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:  

 

http://www.Blue Tooth.com/

 

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 Denmark and Norway and is said to have brought Christianity to Scandinavia.  The name Blatand loosely translates to “Blue Tooth”.  The king was said to have a great affinity for blueberries according to folklore.  This may explain his name.

            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:

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:

 

http://www.Blue Tooth.com/

 

http://www.compinfo-center.com/tel/Blue Tooth.htm

http://www.mobileBlue Tooth.com/whatis.asp

http://www.links2mobile.com/ListSubs.asp?cid=24&hd=Blue Tooth&ban=4

http://www.palowireless.com/bluetooth/

http://www.palowireless.com/infotooth/tutorial.asp   (a tutorial)

http://www.overture.com/d/search/p/befree/?Promo=befree00390616184244706017&Keywords=blue+tooth&Go=Go&Promo=befree

http://www.compinfo-center.com/tel/Blue Tooth.htm#related

www.apple.com/Blue Tooth/