Building Wireless Community Networks, Second Edition

Chapter 1. Wireless Community Networks

A year is an eternity in networking.

—Anonymous

In the time since the first edition of this book was published, millions of wireless networking components have shipped into the eagerly waiting hands of consumers. We’ve seen consumer-grade wireless equipment prices fall dramatically as more and more manufacturers integrate wireless into their own products. Articles about various aspects of wireless networking have made international news, including strange tales of WarChalking, WarDriving, and Pringles can-wielding Secret Service agents (as reported at http://www.securityfocus.com/news/899). Wireless access is now available in many coffeehouses, parks, schools, offices, and homes.

What is it about wireless networking that has so many people worked into such a frenzy? I believe that people’s fascination with wireless is simple to understand. Wireless data networking is probably the most “magical” technology to evolve in recent times. Think of it: by installing an inexpensive PC card, your laptop can suddenly send and receive data at a very high speed, to anyone in range, even through walls! Many laptops have dispensed with the PC card altogether, and seem to magically just “be” online. Combined with the power of the Internet, your tiny battery-powered computer can now communicate globally, wherever an otherwise invisible wireless network happens to exist. More than any other networking technology, people just think it’s cool to use wireless (never mind that it is extremely useful, cheap, and can do things that wired networks will never be able to do).

In the past year and a half, we have also seen more than a few wireless start-ups come and go. Wireless networking may be cheap and easy for the individual, but it has certainly proven to be far from a “slam-dunk” business for would-be wireless ISPs. In the same time period, the project list at PersonalTelco (available on their site at http://www.personaltelco.net/index.cgi/WirelessCommunities) has grown to five times the size, now listing over 250 active community networking efforts. While public wireless networks haven’t yet proven to be a stunning commercial success, something is certainly happening with wireless. This book is an exploration of many aspects of that something.

Why Now?

In recent times, the velocity of technology development has exceeded “blur” and is now moving at speeds that defy description. Internet technology in particular has made astounding strides in the last few years. Where only a few short years ago 56Kbps modems were all the rage, many tech heads now find themselves complaining about how slow their company’s T1 connection seems compared to their 6MBps DSL connection at home.

Never before have so many had free and fast access to so much information. As more people get a taste of millisecond response times and megabit download speeds, they seem to only hunger for more. In most places, the service that everyone is itching for is DSL, or Digital Subscriber Line service. It provides relatively high bandwidth (anywhere from 128Kbps to 6Mbps) over standard copper telephone lines, if your installation is within about three miles of the telephone company’s CO, or central office (this is a technical constraint of the technology). DSL is generally preferred over cable modems, because a DSL connection provides guaranteed bandwidth (at least to the telephone company) and thus is not directly affected by the traffic habits of everyone else in your neighborhood. It isn’t cheap (ranging anywhere from $40 to $300 per month, plus ISP and equipment charges), but that doesn’t seem to be discouraging demand.

Telephone companies, of course, are completely enamored with this state of affairs. In fact, the intense demand for high-bandwidth network access has led to so much business that enormous lead times for DSL installations are the rule in many parts of the country. In many areas, if you live outside of the perceived “market” just beyond range of the CO, lead times are sometimes quoted at “two to three years” (marketing jargon for “never, but we’ll take your money anyway if you like”). Worse than that, in the wake of widespread market consolidation, some customers who were quite happy with their DSL service are finding themselves stranded when their local ISP goes out of business.^[1]

What are the alternatives for people who desire high-speed Internet access, but aren’t willing to wait for companies to package a solution for them? The telephone companies own the copper, and the cable companies own the coax.

Community wireless networks now provide easy, inexpensive, high-bandwidth network services for anyone who cares to participate.

Approved in 1997 by the IEEE Standards Committee, the 802.11 specification details the framework necessary for a standard method of wireless networked communications. It uses the 2.4GHz microwave band designated for low-power, unlicensed use by the FCC in the U.S. in 1985. 802.11 provided for network speeds of one or two megabits, using either of two incompatible encoding schemes: Frequency Hopping Spread Spectrum (FHSS), or Direct Sequence Spread Spectrum (DSSS).

In September of 1999, the 802 committee extended the specification, deciding to standardize on DSSS. This extension, 802.11b, allowed for new, more exotic encoding techniques. This pushed up the throughput to a much more respectable 5.5 or 11Mbps. While breaking compatibility with FHSS schemes, the extensions made it possible for new equipment to continue to interoperate with older 802.11 DSSS hardware. The technology was intended to provide “campus” access to network services, allowing a typical range of about 1,500 feet. As we’ll see in Chapter 2, a few new important protocols have been approved that push available wireless bandwidth even higher: all the way up to 54Mbps (but more on that later). While these developments are certainly important, the ratification and wide acceptance of 802.11b in late 1999 is widely regarded as the start of the popular wireless networking phenomenon.

It didn’t take long for some sharp hacker types (and, indeed, a few CEO and FCC types) to realize that by using wireless client gear in conjunction with standard radio equipment, effective range can extend to more than 20 miles and potentially provide thousands of people with bandwidth reaching DSL speeds, for minimal hardware cost. Connectivity that previously had to creep up monopoly-held wires can now fly in through the walls with significantly higher performance. And since consumer-grade wireless equipment uses unlicensed radio spectrum, full-time connections can be set up without paying a dime in airtime or licensing fees.

While trumping the telco and cable companies with off-the-shelf magical hardware may be an entertaining fantasy, how well does wireless equipment designed to serve a few local clients actually perform in the real world? How can it be effectively applied to provide generalized access to the Internet?

The Problem

An obvious application for wireless is to provide the infamous "last mile” network service. This term refers to the stretch that sits between those who have good access to the Internet (ISPs, Telcos, and cable companies) and those who want it (consumers). This sort of arrangement requires wireless equipment at both ends of the stretch (for example, at an ISP’s site and at a consumer’s home).

Unfortunately, the nature of radio communications at microwave frequencies requires line of sight for optimal performance. This means that there should be an unobstructed view between the two antennas, preferably with nothing but a valley between them. This is absolutely critical in long-distance, low-power applications. Radio waves penetrate many common materials, but range is significantly reduced when going through anything but air. Although increasing transmission power can help get through trees and other obstructions, simply adding amplifiers isn’t always an option, as the FCC imposes strict limits on power. (We will return to this subject in detail in Chapter 7.)

Speaking of amplifiers, a related technical obstacle to wireless nirvana is how to deal with noise in the band. The 2.4Ghz band isn’t reserved for use solely by wireless networking gear. It has to share the band with many other devices, including cordless phones, wireless X-10 cameras, Bluetooth equipment, burglar alarms, and even microwave ovens! Using amplifiers to try to “blast” one’s way through intervening obstacles and above the background noise is the social equivalent of turning your television up to full volume so you can hear it in your front yard (maybe also to hear it above your ringing telephone and barking dog, or maybe even your neighbor’s loud television...).

If data is going to flow freely over the air, there has to be a high degree of coordination between those who set it up. As the airwaves are a public resource, the wireless infrastructure should be built in a way that benefits the most people possible, for the lowest cost. How can wireless networking effectively connect people to each other?

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^[1] One currently circulating meme deems a stranded customer "Northpointed,” in honor of the ISP NorthPoint.net, which went out of business in March of 2001, leaving thousands without access.