Blue Tooth
The term Blue Tooth refers to an open
specification technology that enables short-range wireless voice and data
communications anywhere in the world.
Blue Tooth
does NOT involve mobile network transactions- its spectrum is freely available
to use in the unlicensed radio frequency spectrum area (at 2.45 gigahertz).
Data transmission speeds using Blue Tooth are expected to be between 720 kbps
and one megabit per second (Mbps).
Blue Tooth
encompasses both a standard communications interface and a low-cost computer
chip. It is a cross between the DECT (Digital European Cordless Telephone) and
iRDA (infra Red Data Association) technologies.
Open
Specification:
The Blue Tooth Special Interest Group (SIG) has
produced a specification for Blue Tooth wireless communication that is publicly
available and royalty free.
The organization has its own web site to foster widespread
acceptance and use of the technology. It even provides a qualification program for
users of the technology at its web site. Its user specifications are readily available
at the website:
Where did
the name come from?
Blue Tooth
is named after Harald Blatand, the King of Denmark from 940 to 985 A.D. During King Harald’s reign, he united
Since Blatand united countries, it was felt his name would be a good name for a group of companies united in a technology aim from many countries.
What’s so
good about Blue Tooth technology?
The Blue Tooth technology was conceived as a
global short-range wireless communications system. It was begun by Ericsson as a project to
produce a low-power, and low-cost radio interface between mobile phones and
their accessories.
The Blue
Tooth wireless technology is ideally suited for replacing the many cables that
are associated with today’s pervasive devices that use cables for links to accessories. The Blue Tooth specification explicitly
defines a means for wireless transports to replace serial cables and other
cables such as those associated with computer peripherals. Blue Tooth’s radio frequency technology does
not require a “line of sight” between the transmitter and the receiver as is
the case in infrared technology.
The Blue
Tooth radio frequency technology is designed for operation in the 2.4 gigahertz
spectrum (A gigahertz equals one billion cycles per second.) By
international agreement, this range requires no license for use anywhere in the
world.
The
spectrum used by Blue Tooth is divided into 79 channels, with a bandwidth of
1megahertz per channel. Frequency
hopping spread spectrum communication is employed. Since other technologies also use this
spectrum, Blue Tooth is designed to take maximum channel bandwidth and to
minimize RF interference and its effects while operating at very low power.
With Blue
Tooth communications, the available spectrum is divided in a method called
Frequency Hopping. Frequency hopping is
achieved by dividing the available spectrum into frequencies or channels. A single message packet is transmitted on a
selected channel, then the radio selects a new channel (this selection process
is called hopping) to transmit the next packet.
The process repeats, thereby spreading the message across the available
spectrum. This process reduces
interference since all radios hop (often in some rapid, randomly defined manner-1,600
times per second) and the possibility of packet collision (one cause of
interference) is significantly reduced.
In addition, when collisions do occur, their effects are lessened, since
only a single packet is lost and that packet could be retransmitted at a new
frequency, where again it is less likely to encounter interference.
This Frequency
Hopping requires a receiver to have a pattern synchronized to this method to
retrieve and reassemble the message packets.
The rapidity and the digital base for the Blue Tooth technology also
give a degree of security for the communications in that only the receiver that
knows the hopping pattern for a given spectrum could follow that hopping
pattern.
Another
advantage of the Blue Tooth technology is its interoperability. At the baseband level, when two devices
establish a Blue Tooth link, one acts in the role of master, and the other in
the role of a slave. This specification
permits any Blue Tooth radio to assume either
role. Furthermore, Blue Tooth
technology allows a device to act as a master for one communication link and as
a slave for another link. The role of
master does not imply special privileges or authority; instead it governs the
synchronization of the Frequency Hopping Spread Spectrum communications between
the devices. The master device (the
device that initiates the communication) determines the frequency hopping
pattern (based upon it Blue Tooth device address) and the phase for the hopping
sequence (based upon its clock). All
slaves communicating with the given master hop together in unison with the
master in a relationship called a piconet.
A master can communicate with up to seven active slaves (in direct
instantaneous communication with the master) and up to 255 parked slaves (in
communication with the master but the link is not direct and instantaneous).
It is
important to understand that the master-slave relationship is necessary in low
level communications, but in general devices operate as peers. When one device establishes a point-to-point
link with another device, the role that each device assumes is irrelevant to
higher level protocols and to the user of the device.
New
Applications:
The integration of Blue Tooth wireless technology brings new functionality to familiar products while also setting the stage for entirely new applications with revolutionary connectivity implications. Devices enabled with Blue Tooth wireless technology will be able to:
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Transfer and
synchronize data wirelessly |
|
Take
advantage of localized content services in public areas |
|
Exchange
files, business cards, and calendar appointments |
|
Wireless
headset features for voice activated software |
|
Function as
remote controls, keys, tickets and e-cash wallets Bluetooth chips in freight
containers to identify cargo when a truck drives into a storage depot |
Good
General Sources on Blue Tooth with additional link sites to Vendors and
Developers:
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|
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http://www.links2mobile.com/ListSubs.asp?cid=24&hd=Blue
Tooth&ban=4 |
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http://www.palowireless.com/infotooth/tutorial.asp (a tutorial) |