Basics of Bluetooth Wireless Technology
Bluetooth technology is a short-range communications technology that is
simple, secure, and everywhere. You can find it in billions of devices
ranging from mobile phones, laptops, tablets and computers to medical
devices and home entertainment products. It is intended to replace the cables
connecting devices, while maintaining high levels of security.
The key features of Bluetooth technology are robustness, low power, and
low cost. The Bluetooth Specification defines a uniform structure for a wide
range of devices to connect and communicate with each other.
When two Bluetooth enabled devices connect to each other, this is called
pairing. The structure and the global acceptance of Bluetooth technology means
any Bluetooth enabled device, almost everywhere in the world, can connect to
other Bluetooth enabled devices located in proximity to one another.
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 meaning that you can easily
connect whenever and wherever it's convenient for you.
Each device in a piconet can also simultaneously communicate with up to
seven other devices within that single piconet and each device can also belong
to several piconets simultaneously. This means the ways in which you can
connect your Bluetooth devices is almost limitless.
A fundamental strength of Bluetooth wireless technology is the ability to
simultaneously handle data and voice transmissions. which provides users with a
variety of innovative solutions such as hands-free headsets for voice calls,
printing and fax capabilities, and synchronization for PCs and mobile phones,
just to name a few.
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.
Bluetooth Core Specification
Unlike other wireless standards, the Bluetooth Core Specification provides
product developers both link layer and application layer definitions, which
support data and voice applications.
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.
Interference
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 this hopping provides greater performance
even when other technologies are being used along with Bluetooth technology.
Range
Range is application specific and although a minimum range is mandated by
the Core Specification, there is not a limit and manufacturers can tune their
implementation to support the use case they are enabling.
Range may vary depending on class of radio used in an implementation:
- Class 3
radios – have a range of up to 1 meter or 3 feet
- Class 2 radios
– most commonly found in mobile devices – have a range of 10 meters or 33
feet
- Class 1
radios – used primarily in industrial use cases – have a range of 100
meters or 300 feet
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. This is reinforced
in the specification by 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.
Bluetooth low energy technology, optimized for devices requiring maximum
battery life instead of a high data transfer rate, consumes between 1/2 and
1/100 the power of classic Bluetooth technology.
