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Table of Contents

Introduction xxiv

Chapter 1 Introduction to Wireless LANs 1

The Wireless LAN Market 2
Today’s Wireless LAN Standards 3
Applications of Wireless LANs 3
Access Role 4
Network Extension 5
Building-to-Building Connectivity 5
Last Mile Data Delivery 6
Mobility 7
Small Office-Home Office 8
Summary 10
Key Terms 11
Review Questions 12
Answers to Review Questions 15

Chapter 2 Radio Frequency (RF) Fundamentals 17

Radio Frequency 18
RF Behaviors 19
Gain 19
Loss 19
Reflection 20
Refraction 21
Diffraction 22
Scattering 23
Absorption 23
Voltage Standing Wave Ratio (VSWR) 24
VSWR Measurements 25
Effects of VSWR 25
Solutions to VSWR 25
Principles of Antennas 25
Line of Sight (LOS) 26
Fresnel Zone 26
Obstructions 27
Antenna Gain 28
Intentional Radiator 28
Equivalent Isotropically Radiated Power (EIRP) 29
Radio Frequency Mathematics 29
Units of Measure 30
Watts (W) 30
Milliwatt 30
Decibels 31
dBm 32
dBi 34
Accurate Measurements 35
Key Terms 37
Review Questions 38
Answers to Review Questions 43

Chapter 3 Spread Spectrum Technology 45

Introducing Spread Spectrum 46
Narrow Band Transmission 46
Spread Spectrum Technology 47
Uses of Spread Spectrum 48
Wireless Local Area Networks 48
Wireless Personal Area Networks 49
Wireless Metropolitan Area Networks 49
FCC Specifications 49
Frequency Hopping Spread Spectrum (FHSS) 50
How FHSS Works 50
Effects of Narrow Band Interference 51
Frequency Hopping Systems 51
Channels 51
Dwell Time 52
Hop Time 53
Dwell Time Limits 53
FCC Rules affecting FHSS 54
Direct Sequence Spread Spectrum (DSSS) 55
How DSSS Works 55
Direct Sequence Systems 55
Channels 56
Effects of Narrow Band Interference 58
FCC Rules affecting DSSS 58
Comparing FHSS and DSSS 58
Narrowband Interference 58
Cost 59
Co-location 59
Equipment compatibility and availability 60
Data rate & throughput 60
Security 61
Standards Support 61
Key Terms 62
Review Questions 63
Answers to Review Questions 68

Chapter 4 Wireless LAN Infrastructure Devices 71

Access Points 72
Access Point Modes 73
Root Mode 74
Bridge Mode 74
Repeater Mode 75
Common Options 76
Fixed or Detachable Antennas 76
Advanced Filtering Capabilities 76
Removable (Modular) Radio Cards 77
Variable Output Power 77
Varied Types of Wired Connectivity 77
Configuration and Management 78
Wireless Bridges 80
Wireless Bridge Modes 81
Root Mode 81
Non-root Mode 82
Access Point Mode 82
Repeater Mode 82
Common Options 83
Fixed or Detachable Antennas 83
Advanced Filtering Capabilities 84
Removable (Modular) Radio Cards 84
Variable Output Power 84
Varied Types of Wired Connectivity 84
Configuration and Management 85
Wireless Workgroup Bridges 85
Common Options 86
Configuration and Management 86
Wireless LAN Client Devices 87
PCMCIA & Compact Flash Cards 87
Wireless Ethernet & Serial Converters 88
USB Adapters 89
PCI & ISA Adapters 89
Configuration and Management 90
Driver Installation 90
Manufacturer Utilities 90
Wireless Residential Gateways 91
Common Options 92
Configuration and Management 93
Enterprise Wireless Gateways 93
Configuration and Management 95
Key Terms 96
Review Questions 97
Answers to Review Questions 101

Chapter 5 Antennas and Accessories 105

RF Antennas 107
Omni-directional (Dipole) Antennas 107
Usage 109
Semi-directional Antennas 110
Usage 111
Highly-directional Antennas 112
Usage 113
RF Antenna Concepts 113
Polarization 113
Gain 115
Beamwidth 115
Free Space Path Loss 116
The 6dB Rule 117
Antenna Installation 117
Placement 118
Mounting 118
Appropriate Use 119
Orientation 119
Alignment 120
Safety 120
Maintenance 121
Power over Ethernet (PoE) Devices 121
Common PoE Options 122
Single-port DC Voltage Injectors 123
Multi-port DC Voltage Injectors 123
Active Ethernet Switches 124
PoE Compatibility 124
Types of Injectors 125
Types of Picker / Taps 125
Voltage and Pinout Standards 125
Fault Protection 126
Wireless LAN Accessories 126
RF Amplifiers 127
Common Options 127
Configuration & Management 128
Special Stipulations 128
RF Attenuators 130
Common Options 130
Configuration and Management 131
Lightning Arrestors 131
Common Options 133
Configuration & Maintenance 135
RF Splitters 135
Choosing an RF Splitter 136
RF Connectors 138
Choosing an RF Connector 139
RF Cables 139
RF "Pigtail" Adapter Cable 141
Frequency Converter 142
Bandwidth Control Units 143
Test Kits 144
Key Terms 145
Review Questions 146
Answers to Review Questions 150

Chapter 6 Wireless LAN Organizations and 153

Standards 153
Federal Communications Commission 154
ISM and UNII Bands 154
Advantages and Disadvantages of License-Free Bands 155
Industrial Scientific Medical (ISM) Bands 155
900 MHz ISM Band 156
2.4 GHz ISM Band 156
5.8 GHz ISM Band 156
Unlicensed National Information Infrastructure (UNII) Bands 156
Lower Band 157
Middle Band 157
Upper Band 157
Power Output Rules 157
Point-to-Multipoint (PtMP) 157
Point-to-Point (PtP) 158
Institute of Electrical and Electronics Engineers 159
IEEE 802.11 160
Contents xi
IEEE 802.11b 160
IEEE 802.11a 161
IEEE 802.11g 161
Major Organizations 162
Wireless Ethernet Compatibility Alliance 162
European Telecommunications Standards Institute 163
Wireless LAN Association 163
Competing Technologies 164
HomeRF 164
Bluetooth 165
Infrared Data Association (IrDA) 166
Infrared 166
Wireless LAN Interoperability Forum (WLIF) 167
Key Terms 168
Review Questions 168
Answers to Review Questions 173

Chapter 7 802.11 Network Architecture 175

Locating a Wireless LAN 176
Service Set Identifier 176
Beacons 176
Time Synchronization 177
FH or DS Parameter Sets 177
SSID Information 177
Traffic Indication Map (TIM) 177
Supported Rates 177
Passive Scanning 178
Active Scanning 179
Authentication & Association 180
Authentication 180
Association 180
States of Authentication & Association 181
Unauthenticated and Unassociated 181
Authenticated and Unassociated 181
Authenticated and Associated 181
Authentication Methods 182
Open System Authentication 182
Shared Key Authentication 183
Authentication Security 184
Shared Secrets & Certificates 185
Emerging Wireless Security Solutions 185
Service Sets 189
Basic Service Set (BSS) 189
Extended Service Set (ESS) 190
Independent Basic Service Set (IBSS) 190
Roaming 191
Standards 192
Connectivity 194
Reassociation 194
VPN Use 195
Layer 2 & 3 Boundaries 196
Load Balancing 198
Power Management Features 199
Continuous Aware Mode 199
Power Save Polling 199
PSP Mode in a Basic Service Set 200
PSP in an Independent Basic Service Set 201
Key Terms 203
Review Questions 204
Answers to Review Questions 208

Chapter 8 MAC and Physical Layers 211

How Wireless LANs Communicate 212
Wireless LAN Frames vs. Ethernet Frames 212
Collision Handling 214
Fragmentation 214
Dynamic Rate Shifting (DRS) 215
Distributed Coordination Function 216
Point Coordination Function 216
The PCF Process 217
Interframe Spacing 217
Three Types of Spacing 217
Short Interframe Space (SIFS) 218
Point Coordination Function Interframe Space (PIFS) 219
Distributed Coordination Function Interframe Space (DIFS) 219
Slot Times 220
The Communications Process 220
Request to Send/Clear to Send (RTS/CTS) 223
Configuring RTS/CTS 224
Modulation 225
Key Terms 227
Review Questions 228
Answers to Review Questions 232

Chapter 9 Troubleshooting Wireless LAN 235

Installations 235
Multipath 236
Effects of Multipath 237
Decreased Signal Amplitude 237
Corruption 237
Nulling 238
Increased Signal Amplitude 239
Troubleshooting Multipath 240
Solutions for Multipath 241
Hidden Node 242
Troubleshooting Hidden Node 243
Solutions for Hidden Node 244
Use RTS/CTS 244
Increase Power to the Nodes 245
Remove Obstacles 245
Move the Node 245
Near/Far 245
Troubleshooting Near/Far 246
Solutions for Near/Far 247
System Throughput 247
Co-location Throughput (Theory vs. Reality) 248
Theory: What Should Happen 249
Reality: What Does Happen 250
Solutions for Co-location Throughput Problems 251
Use Two Access Points 251
Use 802.11a Equipment 252
Summary 252
Types of Interference 253
Narrowband 253
All-band Interference 255
Weather 256
Wind 256
Stratification 257
Lightning 257
Adjacent Channel and Co-Channel Interference 257
Adjacent Channel Interference 258
Co-channel Interference 259
Range Considerations 260
Transmission Power 261
Antenna Type 261
Environment 261
Key Terms 262
Review Questions 263
Answers to Review Questions 267

Chapter 10 Wireless LAN Security 271

Wired Equivalent Privacy 272
Why WEP Was Chosen 273
WEP Keys 274
Static WEP Keys 275
Centralized Encryption Key Servers 276
WEP Usage 277
Advanced Encryption Standard 278
Filtering 278
SSID Filtering 278
MAC Address Filtering 280
Protocol Filtering 281
Attacks on Wireless LANs 282
Passive Attacks 282
Active Attacks 283
Jamming 284
Man-in-the-middle Attacks 286
Emerging Security Solutions 287
WEP Key Management 287
Wireless VPNs 287
Temporal Key Integrity Protocol (TKIP) 288
AES Based Solutions 289
Wireless Gateways 289
802.1x and Extensible Authentication Protocol 290
Corporate Security Policy 291
Keep Sensitive Information Private 292
Physical Security 292
Wireless LAN Equipment Inventory & Security Audits 293
Using Advanced Security Solutions 294
Public Wireless Networks 294
Limited and Tracked Access 294
Security Recommendations 295
WEP 295
Cell Sizing 295
User Authentication 296
Security Needs 296
Use Additional Security Tools 297
Monitoring for Rogue Hardware 297
Switches, not hubs 297
Wireless DMZ 297
Firmware & Software Updates 298
Key Terms 299
Review Questions 300
Answers to Review Questions 305

Chapter 11 Site Survey Fundamentals 307

What is a Site Survey? 308
Preparing for a Site Survey 309
Facility Analysis 310
Existing Networks 311
Area Usage & Towers 313
Purpose & Business Requirements 314
Bandwidth & Roaming Requirements 315
Available Resources 317
Security Requirements 318
Preparation Exercises 319
Preparation Checklist 319
Site Survey Equipment 320
Access Point 320
PC Card and Utilities 321
Laptops & PDAs 323
Paper 323
Outdoor Surveys 324
Spectrum Analyzer 324
Network Analyzer (a.k.a. "Sniffer") 325
Site Survey Kit Checklist 326
Conducting a Site Survey 328
Indoor Surveys 328
Outdoor Surveys 329
Before You Begin 329
RF Information Gathering 330
Range and Coverage Patterns 331
Data Rate Boundaries 333
Documentation 333
Throughput Tests & Capacity Planning 334
Interference Sources 334
Wired Data Connectivity & AC Power Requirements 337
Outdoor Antenna Placement 338
Spot Checks 339
Site Survey Reporting 339
Report Format 339
Purpose and Business Requirements 340
Methodology 340
RF Coverage Areas 340
Throughput 340
Interference 340
Problem Areas 340
Drawings 341
Hardware placement & configuration information 341
Additional Reporting 342
Key Terms 344
Review Questions 345
Answers to Review Questions 350
Appendix A
RF in Perspective 353
RF in Perspective 354
Radio acts like light 354
Light bulb analogy 354
Transmit Range Tests 354
Receive range tests 355
Obstacles 356
Fresnel Zone 356
Increasing power at the tower 357
Reflection 357
RF Summary 357 Glossary 359