Historical overview

In the 10th century Denmark there was a Viking king named Harald Blatand. His name is translated in English as Bluetooth. The main achievement of Blatand was unification of many tribes belonging to Norway, Denmark and Sweden (just like mobile devices communicate with each other and share information). As Bluetooth was invented in Sweden hence it is named after the king.

Blatand means dark complexion. Some historians suggest that Blatand had dark hair, which was not common among Vikings; therefore he was given the name. Another interesting view about origin of the name suggests that Harald liked eating Blueberries so much that his teeth got stained with blue color. Though interesting, this version seems more of a bedtime story.

Technical Details of Bluetooth

Bluetooth is a type of PANs (Personal Area Networks). It is also known as IEEE 802.15.1. The technology is used for wireless communication between different devices like mobile phones, PDAs, digital cameras, computers and printers etc. It offers a cheap and short range alternative of WiFi. Ericsson played the lead role in developing specifications for Bluetooth. Later a group named SIG (Special Interest Group) was established in 1999 as a result of joint venture by Sony Ericsson, Nokia, Toshiba, IBM and Intel.

Bluetooth protocol operates at 2.45 GHz in the ISM band. To avoid interference with other devices operating at the same frequency, Bluetooth divides the band into 79, 1MHz wide channels. These channels are changed at the rate of 1600 times a second. This technique ensures minimal interference.

Bluetooth devices are classified as Class 1, 2 and 3, depending on their range and power consumption. Devices belonging to Class 3 consume the least amount of power, about 1 mW, and have a range of about 1 meter. Class 2 devices consume about 2.5 mW power can cover a range of 10 meters. Coverage offered by Class 3 is about 100 meters with a power consumption of 100 mW. The latest version of Bluetooth is 2.0. This version has backward compatibility with version 1 and offers a data rate of 2.1 Mbps.

Bluetooth Communication and Pairing

There are two roles of a Bluetooth device i.e. “slave” or “master”. There can be at most 7 slaves connected to a master device. This configuration is known as a “piconet”. Theoretically master can transmit data to more than one slave simultaneously, but it is not practical. Two or more piconets can merge together to form a scatternet. In this scenario some of the Bluetooth devices have to play a dual role, master in one network and slave in the other. These devices are not yet available and are expected to hit consumer market later this year.

Trusted Bluetooth devices can be paired together. At the time of pairing a pass key required for each device. Once the pass key is authenticated at both nodes, the devices can communicate with each other over an encrypted channel. If name of any Bluetooth device in a pair is changed, pairing will still be valid. The reason is that pairing is performed on the basis of hardware address, which is unique.