Beamspace MU-MIMO for high-density gigabit small cell access at millimeter-wave frequencies

Through orders-of-magnitude larger bandwidths and small wavelengths that enable high-dimensional multiple-input multiple-output (MIMO) operation, millimeter-wave (mm-wave) systems operating from 30-300 GHz provide a unique opportunity for meeting the exploding capacity demands on wireless networks. Previously, the performance of multiuser MIMO (MU-MIMO) precoders that exploit the concept of beamspace MIMO (B-MIMO) communication - multiplexing data onto orthogonal spatial beams - was explored for access points (APs) equipped with n-dimensional uniform linear arrays (ULAs). It was shown that APs using reduced complexity B-MIMO transceivers achieve near-optimal performance with complexity that tracks the number of mobile stations (MSs). In this paper we explore the application of the reduced complexity B-MIMO transceivers to APs equipped with uniform planar arrays (UPAs) serving small cells. First, we apply B-MIMO theory to develop a framework for analyzing the small cell in terms of the orthogonal beam footprints. We then examine the effect of several parameters on the system performance and demonstrate that the low-complexity transceivers enable 1000s of Gigabit/s aggregate rates in mm-wave small cells serving hundreds of MSs.