Bluetooth

Bluetooth

An industrial standard for low power, short range, radio communication between devices. Bluetooth is used to allow mobile phones, computers, PDAs and the like to communicate across short distances, i.e. providing a personal area network (PAN).

Bluetooth operates in the 2.4 GHz band (2.4GHz to 2.4835GHz in US and Europe or 2.472GHz to 2.497GHz in Japan). Cordless phones and Wi-Fi devices also operate in this band, so there is potential for interference. Bluetooth uses Adaptive Frequency Hopping (AFH) to reduce interference by hopping through the available frequencies to minimize the effects of interference.

The Bluetooth specification allows for thee classes of device, each with difference power requirements and maximum ranges. These classes are:

Class	Power		Approximate Range
Class 1	100mW	20 dBm	100 meters
Class 2	2.5mW	4dBm	10 meters
Class 3	1 mW	0dBm	1 meter

Bluetooth allows data to be transmitted at up to 1mbps, or up to 3mbps with EDR (Enhanced Data Rate - available from November 2004). Each Bluetooth device is uniquely identified by a unique 48-bit identifier (similar in concept to a MAC address, but not to be confused as the same).

For more information see:

• www.bluetooth.com - The official Bluetooth Wireless information site.
• www.tech-faq.com/bluetooth.shtml - Details on Bluetooth including a good overview of the security and weaknesses inherent in bluetooth.
• www.wi-fiplanet.com/tutorials/article.php/1379911 - reasons for Bluetooth interference with WiFi and steps to minimize such interference.
• www.geekzone.co.nz/content.asp?contentid=108 - What is Bluetooth?