Introduction to Bluetooth technology
Bluetooth is a wireless personal area network technology (WPAN for short), a low-range wireless network technology used for linking devices to one another without a hard-wired connection. Unlike the IrDa technology (which uses an infrared connection), Bluetooth devices do not need a direct line of sight to communicate, which makes them more flexible in use and allows room-to-room communication in small spaces.
The aim of Bluetooth is to transmit voice or data between devices with low-cost radio circuits, over a range of about ten to just under a hundred metres, using very little power.
Bluetooth technology is designed mainly for linking devices (such as printers, mobile phones, home appliances, wireless headsets, mouses, keyboards, etc.), computers, or PDAs to one another, without using a wired connection. Bluetooth is also becoming more and more commonly used in mobile phones, allowing them to communicate with computers or PDAs, and is especially widespread in hands-free accessories like Bluetooth headsets. Bluetooth headsets act as advanced earpieces which include remote control features.
Bluetooth technology was originally developed by Ericsson in 1994. In February 1998, a group called the Bluetooth Special Interest Group (Bluetooth SIG), with over 2000 companies including Agere, Ericsson, IBM, Intel, Microsoft, Motorola, Nokia and Toshiba, was formed in order to produce the specifications for Bluetooth 1.0, which were published in July 1999.
The name "Bluetooth" comes from the Danish king Harald I (910-986), nicknamed Harald I Bl├ątand ("the blue-toothed"), who is credited with uniting Sweden and Norway, as well as introducing Christianity to Scandinavia.
Bluetooth can reach transfer speeds of about 1 Mbps, which corresponds to 1600 hops per second in full-duplex mode, with a range of roughly ten metres when using a class II transmitter, and a little under a hundred metres using a class I transmitter.
The Bluetooth standard actually defines 3 classes of transmitters, whose range varies as a function of their radiating power:
||Power (signal loss)
|I ||100 mW (20 dBm)
|II ||2.5 mW (4 dBm)
|III ||1 mW (0 dBm)
Unlike IrDA, the primary competing technology, which uses light radiation to send data, Bluetooth uses radio waves (in the 2.4 GHz frequency band) to communicate, and as a result, Bluetooth devices don't have to be in visual communication to exchange data. This means that two devices can communicate even if they are on either side of a wall, and best of all, Bluetooth devices can detect one another without the user's involvement, so long as they are within each other's range.
The Bluetooth standard is broken down into multiple norms:
- IEEE 802.15.1 defines Bluetooth 1.x, which can reach speeds of 1 Mbps;
- IEEE 802.15.2 recommends practices for using the 2.4 GHz frequency band (the frequency also used by WiFi). However, this standard has not yet been approved;
- IEEE 802.15.3 is a standard currently being developed, which would offer broadband speed (20 Mbps) with Bluetooth;
- IEEE 802.15.4 is a standard currently being developed for use with low-speed Bluetooth applications.