Multipath Directivity and Spatial Selectivity in Three-Dimensional Wireless Channels

A generalized definition is presented of multipath angular spread, used to study the spatial correlation of the signal envelope in a three-dimensional wireless channel, both in the cases of a three-dimensional and a horizontal travel direction. Previous results from two-dimensional modeling are shown to be a special case of this general analysis when the multipath power and the travel direction are confined to a single plane in space. The results show that the main lobe of the spatial correlation of the signal envelope at a given distance has an approximately Gaussian dependence on the three-dimensional multipath directivity metric proposed in this paper, for both cases for the travel direction.