Sum Rate Analysis of Multicell MU-MIMO with 3D User Distribution and Base Station Tilting

At present, the joint utilization of the elevation factor in three-dimension (3D) channel model and antenna tilt angle in 3D base station is rarely investigated. In this paper, we consider the uplink of a multicell multiuser multiple-input multiple-output (MU-MIMO) system with a 3D base station exploiting variable antenna tilt angles. To illustrate clearly, we model a tall building with several floors. Users are distributed horizontally and vertically according some rules. Due to the storey height, elevations from one BS to different floors also differ, i.e. elevation variation occurs. For such a scenario, we derive the expression of sum rate considering the elevation factor, and discuss the effects of the tilt angle and user distribution on the sum rate. Sum rate at high signal-to-noise ratio (SNR) and large number of base station antennas is also studied. Finally, we analyze the relationship between the sum rate and the user number. This work can be seen as a first attempt to analyze the sum rate performance for high-rise buildings and used as a reference for infrastructure.