Designing and deploying 802 11n wireless networks

Designing and Deploying
802.11n Wireless
Networks
Jim Geier

Cisco Press
800 East 96th Street
Indianapolis, IN 46240


ii

Designing and Deploying 802.11n Wireless Networks

Designing and Deploying 802.11n Wireless Networks
Jim Geier
Copyright © 2010 Cisco Systems, Inc.
Published by:
Cisco Press
800 East 96th Street
Indianapolis, IN 46240 USA
All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means,
electronic or mechanical, including photocopying, recording, or by any information storage and retrieval
system, without written permission from the publisher, except for the inclusion of brief quotations in a
review.
Printed in the United States of America
First Printing June 2010
Library of Congress Cataloging-in-Publication Data
Geier, James T.
Designing and deploying 802.11n wireless networks / Jim Geier.

p. cm.
ISBN 978-1-58705-889-9 (hardcover)
1. Wireless LANs. 2. IEEE 802.11 (Standard) I. Title.
TK5105.78.G448 2010
004.6'8--dc22
2010019130
ISBN-13: 978-1-58705-889-9
ISBN-10: 1-58705-889-8

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iii

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iv

Designing and Deploying 802.11n Wireless Networks

About the Author
Jim Geier is the founder and principal consultant of Wireless-Nets, Ltd., an independent
consulting firm assisting organizations with the development and deployment of wireless
networks. His 25 years of experience includes the planning, analysis, design, implementation, installation, and support of numerous wireless network-based solutions for enterprises, municipalities, hospitals, universities, airports, warehouses, and product manufacturers worldwide. Jim is the author of more than a dozen books, including Deploying
Voice over Wireless LANs (Cisco Press), Wireless Networks: First Step (Cisco Press),
Implementing 802.1X Security Solutions (Wiley), and Network Reengineering
(McGraw-Hill). He is the author of numerous tutorials and other publications and has
developed and instructed dozens of training courses on wireless networking topics. Jim
has been active within the Wi-Fi Alliance, responsible for certifying interoperability of
802.11 (Wi-Fi) wireless LANs. He has also been active with the IEEE 802.11 Working
Group, responsible for developing international standards for wireless LANs. He served
as Chairman of the IEEE Computer Society, Dayton Section, and Chairman of the IEEE
International Conference on Wireless LAN Implementation. Jim’s education includes a
Bachelor’s and Master’s degree in electrical engineering, with emphasis in wireless communications.
Jim Geier’s contact information:
E-mail:
Website: www.wireless-nets.com

About the Technical Reviewers
Tom Carpenter is the Senior Consultant for the Systems Education and Consulting
Company (SYSEDCO) located in Marysville, Ohio. Tom holds several industry certifications, including CWNA, CWSP, and vendor-specific certifications in the wireless industry. He has authored several books on wireless networking and VoIP and database solutions, and he speaks regularly at training events and technical conferences. Tom lives with
his wife and four wonderful children in central Ohio.
Christian J. Estes is a Senior Wireless Engineer on the Escalation / CAP Team in the
Wireless Business Unit at Cisco Systems, located in Silicon Valley. During the four years
he has been at Cisco, he has participated in the design, deployment, and remediation of
enterprise class wireless architectures and specializes in Voice over Wireless LAN technologies, protocols, and applications. He was a member of the CCIE Certification

Development Team for the Wireless track and holds the CCNP, CCVP, and CWNE certifications. In addition, he is currently in the process of acquiring the CCIE certification.
He has degrees in computer engineering and organizational leadership and is currently
pursuing a graduate degree from Stanford University in management science and engineering.


v

Dedications
I dedicate this book to my wife, Debbie.

Acknowledgments
I want to thank the Pearson production team for their time and effort with creating this
book:
■

Thanks to Mary Beth Ray for getting this book contracted and managing the process
from beginning to end.

■

Thanks to Christopher Cleveland, Mandie Frank, and Keith Cline for their fantastic
editing of the book.

■

Thanks to the many others at Pearson who were part of developing and producing
this book.

I also want to thank Tom Carpenter for providing technical feedback on the many topics
that this book covers. Also, thanks to Christian Estes for providing technical feedback

about Cisco solutions.


vi

Designing and Deploying 802.11n Wireless Networks

Contents at a Glance
Introduction

xxv

Part I

Fundamental Concepts

Chapter 1

Introduction to Wireless LANs

Chapter 2

Radio Wave Fundamentals

Chapter 3

Wireless LAN Types and Components

Chapter 4

Wireless LAN Implications

Part II

The 802.11 Standard

Chapter 5

Introduction to IEEE 802.11 and Related Standards

Chapter 6

IEEE 802.11 Medium Access Control (MAC) Layer

Chapter 7

IEEE 802.11 Physical Layers

Part III

Wireless Network Design

Chapter 8

Planning a Wireless LAN Deployment

Chapter 9

Defining Requirements for a Wireless LAN

Chapter 10

System Architecture Considerations

Chapter 11

Range, Performance, and Roaming Considerations

Chapter 12

Radio Frequency Considerations

Chapter 13

Security Considerations

Part IV

Wireless Network Installation and Testing

Chapter 14

Test Tools

Chapter 15

Performing a Wireless Site Survey

Chapter 16

Installing and Configuring a Wireless LAN

Chapter 17

Testing a Wireless LAN

Part V

Operational Support Considerations

Chapter 18

Managing a Wireless LAN

Chapter 19

Troubleshooting a Wireless LAN

Chapter 20

Preparing Operational Support Staff
Glossary
Index

1

39
55

87

463

135

177

201
237

263
299

327

339

353

455

115

367
387

405

421
439

449


vii

Contents
Introduction

xxv

Part I

Fundamental Concepts

Chapter 1

Introduction to Wireless LANs

1

Wireless LAN Markets and Applications
Retail

1

2

Warehousing

3

Healthcare

4

Hospitality

9

Voice over WLAN

9

Video Surveillance

11

Home and Small Office

12

General Enterprise Systems

13

Location-Aware Wireless Applications
Benefits of Wireless Networks
Mobility

13

15

15

Installation in Difficult-to-Wire Areas
Increased Reliability

17

Reduced Installation Time
Long-Term Cost Savings

17
17

Productivity Gain Is the Answer
Wireless Network Technologies
IEEE 802.11 (Wi-Fi)
Initial 802.11
802.11a

21

802.11b

21

802.11g

22

802.11n

23

16

18

19

20

20

Comparison of 802.11 Standards
Wi-Fi Certification

24

24

Other Wireless Network Technologies
IEEE 802.16 (WiMAX)
IEEE 802.15 (Bluetooth)
IEEE 802.15.4 (ZigBee)

26
30

32

26


viii

Designing and Deploying 802.11n Wireless Networks

Certified Wireless USB

33

Wireless LANs: A Historical Perspective
The Early Days

Initial 802.11 Standardization
802.11n Standardization
Chapter 2

Radio Wave Attributes
40

Frequency

40

Phase

35

36

Radio Wave Fundamentals
Amplitude

34

34

39

39

41

RF System Components
RF Transceiver

41

41

RF Modulation

43

Amplitude Shift-Keying

43

Frequency Shift-Keying

44

Phase Shift-Keying

45

Quadrature Amplitude Modulation
Spread Spectrum

45

45

Orthogonal Frequency-Division Multiplexing
RF Signal Propagation
Attenuation

48

48

Free Space Loss

49

Physical Obstacles

50

Multipath Propagation

51

Noise and Signal-to-Noise Ratio
RF Mathematics

53

Converting Units
Chapter 3

51

53

Wireless LAN Types and Components
Types of Wireless LANs

55

Ad Hoc Wireless LANs

55

Infrastructure Wireless LANs
Mesh Wireless Networks
Wireless LAN Components

Client Devices
Client Radio

57

59
62

62
63

Industry Standard Architecture

65

55

48


ix

Peripheral Component Interconnect
Mini-PCI
PC Card

66
66

ExpressCard

67

CompactFlash

67

Universal Serial Bus
Access Points

67

68

Autonomous Access Points

68

Controller-Based Access Points
Wi-Fi Routers
Mesh Nodes
Antennas

Bridges

69

69
72

72

RF Amplifiers
Repeaters

74

75
75

Network Infrastructure Components
Network Distribution Systems
Switches

77

77

77

Optical Fiber

79

Power over Ethernet

79

Application Connectivity Software
Terminal Emulation

83

Direct Database Interfaces
Wireless Middleware

Security Vulnerabilities

87

87
88

Unauthorized Access
Denial of Service

84

84

Wireless LAN Implications
Passive Monitoring

82

82

Browser-Based Approaches

Chapter 4

66

91

95

Radio Signal Interference

97

Microwave Oven Interference
Cordless Phone Interference
Bluetooth Interference

99
101

103

Neighboring Wireless LAN Interference
Impacts of Multipath Propagation

108

105


x

Designing and Deploying 802.11n Wireless Networks

Roaming Issues

109

Battery Limitations

110

Interoperability Problems
Installation Issues

111

112

Part II

The 802.11 Standard

Chapter 5

Introduction to IEEE 802.11 and
Related Standards 115
The Importance of Standards
Types of Standards

115

115

Institute for Electrical and Electronic Engineers
Benefits of the 802.11 Standard

117

Appliance Interoperability

118

Fast Product Development

119

Stable Future Migration
Price Reductions
Avoiding Silos

119

119
119

The IEEE 802 LAN Standards Family
802.11 MAC Sublayer

121

802.11 Physical Layer

123

IEEE 802.2

120

123

Unacknowledged Connectionless Service
Connection-Oriented Service
Continuous ARQ

125

126

Stop-and-Wait ARQ

127

Acknowledged Connectionless Service
IEEE 802.11 Features

129

Station Services

130

Authentication

130

Deauthentication
Privacy

131

131

Distribution System Services
Association

131

Disassociation
Distribution
Integration

124

131
131

132

131

128

117


xi

Reassociation

132

Station States and Corresponding Frame Types
Chapter 6

132

IEEE 802.11 Medium Access Control (MAC) Layer
Primary 802.11 MAC Layer Functions
Data Delivery

135

136

Medium Access

137

Distributed Coordination Function
Hybrid Coordination Function
Error Recovery

140

Data Frame Acknowledgments
Dynamic Rate Switching
Data Frame Aggregation

140

141
142

MSDU Aggregation

143

MPDU Aggregation

143

Data Frame Fragmentation
Encryption

138

139

143

145

Wired Equivalent Privacy

145

Temporal Key Integrity Protocol
Advanced Encryption Standard
Multicasting
Connectivity

146
146

147

148

Scanning for Networks
Authentication

149

151

Open System Authentication
Shared Key Authentication

151
152

IEEE 802.1X Port-Based Authentication
Association

154

Reassociation

155

Timing and Synchronization
Short IFS

156

PCF IFS

157

DCF IFS

157

Extended IFS
RTS/CTS

156

157

158

Power Management

159

802.11 MAC Frame Structures

160

153

135


xii

Designing and Deploying 802.11n Wireless Networks

Protocol Version Field
Type Field

160

161

Subtype Field
To DS Field

161
161

From DS Field

161

More Frag Field
Retry Field

161

163

Power Management Field
More Data Field

164

Protected Frame Field
Order Field

163

164

164

Duration/ID Field

164

Address 1, 2, 3, and 4 Fields
Sequence Control Field
QoS Control Field
HT Control Field

164

165

166
166

Frame Body Field

166

Frame Check Sequence Field
MAC Frame Types

166

166

Management Frames

167

Association Request Frame

167

Association Response Frame

167

Reassociation Request Frame

167

Reassociation Response Frame
Probe Request Frame
Probe Response Frame
Beacon Frame
ATIM Frame

168

168
170

Disassociation Frame

170

Authentication Frame

170

Deauthentication Frame
Action Frame

167

168

170

170

Action No ACK Frame

171

Management Frame Body Contents
Control Frames

172

Control Wrapper Frame
Block ACK Request Frame

172
172

171


xiii

Block ACK Frame

172

Power-Save Poll Frame

173

Request-to-Send Frame

173

Clear-to-Send Frame

173

Acknowledgment Frame

173

Contention-Free End Frame
CF End + CF ACK Frame

Chapter 7

Data Frames

174

Interoperability

174

173

173

IEEE 802.11 Physical Layers

177

802.11 Physical Layer Architecture
PLCP Sublayer

177

PMD Sublayer

178

802.11 Physical Layer Functions
Carrier-Sense Function
Transmit Function
Receive Function

177

179

179

179
180

Legacy 802.11 Physical Layers

180

Frequency-Hopping Spread-Spectrum PHY
Direct-Sequence Spread-Spectrum PHY
Infrared PHY

180

182

185

Orthogonal Frequency Division Multiplexing PHY (802.11a)

185

High-Rate Direct-Sequence Spread-Spectrum PHY (802.11b)

188

Extended-Rate PHY (802.11g)
HT-OFDM (802.11n)

190

MIMO Concepts

190

Transmit Beamforming
Spatial Multiplexing
Channel Bonding

190
191

193

802.11n Modulation
Interoperability

190

194

198

Part III

Wireless Network Design

Chapter 8

Planning a Wireless LAN Deployment
Project Management Principles

201

202

Wireless LAN Deployment Planning Steps
Step 1: Defining the Project Scope

204

204


xiv

Designing and Deploying 802.11n Wireless Networks

Project Charter
Assumptions
Constraints

204
204

205

Step 2: Developing the Work Breakdown Structure
Requirements Definition Phase
Design Phase

206

207

Implementation Phase

209

Operations and Maintenance Phase
Step 3: Identifying Staffing

214

Step 4: Creating a Schedule

217

Step 5: Developing a Budget

211

218

Preliminary Requirements and Design
Hardware and Software Costs
Deployment Services Costs

218

219

221

Ongoing Operations and Maintenance Costs
Step 6: Evaluating Risks

Benefits

227

228
228

Impacts on Users

229

Impacts on Existing Systems

229

Making the Decision to Proceed
Executing the Project
Periodic Activities

229

232

The Kick-Off Meeting

232

233

Evaluating the Outcome of the Project
Chapter 9

223

225

Step 7: Analyzing Feasibility
Costs

206

233

Defining Requirements for a Wireless LAN
Requirements Attributes

238

Requirements Definition Steps

238

Step 1: Gathering Information

239

Interviewing Users
Interviewing IT Staff

237

239
240

Reviewing the Existing Infrastructure and Systems
Step 2: Analyzing Requirements
Application Requirements
Client Device Requirements

241

241
243

240


xv

Signal Coverage Requirements
Utilization Requirements

246

Mobility Requirements

248

Continuous Movement
Portable Access

244

248

249

Stationary Access

249

Security Requirements

250

Sensitivity of Information and Systems
Organization Security Policies
Network Access Privileges

251

251

Existing Security Mechanisms
Scalability Requirements

250

252

253

Existing Network Infrastructure Requirements
Integration Requirements

255

Environmental Requirements

256

Building Construction and Obstacles
Floor Plans

256

257

Aesthetic Requirements

258

Step 3: Documenting Requirements

Chapter 10

256

256

Temperature and Humidity
Durability

254

259

Step 4: Obtaining Requirements Approval

260

System Architecture Considerations

263

Architectural Considerations
Wireless Access Networks

264
264

Autonomous Access Point Architecture

265

Controller-Based Access Point Architecture
Mesh Network Architecture
Ad Hoc Architecture
2.4 GHz Versus 5 GHz

267

269

270
272

Geographical Location Considerations
Performance Considerations

272

Existing Client Device Considerations
Facility Size Considerations

272
273

273

Radio Signal Interference Considerations
Hybrid Frequency Band Considerations

273
274

xvi

Designing and Deploying 802.11n Wireless Networks

Common Infrastructure Considerations
Migration Considerations

276

Redundancy Considerations
Controller Redundancy

279

282

Switch Considerations
PoE Considerations

277

277

Access Point Redundancy
Distribution Systems

274

282

282

Voice over WLAN Systems

284

Single-Site Architecture

284

Multisite WAN with Centralized Call Processing

285

Multisite WAN with Distributed Call Processing

287

Application Connectivity

289

Terminal Emulation Considerations

289

Browser-Based Connectivity Considerations
Direct Database Considerations

293

Wireless Middleware Considerations
Chapter 11

292

294

Range, Performance, and Roaming Considerations
Range Versus Performance
Range Considerations

299

300

Signal Coverage Requirements
Radio Frequency Bands

301

Transmit Power Settings

302

Transmission Channel Settings
Data Rate Settings
Antennas

Amplifiers
Repeaters

300

303

304

306
307
308

Physical Obstacles

309

Radio Signal Interference

309

Performance Considerations

311

Throughput Versus Data Rate
Radio Frequency Bands

313

Transmit Power Settings

313

Transmission Channel Settings

312

314

299


xvii

Data Rate Settings
Antennas

315

315

Amplifiers

316

Radio Signal Interference

316

Channel Width Settings
Signal Coverage

316

317

Fragmentation Settings
RTS/CTS Settings

317

318

Bandwidth Control Mechanisms

319

Microcell Deployment Strategies

319

Roaming Considerations
Roaming Levels

321

322

Access Point Roaming

Subnet Roaming

322

323

Wireless ISP Roaming

324

Wireless IP Phone Roaming
Mobility Settings
Chapter 12

324

325

Radio Frequency Considerations
Frequency Band Selection

327

2.4-GHz Frequency Band
5-GHz Frequency Band

327
328

Transmission Channel Settings

Manual Channel Settings
Single-Level Facilities
Multilevel Facilities

328
328

329
330

Adaptive Channel Settings
Difficult-to-Cover Areas

Chapter 13

327

332

333

Signal Coverage in Elevators

333

Signal Coverage in Stairwells

336

Signal Coverage in Parking Areas

336

Radio Signal Interference Reduction

337

Security Considerations
Security Elements
Encryption

339

340

Authentication

342

339


xviii

Designing and Deploying 802.11n Wireless Networks

EAP Methods

342

Authentication Servers
Guest Access

344

345

Rogue Access Point Detection
RF Shielding

346

347

Wireless Security Polices

349

Part IV

Wireless Network Installation and Testing

Chapter 14

Test Tools

353

Tool Considerations

353

Spectrum Analyzers

354

Real-Time Fast Fourier Transform
FFT Duty Cycle

356

Swept Spectrogram
Active Devices

357

357

Recording Spectrum Data
Signal Coverage Testers
Heat Maps

358

Positioning

360

358

358

Passive Versus Active Modes
Simulation

354

361

361

Free Signal Coverage Tester: NetStumbler
Wireless Protocol Analyzers
Filtering Frames

362

363

Recording Traces

363

Free Protocol Analyzer: WireShark
Chapter 15

Performing a Wireless Site Survey
Wireless Site Survey Considerations
Reviewing Requirements
Obtaining Floor Diagrams

Inspecting the Facility

364
367
368

369

Selecting Site Survey Tools

370
371

372

Assessing the Existing Network Infrastructure
Communications Rooms

372

Switches and Power over Ethernet
WAN

373

361

373

372

xix

Identifying Potential Radio Signal Interference

373

Defining Signal Values for Acceptable Signal Coverage
Minimum Received Signal Strength
Minimum SNR

376

376

376

Uplink Versus Downlink Signal Values

377

Identifying Optimum Access Point Antenna Installation Locations
Propagation Testing

379

Test Access Point Configuration
Antenna Considerations

379

Identifying Test Locations
Measuring Test Signals

379

380

381

Assessing Propagation Test Results
Cell Overlap Considerations

382

383

Annotate Access Point Antenna Installation Locations
Writing an RF Site Survey Report
Chapter 16

385

Installing and Configuring a Wireless LAN
Wireless LAN Installation Considerations
Planning the Installation

Developing an Installation Plan
Points of Contact

Safety Tips

388

388

389

Installation Procedures

389

Required Facility Changes
Tools

390

390

Reference to Design Documentation
Schedule

Risks

390

390

Resources
Budget

387

388

391

391
391

Coordinating the Installation
Staging the Components

391

392

Installing Ethernet Switches and Cabling
Installing Access Points

394

Mounting Practices

394

Antenna Alignment

395

Configuration Setting Access

396

393

387

384

379


xx

Designing and Deploying 802.11n Wireless Networks

Firmware

396

Access Point Configuration Settings
802.11n Enable
SSID

396

DTIM Interval

397

Beacon Interval

397

Radio Frequency Bands
Transmit Power

398

398

Transmission Channel
Data Rates

399

399

Antenna Diversity
Channel Width

399

401

Fragmentation Threshold
RTS/CTS Threshold
Testing the Installation

401

402
402

Documenting the Installation
Chapter 17

396

396

Testing a Wireless LAN

403

405

Wireless LAN Testing Considerations
Signal Coverage Testing

405

406

Wireless Site Survey Coverage Testing
As-Installed Coverage Testing
Consider Beacon Rates

407

407

Performance Testing

408

Association Tests

408

Registration Tests

409

Network Connection Tests
Authentication Tests

409

410

Application Connection Tests
Application Tests
Load Tests

410

410

411

In-Motion Testing

412

Security Vulnerability Testing

413

Security Settings Verification
Penetration Testing
Private-Side Testing
Public-Side Testing

414
414
414

413

406


xxi

Acceptance/Verification Testing
Simulation Testing

416

Prototype Testing

417

Pilot Testing

415

418

Test Documentation

419

Part V

Operational Support Considerations

Chapter 18

Managing a Wireless LAN

421

Operational Support Considerations
Help Desk

421

422

Connection Problems

422

Poor Signal Coverage

423

Poor Performance
System Status

423

423

Additional Considerations
Network Monitoring

423

424

Performance Monitoring

424

Access Point Monitoring

424

Configuration Monitoring

425

Security Policy Management

425

Installation Control Policies

425

Monitoring Policies

425

Periodic Testing Policies
Maintenance

426

426

Inoperative Access Points
Poor Performance

426

Poor Signal Coverage
Broken Hardware

426

426

427

Firmware Updates

427

Signal Coverage Verification
Access Point Inspections
Troubleshooting
Sparing
Engineering

427

428

428

428
428

Advanced Problem Resolution
Coverage Expansion

429

429


xxii

Designing and Deploying 802.11n Wireless Networks

Capacity Increases

429

Firmware Review

429

Technology Upgrades
Design Review

430

430

Configuration Management

430

Change-Control Processes

Security Management

430

431

Review Existing Security Policies
Review the System Architecture

432
432

Review Management Tools and Procedures
Interview Users

432

433

Verify Configurations of Wireless Devices

433

Investigate Physical Installations of Access Points
Identify Rogue Access Points
Perform Penetration Tests
Analyze Security Gaps

433

434

434

Recommend Improvements
Trouble Ticket Coordination
Help Desk Group

434

435

435

Desktop Support Group

436

Network Support Group

436

Preparing for the Transfer to Operational Mode
Chapter 19

Troubleshooting a Wireless LAN
Troubleshooting Methodology
Identify the Problem

439

439

439

Identify the Underlying Cause of the Problem
Fix the Problem

440

Connection Problems

440

Insufficient Signal Coverage
Radio Signal Interference
Access Point Failure

441

442

442

Incompatible Client Radio
Faulty Firmware

442

443

Incorrect Client Radio Configuration
Performance Problems

436

444

443

440

433


xxiii

Insufficient Signal Coverage
Radio Signal Interference
Faulty Firmware

444

445

Nonoptimal Client Radio Configuration

445

Nonoptimal Access Point Configuration

445

Misaligned Antennas
High Utilization
Chapter 20

444

446

447

Preparing Operational Support Staff
Support Staff Considerations

449

Availability of Existing Staff

450

Experience Requirements

450

Education and Training Requirements
Vendor-Neutral Training

451

Vendor-Specific Training

452

College Education
Certifications

452

Staffing Sources
Glossary
Index

455

463

453

449

452

451


xxiv

Designing and Deploying 802.11n Wireless Networks

Icons Used in This Book
MESH
Access
Point

Wireless LAN
Router

Ethernet
Switch

Voice
Gateway

LWAPP
Lightweight
Access Point

WLAN
Controller

Wireless
Bridge

Router

Multilayer
Switch

Hub

Repeater

Call
Manager

Mesh Access
Point

IP Telephony
Router

PC

Laptop

Printer

Server

Web
Server

Database

Cell Phone

PDA

Wireless
Inventory/Manufacturing
Device

Phone

WiMax Base
Station

Network Cloud

Camera/PC
Video