Enhancing Coexistence in the Unlicensed Band with Massive MIMO

TL;DR

This paper proposes a massive MIMO approach for cellular base stations operating in unlicensed bands, enabling coexistence with Wi-Fi devices by interference management, leading to higher aggregate data rates compared to traditional methods.

Contribution

It introduces a novel mMIMO-U system design with procedures for coexistence, interference suppression, and enhanced sensing, demonstrating improved performance over conventional LBT.

Findings

mMIMO-U enables simultaneous cellular and Wi-Fi transmissions.

It maintains interference below regulatory thresholds.

Performance gains increase with the number of antennas.

Abstract

We consider cellular base stations (BSs) equipped with a large number of antennas and operating in the unlicensed band. We denote such system as massive MIMO unlicensed (mMIMO-U). We design the key procedures required to guarantee coexistence between a cellular BS and nearby Wi-Fi devices. These include: neighboring Wi-Fi channel covariance estimation, allocation of spatial degrees of freedom for interference suppression, and enhanced channel sensing and data transmission phases. We evaluate the performance of the so-designed mMIMO-U, showing that it allows simultaneous cellular and Wi-Fi transmissions by keeping their mutual interference below the regulatory threshold. The same is not true for conventional listen-before-talk (LBT) operations. As a result, mMIMO-U boosts the aggregate cellular-plus-Wi-Fi data rate in the unlicensed band with respect to conventional LBT, exhibiting increasing gains as the number of BS antennas grows.