Radio Engineering E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 543

Veröffentlichungsjahr: 2013

Beschreibung

Software radio ideally provides the opportunity to communicate with any radio communication standard by modifying only the software, without any modification to hardware components. However, taking into account the static behavior of current communications protocols, the spectrum efficiency optimization, and flexibility, the radio domain has become an important factor. From this thinking appeared the cognitive radio paradigm. This evolution is today inescapable in the modern radio communication world. It provides an autonomous behavior to the equipment and therefore the adaptation of communication parameters to better match their needs. This collective work provides engineers, researchers and radio designers with the necessary information from mathematical analysis and hardware architectures to design methodology and tools, running platforms and standardization in order to understand this new cognitive radio domain.

Leseprobe

First published 2011 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd 27–37 St George’s Road London SW19 4EU UK

www.iste.co.uk

John Wiley & Sons, Inc. 111 River Street Hoboken, NJ 07030 USA

www.wiley.com

© ISTE Ltd 2011

The rights of Jacques Palicot to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Cataloging-in-Publication Data

Software and cognitive radio engineering / edited by Jacques Palicot.       p. cm.    Includes bibliographical references and index.    ISBN 978-1-84821-296-1    1. Cognitive radio networks. 2. Software radio. I. Palicot, Jacques.     TK5103.4815.S64 2011     621.384--dc23

2011024239

British Library Cataloguing-in-Publication Data

Table of Contents

Foreword

Acknowledgments

Introduction

PART 1. COGNITIVE RADIO

Chapter 1. Introduction to Cognitive Radio

1.1. Joseph Mitola's cognitive radio

1.2. Positioning

1.3. Spectrum management

1.4. A broader vision of CR

1.5. Difficulties of the cognitive cycle

Chapter 2. Cognitive Terminals Toward Cognitive Networks

2.1. Introduction

2.2. Intelligent terminal

2.3. Intelligent networks

2.4. Toward a compromise

2.5. Conclusion

Chapter 3. Cognitive Radio Sensors

3.1. Lower layer sensors

3.2. Intermediate layer sensors

3.3. Higher layer sensors

3.4. Conclusion

Chapter 4. Decision Making and Learning

4.1. Introduction

4.2. CR equipment: decision and/or learning

4.3. Decision design space

4.4. Decision making and learning from the equipment's perspective

4.5. Decision making and learning from network perspective: game theory

4.6. Brief state of the art: classification of methods for dynamic configuration adaptation

4.7. Conclusion

Chapter 5. Cognitive Cycle Management

5.1. Introduction

5.2. Cognitive radio equipment

5.3. High-level design approach

5.4. HDCRAM's interfaces (APIs)

5.5. Conclusion

PART 2. SOFTWARE RADIO AS SUPPORT TECHNOLOGY

Chapter 6. Introduction to Software Radio

6.1. Introduction

6.2. Generalities

6.3. Major organizations of software radio

6.4. Hardware architectures

6.5. Conclusion

Chapter 7. Transmitter/Receiver Analog Front End

7.1. Introduction

7.2. Antennas

7.3. Nonlinear amplification

7.4. Converters

7.5. Conclusion

Chapter 8. Transmitter/Receiver Digital Front End

8.1. Theoretical principles

8.2. DFE functions

8.3. Synchronization

8.4. The CORDIC algorithm

8.5. Conclusion

Chapter 9. Processing of Nonlinearities

9.1. Introduction

9.2. Crest factor of the signals to be amplified

9.3. Variation of crest factor in different contexts

9.4. Methods for reducing nonlinearities

9.5. Conclusion

Chapter 10. Methodology and Tools

10.1. Introduction

10.2. Methods to identify common operations

10.3. Methods and design tools

10.4. Conclusion

Chapter 11. Implementation Platforms

11.1. Introduction

11.2. Software radio platform

11.3. Hardware architectures

11.4. Characterization of the implementation platform

11.5. Qualitative assessment

11.6. Architectures of software layers

11.7. Some platform examples

11.8. Conclusion

Chapter 12. General Conclusion and Perspectives

12.1. General conclusion

12.2. Perspectives

Appendix A. To Learn More

A.1. The special issues of journals

A.2. Specialized conferences

A.3. Some reference books

Appendix B. SR and CR Projects

B.1. Europeanprojects

B.2. French projects

Appendix C. International Activity in Standardization and Forums

C.1. The IEEE 802.22 Standard

C.2. SCC41 standardization (Standards Coordinating Committee 41,dynamic spectrum access networks)

C.3. P1900.1 standardization (Working group on terminology andconcepts for next-generation radio systems and spectrummanagement)

C.4. P1900.2 standardization (Working group on recommendedpractice for interference coexistence and analysis)

C.5. P1900.3 standardization (Working group on recommendedpractice for conformance evaluation of Software Defined Radiosoftware modules)

C.6. P1900.4 standardization (Working group on architecturalbuilding blocks enabling network ‣ device distributed decisionmaking for optimized radio resource usage in heterogeneouswireless access networks)

C.7. P1900.5 standardization (Working group on policy language andpolicy architectures for managing cognitive radio for dynamicspectrum access applications)

C.8. P1900.6 standardization (Working group on spectrum sensinginterfaces and data structures for dynamic spectrum access andother advanced radio communications systems)

C.9. ITU-R standards (Question ITU-R 241-1/5: cognitive radiosystems inmobile service)

C.10. ETSI technical committee on reconfigurable radio systems(TC-RRS) standardization

C.11. Forum: Wireless Innovation Forum (former by SDR forum)

C.12. Forum: Wireless World Research Forum

Foreword

It is not surprising for an engineering school that started its TSF courses in 1903 with Commander Ferrié to be interested in radio communications in their most advanced scientific forms.

Since then the uses and services, now collectively linked to “mobility”, have exploded. Today there is little prospect of a company without anytime, anywhere availability of simple, affordable access to reliable, seamless, wireless infrastructure.

This already impressive list of functionality can be easily modified and extended to meet every reader's individual expectations. However, as noted in this book, radio as a resource is limited, even if it is infinitely renewable, because of the energy needed for wave generation.

In fact, wireless communication systems themselves (terminals, equipment, and networks) and their connections with wired infrastructure are highly complex systems. For their design, we must involve all the engineering sciences: modeling and simulation, contents and computer systems, interactions and protocols, hardware‐software integration, networking and communications, etc.

This book is titled Radio Engineering: From Software Radio to Cognitive Radio. It looks at the astounding move from mathematical formalism to hardware/software architectures, and tackles issues of methodology, tools, and implementation platforms, as well as standardization.

This broad exploration of radio communications, until their projection in sustainable development problems, illustrates the teaching and research ambitions of Supélec in information sciences, energy, and systems.

I hope that the reader will find, to a great extent, answers and ideas in this book.

Alain Bravo

Director general, Supélec

Acknowledgments

Writing a collective book with more than 10 authors was a very rewarding experience. This book is the result, and we hope that this book it will give the readers all the keys to enter into new areas, which are software radio and cognitive radio.

The authors wish to thank Pierre-Noël Favennec, series editor of Telecoms and Optics at ISTE, for offering the opportunity to write this book.

We are also grateful to Alain Bravo, director general Supélec, who honored us by writing the preface of this book.

Our thanks go initially to all our colleagues who participated in this scientific endeavor and whose works have largely served as base material for this book.

Alphabetically, we thank:

– PhD colleagues: Laurent Alaus, Ali Al Gouwayel, Jean-Philippe Delahaye, Mohamed Ghozzi, Loïg Godard, Sufi Tabassum Gul, Rachid Hachemani, Sajjad Hussain, Stéphane Lecomte, Sylvain Le Gallou, Adel Metref, Hongzhi Wang, and Sidkiéta Zabré;

– Post-doctoral colleagues: Julien Delorme, Thi Minh Hien Ngo, and Virgilio Rodriguez.

We are indebted to all the reviewers who kindly agreed to spare their precious time to review this book and give valuable comments to significantly improve the quality of the book.

Alphabetically, we thank: Eric Bayet, Moïse Djoko Kouam, Damien Ernst, Guy Gognat, Yann Le Guillou, Jérome Martin, Markus Muck, Dominique Noguet, Dominique Nussbaum, Christian Roland, Ronan Sauleau, and Martine Villegas.

Introduction

This book presents an inevitable evolution in today's wireless communication world: it concerns “cognitive radio” (CR). This new concept is based on the work of Joseph Mitola published in 1999 and 2000 [MIT 99a, MIT 00a].

From information theory to cognitive radio

In 1948, through a single 55-page publication, Claude Elwood Shannon [SHA 48] radically changed the vision of modern telecommunications by inventing a new theory known as Information Theory. In this publication, Shannon brought, in particular, the response to a fundamental telecommunications problem: how much information can be transferred between two people communicating in a given environment at a particular time, so that everyone understands the respective information without errors? Ever since the formulation of this response by Shannon, we see around us the development of phones, WiFi cards, etc., capable of transmitting more and more data per second. However, we must not delude ourselves, and it is in this that Shannon's work is so fundamental: the rate of information transmitted without error is naturally limited by the communication environment, the frequency band (commonly called bandwidth) used, and the power of transmitted signals. Hence, if any of these three fundamental resources reaches its limit, we cannot transmit information at a higher rate. Ten years ago, Joseph Mitola saw that a revolution in telecommunications was definitely going to take place right away. The principal perception of Mitola is that the rapid and less efficiently controlled use of telecommunication resources (especially bandwidth) had led to an enormous waste of these resources. The simplest of the examples of wastage is the functioning mode of the global system for mobile communication (GSM) standard (also known as 2G): the latter permits eight users of the mobile telephone network to connect simultaneously to a base station of their service provider. When a single user is connected to the base station, this user, however, only uses one-eighth of the total resources available to it. The static nature of the current communication protocols raises the question of how to make the wireless domain more “flexible”. From this important comprehension, directly affecting the sustainability of modern telecommunications, the field of CR was thus born, which tends to make communication devices more autonomous, capable of deciding which resources to use and how to use them effectively. For example, if no GSM network coverage is present in the room in a house, then why not take advantage of the WiFi access point. The goal would be that a communication system can make such kinds of decisions autonomously. It is even highly desirable that our telecommunications devices can precisely perform this reasoning in an intelligent manner, reflecting that the human being will do the same when faced with such a situation.

From software radio to cognitive radio

In 1995, Joseph Mitola proposed a new concept entitled “software radio” (SR) [MIT 95]. Ideally, this concept permits equipment to communicate with any radio communications standard, without changing any hardware component and only by modifying the embedded software. This technology, which may appear very simple at first glance, not only introduces many new advantages, but also raises numerous technological challenges. This technology and its related problems are addressed in Part 2 of this book. Mitola realized the need to put intelligence simultaneously into both the network and the equipment to satisfy user needs and resource constraints, ultimately resulting in an increase in spectral efficiency. This is why he proposed the idea of CR [MIT 99a]. This intelligence enables the equipment to choose the best conditions to meet its communication needs. The choice ideally implies a realtime change of transmission parameters, even a change of standard. To do this optimally, Mitola showed that the change in real time should be realized by an SR. He concluded that CR would be more effective if it were supported by SR technology. Our orientation in this book is exactly toward this logic. Part 1 will focus on the CR while Part 2 will discuss the SR as a support technology for the concept of CR.

Book structure

The subject of this book is very broad. We do not claim to examine exhaustively all the aspects associated with it. However, a radio designer or a researcher of the domain will find the necessary information useful to understanding the fundamental concepts and identifying other literature sources that could complete explanations contained in this book.

This book contains two main parts. Part 1, entitled “Cognitive Radio”, includes five chapters. It illustrates the expectations and the challenges related to the new concept of CR.

Chapter 1 provides an introduction to CR, starting with the need for optimal spectrum management. Then, a set of definitions is provided. The cognitive cycle based on the work of Mitola is described. The concept of opportunistic radio is presented and various ways of achieving such opportunistic radio are discussed. A more general vision than the classical spectral vision is also proposed, notably due to the notion of “sensorial radio bubble” and a limited “three-layer model” obtained by regrouping the layers of the open system interconnection (OSI) model. Finally, the chapter ends with a state (non-exhaustive) of the current national and international collaborative projects and standardization.

Chapter 2 addresses the question of the intelligence distribution between the network and the terminal equipment. This discussion is far from closed. Clearly, behind this distribution are the industrial and economic interests of different players. Hence, our conclusion is that the intelligence must be in both networks and terminals at the same time.

Chapter 3 focuses on the “sensing” function of the cognitive cycle. The sensors of the three layers of the model are presented and some are described in detail. Particularly, the role of “hole detection sensor” in the spectrum, a sensor considered in the literature as the main CR sensor, is explained. This chapter thus broadens the classical understanding of the sensors in CR, which typically consists of the physical layer sensors.

Chapter 4 points out that with all the available information provided by the sensors of any kind, as explained in Chapter 3, and due to the known behavior rules or the learned rules from past experience, the equipment, in accordance with the cognitive cycle, must make decisions. This aspect of CR is discussed extensively in the literature. It results in a large number of potential solutions, with their advantages and disadvantages. These are described in this chapter. The necessity of learning is emphasized and methods taking into account that learning are presented.

Chapter 5 presents the need to manage the intelligent cycle. This management is crucial for proper functioning of the equipment, both at the design level of this equipment and its functioning in real time. After explaining the need to manage the cycle, we present a solution known as hierarchical and distributed cognitive radio architecture management (HDCRAM in detail.

Part 2, entitled “Software Radio as Support Technology”, includes six chapters. Although the concept of SR dates back to 1995, and despite the rapid technological advances in past 20 years, there remain a large number of difficulties to be overcome before realizing an SR that conforms to the original concept. This part illustrates all these difficulties.

Chapter 6 describes the SR in its historical and economic contexts. It presents the ideal concept and the resulting architecture. After emphasizing the difficulties of implementing such an architecture, the concept of “software-defined radio” (SDR) is proposed, with different possible architectures. Despite reduced difficulties encountered in this SDR architecture, there remain numerous problems to be solved. These are the subject of the subsequent chapters.

Chapter 7, starting from the SDR architecture, in which an analog part is retained, deals with the “transmitter/receiver analog front end” (AFE). In this chapter, three problems, which follow the sequential order of signal processing, are reviewed:

– the first concerns the antennas that must be wideband or multiband and/or highly directive depending on the application context;

– the second deals with the amplification stages. This difficulty is often neglected in the literature, but from our point of view it is fundamental. Indeed, the signals processed by the amplifiers will be the sum of a large number of modulated carriers and therefore present a large variation in power;

– the third concerns the problems of analog-to-digital and digital-to-analog conversion. This was the first identified problem in the beginning of the work on the SR. Indeed, the levels to be sampled are such that no circuit can perform this conversion on a very wideband of several GHz for example. This problem has generated much research activity both in terms of signal processing and electronics. An update on this activity and the most promising solutions is presented in this chapter.

Chapter 8 deals with the second part of the SDR architecture. It follows the analog-to-digital conversion stage and precedes the digital-to-analog conversion stage, in which a number of functions previously processed in analog are processed digitally in the SR context. This part is called “transmitter/receiver digital front end” (DFE). In this chapter, functions such as (de)-modulation, filtering of desired channels, and clock synchronization with the sampling clock are described. A particular point is made on the synchronization function, which in a CR/SR context has new constraints, more difficult than conventional digital reception.

Chapter 9, based on the nonlinear amplification problem described in Chapter 7, proposes a theoretical analysis of the signals involved, and identifies a set of methods to reduce the significant power variation of the signals to be amplified. In the context of dynamic spectrum access, the methods of adding signal over reserved carriers are preferred and detailed.

Chapter 10 explains the need to take into account the real-time (re-)configuration constraints imposed by the SR and by the design phase of the equipment. The advantage of reducing the computational complexity of processing by factorization techniques is emphasized. The technique of parameterization using common operators is also presented in this chapter. To provide a high-level design environment, which is as general as possible, the model-driven architecture (MDA) approach is presented as a pertinent solution. In this framework, several design flow solutions are described.

Chapter 11, the last chapter of this book, describes the objective reality of the SR existence. There is a need to process the data at different frequencies and the nature of this processing involves the use of heterogeneous platforms. Like the management of the intelligent cycle described in Chapter 5, the need for (re-)configuration management is highlighted and the solutions of configuration management are presented. The need for the real-time (re-)configuration and the generated constraints affects the solutions on different platforms. The solution of partial (re-)configuration of field-programmable gate array (FPGA) to this constraint is also described. Finally, some existing platforms with SR capabilities are presented.

We conclude this book by presenting an application, the green cognitive radio, which aims at reducing energy consumption and electromagnetic pollution, and the possible evolutions such as collective intelligence, spontaneous communication, and a radio with aptitudes approaching the cognitive aptitudes of the CR.

PART 1 Cognitive Radio

Chapter 1Introduction to Cognitive Radio1

1.1. Joseph Mitola's cognitive radio

In 1995, Joseph Mitola introduced the new concept of software radio (SR) [MIT 95]. Soon after, during his thesis [MIT 00a], he became interested in the efficient use of the spectrum. He noticed that the spectrum was very inefficiently used and a large part of it was underutilized. He concluded that by locally managing the spectrum intelligently, its use could be significantly increased. Mitola realized the need to put intelligence simultaneously into both the network and the equipment, to satisfy both the user needs and resource constraints, ultimately resulting in an increase in spectral efficiency. This is why he proposed the idea of cognitive radio (CR) [MIT 99a]. He demonstrated that CR would be more efficient if combined with SR technology.

Let us illustrate the CR approach by drawing a simple analogy between radio systems carrying information and land transportation of goods. The railroad is a physical link between two stations. The train on which the goods are to be carried must follow the track and it cannot choose other “routes and/or timings”. The analogy then is that a conventional radio communication link on the global system for mobile communication (GSM) standard has no other options but to follow the track (given frequency and modulation) to ensure that the information reaches the receiver. When the same goods are transported by the road network, a whole infrastructure joining the same two points with no time constraints exists. If we follow this analogy, the SR will act as the infrastructure equivalent to the road network that will offer possible choices (frequency, modulation, etc.) for transmitting information from the sender to the receiver. On this network, the driver will be free to choose the route on the basis of different criteria, e.g. travel time, distance, toll costs, expected traffic, departure time, etc. Similarly, the CR will allow the terminal, i.e. the driver, to move in the radio infrastructure (thanks to SR technology), having many more choices at its disposal, mainly because of its environmental awareness.

1.1.1. Definitions

In his thesis, Mitola wrote: “The term cognitive radio identifies the point at which wireless personal digital assistants (PDAs) and the related networks are sufficiently computationally intelligent about radio resources and related computer-to-computer communications so that they can:

1) detect user communications needs as a function of usage context; and

2) provide radio resources and wireless services most appropriate to these needs”.

Another definition has recently been given by the Federal Communications Commission (FCC) of the United States [FCC 05]. We think that this definition is very limited in scope, but it is largely adopted by the radio domain community: “A cognitive radio is a radio that can change its transmitter parameters based on interaction with the environment in which it operates”. We interpret this definition by FCC as: “A CR is a radio that can change its transmission parameters , through interactions with the environment in which it operates”.