Space division multiple access systems: Computational electromagnetic studies of the physical and network layers

Space Division Multiple Access (SDMA) systems exploit the spatial diversity of mobile users for the purpose of increasing the quality and capacity of cellular communications systems. SDMA systems exploit spatial diversity through the use of smart antenna arrays at the base stations of cellular systems. This dissertation demonstrates how electromagnetic modeling techniques can be applied to the holistic study of SDMA systems. This research develops a foundation for unifying low-level electromagnetic principles with propagation and system-level concepts in communication system performance. Specifically, computational electromagnetics techniques, including electromagnetic ray tracing and the Method of Moments, are applied to study low-level radio frequency propagation statistics and mutual coupling characteristics as well as high-level SDMA system planning issues. Whenever possible, empirical data, collected using the smart antenna testbed at the University of Texas at Austin, is used to guide simulation construction and verify simulation results.; This dissertation demonstrates through field measurements and simulation how consideration of the mutual coupling in an SDMA system can improve direction finding and downlink beamforming performance. This study also illustrates a novel use of computational electromagnetics in the simulation and prediction of the urban vector channel encountered by SDMA systems. Specifically, ray tracing is used to examine power-angle profiles, power-delay profiles, spatial signature angle change, and downlink beamforming in urban environments. In addition, a new vector autoregressive, Kalman filter-based approach is used to predict spatial signatures in a time division duplexed SDMA system. Finally, the tools used in this dissertation culminate in the development of a system-planning and channel visualization software package for SDMA systems. This package is used in a novel study of urban vector channel propagation statistics as well as urban microcell architecture and handoff.