Wireless Home Networking - Index of

Chapter 3: Bluetooth and Other Wireless Networks
To make full use of the 2.4 GHz frequency radio band and to reduce the likelihood
of interference, Bluetooth uses a transmission protocol that hops 1,600
times per second between 79 discrete 1 MHz-wide channels from 2.402 GHz to
2.484 GHz. Each piconet establishes its own random hopping pattern so that
you can have many piconets in the same vicinity without mutual interference.
If interference does occur, each piconet switches to a different channel and
tries again. Even though Wi-Fi (802.11b, g, and n) and Bluetooth both use the
2.4 GHz band, both protocols use hopping schemes that should result in
little, if any, mutual interference.
Understanding Bluetooth versions
Bluetooth has been around for a few years now
and, like most technologies, has undergone
some growing pains and revisions. In fact, multiple
versions of Bluetooth-certified equipment
are available, as newer and more capable variants
of Bluetooth arrive on the market.
The most common variant of Bluetooth is known
as Bluetooth 1.2. This is basically a version of
Bluetooth with all the bugs removed. Bluetooth
1.2 devices (most currently available devices, in
other words) are backward compatible with
earlier Bluetooth 1.0 and 1.1 devices. So, they
work the same way, at the same speeds — just
better. (Some technical advances in 1.2 allow
most devices to have better real-world speeds.)
A growing number of Bluetooth devices support
the Bluetooth 2.0 + EDR (extended data rate)
standard. You can think of Bluetooth 2.0 + EDR
versus the 1.x variants as being similar to
802.11g versus 802.11b. It is faster (with a maximum
speed three times as high — 2.1 Mbps
versus around 700 Kbps for the EDR, or
enhanced data rate), is better at resisting interference,
and just basically works better all
around. If you’re shopping for something that
may be sending larger files or requiring faster
data transfers, such as a Bluetooth-equipped
laptop (or a Bluetooth-enabled smartphone that
can be used as a modem for your laptop), consider
insisting on Bluetooth 2.0 and EDR.
In mid-2007, Bluetooth 2.1 was released. This
version of Bluetooth isn’t any faster than 2.0 +
EDR, but it includes some performance and battery
life improvements. The biggest change in
Bluetooth 2.1 (there are only a handful of 2.1
devices on the market as we write) is the support
for something called NFC (Near Field
Communications). With NFC, a special lowpower
radio system lets two devices in very
close proximity (a few centimeters) “talk” to
each other — two Bluetooth systems with NFC
could be paired (we talk about pairing in
Chapter 15) by simply holding them very close
to each other. This NFC pairing (when it hits the
market) will make using Bluetooth even easier
by significantly reducing the steps needed to
get two devices connected.
Coming down the pike is the Bluetooth 3.0 standard
— and the Bluetooth folks have adopted a
new technology called UWB (see the sidebar
“Ultracool ultra wideband (UWB) is coming” for
more on this technology) to make Bluetooth
even faster in the future. Additionally, Bluetooth
will also incorporate a technology from Nokia
called Wibree, which allows ultra-low-power
implementations of Bluetooth for devices with
limited battery or power supplies.
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