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Electronic Design

Bluetooth 101

Bluetooth is the name of a widely adopted short range wireless technology used to implement personal area networks (PANs).  Bluetooth is the commercial name of the technology based on the IEEE’s 802.15.1 wireless standard.  The standard is maintained by the IEEE and the Bluetooth Special Interest Group (SIG).  The technology was originally developed by Ericsson of Sweden and the first formalized specifications were announced by the Bluetooth SIG in 1998.

Bluetooth is wireless data method that uses the unlicensed spectrum in the 2.4 to 2.483 GHz range.  The original standard called for the use of frequency hopping spread spectrum (FHSS) using 79 hop frequencies spaced by 1 MHz and 1600 hops per second rate.  The modulation is Gaussian FSK giving a gross data rate of 1 Mb/s and a net rate of 723 kb/s.  There are three RF power classes defined by the standard:  Class 1 100 mW (20 dBm), Class 2 2.5 mW (4 dBm), and Class 3 1 mW (0 dBm).  The maximum useable range is approximately 100 meters with Class1, 10 meters using and Class 2 and 1 meter using Class 3 all depending upon the environment. 

A more recent version of the standard is Version 2.1 called Enhanced Data Rate (EDR) and provides a gross data rate of 3 Mb/s and a net data rate of 2.1 Mb/s.  It uses the same FHSS scheme but with either p/4 – DQPSK or 8DPSK modulation.  The most recent version is Bluetooth 3.0 High Speed that uses the same Bluetooth protocol but adopts the 802.11 wireless radio technology to achieve a peak data rate of 24 Mb/s.  There is also a potential future version based on WiMedia’s ultra wideband (UWB) technology that can achieve a peak data rate of 480 Mb/s at a range from 2 to 10 meters.

A key feature of Bluetooth is its networking capability.  A Bluetooth device automatically seeks out other Bluetooth units nearby and forms an ad hoc connection.  One Bluetooth device can serve as a master controller to form a star network called a piconet with up to 7 other Bluetooth devices.

The primary application for Bluetooth today is wireless headsets for cell phones.  It is also used to connect cell phones to PCs or laptops,  hands free auto cell phone connections, wireless audio systems and speakers, and for wireless remote control of toys, games and other devices.  New applications are still being discovered for this versatile wireless method.

TAGS: Wireless
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