Modeling and capacity of realistic spatial MIMO channels

Accurate and tractable channel modeling is critical to realizing the full potential of antenna arrays in wireless communications. In this paper we propose a framework for modeling multi-antenna multipath channels based on the notion of virtual spatial angles. The virtual angles are fixed a priori and are determined by the number of antennas at the transmitter and receiver and the spacing between the antennas. The model essentially corresponds to a coordinate transformation via fixed spatial basis functions at the transmitter and receiver. The resulting linear virtual channel representation encompasses all existing models and provides a natural link between the physical propagation environment and the channel statistics induced by it. For any given scattering environment, the model facilitates realistic estimates of channel capacity and clearly reveals the two key parameters affecting capacity: the number of parallel channels and the level of diversity.