Ultra-Wideband (UWB) systems use very short pulses of electromagnetic radiation to transmit signals, allowing wireless communication at low power levels with minimal interference and potentially high data rates. Unsurprisingly, this technology is of growing interest. This book presents basic theory of UWB wireless communications from a systems-and-signals perspective, covering aspects of signal processing, information theory, and networking. The authors emphasize the cutting-edge developments including transmission and modulation, spectrum shaping, channel modeling, receiver structures, multi-access approaches, synchronization, localization and narrowband interference issues. This book provides a comprehensive and integrated account of the recent progress in UWB theory and applications, covering the theoretical innovations as well as some of the issues involved in implementation. Suitable for graduate students of electrical engineering, and researchers and practitioners in the wireless industry.