| |
What is Bluetooth wireless
technology?
Bluetooth technology is how mobile phones, computers, and
personal digital assistants (PDAs), not to mention a broad
selection of other devices, can be easily interconnected
using a short-range wireless connection. Using this
technology, users can have all mobile and fixed computer
devices be totally coordinated.
Bluetooth wireless technology is a short-range
communications technology intended to replace the cables
connecting portable and/or fixed 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.
Bluetooth technology has achieved global acceptance such
that any Bluetooth enabled device, almost everywhere in the
world, can connect to other Bluetooth enabled devices in
proximity. Bluetooth enabled electronic devices connect and
communicate wirelessly through short-range, ad hoc networks
known as piconets. Each device can simultaneously
communicate with up to seven other devices within a single
piconet. Each device can also belong to several piconets
simultaneously. Piconets are established dynamically and
automatically as Bluetooth enabled devices enter and leave
radio proximity.
A fundamental Bluetooth wireless technology strength is the
ability to simultaneously handle both data and voice
transmissions. This enables users to enjoy variety of
innovative solutions such as a hands-free headset for voice
calls, printing and fax capabilities, and synchronizing PDA,
laptop, and mobile phone applications to name a few.
Core Specification Versions
Version 2.0 + Enhanced Data Rate (EDR), adopted November,
2004
Version 1.2, adopted November, 2003
Specification Make-Up
Unlike many other wireless standards, the Bluetooth wireless
specification gives product developers both link layer and
application layer definitions, which supports 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 detecting other devices in the
spectrum and avoiding the frequencies they are using. This
adaptive hopping allows for more efficient transmission
within the spectrum, providing users with greater
performance even if using other technologies along with
Bluetooth technology. The signal hops among 79 frequencies
at 1 MHz intervals to give a high degree of interference
immunity
Range
The operating range depends on the device class:
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 30 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
Data Rate
1 Mbps for Version 1.2; Up to 3 Mbps supported for Version
2.0 + EDR
Why Choose Bluetooth wireless
technology?
Bluetooth wireless technology is the simple choice for
convenient, wire-free, short-range communication between
devices. It is a globally available standard that wirelessly
connects mobile phones, portable computers, cars, stereo
headsets, MP3 players, and more. Thanks to the unique
concept of “profiles,” Bluetooth enabled products do not
need to install driver software. The technology is now
available in its fourth version of the specification and
continues to develop, building on its inherent strengths —
small-form factor radio, low power, low cost, built-in
security, robustness, ease-of-use, and ad hoc networking
abilities. Bluetooth wireless technology is the leading and
only proven short-range wireless technology on the market
today shipping over five million units every week with an
installed base of over 500 million units at the end of 2005.
Globally Available
The Bluetooth wireless technology specification is available
free-of-charge to our member companies around the globe.
Manufacturers from many industries are busy implementing the
technology in their products to reduce the clutter of wires,
make seamless connections, stream stereo audio, transfer
data or carry voice communications. Bluetooth technology
operates in the 2.4 GHz, one of the unlicensed industrial,
scientific, medical (ISM) radio bands. As such, there is no
cost for the use of Bluetooth technology. While you must
subscribe to a cellular provider to use GSM or CDMA, with
Bluetooth technology there is no cost associated with the
use beyond the cost of your device.
Range of Devices
Bluetooth technology is available in an unprecedented range
of applications from mobile phones to automobiles to medical
devices for use by consumers, industrial markets,
enterprises, and more. The low power consumption, small size
and low cost of the chipset solution enables Bluetooth
technology to be used in the tiniest of devices. Have a look
at the wide range products made available by our members in
the Bluetooth product directory and the component product
listing.
Ease of Use
Bluetooth technology is an ad hoc technology that requires
no fixed infrastructure and is simple to install and set up.
You don’t need wires to get connected. The process for a new
user is easy – you get a Bluetooth branded product, check
the profiles available and connect it to another Bluetooth
device with the same profiles. The subsequent PIN code
process is as easy as when you identify yourself at the ATM
machine. When out-and-about, you carry your personal area
network (PAN) with you and can even connect to others.
Globally Accepted Specification
Bluetooth wireless technology is the most widely supported,
versatile, and secure wireless standard on the market today.
The globally available qualification program tests member
products as to their accordance with the standard. Since the
first release of the Bluetooth specification in 1999, over
4000 companies have become members in the Bluetooth Special
Interest Group (SIG). Meanwhile, the number of Bluetooth
products on the market is multiplying rapidly. Volumes have
doubled for the fourth consecutive year and are likely to
reach an installed base of 500 million units by the close of
2005.
Secure Connections
From the start, Bluetooth technology was designed with
security needs in mind. Since it is globally available in
the open 2.4 GHz ISM band, robustness was built in from the
beginning. With adaptive frequency hopping (AFH), the signal
“hops” and thus limits interference from other signals.
Further, Bluetooth technology has built-in security such as
128bit encryption and PIN code authentication. When
Bluetooth products identify themselves, they use the PIN
code the first time they connect. Once connected, always
securely connected.
Overview of Operation - Bluetooth
The Bluetooth RF (physical layer) operates in the unlicensed
ISM band at 2.4GHz. The system employs a frequency hop
transceiver to combat interference and fading, and provides
many FHSS carriers. RF operation uses a shaped, binary
frequency modulation to minimize transceiver complexity. The
symbol
rate is 1 Megasymbol per second (Msps) supporting the bit
rate of 1 Megabit per second (Mbps) or, with Enhanced Data
Rate, a gross air bit rate of 2 or 3Mb/s. These modes are
known as Basic Rate and Enhanced Data Rate respectively.
During typical operation, a physical radio channel is shared
by a group of devices that are synchronized to a common
clock and frequency hopping pattern. One device provides the
synchronization reference and is known as the master. All
other devices are known as slaves. A group of devices
synchronized in this fashion form a piconet. This is the
fundamental form of communication for Bluetooth wireless
technology.
Devices in a piconet use a specific frequency hopping
pattern which is algorithmically determined by certain
fields in the Bluetooth specification address and clock of
the master. The basic hopping pattern is a pseudo-random
ordering of the 79 frequencies in the ISM band. The hopping
pattern may be adapted to exclude a portion of the
frequencies that are used by interfering devices. The
adaptive hopping technique improves Bluetooth technology
co-existence with static (non-hopping) ISM systems when
these are co-located.
The physical channel is sub-divided into time units known as
slots. Data is transmitted between Bluetooth enabled devices
in packets that are positioned in these slots. When
circumstances permit, a number of consecutive slots may be
allocated to a single packet. Frequency hopping takes place
between the transmission or reception of packets. Bluetooth
technology provides the effect of full duplex transmission
through the use of a time-division duplex (TDD) scheme.
Above the physical channel there is a layering of links and
channels and associated control protocols. The hierarchy of
channels and links from the physical channel upwards is
physical channel, physical link, logical transport, logical
link and L2CAP channel.
Within a physical channel, a physical link is formed between
any two devices that transmit packets in either direction
between them. In a piconet physical channel there are
restrictions on which devices may form a physical link.
There is a physical link between each slave and the master.
Physical links are not formed directly between the slaves in
a piconet.
The physical link is used as a transport for one or more
logical links that support unicast synchronous, asynchronous
and isochronous traffic, and broadcast traffic. Traffic on
logical links is multiplexed onto the physical link by
occupying slots assigned by a scheduling function in the
resource manager.
A control protocol for the baseband and physical layers is
carried over logical links in addition to user data. This is
the link manager protocol (LMP). Devices that are active in
a piconet have a default asynchronous connection-oriented
logical transport that is used to transport the LMP protocol
signaling. For historical reasons this is known as the ACL
logical transport. The default ACL logical transport is the
one that is created whenever a device joins a piconet.
Additional logical transports may be created to transport
synchronous data streams when this is required.
The link manager function uses LMP to control the operation
of devices in the piconet and provide services to manage the
lower architectural layers (radio layer and baseband layer).
The LMP protocol is only carried on the default ACL logical
transport and the default broadcast logical transport.
Above the baseband layer the L2CAP layer provides a
channel-based abstraction to applications and services. It
carries out segmentation and reassembly of application data
and multiplexing and de-multiplexing of multiple channels
over a shared logical link. L2CAP has a protocol control
channel that is carried over the default ACL logical
transport. Application data submitted to the L2CAP protocol
may be carried on any logical link that supports the L2CAP
protocol. |
|
