WARLES HACK

1.1 Hacks #1-12

The mad rush to bring wireless products to market has left a slew of similar sounding yet often completely incompatible acronyms in its wake. 802.11b is the sequel to 802.11a, right? (Wrong.) If I just buy Wi-Fi, then everything will work together, right? (Unfortunately, no.) What is the difference between 802.11 a/b/g, 802.16, and 802.1x? How about GSM, GPRS, GMRS, and GPS? Where does Bluetooth fit into the picture?

Before we can jump into the more advanced hackery that is possible with wireless communications, it is important to understand what we have to work with. Remember that no technology is inherently "better" than any other; which one you should use depends on what you want to accomplish and the resources you have to work with. The goal of this chapter is to familiarize you with many of the popular wireless technologies available today, and to give you an idea of their relative strengths and weaknesses.

Hack 1 802.11: The Mother of All IEEE Wireless Ethernet

While definitely showing its age, the original 802.11 gear still has its uses.

The first wireless standard to be defined in the 802 wireless family was 802.11. It was approved by the IEEE in 1997, and defines three possible physical layers: Frequency Hopping Spread Spectrum (FHSS) at 2.4 GHz, Direct Sequence Spread Spectrum (DSSS) at 2.4 GHz, or Infrared. 802.11 could achieve data rates of 1 or 2 Mbps. 802.11 radios that use DSSS are interoperable with 802.11b and 802.11g radios at those speeds, while FHSS radios and Infrared obviously are not.

The original 802.11 devices are increasingly hard to come by, but can still be useful for point-to-point links with low bandwidth requirements.

Pros

• Very inexpensive (a few dollars or even free) when you can find them.

• DSSS cards are compatible with 802.11b/g.

• Infrared 802.11 cards (while rare) can offer interference-free wireless connections, particularly in noisy RF environments.

• Infrared also offers increased security due to significantly shorter range.

Cons

• No longer manufactured.

• Low data rate of 1 or 2 Mbps.

• FHSS radios are incompatible with everything else.

Recommendation

802.11 devices can still be useful, particularly if you find that you already have a few on hand. But the ever falling price of 802.11b and 802.11g gear makes the old 802.11 equipment less attractive each day. The FHSS and Infrared cards talk only to cards of the same era, so don't expect them to work outside of your own projects. Infrared requires an absolutely clean line of sight between devices and offers limited range, but it operates well away from the popular ISM and UNII bands. This means that it won't interfere with (or see interference from) other networking devices, which can be a huge advantage in some situations.

I probably wouldn't go out of my way to acquire 802.11 equipment, but you can still build a useful network if it's all you have to work with. They are probably best used for building point-to-point links, but might be better avoided altogether.