Space-time array communications have gained a great deal of interest in recent years. Its superior performance in practical multipath propagation environments has established it as a core aspect in the next generation mobile networks. In fact the employment of the sensor array component has already been provided for in the current UMTS standard, and there is presently a major thrust to make space-time processing an important part of 3G networks. This book hence attempts to bridge the knowledge gap, looking at the integration of two emerging technologies from an array manifold perspective -- space-time array processing and spread spectrum multiple access communications. It covers a range of novel multiuser channel estimation and reception, which is designed to provide mitigations of the various associated channel impairments in accordance to its environmental context. For convenience of the readers, the book is written in a self-contained modular format with its mathematical frameworks and tools readily extendable to other research domains.