Building Wireless Community Networks: A Book Review
So you want to join your local community wireless networking group, but you need an introduction to the secrets of 802.11b (WiFi) networking so you can participate cluefully. Pick up Rob Flickenger's thin but information-dense Building Wireless Community Networks (O'Reilly, 2002), and you'll be ready to get on the air. The author is a sysadmin for O'Reilly and Associates and founder of the wireless project nocat.net, and he brings a lot of hands-on experience to the task of explaining the strange combination of radio technology and system administration that is WiFi.
WiFi is great for setting up a simple office network (see the February 2002 Linux Journal), and much of the information in this book is applicable to such projects. But, Flickenger explains, "It didn't take long for some sharp hacker types (and, indeed, a few CEO and FCC types) to realize that by using 802.11b client gear in conjunction with standard radio equipment, effective range can extend to more than twenty miles, and potentially provide thousands of people with bandwidth reaching DSL speeds, for minimal hardware cost."
To understand the technology, you need to know something about the physical properties of the radio signals involved and the FCC's rules for using them. For example, new spring leaves can block a connection that worked fine in winter, and 802.11b channels overlap--so you can use 1, 6 and 11 next to each other, but not 2, 6 and 10. Flickenger covers the basics well.
There's a description of the difference between BSS, ESS and IBSS. But, unfortunately, WiFi vendors and software writers aren't standard in identifying the modes and simply use whatever words they like, "Managed", "Ad-Hoc" or whatever. It would be good to include some of the vendor terms in the book, or better yet, get the vendors to standardize the official terms.
There's quite a bit of good information on setting up WiFi access points to do more than their default. Chapter 4 is focused on the popular Apple AirPort/Orinoco RG-1000 (they're the same inside, Flickenger says). Yes, you can tweak your access point from Linux, using either a proprietary, downloadable command-line utility or a free Java one. The advice on how to make the access point a transparent bridge to the wire and how to troubleshoot DHCP will be particularly helpful. If you don't need a full-featured box with DHCP and masquerading and all that stuff, just a radio on the wall, this will be a good option for you.
The real fun part starts in Chapter 5, where there's a good introduction to the basics of turning an old laptop into an access point that includes setting up masquerading and DHCP. You can do more interesting things with a real Linux box than with just an access point. If you have or can buy an old laptop, this is the method we at Linux Journal prefer.
There's a wealth of reference information on antennas, cables and where to put them, including surveying with the aid of a GPS. After reading this, you should be able to order a "pigtail" or an "omni" for your site with confidence. If you prefer to build your own, there are plans, photos and instructions for making the famous Pringles can antenna. To solve lack of line-of-sight, you can build a repeater out of two Airports or a surplus 486 "tablet" PC. The projects will inspire your own ideas, and the connector information certainly won't change as rapidly as the software does.
Finally, there's the question of authentication and a partial answer in the form of an intro to NoCatAuth, a web-based login service similar to those you might have encountered in a hotel. It's under development and looks very promising as a way to keep possible abusers under control.
If I had to come up with some savage criticism of this book, it would be that Flickenger's web articles, and others out there, are good enough that you could probably get started with just on-line information. But the book does provide a way to get the basics down, get up to speed, order parts with a lower chance of getting the wrong thing and having to return it, and find other local enthusiasts who want to network with you.