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IEEE 802.11 Handbook: A Designer's Companion, 2nd Edition



IEEE 802.11 Handbook: A Designer's Companion, 2nd Edition

Bob O'Hara, Al Petrick

ISBN: 978-0-738-14449-8 January 2005 404 Pages

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The first generation 802.11 wireless market, once struggling to expand, has spread from largely vertical applications such as healthcare, point of sale, and inventory management to become much more broad as a general networking technology being deployed in offices, schools, hotel guest rooms, airport departure areas, airplane cabins, entertainment venues, coffee shops, restaurants, and homes. This has led to the tremendous growth of new sources of IEEE 802.11 devices. IEEE 802.11 equipment is now moving into its second stage, where the wireless LAN is being treated as a large wireless communication system. As a system, there is more to consider than simply the communication over the air between a single access point and the associated mobile devices. This has lead to innovative changes in the equipment that makes up a wireless LAN. The IEEE 802.11 Handbook: A Designer’s Companion, Second Edition is for the system network architects, hardware engineers and software engineers at the heart of this second stage in the evolution of 802.11 wireless LANs and for those designers that will take 802.11 to the next stage.

Introduction xxv

Acronyms and abbreviations xxxi

Chapter 1 Similarities and differences between wireless and wired local area networks (LANs) 1

Similarities between WLANs and wired LANs 1

Differences between WLANs and wired LANs 1

Chapter 2 IEEE 802.11: First international standard for WLANs 5

IEEE 802.11 architecture 5


Basic service set (BSS) 6

Extended service set (ESS) 8

Distribution system (DS) 9

Services 10

STA services 10

Distribution services 11

Interaction between some services 12

Summary 15

Chapter 3 Medium access control (MAC) 17

MAC functionality 17

MAC frame exchange protocol 17

Dealing with the media 18

Hidden node problem 18

Retry counters 21

Basic access mechanism 22

Timing intervals 23

Distributed coordination function (DCF) 24

Centrally controlled access mechanism (i,e„ PCF) 24

Frame formats 28

General frame format 29

Frame Control field 31

Duration/ID field 37

Address fields 37

Sequence Control field 39

Frame Body field 40

FCS field 40

Control frame subtypes 41

Request to Send (RTS) [control] frame 41

Clear to Send (CTS) [control] frame 42

Acknowledge (ACK) [control] frame 42

Power Save Poll (PS-Poll) [control] frame 44

Contention-Free End (CF-End) and CF-End plus ACK (CF-End + ACK) [control] frames 44

Data frame subtypes 45

Simple data frame 45

Data with Contention-Free Acknowledgment (Data + CF-ACK) frame 48

Data with Contention-Free Poll (Data + CF-Polt) frame 48

Data + CF-ACK + CF-Poll frame 49

Null Function (no data) frame 49

Con tent ion-Free Acknowledgment (CF-ACK) (no data) frame 49

Contention-Free Poll (CF-Poll) (no data) frame 49

CF-ACK + CF-Potl (no data) frame 50

Management frame subtypes 50

Beacon [management] frame 51

Probe Request and Probe Response [management] frames 52

Authentication [management] frame 53

Deauthentication [management] frame 54

Association Request and Association Response [management] frames 54

Reassociation Request and Reassociation Response [management] frames 54

Disassociation [management] frame 55

Announcement Traffic Indication Message (ATIM) [management] frame 55

Action [management] frame 55

Components of the management frame body 55

Fixed fields 55

Information elements 68

Other MAC operations 86

Fragmentation 86

Privacy 89

WEP details 92

Chapter 4 IEEE 802.11i security enhancements 95

Robust security network (RSN) 96

IEEE 802.1 X Authentication and Key Management Protocol (AKMP) 105

Details of IEEE 802.1X EAP AKMP operation 108

EAPOL-Key frames 109


Details of PSK AKMP operation 113

PMK caching 114

Preauthentication 114

Transition security networks (TSNs) 115

Confidentiality: New encryption algorithms 116

Fixing WEP: Temporal Key Integrity Protocol (TKIP) 116

TKIP operation 117

Michael MIC 120

TKIP-encrypted frame description 120

Attack countermeasures 122

New transforms 122

CCMP-encrypted frame description 124

Security management 126

Changes to existing attributes and tables 126

New attributes and tables 127

Chapter 5 IEEE P802.11e quality of service (QoS) enhancements 137

Background: What is QoS and why is QoS needed? 137

IEEE P802.1 le: What’s in and what’s out 138

The Scope of IEEE 802.11 standard 138

Mandatory and optional features 138

Limits of WLANs 138

Background of the legacy IEEE 802.11 MAC 139

Fundamentals of IEEE P802.1 le operation 140

Hybrid coordination function (HCF) 140

Enhanced distributed channel access (EDCA) 142

EDCA admission control 144

HCF controlled channel access (HCCA) 145

IEEE P802.1 le frame formats 145

New control frame subtypes 146

New data frame subtypes 148

New extensions to management frames 154

Action [management] frames 159

New information element formats 169

Optional features in IEEE P802.1 le 182

Contention-free bursts (CFBs) 182

Block acknowledgments 182

Direct link setup (DLS) 183

Automatic power save delivery (APSD) 187

IEEE P802.1 le as part of complete QoS implementation 187

Scheduling and admission control 187

Adapting to varying wireless channel conditions 188

Interface to higher layers 189

Conclusion 190

Chapter 6 IEEE 802.1 lh dynamic frequency selection (DFS) and transmit power control (TPC) 191

Users of the 5 GHz frequency  192

New parts to the IEEE 802.11 protocol 192

Transmit power control (TPC) 197

TPC operation 199

Spectrum management 200

Detection of radar operation 205

Chapter 7 IEEE 802.11d international operation 207

New roaming requirements 208

Country information element 210

International roaming with FH PHYs 212

Request information element and its protocol 214

Chapter 8 IEEE 802.1 IF Inter Access Point Protocol (IAPP) 217

Going beyond the MAC 217

More about mobility 218

Chapter 9 MAC management 221

Tools available to meet the challenges 222

Authentication 223

Association 225

Address filtering (MAC function) 227

Privacy (MAC function) 228

Power management 228

Power management in an IBSS 228

Power management in an infrastructure BSS 230

Synchronization 232

Timer synchronization in an infrastructure BSS 233

Timer synchronization in an IBSS 234

Synchronization with FH PHYs 235

Scanning 235

Joining a BSS 237

Combining management tools 237

Combining power-saving periods with scanning 237

Preauthentication 238

Areas for improvement 239

Scanning and roaming 239

Use of status and reason codes 240

Chapter 10 MAC management information base (M1B) 241

STA management attributes 241

MAC attributes 246

Chapter 11 The physical layer (PHY) 251

PHY functionality 251

Direct sequence spread spectrum (DSSS) PHY 252

DSSS PLCP sublayer 252

Data scrambling 255

DSSS modulation 255

Barker spreading method 256

DSSS operating channels and transmit power requirements 258

Frequency hopping spread spectrum (FHSS) PHY 261

FHSS PLCP sublayer 261

PSDU data whitening 264

FHSS modulation 264

FHSS channel hopping 265

Infrared (IR) PHY 267

1R PLCP sublayer 267

IR PHY modulation method 270

Geographic regulatory bodies 271

Chapter 12 PHY extensions to IEEE 802.11 273

IEEE 802.1 la: Orthogonal frequency division multiplexing (OFDM) PHY 273

OFDM PLCP sublayer 274

IEEE 802.11 a modulation 276

PLCP and data scrambler 276

Convolutional encoding 276

IEEE 802.1 la OFDM 277

OFDM operating channels and regulatory domains 278

Transmit power requirements 281

Geographic regulatory bodies 283

Globalization of spectrum at 5 GHz 284

IEEE 802.1 lb: 2.4 high-rate direct sequence spread spectrum (HR/DSSS) PHY 285

HR/DSSS PLCP sublayer 285

High-rate data scrambling 288

1EEE 802.1 1 high-rate operating channels 289

1EEE 802.1 1 DSSS high-rate modulation and data rates 290

Complementary code keying (CCK) modulation 290

DSSS packet binary convolutional coding (PBCC) 292

Frequency-hopping spread spectrum (FHSS) interoperability 294

Chapter 13 IEEE 802.11j operation in Japan at 4.9 GHz and 5 GHz 295

Expanded Country information element 295

Mandatory and optional modes of operation 299

PLCP header, Signal field, and Rate subfield 300

Extended frequency bands and transmit RF power levels 302

Transmit mask and adjacent channel interference 304

Spurious emissions 306

Regulatory domain references 307

Number of frequency channels and data rates 308

Receiver sensitivity, CCA, and slot time 309

Transmitter error vector magnitude (EVM) 311

Chapter 14 IEEE 802.11g higher data rates in 2.4 GHz frequency band 313

Network deployment and user scenario 313

Mandatory and optional modes of operation 314

Optional modes of operation 316

PPDU formats 319

Operating channels 321

Operation of lEEE 802.llgCSMA/CA and CCA 323

Key system specifications 324

Chapter 15 IEEE 802.1 In higher data rates beyond 54 Mbit/s 327

Channel bonding 328

Higher order modulation 329

Multiple input multiple output (MIMO) 329

Chapter 16 System design considerations for IEEE 802.11 WLANs 333

The Medium 333

Multipath 334

Path loss in a WLAN 337

Es/No vs BER performance 339

Data rate vs aggregate throughput 341

WLAN installation and site survey 341

Interference in the 2.4 GHz frequency band 342

Antenna diversity 343

Power management defined 344

Glossary 349

Index 353