Spatial Characterization of Mimo Wireless Channels

In this paper a novel spatial channel model is developed to provide insight into spatial aspects of multiple antenna communication systems. In particular, we uncouple the antenna configuration and scattering environment effects on the channel matrix, allowing for arbitrary antenna arrays to be studied in a variety environments. We use the underlying physics of free space wave propagation to model the channel in scatterer free regions around the transmitter and the receiver, and represent the rest of the complex scattering media by a parametric model. Using modal expansions of plane waves, we decompose the channel matrix into a product of constant and random matrices, where the constant portion shows the effects of the physical configuration of antenna elements. Using this decomposition we show that there is a limit to the intrinsic degrees of freedom of a multi-antenna system which depends only on the size of the regions containing the antennas, and is independent of the antennas contained within. We finish by briefly discussing some potential applications of the model.