Über die Autorin bzw. den Autor

Professor Xuemin Shen works in the Department of Electrical and Computer Engineering at the University of Waterloo, Canada. His research interests are Wireless/Internet interworking, Resource and mobility management, Voice over mobile IP, WiFi, WAP, Bluetooth, UWB wireless applications, ad hoc wireless networks.

Dr. Mohsen Guizani is Professor and Chair of the Department of Computer Science at Western Michigan university. Dr. Guizani's research interests include Computer Networks, Wireless Communications and Computing, Design and Analysis of Computer Systems, and Optical Networking. He is the founder and Editor-In-Chief of Wireless Communications and Mobile Computing Journal, published by John Wiley.

Professor Robert Caiming works in the Center for Manufacturing Research/Electrical and Computer Engineering Department at Tennessee Technological University, USA. His research interests include Wireless communications and systems (3G, 4G, UWB), Radar/communications signal processing and Time-domain Electromagnetics.

Professor Tho Le-Ngoc works in the Department of Electrical and Computer Engineering at McGill University. His research interests include Broadband Communications: Advanced Transmission, Multiple-Access and Dynamic Capacity Allocation Techniques.

Von der hinteren Coverseite

Ultra-wideband (UWB) technology has great potential for applications in wireless communications, radar and location. It has many benefits due to its ultra-wideband nature, which include high data rate, less path loss and better immunity to multipath propagation, availability of low-cost transceivers, low transmit power and low interference. Despite R&D results so far demonstrating that UWB radio is a promising solution for high-rate short-range wireless communications, further extensive investigation is necessary towards developing effective and efficient UWB communication systems and UWB technology.

Ultra-wideband Wireless Communications and Networks explores both the fundamental aspects and the more advanced topics of networks and applications. Challenges and up-to-date technical progress in the field are presented, with timely reporting of results from cutting-edge research and state-of-the-art technology in UWB wireless communications.

• Unique focus on UWB wireless communications rather than previously covered UWB radar aspects.
• Topics include: radio propagation and large scale variations, pulse propagation and channel modelling, MIMO (Multiple Input – Multiple Output) RF subsystems and ad hoc networks.
• Features a wealth of tables, illustrations and photographs.

This book is aimed at professionals wishing to enhance their knowledge of UWB wireless communications systems for short range communications. It will also appeal to senior undergraduate and graduate students who require information on the key topics in this area.

Aus dem Klappentext

Ultra-wideband (UWB) technology has great potential for applications in wireless communications, radar and location. It has many benefits due to its ultra-wideband nature, which include high data rate, less path loss and better immunity to multipath propagation, availability of low-cost transceivers, low transmit power and low interference. Despite R&D results so far demonstrating that UWB radio is a promising solution for high-rate short-range wireless communications, further extensive investigation is necessary towards developing effective and efficient UWB communication systems and UWB technology.

Ultra-wideband Wireless Communications and Networks explores both the fundamental aspects and the more advanced topics of networks and applications. Challenges and up-to-date technical progress in the field are presented, with timely reporting of results from cutting-edge research and state-of-the-art technology in UWB wireless communications.

• Unique focus on UWB wireless communications rather than previously covered UWB radar aspects.
• Topics include: radio propagation and large scale variations, pulse propagation and channel modelling, MIMO (Multiple Input – Multiple Output) RF subsystems and ad hoc networks.
• Features a wealth of tables, illustrations and photographs.

This book is aimed at professionals wishing to enhance their knowledge of UWB wireless communications systems for short range communications. It will also appeal to senior undergraduate and graduate students who require information on the key topics in this area.

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Ultra-Wideband Wireless Communications and Networks

John Wiley & Sons

Chapter One

Robert Caiming Qiu, Xuemin (Sherman) Shen, Mohsen Guizani and Tho Le-Ngoc

1.1 Fundamentals

1.1.1 Overview of UWB

Ultra-wideband (UWB) transmission has recently received significant attention in both academia and industry for applications in wireless communications. UWB has many benefits, including high data rate, availability of low-cost transceivers, low transmit power, and low interference. It operates with emission levels that are commensurate with common digital devices such as laptops, palm pilots, and pocket calculators. The approval of UWB technology made by the Federal Communications Commission (FCC) of the United States in 2002 reserves the unlicensed frequency band between 3.1 and 10.6 GHz (7.5 GHz) for indoor UWB wireless communication systems. Industrial standards such as IEEE 802.15.3a (high data rate) and IEEE 802.15.4a (very low data rate with ranging) based on UWB technology have been introduced. On the other hand, the Department of Defense (DoD) UWB systems are different from commercial systems in that jamming is a significant concern. Although R&D efforts in recent years have demonstrated that UWB radio is a promising solution for high-rate short-range and moderate-range wireless communications and ranging, further extensive investigation, experimentation, and development are necessary to produce effective and efficient UWB communication systems. In particular, UWB has found a new application for lower-data-rate moderate-range wireless communications, illustrated by IEEE 802.15.4a and DoD systems with joint communication and ranging capabilities unique to UWB. Unlike the indoor environment in 802.15.3a (WPAN), the new environments for sensors, IEEE 802.15.4a, and DoD systems will be very different, ranging from dense foliage to dense urban obstructions. The application of UWB to low-cost, low-power sensors has a promise. The centimeter accuracy in ranging and communications provides unique solutions to applications, including logistics, security applications, medical applications, control of home appliances, search-and-rescue, family communications and supervision of children, and military applications.

1.1.2 History

Although, often considered as a recent breakthrough in wireless communications, UWB has actually experienced well over 40 years of technological developments. The physical cornerstone for understanding UWB pulse propagation was established by Sommerfeld a century ago (1901) when he attacked the diffraction of a time-domain pulse by a perfectly conducting wedge. In fact, one may reasonably argue that UWB actually had its origins in the spark-gap transmission design of Marconi and Hertz in the late 1890s. In other words, the first wireless communication system was based on UWB. Owing to the technical limitations, narrowband communication was preferred to UWB. Much like the spread spectrum or the code division multiple access (CDMA), UWB followed a similar path with early systems designed for military covert radar and communication. After the accelerating development since 1994 when some of the research activities were declassified, UWB picked up momentum after the FCC notice of inquiry in 1998. The interest in UWB was 'sparked' since the FCC issued a Report and Order allowing its commercial deployment with a given spectral-mask requirement for both indoor and outdoor applications.

1.1.3 Regulatory

UWB technology is defined by the FCC as any wireless scheme that occupies a fractional bandwidth W/[f.sub.c] [greater than or equal to] 20 %, where W is the transmission bandwidth and [f.sub.c] is the band center, or more than 500 MHz of absolute bandwidth. The FCC approved [3] the deployment of UWB on an unlicensed basis in the 3.1-10.6 GHz band subject to a modified version of Part 15.209 rules. The essence of the rulings is that power spectral density (PSD) of the modulated UWB signal must satisfy the spectral masks specified by spectrum-regulating agencies. The spectral mask for indoor applications specified by the FCC in the United States is shown in Figure 1.1.

1.1.4 Applications

High data rate (IEEE 802.15.3a): One typical scenario is promising wireless data connectivity between a host (e.g., a desk PC) and associated peripherals such as keyboards, mouse, printer, and so on. A UWB link functions as a 'cable replacement' with transfer data rate requirements that range from 100 Kbps for a wireless mouse to 100 Mbps for rapid file sharing or download of images/graphic files. Additional driver applications relate to streaming of digital media content between consumer electronics appliances (digital TV sets, VCRs, audio CD/DVD, and MP3 players, and so on). In summary, UWB is seen as having potential for applications that to date have not been fulfilled by other wireless short-range technologies currently available, for example, 802.11 LANs and Bluetooth PANs.

Low data rate (IEEE 802.15.4a): Emerging applications of UWB are foreseen for sensor networks that are critical to mobile computing. Such networks combine low- to medium-rate communications (50 kbps to 1 Mbps) with ranges of 100 m with positioning capabilities. UWB allows centimeter accuracy in ranging as well as in low-power and low-cost implementation of communications systems. In fact, the IEEE 802.15.4a, a standard for low-power, low-date-rate wireless communications, is primarily focused on position location applications. The price point will be in the sub-$1 range for asset tracking and tagging, up to $3 to $4 per node for industrial-control applications. These features allow a new range of applications, including military applications, medical applications (monitoring of patients), family communications/supervision of children, search-and-rescue (communications with fire fighters, or avalanche/earthquake victims), control of home applications, logistics (package tracking), and security applications (localizing authorized persons in high-security areas).

1.1.5 Pulse- or Multicarrier-Based UWB

The main stream papers in the literature deal with pulse-based UWB systems. One reason may be due to the fact that the pulse-based UWB was not sufficiently understood compared to orthogonal frequency-division multiplexing (OFDM) based UWB.

The major reasons for the standard body (IEEE 802.15.3a) to adopt multiband scheme are: (1) it has spectrum flexibility/agility. Regulatory regimes may lack large contiguous spectrum allocation. Spectrum agility may ease coexistence with existing services. (2) Energy collected per RAKE finger scales with longer pulse widths used, which prefers fewer RAKE fingers. (3) Reduced bandwidth after down-conversion mixer reduces power consumption and linearity requirements of receiver. (4) A fully digital solution for signal processing is more feasible than single band solution for the same occupied bandwidth. (5) Transmitter pulse shaping is made easier; longer pulses are easier to synthesize and less distorted by integrated circuits (IC) package and antenna systems. (6) It is capable of utilizing a frequency-division multiple-access (FDMA) mode for severe near-far scenarios.

Multiband pulsed scheme: The main disadvantage of narrow time-domain pulses is that building RF and analog circuits as well as high-speed analog-to-digital converters (ADCs) to process the signal of extremely wide bandwidth is challenging, and usually results in high power consumption....