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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.