Specifications

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Communication Overview
35
COM
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 721 kbps,
even in noisy environments. Like USB (see page 22) and IEEE
1394 (see page 24), the specification incorporates both rules for
implementing the interface and rules for designing compatible
peripherals for the network.
The Bluetooth Special Interest Group (SIG), comprised of leaders
in the telecommunications, computing, and network industries,
is driving development of the technology and bringing it to
market. As an Associate Member of the SIG, Quatech is kept up
to date on all the latest specifications, so you can be sure that all
Bluetooth products from Quatech will be compatible with other
Bluetooth devices on the market.
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
Scatternet
Piconet, point-to-point Piconet, point-to-multipoint
(Bluetooth multiple piconet communication structure)
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.
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, and a high power level that can
accommodate a medium range, such as an entire building.
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.
*Bluetooth is a trademark owned by the
Bluetooth SIG, Inc. and used by Quatech, Inc.
under license.
TM