Ray tracing results for elevation angle spread of departure and its impact on system performance

Elevation spread of departure angles (ESD) is the key parameter characterizing a 3D fast-fading channel model. 3D channel modeling is currently being studied in 3GPP to enable the development of MIMO techniques exploiting both azimuth and elevation dimensions of the channel. In this paper we use ray-tracing techniques to estimate the ESD behavior in Manhattan and Copenhagen city environments and compare it with the 3GPP ESD model. We also investigate the ESD spread within a cluster of rays and show that the ESD within a cluster depends significantly on the distance of the mobile from the base-station. This characterization addresses a gap in the existing literature. Simulation results show that the performance of MIMO techniques such as vertical sectorization depends significantly on the ESD of the underlying environment. This observation also underscores the importance of an accurate ESD model.