Linux Unwired

Preface

Take a trip to the computer store, buy a Wi-Fi card, and insert it into your Linux notebook. You will probably hear two beeps; are they both happy beeps, or is one of them an angry beep? It’s possible that you will receive a happy beep, but with the variety of hardware, firmware, and software drivers for Wi-Fi cards, it’s quite likely that you will receive the angry beep. Next, go through this exercise with a Bluetooth adapter, cell phone, and some other random wireless hardware.

This book is all about hearing the happy beeps.

Wireless networks are popping up everywhere; from Wi-Fi hotspots to cellular data plans, you can connect to the Internet virtually anywhere. You can even cut more cables with technologies like Bluetooth and Infrared. Linux is already an amazing operating system, and combined with wireless, its strengths are amplified.

But things really shine when you combine wireless technologies. This book also discusses using wireless technology in combination, whether you want to share your Wi-Fi connection to Bluetooth devices or map out Wi-Fi networks with a Global Positioning System (GPS) device.

What This Book Covers

This book explains how to use the following wireless technologies with Linux:

Wireless Fidelity (Wi-Fi)

Wi-Fi is short-range wireless networking that supports raw speeds up to 54 Mbps (about 20-25 Mbps actual speeds). It’s an affordable replacement for wired Ethernet, and includes the 802.11b, 802.11g, and 802.11a protocols. Chapter 1 through Chapter 6 discuss Wi-Fi.

Bluetooth

Bluetooth is a wireless cable-replacement that allows you to get rid of USB and serial cables. You can use it to connect a Personal Digital Assistant (PDA), such as a Palm or Pocket PC, to Linux; create an ad-hoc network; or transfer files between computers. Bluetooth is covered in Chapter 7.

Infrared

Infrared has been available for a long time, and in some cases, it’s the only way that two devices will talk to each other, particularly with older PDAs. Infrared uses light waves that are just outside the range of visible light. Infrared is covered in Chapter 8.

Cellular networking

Although Wi-Fi is fast and reliable, it disappears the moment you leave its useful range. Cellular networks cover large areas, reach speeds between 40 kbps and 100 kbps, and even work reliably while you are in a moving vehicle. With unlimited data plans starting at $19.99 a month from some providers, cellular data plans can be a useful complement to Wi-Fi. Chapter 9 covers cellular data.

Global Positioning System (GPS)

Use a GPS to figure out your location in two or three dimensions. Plugged into a Linux computer, a GPS device becomes a source of location data that can be combined with freely available maps to plot locations of wireless networks, figure out where you are, or map out whatever interests you. GPS is covered in Chapter 10.

Conventions Used in This Book

This book uses the following abbreviations:

Hz, kHz, MHz, and GHz

Hertz (cycles per second), kilohertz (one thousand hertz), megahertz (one million hertz), and gigahertz (one billion, or 10⁹ hertz)

bps, kbps, Mbps

Bits per second, kilobits (1,024 bits) per second, and megabits (1,048,576 bits) per second

KB/s, MB/s

Kilobytes (1,024 bytes) per second and megabytes (1,048,576 bytes) per second

MB

Megabytes (1,048,576 bytes) of hard disk or RAM storage

mW

Milliwatts; one thousandth of a watt of power output

This book uses the following typographic conventions:

Constant width

Used for listing the output of command-line utilities

Constant width italic

Used to show items that need to be replaced in commands

Italic

Used for emphasis, for first use of a technical term, and for example URLs

...

Indicates text that has been omitted for clarity

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Acknowledgments

Roger Weeks

Writing this book would not have been possible without the backing and inspiration of my wife, Cynthia. Despite a house sometimes too cluttered with geek gear, long technical conversations, and more than one late night, she’s always there for me.

Many thanks also to Schuyler Erle, who not only got the book approved by O’Reilly, but somehow managed to convince them that I should be the author.

All of the “Cats” should be thanked publicly for their amazing amounts of knowledge, friendship, and hard work: Rob Flickenger, Schuyler Erle, Adam Flaherty, Nate Boblitt, Jim Rosenbaum, and Rich Gibson. Without them, significant parts of the West Coast would be very boring, and the wireless community would be much poorer.

Finally, many thanks to Brad Silva for excellent hardware advice and soldering skills.

Edd Dumbill

I would like to thank Marcel Holtmann and Maxim Krasnyansky for their devoted work on the BlueZ Linux Bluetooth stack and, of course my wife Rachael for her patient support.

Brian Jepson

My thanks go out to Schuyler Erle and Rob Flickenger for helping to develop the original outline of this book and for technical review. Thanks also to Adam Flaherty for technical review. I’m very grateful to Roger and Edd for being such great coauthors.

I’d especially like to thank my wife, Joan, and my stepsons, Seiji and Yeuhi, for their support and encouragement through my late night and weekend writing sessions, my occasional trips around town in a car full of Wi-Fi and GPS equipment, and the various milliwattage that soaked through the walls of my home office while I worked on this book.