Preface

Sometimes history seems to repeat. Even in the so-called 'mature' technological fields. When the radio pioneers such as Heinrich Hertz, Guglielmo Marconi, and Alexander Stepanovich Popov made their first experiments of wireless transmission more than a hundred years ago using spark-gap transmitters with simple coherer-detectors they did not care which 'frequency band' they were using, nor did they worry about their signals being 'spectrally efficient' or 'band limited'. The world of radio frequency regulation was very simple then since regulations have not yet existed. Over the years this has dramatically changed. The frequency band was subdivided into small 'boxes' of different sizes, regulated and supervised. The rules governing these 'bands' are strict and vary with the respective region, time and demand. Sometimes even frequency bands of a few tens or hundreds MHz are sold by auction for millions or even billions of dollars. Hence 'Spectral Dividend' became a key word in the media. Scientists worldwide have begun an intensive search for a more efficient usage of the available frequency spectrum. One of the ideas, which came more and more into the center of attention, was to use signals with very low spectral density yet huge instantaneous bandwidth. This 'underlaying' technique allows the reuse of the spectrum, which is already occupied by other narrowband users. The proactive release of a 'new' frequency band of several GHz (3.1 GHz – 10.6 GHz) in February 2002 by the Federal Communications Commission (FCC) hastened research in this field immensely. With such a technique the ultra-wide frequency band can be used without any further spectral slicing even though there are already a large number of established users and services within it! Thus, contrary to the mainstream of contemporary wireless technology, bandwidth efficiency becomes of minor concern again for interference mitigation as in the early days of Hertz and Marconi. However, severe limitations in terms of power spectral density emission are placed on the emitted signals as the first measure of interference mitigation and to avoid a slipshod use of our limited spectral resources as in the early days of Marconi.

So, what is it that makes ultra-wideband (UWB) so interesting for research and emerging applications? What are the paradigm shifts and challenges for circuit and system design? What does it hold for new and pioneering applications? In order to answer these questions the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) has funded a nation-wide priority-funding program called 'Ultra-Wideband Radio Technologies for Communications, Localization and

### XX Preface

Sensor Applications (UKoLoS)'. UKoLoS started in 2006 and ended in 2012. Altogether 14 research partners participated in the research program, which are mainly universities. Most of the projects are conducted as a cooperative research between two to four partners. The initial aim of UKoLoS was the joint UWB research in the areas of communications, localization, and sensors. Remarkable synergy effects and technological advancement and development are expected. This book gives an overview of the scope and results of the UKoLoS program.

Preface XXI

many different interdisciplinary questions, since non-electrical properties and their relation to the ultra-wideband electro-magnetic field will become essential knowledge.

As mentioned before, UWB utilizes an extremely large bandwidth of potentially several GHz at a comparably low frequency of a few GHz. Associated with the extremely large bandwidth is the potential for super high data rates, yet limited by low power constraints. Therefore, and especially due to the extremely high relative bandwidth, the UWB technology not only promises new and outstanding performance features but also adds new and highly challenging design demands on the envisioned UWB circuits and systems. UWB radio interfaces require innovative integrated hardware architecture, design and implementation. This includes UWB front-ends, antennas and data processing units as a whole. Efficient small antennas with optimal time-domain behavior in real propagation environments are just but one example. Known space-time signal processing algorithms must be tested against the properties of UWB signals and subsequently improved and new processing schemes have to be developed as well. Generally speaking, UWB requires a change of paradigm from narrowband to wideband principles in both algorithms and hardware. Linearity, impulse response, stability, robustness, and power consumption are very important properties, which lead to new requirements in design strategies for UWB circuits. Modern microwave semiconductor technologies such as Silicon-Germanium (SiGe) together with new manufacturing processes and packaging technologies play a key role in the implementation of complex UWB

When the FCC published their report and order that authorizes the unlicensed use of the ultra-wideband (UWB) of 3.1–10.6 GHz a great storm of research, publications, standard proposals, etc. emerged. The usage of the UWB band seemed extremely promising since the very large bandwidth could support high data rates in wireless communications or a good range resolution in sensors. However the hype is now over. On one hand, there are indeed some UWB radio access devices on the market. UWB has become the foundation of Wireless USB and WiMedia access. Yet the anticipated big economic success of UWB still remains to be seen. The last ten years of UWB research has however brought us many insights to a completely new and alternative radio access philosophy. Whereas the first hype was driven by the expectation of a big economic success in the electronic mass market, now the motivation is clearly driven by the physical advantage of such a huge bandwidth at low frequencies. New and innovative applications are generated, which are not yet mainstream. So the initial idea of high data rate wireless UWB systems may have taken a backseat in favor of UWB based systems for medical diagnostics, localization, sensing etc. But the coming years will show if these new ideas will launch UWB into a broad commercial success or at least as indispensable technology in the niche markets. This book at hand is

systems on a single integrated circuit.

meant to provide some important basics for that goal.

In contrast to the conventional frequency multiplexed radio approach, ultra-wideband radio systems earmark a completely new technological philosophy. Since UWB frequencies are already occupied by other radio services, coexistence with the existing systems is a serious concern. Hence it must be made clear that the aim of the UWB technologies is not to replace the current existing systems but to simply coexist with them. Therefore, the transmit power for UWB systems is strictly limited and intelligent interference mitigation methods and cognitive access schemes are being investigated and developed.

For short-range communication and sensor networks, the UWB technology offers a very interesting alternative to the current conventional systems since very high data rates at low power radio interfaces can be achieved. The current research in UWB communications addresses optimal energy-efficient modulation-, access-, coding-, and detection schemes. New results from information theory are needed to determine the basic capabilities of UWB systems under real network- and propagation conditions as well as to unveil optimal system concepts. Further research into variable data rates in sensor networks, dedicated short-range access, secure communication, cooperative detection and integrated communication, sensor and location functions for sensor networks, etc., are also being done.

For localization and sensing applications, the huge UWB bandwidth allows the unprecedented time delay resolution. Precise range estimates in strong multipath environments become possible making UWB the key technology for indoor radio localization, be it infrastructure-based localization, relative inter-terminal localization in ad-hoc networks, or passive localization (e.g. radar imaging). Interaction of the UWB wave field with materials and objects delivers vast information about object's shape, position, motion dynamics, structural time variance, material composition, etc. Since the extremely large bandwidth of UWB is provided at a comparably low frequency (for sensor applications the lower frequency limit may be as low as several hundreds of MHz), UWB can also penetrate materials and obstacles. Information about the inner structure of objects can be made available and the investigation of objects that are hidden by obstacles becomes feasible. Such capabilities open up many applications for use in the industry, e.g. in civil engineering, surveillance, security and safety operations, and even medicine. However basic research is still required to investigate the theory behind the interaction between UWB radio signals and objects, material, environments, technical, or biomedical processes, etc. This will then lead to many different interdisciplinary questions, since non-electrical properties and their relation to the ultra-wideband electro-magnetic field will become essential knowledge.

XX Preface

and developed.

networks, etc., are also being done.

Sensor Applications (UKoLoS)'. UKoLoS started in 2006 and ended in 2012. Altogether 14 research partners participated in the research program, which are mainly universities. Most of the projects are conducted as a cooperative research between two to four partners. The initial aim of UKoLoS was the joint UWB research in the areas of communications, localization, and sensors. Remarkable synergy effects and technological advancement and development are expected. This book gives an

In contrast to the conventional frequency multiplexed radio approach, ultra-wideband radio systems earmark a completely new technological philosophy. Since UWB frequencies are already occupied by other radio services, coexistence with the existing systems is a serious concern. Hence it must be made clear that the aim of the UWB technologies is not to replace the current existing systems but to simply coexist with them. Therefore, the transmit power for UWB systems is strictly limited and intelligent interference mitigation methods and cognitive access schemes are being investigated

For short-range communication and sensor networks, the UWB technology offers a very interesting alternative to the current conventional systems since very high data rates at low power radio interfaces can be achieved. The current research in UWB communications addresses optimal energy-efficient modulation-, access-, coding-, and detection schemes. New results from information theory are needed to determine the basic capabilities of UWB systems under real network- and propagation conditions as well as to unveil optimal system concepts. Further research into variable data rates in sensor networks, dedicated short-range access, secure communication, cooperative detection and integrated communication, sensor and location functions for sensor

For localization and sensing applications, the huge UWB bandwidth allows the unprecedented time delay resolution. Precise range estimates in strong multipath environments become possible making UWB the key technology for indoor radio localization, be it infrastructure-based localization, relative inter-terminal localization in ad-hoc networks, or passive localization (e.g. radar imaging). Interaction of the UWB wave field with materials and objects delivers vast information about object's shape, position, motion dynamics, structural time variance, material composition, etc. Since the extremely large bandwidth of UWB is provided at a comparably low frequency (for sensor applications the lower frequency limit may be as low as several hundreds of MHz), UWB can also penetrate materials and obstacles. Information about the inner structure of objects can be made available and the investigation of objects that are hidden by obstacles becomes feasible. Such capabilities open up many applications for use in the industry, e.g. in civil engineering, surveillance, security and safety operations, and even medicine. However basic research is still required to investigate the theory behind the interaction between UWB radio signals and objects, material, environments, technical, or biomedical processes, etc. This will then lead to

overview of the scope and results of the UKoLoS program.

As mentioned before, UWB utilizes an extremely large bandwidth of potentially several GHz at a comparably low frequency of a few GHz. Associated with the extremely large bandwidth is the potential for super high data rates, yet limited by low power constraints. Therefore, and especially due to the extremely high relative bandwidth, the UWB technology not only promises new and outstanding performance features but also adds new and highly challenging design demands on the envisioned UWB circuits and systems. UWB radio interfaces require innovative integrated hardware architecture, design and implementation. This includes UWB front-ends, antennas and data processing units as a whole. Efficient small antennas with optimal time-domain behavior in real propagation environments are just but one example. Known space-time signal processing algorithms must be tested against the properties of UWB signals and subsequently improved and new processing schemes have to be developed as well. Generally speaking, UWB requires a change of paradigm from narrowband to wideband principles in both algorithms and hardware. Linearity, impulse response, stability, robustness, and power consumption are very important properties, which lead to new requirements in design strategies for UWB circuits. Modern microwave semiconductor technologies such as Silicon-Germanium (SiGe) together with new manufacturing processes and packaging technologies play a key role in the implementation of complex UWB systems on a single integrated circuit.

When the FCC published their report and order that authorizes the unlicensed use of the ultra-wideband (UWB) of 3.1–10.6 GHz a great storm of research, publications, standard proposals, etc. emerged. The usage of the UWB band seemed extremely promising since the very large bandwidth could support high data rates in wireless communications or a good range resolution in sensors. However the hype is now over. On one hand, there are indeed some UWB radio access devices on the market. UWB has become the foundation of Wireless USB and WiMedia access. Yet the anticipated big economic success of UWB still remains to be seen. The last ten years of UWB research has however brought us many insights to a completely new and alternative radio access philosophy. Whereas the first hype was driven by the expectation of a big economic success in the electronic mass market, now the motivation is clearly driven by the physical advantage of such a huge bandwidth at low frequencies. New and innovative applications are generated, which are not yet mainstream. So the initial idea of high data rate wireless UWB systems may have taken a backseat in favor of UWB based systems for medical diagnostics, localization, sensing etc. But the coming years will show if these new ideas will launch UWB into a broad commercial success or at least as indispensable technology in the niche markets. This book at hand is meant to provide some important basics for that goal.

### **Acknowledgement**

All the authors and their corresponding researchers from the various institutions supported by this program would like to express their utmost gratitude to DFG for funding these research projects over 6 years and to enable many revolutionary discoveries to be made in the field of UWB. We would also like to thank the panel of reviewers for their time and effort in reviewing all the submitted project proposals. Last but not least much appreciation goes to Dr. Klaus Wefelmeier and his successor Dr. Damian Dudek for their great support and their personal commitment. We hope that this collective research effort will propel the technology to greater heights and to inspire new innovations.

**Reiner Thomä, Reinhard Knöchel, Jürgen Sachs, Ingolf Willms, Thomas Zwick** 

XXII Preface

**Acknowledgement** 

inspire new innovations.

All the authors and their corresponding researchers from the various institutions supported by this program would like to express their utmost gratitude to DFG for funding these research projects over 6 years and to enable many revolutionary discoveries to be made in the field of UWB. We would also like to thank the panel of reviewers for their time and effort in reviewing all the submitted project proposals. Last but not least much appreciation goes to Dr. Klaus Wefelmeier and his successor Dr. Damian Dudek for their great support and their personal commitment. We hope that this collective research effort will propel the technology to greater heights and to

**Reiner Thomä, Reinhard Knöchel, Jürgen Sachs, Ingolf Willms, Thomas Zwick** 

**Chapter 1**

**Chapter 1**

**MIRA – Physical Layer Optimisation for the**

**Multiband Impulse Radio UWB Architecture**

Future wireless communication systems have to be realised in a simple and energy efficient manner while guaranteeing sufficient performance. Furthermore, the available frequency resources have to be used flexibly and efficiently. In this context two different approaches have been considered in recent years: On one hand OFDM-based overlay systems in which a primary user dynamically allocates unused frequencies to one or more secondary users [57] and on the other hand unlicensed, easy-to-realise and low-cost ultra-wideband (UWB) systems. This underlying technology operates with an extremely low transmission power over a wide frequency range and does not interfere with existing licensed systems [15].

In order to establish UWB on the consumer market it has to get along with some challenges. Such challenges are, e.g., the realisation of practical, low-complex and energy-efficient transceiver architectures, the investigation of methods for accurate synchronization and channel estimation or the handling of high sample rates. To meet these requirements this chapter considers a non-coherent multiband impulse radio UWB (MIR-UWB) system [11, 45, 46]. The MIR-UWB system focuses on short-range high data rate communication applications. The MIR-UWB system is an alternative to the architectures Multiband OFDM UWB [2] and Direct Sequence UWB [16] which have been proposed within the IEEE 802.15.3a

The chapter is organised as follows: Section 2 gives a short introduction into the physical layer architecture of the non-coherent MIR-UWB system. In the following section 3 the performance of the energy detection receiver is analysed with respect to different aspects. In contrast section 4 deals with interference investigations for the non-coherent MIR-UWB system aiming at an efficient and intelligent interference handling. The chapter concludes with section 5 in

> ©2013 Dehner et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0),which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly

©2013 Dehner et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Rainer Moorfeld, Adolf Finger, Hanns-Ulrich Dehner, Holger Jäkel,

Martin Braun and Friedrich K. Jondral

http://dx.doi.org/10.5772/55076

**1. Introduction**

standardization process.

which a summary is given.

cited.

Additional information is available at the end of the chapter
