On the Capacity of One-sided Two user Gaussian Fading Broadcast Channels

TL;DR

This paper analyzes the capacity limits of a two-user Gaussian fading broadcast channel with one non-fading user, deriving bounds that are tight in certain cases and close in general, using entropy power inequalities and superposition coding.

Contribution

It introduces new upper and lower bounds on the sum-capacity for channels with one constant and one fading user, utilizing the Costa EPI and optimization techniques.

Findings

Upper and lower bounds meet in special cases.

Achievable sum-rate is within a constant of the outer bound.

The bounds provide tight capacity estimates for the channel.

Abstract

In this paper, we investigate upper and lower bounds on the capacity of two-user fading broadcast channels where one of the users has a constant (non-fading) channel. We use the Costa entropy power inequality (EPI) along with an optimization framework to derive upper bounds on the sum-capacity and superposition coding to obtain lower bounds on the sum-rate for this channel. For this fading broadcast channel where one channel is constant, we find that the upper and lower bounds meet under special cases, and in general, we show that the achievable sum-rate comes within a constant of the outer bound.