Elevation Characteristics of Outdoor-to-Indoor Macrocellular Propagation Channels

There has been an increasing interest in Full- Dimension (FD) MIMO, i.e., exploiting the elevation domain (in addition to the azimuth domain) for increasing the capacity of multi-antenna systems. A first prerequisite for designing FD MIMO is an understanding of the elevation characteristics of wireless propagation channels, in particular elevation at the base station. This paper utilizes a state-of-art ray-tracing simulation software to investigate and quantify these elevation characteristics in urban macro cellular (UMa) environments. We study in detail the height and distance dependency of these channel parameters such as mean elevation angle and elevation spread. More importantly we find that several of these parameters exhibit markedly different characteristics depending on whether the UEs are close to exterior walls or they are deeper inside the buildings. Thus, the traditional method of "factoring" the propagation into an outdoor part and an indoor part is not applicable, and we propose more accurate fitting equations.