A unified approach to the analysis of temporal oversampling and multiple receive antennas

A major challenge in the design of wireless communication systems is the efficient use of the available spectrum. However, this goal is often achieved at the expense of increased interference in the form of Multiuser Interference (MUI) and Inter-Symbol Interference (ISI). In this dissertation, we quantify the interference suppression capabilities of an equalizer-combiner utilizing both temporal oversampling and multiple receive antennas. Oversampling in the temporal domain in this work refers to sampling the received signal at a rate higher than the symbol rate. It is understood that the amount of interference suppressible by an equalizer-combiner is related to the available dimensionality, which increases through oversampling in the temporal domain or by increasing the number of receive antennas. The fundamental question is to what extent and under what system conditions the expanded dimensionality provides a gain in system user capacity and performance.; We develop a generalized theory on temporal oversampling and the use of multiple antennas at a receiver by imposing a minimal set of restrictions within the system. The goal is to provide a unified analysis of both temporal oversampling and multiple receive antennas to highlight and clarify any tradeoffs and dualities. We present our concept of the effective rank, which is a measure of dimensionality incorporating system parameters and channel conditions. Furthermore, we address the issue of system user capacity by quantifying the effective rank under two multipath environments: a channel with uniformly distributed angles of arrival and a channel based on discrete angles of arrival. We furthermore apply the developed general theory to a Code Division Multiple Access system. This particular application of our theory allows the assessment of the system user capacity and performance gains within a real system structure. We demonstrate an increased system user capacity through the use of asynchronous spreading codes, whose performance is verified through a system level simulation.