Bluetooth Communication Overview
A Short-Range Mobile Solution
Bluetooth is a specification for a small form-factor, low-cost, short-range
radio solution for providing links between mobile computers, mobile
phones, and other portable and hand-held devices, and for providing
connectivity to the internet. It is based on a radio link that provides
fast and reliable transmission of both voice and data. It can carry
up to three high-quality voice channels simultaneously at speeds to
1 Mbit/sec, even in noisy environments. Like USB, the specification
incorporates both rules for implementing the interface and rules for
designing compatible peripherals for the network.
Connectivity
Bluetooth allows users to connect to a wide range of devices at
one time without cables, and potentially without actively initiating
the connection. For example, your PDA could automatically update
a copy of your schedule stored on a desktop PC the minute you walked
into your office. This connectivity is enabled by a tiny microchip
incorporating a radio transceiver that is built into Bluetooth devices.
This radio transceiver provides the advantage of being effective
through obstacles. Thus, you could ostensibly use a Bluetooth connection
to send data from a computer in one room to a printer in the next--right
through the wall.
One concern when using such a system is privacy. As Bluetooth operates
in the globally available 2.4 GHz frequency, it is conceivable that
an unintended recipient could intercept a signal. To combat this,
all Bluetooth devices are keyed for their own networks. The transmissions
use a sophisticated encoding specification that not only guards
against interference, it also ensures that only devices specifically
programmed to receive a broadcast will be able to decode it.
Bluetooth uses a flexible, multiple piconet structure for communication.
It supports both point-to-point and multipoint connections for full-duplex
networks. Currently up to seven slave devices can be configured
to use a master radio in one device. Several of the piconets can
be established and linked in scatternets to allow flexibility among
configurations. Devices in the same piconet have priority synchronizations,
but other devices can enter the network at any time. In a full-duplex
network, a multiple piconet structure with 10 fully loaded, independent
piconets, can maintain aggregate data transfer speeds of up to 6
Mbps.
Class 1 and Class 2 Bluetooth
The major difference between the 2 classes of Bluetooth adapter
is communication range and power requirements. As a rule, you will
typically trade power consumption for distance (though all Bluetooth
devices typically have low power requirements relative to other
types of computer add-in devices.) Class 2 Bluetooth devices have
a communication range of 10 meters (30 feet), and Class 1 adapters
provide a communication range of 100 meters (300 feet).
High and Low Power
The Bluetooth specification implements two power levels: a low power
level designed for short distance communication such as within an
office (Class 2), and a high power level that can accommodate a
medium range, such as an entire building (Class 1). Additionally,
Bluetooth limits power output to exactly what the device requires
at any given time. For instance, when two devices connect and determine
that they are close together, the transmitter immediately modifies
its signal to the strength needed to accommodate that range. When
traffic volume across a connection slows down, or stops completely,
a receiving device will shift to a low power sleep mode that is
intermittently interrupted for very short periods in order to maintain
the network connection. With these power saving features, Bluetooth
devices consume very small amounts of power, making them ideal for
portable applications.
Bluetooth for Data Communication
Bluetooth technology makes data communication fast, easy, and convenient.
As speeds and distances are currently limited, it should be viewed
as a short-range solution for low to medium speed applications.
It does provide remarkable flexibility, by communicating through
walls and other obstacles, that makes it an ideal choice for home
or office networks--for example sharing a printer among multiple
PCs located in different rooms on the same floor. It also expands
the functionality of a mobile phone, allowing it to serve as a modem
for Internet connections, or allowing it to communicate with other
devices--such as the prospect of using mobile phones to purchase
drinks from vending machines.
To learn more:
These expert sources provide detailed information about Bluetooth
and Bluetooth devices:
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