Geometrical Model for Massive MIMO Systems

Recently, massive multiple-input multiple-output (MIMO) systems have attracted considerable research interest and have been regarded as a candidate technology for the 5th generation (5G) cellular networks. In massive MIMO systems, a base station (BS) is equipped with a large number of antennas which are serving several simultaneous single antenna users. An increasing number of antennas is difficult to be placed in a limited space, and the antenna space limitation causes a high spatial correlation between the antennas, further resulting in systems performance degradation. In this paper, we establish a 3-D geometrical channel model for massive MIMO systems. We focus on the massive MIMO antennas correlation and channel capacity. We consider the far-field effect using the plane wave (PW) and use the spherical wave (SW) to model the near-field effect. We derive average correlation for certain single antenna to describe the single antenna correlation degree in the whole massive MIMO system, and define average correlation for the whole system antennas to describe the whole antennas correlation degree.