Bluetooth Technology

BLUETOOTH

The convergence of computing and communications has led to the development of Bluetooth technology. Taking the short-range wireless data usage to a new level, this technology is predicted to dominate both the home and business markets.

Now no more complicated tangle of cables and wires are required to connect electronic equipment. A revolutionary technology called Bluetooth allows for the replacement of the cumbersome cables used today to connect a laptop to a cellular phone with one universal low-cost, short-range radio link. Printers, PDAs, desktops, fax machines, keyboards, and virtually any other digital device can be a part of the Bluetooth system. Bluetooth is faster than mobile phones, including the upcoming third-generation, or 3G, high-speed wireless data transmission.

The technology

Bluetooth is a universal radio interface in the 2.45GHz ISM frequency band to function on a worldwide basis. The interface consists of hardware using ICs, a radio frequency chip, and a baseband chip. These parts work together to put a radio signal into the air that can communicate to another chipset imbedded in other product. This makes it easier to do everything, from networking different types of computers to transferring data between digital telephones.

Bluetooth can transmit through solid, non-metal objects. Its nominal link range is from 10 cm to 10 m, which can be extended to 100 m by increasing the transmit power. Designed to operate in a noisy radio frequency environment, the Bluetooth radio uses a fast acknowledgement and frequency hopping scheme to make the link robust. Bluetooth radio modules avoid interference from other signals by hopping to a new frequency after transmitting or receiving packet.

Short range and fast hopping limit the impact of domestic and professional microwave ovens. Use of forward error correction (FEC) limits the impact of random noise on long-distance links. The encoding is optimized for an uncoordinated environment.

The Bluetooth baseband protocol is a combination of circuit and packet switching. Slots can be reserved for synchronous packets. Each packet is transmitted in a different hop frequency. A packet nominally covers a single slot, but can be extended to cover up to five slots.

The technology supports both isochronous and asynchronous services; easy integration of TCP/IP for networking. It can support an asynchronous data channel, up to three simultaneous synchronous voice channels, or a channel which simultaneously supports asynchronous data and synchronous voice. Each voice channel supports 64kbps synchronous (voice) link. The asynchronous channel can support an asymmetric link of maximally 721 kbps in either direction, while permitting 57.6 kbps in the return direction, or a 432.6kbps symmetric link.

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How it works

A Bluetooth system comprises a radio unit, a link controller, link manager, and software.

The Bluetooth radio interface is based on a nominal antenna power of 0 dBm . The air interface complies with the FCC rules for the ISM band at power levels up to 0  dBm. Spectrum spreading facilitates optional operation at power levels up to 100 mW worldwide. It is accomplished by frequency hopping in 79 hops displaced by 1 MHz, starting at 2.402 GHz and stopping at 2.480 Hz. The bandwidth is controlled by an internal software switch. The maximum frequency hopping rate is 1,600 hops/sec.

The baseband describes the specifications of the digital signal processing part of the hardware the Bluetooth link controller, which carries out the baseband protocols and other low-level link routines.

A piconet is a group of two to eight devices connected via Bluetooth technology. Before any connections in a piconet are created, all devices are in standby mode. In this mode, an unconnected unit periodically listens for messages every 1.28 seconds. Each time a device wakes up, it listens on a set of 32 hop frequencies defined for that unit. The number of hop frequencies is 32 for most countries, except Japan, Spain, and France.

Any of the devices becomes the master by initiating the connection procedure.

 

Technology developers
Bluetooth technology is being developed through the combined contributions of the members of the Bluetooth Special Interest Group. Intel brings architectural knowledge, advanced silicon technology, manufacturing expertise, and software components to the group. Ericsson contributed the basic radio technology. Nokia contributed the radio technology and mobile handset software. IBM and Toshiba developed a common specification for integrating Bluetooth technology into mobile devices. Microsoft, Lucent technologies, Motorola, and 3Com have signed on as primary Bluetooth promoters. Many smaller companies worldwide have also signed up for royalty-free rights to the emerging standard.
The final word
Bluetooth technology is being developed as an open specification, and will be licensed royalty-free to all companies who sign up to become members of the Bluetooth initiative. This will allow a quick proliferation of the technology through a wide-range of mobile products and devices. Products integrated with Bluetooth radios are expected to hit the market shortly.