Modeling Three Dimensional Channel Characteristics in Outdoor-to-Indoor LTE Small Cell Environments

The main contribution of the paper is demonstrating a ray tracing framework to extract the three dimensional (3D) channel parameters as input to stochastic models in studying small cell environments. We focus on Long Term Evolution (LTE) small cells, taking as reference outdoor small cells deployments providing services to indoor users. Many stochastic channel models model the channel parameters in two dimensions and ignore the variation in the elevation plane. They are designed to capture the characteristics of macrocellular networks where eNBs are placed hundreds of meters away from each other. In such scenarios the two-dimensional channel characteristics might be sufficient to capture the channel properties. In contrast, small cells are deployed much more closely to each other. The performance of small cells is highly dependent on 3D antenna patterns, the environment specific characteristics such as 3D geometry of the buildings, materials used for building construction and their specific propagation properties. Therefore in small cell environments the site specific modeling of channel parameters in three dimensions is needed. Measurements to determine the channel parameters may not be available for every environment of interest. Ray tracing could close the gap in extracting the 3D site-specific channel parameters pertaining to small cell environments.