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A wireless personal area network (WPAN) for short-range transmission of digital voice and data. Using omnidirectional radio waves, Bluetooth transmits through walls and other non-metal barriers. Although the term is practically synonymous with cellphone headsets and in-vehicle, hands-free telephony, Bluetooth is also used in many other applications, including wireless keyboards, mice and game controllers (for more details, see Bluetooth profiles).

     The name comes from ancient King Harald Blatan (Bluetooth in English) of Denmark. Ericsson, a Scandinavian company, first developed the specification and was a co-founder in 1998 of the Bluetooth Special Interest Group (www.bluetooth.com), which governs the specification. Bluetooth is also standardized as an IEEE wireless personal area network (see 802.15). See Bluetooth glossary.

Bluetooth Specifications
Bluetooth transmits in the same unlicensed 2.4 GHz band as Wi-Fi, but with a different transmission method. It uses frequency hopping spread spectrum (FHSS), which changes its signal randomly to one of 79 channels 1,600 times per second. If there is interference from other devices, transmission continues, but speed is downgraded. However, Bluetooth 2.0 + EDR (Enhanced Data Rate) avoids channels that are interfering with other wireless devices. Future versions of Bluetooth are expected to use UWB transmission (see WiMedia Alliance). See spread spectrum.

     Supporting point-to-point and multipoint (see piconet), following are Bluetooth's data rates and power ratings:

            Data              Maximum    Approx.
            Rate               Power     Range
  Version  (Mbps)       Class   (mW)    (meters)

   1.2        1           1     100       100
   2.0+EDR    3           2       2.5      10
                          3       1         1

Wibree - Ultra Low Power (ULP) Bluetooth
In 2007, Nokia's Wibree technology was added to the Bluetooth specification and renamed ULP Bluetooth. Using up to a quarter of the power of Bluetooth at 1 Mbps, Wibree enables sensors, wristwatches and toys with tiny batteries to employ wireless. To use Bluetooth and Wibree at the same time, a dual-mode device is required.




Two Wireless Systems
All Bluetooth cellphone users are employing two wireless technologies: Bluetooth between ear and cellphone and the carrier's transmission technology between cellphone and cell tower (see GSM and CDMA).





Game Controllers
This "gamepad" from Sony uses Bluetooth to communicate with the PlayStation3 game console. See video game controller. (Image courtesy of Sony Corporation.)





The Bluetooth Logo
The stylized "B" displayed on this cellphone means it has been synchronized with a Bluetooth device.