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.
@article{arxiv.1703.05690,
title = {Enhancing Coexistence in the Unlicensed Band with Massive MIMO},
author = {Giovanni Geraci and Adrian Garcia-Rodriguez and David López-Pérez and Andrea Bonfante and Lorenzo Galati Giordano and Holger Claussen},
journal= {arXiv preprint arXiv:1703.05690},
year = {2017}
}