Feedback Gains for Gaussian Massive Multiple-Access Channels

TL;DR

This paper demonstrates that feedback can significantly enhance the sum-rate capacity of massive Gaussian multiple-access channels, achieving near-optimal bounds and unbounded power gains as the number of users grows.

Contribution

It establishes the tightest known bounds on capacity gains from feedback in large K-user Gaussian MACs, surpassing previous results and showing unbounded power benefits.

Findings

Feedback increases sum-rate capacity by up to 1.54 times.

The new capacity bound is asymptotically tight for large number of users.

Feedback yields unbounded power gains as the number of users increases.

Abstract

Feedback is shown to increase the sum-rate capacity of K-user Gaussian multiple-access channels by at most a factor of approximately 1.54, improving Thomas' doubling bound (1987). The new bound is the best possible in the sense that it can be approached as closely as desired for a massive number of users. Moreover, feedback provides unbounded power gain in K for a fixed transmit power per user.