3-Dimensional Channel Modeling Using Spherical Statistics for Multiple Input Multiple Output Systems

Abstract

Recently, the Third Generation Partnership standards bodies (3GPP/3GPP2) have defined a channel model for multiple input multiple output (MIMO) systems. This model is a 2D model where the propagating plane waves are assumed to arrive only from the azimuthal direction and does not include the elevation domain. As a result of this assumption the derived angle of arrival (AoA) distribution is characterized only by the azimuth direction of these waves. In this paper the distribution of scatterers is modeled in a novel 3D approach. The Von Mises Fisher (VMF) probability density function (PDF) is used to describe their distribution within the propagation environment in azimuth and coelevation. As a result the AoA distribution of the incoming multipaths is characterized in the same way. More specifically the model proposed uses a mixture of VMF distributions. A mixture can be composed of any number of clusters and this is environment/clutter specific. The parameters of the individual clusters of scatterers within the mixture are derived and an estimation of those parameters is achieved using the soft-expectation maximization (EM) algorithm. The results indicate that the proposed model fits well with MIMO experimental data obtained from a measurement campaign in Germany. The measurements obtained from the RUSK channel sounder were post-processed using the RiMAX algorithm. The data was subsequently clusterized using the soft-EM for mixtures of VMF distributions.