Multi-User Digital Beamforming Based on Path Angle Information for mm-Wave MIMO Systems

In millimeter-wave wireless communications, beamforming, also known as beamsteering is a promising technique that enables the base station, with a large number of antennas, to mitigate the tremendous path loss. This paper aims to assess the performance of two digital beamformers, namely, conjugate beamforming (CB) and digital beamsteering (DBS) in a millimeter-wave environment based on geometric aspects, such as the antenna array topology or the location of the user in the cell. The realistic channel model NYUSIM, from New York University, reproduces a mono- and multi-path urban scenario. We show that DBS, with only line-of-sight path angle information at the transmitter, outperforms CB, with full channel state information at the transmitter, in mono-path environment. However, in multipath scenario, DBS is not able to exploit the diversity of nonline-of-sight paths and CB outperforms DBS.