Wireless Hacks

Hack 6 Bluetooth: Cable Replacement for Devices

Bluetooth eliminates the need for cables that tether your tiny devices.

While the 802.11 protocols were designed to replace the ubiquitous CAT5 networking cable, Bluetooth aims to replace all of the other cables connected to your computer (with the sad exception of the power cable). Operating as a frequency hopper in the 2.4 GHz ISM band, it shares the same spectrum as 802.11b/g and many other devices. It is designed to create a so-called "Personal Area Network" for devices like cell phones, digital cameras, PDAs, headsets, keyboards and mice, and of course, computers. While it is possible to use Bluetooth for an actual Internet connection, it seems to be better suited for low bandwidth data and voice applications.

Pros

• Very low power requirements, making it ideal for small battery-powered devices such as handhelds, phones, and headsets.

• Simple interface and security model.

• Exceptional interoperability between devices.

• Built-in support for simultaneous data and voice traffic.

Cons

• Relatively low data throughput (about 720 Kbps maximum).

• Shares the 2.4 GHz band with many other devices, including 802.11b/g.

• Very limited range, by design.

Recommendation

Bluetooth uses an aggressive full duplex frequency-hopping scheme (changing channels up to 1,600 times per second) to attempt to avoid noise in the 2.4 GHz band. While this may be good for Bluetooth, high power frequency-hopping devices can cause considerable interference for other devices using the band. Fortunately, most Bluetooth products operate only at 1mW, keeping most interference limited to a very small area. Even when using Bluetooth alongside an 802.11b connection, the perceived interference turns out to be minimal, and most people don't even notice the difference with normal usage. If you are using 802.11a in the presence of Bluetooth devices, the two will not interfere with each other at all.

The 802.11 protocols and Bluetooth are complementary and solve very different problems. I will show you some cool things you can do with Bluetooth in Chapter 2, and much of the rest of this book will focus on fun with 802.11.