12 April 2007

Bluetooth

Bluetooth is a form of wireless interface between devices supposedly belonging to a single user. More formally, it is the specification for connecting cell phones, computers, and personal digital assistants (PDAs) using short range radio transmissions. It is different from Wi-Fi in so far as Wi-Fi connects many computers at a single address (to the Internet), Bluetooth is used to connect a small number of electronic devices to each other.

("At a single address" is a deliberately vague term. "Address," here, refers to an office, cafeteria, residence, of any physical size. Some Wi-Fi hot spots are immense, such as the City of Philadelpha.)


General Outline
Evidently, many hardcore aficionados of intimate computing think of their collection of gadgets as so many warring tribes. The same person may own a cell phone, a laptop, a desktop, a Blackberry, a digital camera, and a printer. The media adapter was developed as a specialized Wi-Fi (802.11)-based solution, but of course media adapters/media extenders are confined to interface between television or stereo equipment (on the one hand) and computers/PDA's. A common headache for owners of multiple PDA's and/or computers is integrating different calendars, uploading info to databases from different points of input, and so on.


The Special Interest Group for the standard decided to name it after Harald "Bluetooth" Gormson, a king of Denmark who had united many rival Viking states. No doubt the mistranslation of "Bl├ątand" as "Bluetooth" was the arresting detail that made it the winning nickname.1 Electronic components need to have the microchip transmitter/receiver embedded in them. Bluetooth wireless connections are limited to a range of 10 meters, and the 2.45 GHz frequency (just slightly higher than most Wi-Fi). The volume of data transmission is much lower than Wi-Fi: 2 Mbps, sufficient for multiple-channel audio transmissions.


The most common application of Bluetooth is for hands-free cell phone headsets, but Bluetooth was intended to bypass all data cables, particularly USB cables. Bluetooth "networks" require no setup: the devices merely have to be in physical range and on the same channel, and there can be a maximum of eight devices involved. One device is a master, and the others are all "invited" to join the network as "slaves."

Modulation
While Wi-Fi architecture is dominated by multiplexing concerns, Bluetooth is not. That's because in a Bluetooth network, there is only one master communicating with individual slaves, one at a time. The modulation involves frequnecy jumping at 1,600 cchannel shifts per second, sharply reducing any risk of interference (including interference with Wi-Fi networks).



Notes
1 "Bluetooth Overview," SearchMobileComputing.com (15 Feb 2006).
In 1994 Ericsson Mobile Communications initiated a study to investigate the feasibility of a low-power low-cost radio interface between mobile phones and their accessories. In Feb 1998, five companies Ericsson, Nokia, IBM, Toshiba and Intel formed a Special Interest Group (SIG). The group contained the necessary business sector members - two market leaders in mobile telephony, two market leaders in laptop computing and a market leader in digital signal processing technology.
Korak Dasgupta, "Bluetooth Protocol and Security Architecture Review," part 4



Additional Reading & Sources

"Bluetooth Overview," SearchMobileComputing.com (15 Feb 2006)

"IEEE 802.15 and Bluetooth: WPAN Communications" www.NetworkDictionary.com (2008)

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