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好书一本
Wireless Networking Technology
From Principles to Successful Implementation
Steve Rackley
Chapter 1: Introducing Wireless Networking ...................................1
Development of Wireless Networking ................................................. 1
The Diversity of Wireless Networking Technologies .......................... 2
Organisation of the Book ..................................................................... 3
PART I: Wireless Network Architecture .................... 7
Introduction ........................................................................................ 7
Chapter 2: Wireless Network Logical Architecture ........................... 9
The OSI Network Model ..................................................................... 9
Network Layer Technologies ............................................................. 13
Data Link Layer Technologies .......................................................... 20
Physical Layer Technologies ............................................................. 25
Operating System Considerations ..................................................... 34
Summary ............................................................................................ 36
Chapter 3: Wireless Network Physical Architecture ....................... 37
Wired Network Topologies – A Refresher ........................................ 37
Wireless Network Topologies ............................................................ 40
Wireless LAN Devices ...................................................................... 45
Wireless PAN Devices ....................................................................... 60Wireless MAN Devices ..................................................................... 62
Summary of Part I ............................................................................. 66
PART II: Wireless Communication ........................... 69
Introduction ........................................................................................ 69
Chapter 4: Radio Communication Basics ....................................... 71
The RF Spectrum ............................................................................... 71
Spread Spectrum Transmission ......................................................... 76
Wireless Multiplexing and Multiple Access Techniques .................. 87
Digital Modulation Technique ........................................................... 95
RF Signal Propagation and Reception ............................................ 106
Ultra Wideband Radio ..................................................................... 119
MIMO Radio ................................................................................... 124
Near Field Communications ............................................................ 126
Chapter 5: Infrared Communication Basics ................................. 129
The Ir Spectrum ............................................................................... 129
Infrared Propagation and Reception ................................................ 129
Summary of Part II .......................................................................... 134
PART III: Wireless LAN Implementation ................ 137
Introduction ...................................................................................... 137
Chapter 6: Wireless LAN Standards ............................................ 139
The 802.11 WLAN Standards ......................................................... 139
The 802.11 MAC Layer ....................................................................144
802.11 PHY Layer ........................................................................... 148
802.11 Enhancements ...................................................................... 156
Other WLAN Standards .................................................................. 170
Summary .......................................................................................... 173
Contents
viChapter 7: Implementing Wireless LANs ..................................... 175
Evaluating Wireless LAN Requirements ......................................... 176
Planning and Designing the Wireless LAN...................................... 183
Pilot Testing ..................................................................................... 190
Installation and Configuration ......................................................... 190
Operation and Support ..................................................................... 197
A Case Study: Voice over WLAN ................................................... 199
Chapter 8: Wireless LAN Security ................................................ 205
The Hacking Threat ......................................................................... 205
WLAN Security ............................................................................... 208
WEP – Wired Equivalent Privacy Encryption ................................. 209
Wi-Fi Protected Access – WPA ....................................................... 212
IEEE 802.11i and WPA2 ................................................................. 219
WLAN Security Measures .............................................................. 230
Wireless Hotspot Security ............................................................... 236
VoWLAN and VoIP Security ........................................................... 239
Summary .......................................................................................... 240
Chapter 9: Wireless LAN Troubleshooting ................................... 241
Analysing Wireless LAN Problems ................................................. 241
Troubleshooting using WLAN Analysers ....................................... 243
Bluetooth Coexistence with 802.11 WLANs .................................. 247
Summary of Part III ......................................................................... 249
PART IV: Wireless PAN Implementation ................ 251
Introduction ...................................................................................... 251
Chapter 10: Wireless PAN Standards .......................................... 253
Introduction ...................................................................................... 253
Bluetooth (IEEE 802.15.1) .............................................................. 254
Wireless USB ................................................................................... 265
Contents
viiZigBee (IEEE 802.15.4) .................................................................. 273
IrDA ................................................................................................. 280
Near Field Communications ............................................................ 287
Summary .......................................................................................... 292
Chapter 11: Implementing Wireless PANs ................................... 295
Wireless PAN Technology Choices ................................................. 295
Pilot Testing ..................................................................................... 300
Wireless PAN Security .................................................................... 300
Summary of Part IV ......................................................................... 306
PART V: Wireless MAN Implementation ................ 307
Introduction ...................................................................................... 307
Chapter 12: Wireless MAN Standards ......................................... 309
The 802.16 Wireless MAN Standards ............................................. 309
Other WMAN Standards ................................................................. 319
Metropolitan Area Mesh Networks ................................................. 321
Summary .......................................................................................... 322
Chapter 13: Implementing Wireless MANs .................................. 323
Technical Planning .......................................................................... 323
Business Planning ............................................................................ 332
Start-up Phase .................................................................................. 337
Operating Phase ............................................................................... 339
Summary of Part V .......................................................................... 340
PART VI: The Future of Wireless
Networking Technology .......................................... 343
Introduction ...................................................................................... 343
Contents
viiiChapter 14: Leading Edge Wireless Networking Technologies ..... 345
Wireless Mesh Network Routing .................................................... 345
Network Independent Roaming ....................................................... 347
Gigabit Wireless LANs .................................................................... 350
Cognitive Radio ............................................................................... 355
Summary of Part VI ......................................................................... 358
PART VII: Wireless Networking
Information Resources ........................................... 361
Introduction ...................................................................................... 361
Chapter 15: Further Sources of Information ................................ 363
General Information Sources ........................................................... 363
Wireless PAN Resources by Standard ............................................. 364
Wireless LAN Resources by Standard ............................................ 367
Wireless MAN Resources by Standard ........................................... 369
Chapter 16: Glossary .................................................................. 371
Networking and Wireless Networking Acronyms ........................... 371
Networking and Wireless Networking Glossary ............................. 381
Subject Index ............................................................................... 397
Contents
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CHAPTER
1
Introducing Wireless Networking
Development of Wireless Networking
Although the origins of radio frequency based wireless networking can be
traced back to the University of Hawaii’s ALOHANET research project
in the 1970s, the key events that led to wireless networking becoming
one of the fastest growing technologies of the early 21st century have
been the ratification of the IEEE 802.11 standard in 1997, and the
subsequent development of interoperability certification by the Wi-Fi
Alliance (formerly WECA).
From the 1970s through the early 1990s, the growing demand for
wireless connectivity could only be met by a narrow range of expensive
hardware, based on proprietary technologies, which offered no
interoperability of equipment from different manufacturers, no security
mechanisms and poor performance compared to the then standard
10 Mbps wired Ethernet.
The 802.11 standard stands as a major milestone in the development of
wireless networking, and the starting point for a strong and recognisable
brand — Wi-Fi. This provides a focus for the work of equipment
developers and service providers and is as much a contributor to the
growth of wireless networking as the power of the underlying
technologies.
While the various Wi-Fi variants that have emerged from the original
802.11 standard have grabbed most of the headlines in the last decade,
other wireless networking technologies have followed a similar timeline,
with the first IrDA specification being published in 1994, the same yearthat Ericsson started research on connectivity between mobile phones and
accessories that led to the adoption of Bluetooth by the IEEE 802.15.1
Working Group in 1999.
During this period of rapid development, the variety of wireless
networking technologies has expanded to fill the full range of requirements
for data rate (both high and low), operating range (long and short) and
power consumption (low and very low), as shown in Figure 1-1.
The Diversity of Wireless Networking Technologies
Wireless networks now operate over four orders of magnitude in data rate
(from ZigBee at 20 kbps to wireless USB at over 500 Mbps), and six
orders of magnitude in range (from NFC at 5 cm to WiMAX, and also
Wi-Fi, at over 50 km).
To deliver this breadth of capabilities, the many companies, research
institutions and individual engineers who have contributed to these
developments have called into service a remarkable range of technologies;
from Frequency Hopping Spread Spectrum, the inspired World War II
invention of a film actress and a screen composer that is the basis of the
Bluetooth radio, to Low Density Parity Check Codes, a breakthrough in
high efficiency data transmission that lay gathering dust for forty years
Chapter One
2
Bluetooth
Class 3
Bluetooth
Class 2
Bluetooth
Class 1 NFC
Zigbee
WUSB (Optional)
WUSB (Mandatory)
0.1 1 10 100 1000
IrDA VFIR
Range (meters)
PHY layer data rate (Mbps)
1000
100
10
1
0.1
IrDA SIR
3G
WCDMA
(3.5G)
802.11a
802.11b
802.11n
802.16d
WiMax
802.16 (10 -66 GHz)
802.11g
Figure 1-1: Wireless Networking Landscape (rate vs. range)after its development in 1963 and has proved to be an enabling technology
in the most recent advances towards gigabit wireless networks.
Technologies that started from humble origins, such as OFDM — used in
the 1980s for digital broadcasting, have been stretched to new limits and
combined with other concepts, so that Ultra Wideband (UWB) radio now
uses multi-band OFDM over 7 GHz of radio spectrum with a transmitted
power below the FCC noise limit, while OFDM combined with Multi-
Carrier Code Division Multiple Access is another gigabit wireless
network enabler.
Techniques to satisfy the every growing demand for higher data rates have
gone beyond the relatively simple approaches of shortening the time to
transmit each bit, using both the phase and amplitude of the carrier to
convey data or just using more radio bandwidth, as in UWB radio, and
arrived at the remarkable concept of spatial diversity — of using the
same space several times over for concurrent transmissions over multiple
paths — as applied in MIMO radio.
This fascinating breadth and variety of technologies is the first motivation
behind this book, which aims to give the reader an insight into these
technologies of sufficient depth to gain an understanding of the
fundamentals and appreciate the diversity, while avoiding getting down to
the level of detail that would be required by a system developer.
As well as seeking to appeal to the reader who wants to gain this
technical insight, the book also aims to use this understanding of the
principles of wireless networking technologies as a foundation on which,
a discussion of the practical aspects of wireless network implementation
can be grounded.
Organisation of the Book
This book is arranged in seven parts, with Parts I and II providing an
introduction to wireless networking and to wireless communication that
lays the foundation for the more detailed, technical and practical
discussion of the local, personal and metropolitan areas scales of wireless
networking in Parts III to V.
Part I — Wireless Network Architecture — introduces the logical and
physical architecture of wireless networks. The 7 layers of the OSI
Introducing Wireless Networking
3network model provide the framework for describing the protocols and
technologies that constitute the logical architecture, while wireless
network topologies and hardware devices are the focus of the discussion
of the physical architecture.
Some of the key characteristics of wired networking technologies are also
briefly described in the two chapters of Part I, in order to provide a
background to the specific challenges addressed by wireless technologies.
In Part II — Wireless Communication — the basics of wireless
communication are described; spread spectrum, signal coding and
modulation, multiplexing and media access methods and RF signal
propagation including the important topic of the link budget. Several new
or emerging radio communication technologies such as ultra wideband,
MIMO radio and Near Field Communications are introduced. Part II
closes with a similar overview of aspects of infrared communications.
Part III — Wireless LAN Implementation — focuses on what is perhaps
the most important operating scale for wireless networks — the local area
network. Building on the introductory description of Part I, local area
wireless networking technologies are reviewed in more detail — including
the full alphabet of 802.11 standards and enhancements. The practical
aspects of wireless LAN implementation are then described, from the
identification of user requirements through planning, pilot testing,
installation, configuration and support.
A chapter is devoted to the important topic of wireless LAN security,
covering both the standards enhancements and practical security measures,
and Part III closes with a chapter on wireless LAN troubleshooting.
Part IV — Wireless PAN Implementation — takes a similar detailed look
at wireless networking technologies on the personal area scale, including
Bluetooth, wireless USB, ZigBee, IrDA and Near Field Communications.
The practical aspects of wireless PAN implementation and security are
covered in the final chapter of Part IV.
Part V — Wireless MAN Implementation — looks at how the
metropolitan area networking challenges of scalability, flexibility and
quality of service have been addressed by wireless MAN standards,
particularly WiMax. Non-IEEE MAN standards are briefly described, as
well as metropolitan area mesh networks.
Chapter One
4The practical aspects of wireless MAN implementation are discussed,
including technical planning, business planning and issues that need to be
addressed in the start-up and operating phases of a wireless MAN.
Part VI — The Future of Wireless Networking Technology — looks at
four emerging technologies — namely wireless mesh routing, network
independent handover, gigabit wireless LANs and cognitive radio — that,
taken together, look set to fulfil the promise of ubiquitous wireless
accessibility and finally lay to rest the recurring technical challenges of
bandwidth, media access, QoS and mobility.
Finally Part VII — Wireless Networking Information
Resources — provides a quick reference guide to some of the key online
information sites and resources relating to wireless networking, a
comprehensive listing of acronyms and a glossary covering the key
technical terms used throughout the book.
Introducing Wireless Networking
5This page intentionally left blankPART
I
WIRELESS NETWORK
ARCHITECTURE
Introduction
In the next two chapters, the logical and physical architecture of wireless
networks will be introduced. The logical architecture is introduced in
terms of the 7 layers of the OSI network model and the protocols that
operate within this structure, with an emphasis on the Network and Data
Link aspects that are most relevant to wireless networking — IP addressing,
routing, link control and media access.
Physical layer technologies are introduced, as a precursor to the more
detailed descriptions later in the book, and the physical architecture of
wireless networks is described, focussing on wireless network topologies
and hardware devices.
At each stage, some of the key characteristics of wired networking
technologies are also briefly described, as a preliminary to the introduction
of wireless networking technologies, in order to provide a background to
the specific challenges addressed by wireless technologies, such as media
access control.
After this introduction, Part II will describe the basic concepts and
technologies of wireless communication — both radio frequency and
infrared. |
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