On Achievable Rates of the Two-user Symmetric Gaussian Interference Channel

TL;DR

This paper analyzes the Han-Kobayashi achievable sum rate for the symmetric Gaussian interference channel, deriving a closed-form expression for optimal power split and revealing that asymmetric power splitting can significantly enhance sum rate performance.

Contribution

It provides a closed-form solution for optimal power splitting in the Han-Kobayashi scheme and demonstrates the benefits of asymmetry in power allocation for symmetric channels.

Findings

Asymmetric power splitting can significantly improve sum rate.

A closed-form expression for the optimal power split ratio is derived.

Asymmetry outperforms symmetry above a certain interference threshold.

Abstract

We study the Han-Kobayashi (HK) achievable sum rate for the two-user symmetric Gaussian interference channel. We find the optimal power split ratio between the common and private messages (assuming no time-sharing), and derive a closed form expression for the corresponding sum rate. This provides a finer understanding of the achievable HK sum rate, and allows for precise comparisons between this sum rate and that of orthogonal signaling. One surprising finding is that despite the fact that the channel is symmetric, allowing for asymmetric power split ratio at both users (i.e., asymmetric rates) can improve the sum rate significantly. Considering the high SNR regime, we specify the interference channel value above which the sum rate achieved using asymmetric power splitting outperforms the symmetric case.