Bluetooth® wireless technology[1] is a short-range communications
technology intended to replace the cables connecting portable and/or fixed
devices while maintaining high levels of security.
The global acceptance of Bluetooth and
the structure of Bluetooth technology allows any Bluetooth-enabled device to
connect to any other Bluetooth-enabled device located within a specified
proximity.
All the information within this
section and more detailed technology description are available on www.bluetooth.com web site.
Connections between
Bluetooth-enabled electronic devices allow these devices to communicate
wirelessly through short-range, ad hoc
networks known as piconets. Piconets are established dynamically and
automatically as Bluetooth-enabled devices enter and leave radio
proximity. Each device in a piconet can simultaneously communicate with up
to seven other devices within that single piconet and each device can also
belong to several piconets simultaneously. The ways in which you can connect
your Bluetooth devices are almost
limitless.
The range of Bluetooth technology is
application-specific. The Core Specification mandates a minimum range of
10 meters or 30 feet, but there is no set limit and manufacturers can
tune their implementations to provide the range needed to support the use cases
for their solutions.
Spectrum
Bluetooth technology operates in
the unlicensed industrial, scientific and medical (ISM) band at 2.4 to
2.485 GHz, using a spread spectrum, frequency hopping, full-duplex signal
at a nominal rate of 1600 hops/sec. The 2.4 GHz ISM band is
available and unlicensed in most countries.
Bluetooth technology’s adaptive
frequency hopping (AFH) capability was designed to reduce interference between
wireless technologies sharing the 2.4 GHz spectrum. AFH works within the
spectrum to take advantage of the available frequency. This is done by the
technology detecting other devices in the spectrum and avoiding the frequencies
they are using. This adaptive hopping among 79 frequencies at 1 MHz
intervals gives a high degree of interference immunity and also allows for more
efficient transmission within the spectrum. For users of Bluetooth technology frequency hopping
provides greater performance even if other technologies are being used along
with Bluetooth technology.
Range may vary depending
on class of radio used in an implementation:
Power
The most commonly used radio is
Class 2 and uses 2.5 mW of power. Bluetooth technology is designed to
have very low power consumption including allowing radios to be powered down
when inactive.
The Generic Alternate MAC/PHY in
Version 3.0 HS enables the discovery of remote AMPs for high speed
devices and turns on the radio only when needed for data transfer giving a
power optimization benefit as well as aiding in the security of the radios.