subject: Bluetooth - Background, Implementation & Limitations [print this page] Bluetooth - Background, Implementation & Limitations
Background:
Bluetooth is the name of a new technology that is now becoming commercially available. It is an open wireless technology standard for exchanging data over short distances (using short length radio waves) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security. It is named after a Danish Viking and King, Harald Bltand (translated as Bluetooth in English), who lived in the latter part of the 10th century. Harald Bltand united and controlled Denmark and Norway (hence the inspiration on the name: uniting devices through Bluetooth). He got his name from his very dark hair which was unusual for Vikings, Bltand means dark complexion. However a more popular, (but less likely reason), was that Old Harald had an inclination towards eating Blueberries, so much so his teeth became stained with the color, leaving Harald with a rather unique set of molars.
Conceived initially by telecoms vendor Ericsson in 1994 as a wireless alternative to RS-232 data cables, before being adopted by a myriad of other companies, Bluetooth is a standard for a small, cheap radio chip to be plugged into computers, printers, mobile phones, etc. A Bluetooth chip is designed to replace cables by taking the information normally carried by the cable, and transmitting it at a special frequency to a receiver Bluetooth chip, which will then give the information received to the computer, phone whatever. That was the original idea, but the originators of the original idea soon realized that a lot more was possible. If you can transmit information between a computer and a printer, why not transmit data from a mobile phone to a printer, or even a printer to a printer? The projected low cost of a Bluetooth chip, and its low power consumption, means you could literally place one anywhere. With this viewpoint interest in Bluetooth is soaring, lots of ideas are constantly emerging, some practical and feasible e.g. -- Bluetooth chips in freight containers to identify cargo when a lorry drives into a storage depot, or a headset that communicates with a mobile phone in your pocket, or even in the other room, other ideas not so feasible: Refrigerator communicating with your Bluetooth-enabled computer, informing it that food supply is low, and to inform the retailer over the internet.
How it works:
It uses a radio technology called frequency-hopping spread spectrum, which chops up the data being sent and transmits chunks of it on up to 79 bands of 1 MHz width in the range 2402-2480 MHz. This is in the globally unlicensed Industrial, Scientific and Medical (ISM) 2.4 GHz short-range radio frequency band.
In Classic Bluetooth, which is also referred to as basic rate (BR) mode, the modulation is Gaussian frequency-shift keying (GFSK). It can achieve a gross data rate of 1 Mbit/s. In extended data rate (EDR) /4-DQPSK and 8DPSK are used, giving 2, and 3 Mbit/s respectively. Read more...
