Linux Unwired [Electronic resources] نسخه متنی

1.4 Bluetooth

Bluetooth
is a low-power radio technology aimed at replacing cables for
connecting devices. It was originally developed by the Swedish
telecommunications manufacturer Ericsson and then formalized by an
industry consortium. The name is taken from a Danish king, Harald
Bluetooth, who ruled Denmark and Norway in A.D. 936.

The standards for Bluetooth define a low-power radio with a maximum
range of 300 feet. The radios are actually on a transceiver microchip
to keep size and power consumption to a minimum. Bluetooth uses the
2.45 GHz band of the ISM radio spectrum and divides the band into 79
channels. To further reduce any crosstalk into other ISM bands,
Bluetooth devices can change channels up to 1,600 times per second.

Bluetooth is becoming widely available on mobile phones and
PDAs, and one of its
"killer" applications is
hands-free wireless headsets for mobile
phones. Bluetooth is also a popular way to
"tether" a notebook computer to a
cellular phone, which allows you to connect to the Internet even when
an 802.11 network is not available (because current cellular data
speeds are much slower than Bluetooth, Bluetooth's
relatively slow speeds are not the limiting factor). Bluetooth
adapters are available for PDAs, desktops, and notebooks. There are
some printers and keyboards available that use Bluetooth to
communicate with the host device as well.

Compared to Wi-Fi, Bluetooth speeds are not impressive, but they are
quite useful for transferring small amounts of data. Download speeds
can max out at 720 kbps with a simultaneous upload speed of 56 kbps.
Every Bluetooth device can simultaneously maintain up to seven
connections, making a personal Bluetooth LAN a real possibility.