The Effective Range of Bluetooth

By David Dunning

Bluetooth, named after the 10th century Danish King Harald Blatand (Bluetooth), is a technology industry specification for short-range wireless connectivity. It's used to create small personal area networks, which can consist of computer devices, telephones, PDAs, printers and digital cameras. Bluetooth was originally invented by the Swedish company Ericsson in 1994.

Range

Bluetooth 1.0 can link up to eight devices within a radius of about 33 feet with a capacity, or bandwidth, of 700Kbps. A later revision of the Bluetooth specification, Bluetooth 2.0, can transmit at up 2.1Mbps within a radius of about 100 feet. Bluetooth 3.0, adopted in 2009, increased bandwidth to 24Mbps, while the Bluetooth 4.0 specification, adopted in 2010, has a theoretical range of up to 200 feet. The Bluetooth specification stipulates a minimum range of 33 feet, but the maximum range is determined only by the output power of the device.

Frequency Band

Bluetooth technology operates in the industrial, scientific and medical frequency band of the radio spectrum between 2.4 and 2.485 gigahertz. This frequency band is available and unlicensed in most countries. It's also the same frequency band used by the Institute of Electrical and Electronics Engineers 802.11 suite of standards -- 802.11b and 802.11g -- otherwise known as Wi-Fi.

WPAN

Bluetooth is actually the commercial name for IEEE standard 802.15, or wireless personal area network, and isn't intended to compete directly with the IEEE 802.11 standards. It's intended to allow the creation of a network of data and/or voice devices, known as a piconet, in a very small area. One device on the piconet is designated the master and all the other devices are slaves. Communication takes place between master and slave and vice versa, but never directly between slaves.

Limitations

The inability of Bluetooth devices to function efficiently in the vicinity of Wi-Fi signals is one of the biggest drawbacks of the technology. The effective range of Bluetooth is reduced by interference by Wi-Fi and the quoted figures assume an environment without Wi-Fi equipment. Indeed, Bluetooth took many years to establish itself in the marketplace and still faces stiff competition from newer standards, such as Ultra Wideband, which offer higher data rates and co-exist quite happily with Wi-Fi. However, provided that no Wi-Fi network interface card or access point is placed within about 6 feet of a Bluetooth piconet and only a small number of piconets are operating in the area, it's possible for Bluetooth and Wi-Fi to co-exist without major problems.