cannot be achieved by the Shaviv-Steinberg scheme). Furthermore, we numerically evaluate our achievable region with a specific (Gaussian) choice of random variables for the memoryless two-user Gaussian MAC. Our simulation results show that for some parameters of the Gaussian MAC and the feedback rate, our scheme achieves a strictly larger sum-rate than the Shaviv-Steinberg scheme.