Achievable Rates in Two-user Interference Channels with Finite Inputs and (Very) Strong Interference

TL;DR

This paper explores the achievable communication rates in two-user interference channels with very strong interference when using finite input constellations, demonstrating that input rotation can enhance rates and influence thresholds.

Contribution

It introduces the analysis of finite constellation inputs in interference channels with very strong interference and shows how input rotation improves achievable rates.

Findings

Rotating input constellations increases the achievable rate region.

The threshold for single-user rate achievement depends on the input rotation.

Finite constellations can approach capacity in strong interference scenarios.

Abstract

For two-user interference channels, the capacity is known for the case where interference is stronger than the desired signal. Moreover, it is known that if the interference is above a certain level, it does not reduce the capacity at all. To achieve this capacity, the channel inputs need to be Gaussian distributed. However, Gaussian signals are continuous and unbounded. Thus, they are not well suited for practical applications. In this paper, we investigate the achievable rates if the channel inputs are restricted to finite constellations. Moreover, we will show by numerical simulations that rotating one of these input alphabets in the complex plane can increase the achievable rate region. Finally, we show that the threshold at which the single-user rates are achieved also depends on this rotation.