Full-Dimension MIMO arrays with large spacings between elements

Full-Dimension MIMO is identified as a promising MIMO technique for next cellular standards. It is based on performing beamforming not only in the azimuth but also in the elevation dimension. In this paper, it is studied how the beamforming performance can be enhanced by increasing the spacing between antenna elements. The major claims are that the system capacity can be enhanced by increasing the antenna spacing until the limit in which the grating lobes start falling inside the desired sector. For larger spacings, the benefits of reduced beamwidths are cancelled out by the interference introduced by grating lobes.