Analysis of beam pattern and spatial capacity of massive antenna array networks with non-uniform user distribution

In this paper, we study the array property, propagation characteristics and the spatial capacity of a massive antenna array system. Within such a system, the base station (BS) is able to generate very sharp beam patterns. We show that the beamformer is able to focus its energy into small regions covering the intended user equipment (UE) when the number of antenna elements at the BS is large. The UE is surrounded by a cluster of local scatterers with a relatively small angular spread, such that it undergoes a multipath channel propagation. Furthermore, we apply a realistic two-tier UE distribution model where some tier-one virtual points are uniformly distributed in the cell range, and UEs are located in the coverage of those virtual points with a uniform distribution in the second tier. We explore the statistical distribution of the UE's geographical position, and derive an upper bound for the spatial capacity when the number of antennas at the BS grows very large. Numerical results are presented to validate our theoretical analysis.