Wireless and Bluetooth

Topics: Bluetooth, Wireless, Mobile phone Pages: 7 (1978 words) Published: May 13, 2006
Bluetooth Technology

Bluetooth is a Radio Frequency (RF) specification for short-range, point-to-point and point-to-multi-point voice and data transfer. Bluetooth will enable users to connect to a wide range of computing and telecommunications devices without the need for proprietary cables that often fall short in terms of ease-of-use.

A global specification for wireless connectivity:

Bluetooth, named for Denmark's first Christian king and not a dire dental condition, is the name of a technology specification for small form factor, low-cost, short-range radio links between PCs,handhelds, mobile phones, and other computing and electronic devices. The Bluetooth SIG (Special Interest Group) is an industry group consisting of leaders in the telecommunications and computing industries that are driving development of the technology and bringing it to market. Over 2000 companies have executed the Bluetooth adopter's agreement and are members of the Bluetooth SIG.

Technical Features:

Note: A piconet is a collection of devices connected via Bluetooth technology in an ad hoc fashion. A piconet starts with two connected devices, such as a portable PC and cellular phone, and may grow to eight connected devices. All Bluetooth devices are peer units and have identical implementations. However, when establishing a piconet, one unit will act as a master and the other(s) as slave(s) for the duration of the piconet connection.

Bluetooth technology provides a 10-meter personal bubble that supports simultaneous transmission of both voice and data for multiple devices. Up to 8 data devices can be connected in a piconet, and up to 10 piconets can exist within the 10-meter bubble. Each piconet supports up to 3 simultaneous full duplex voice devices (CVSD).

The gross data rate is 1Mb/s, but the actual data rates are 432Kbps for full duplex transmission, 721/56Kbps for asymmetric transmission, and 384 Kbps for TMS2000 transmission. A Time Division Duplex scheme is used for full-duplex transmission. Bluetooth uses a frequency hopping spread spectrum technique. Spectrum spreading is accomplished by frequency hopping up to 1600 hops per second on 79 channels between 2.402GHz and 2.480 GHz. Bluetooth radio modules avoid interference from other signals by hopping to a new frequency after transmitting or receiving a data packet. The sophisticated mode of transmission adopted in the Bluetooth specification ensures protection from interference and seeks to insure the security of the data.Bluetooth operates in the 2.4 GHz range referred to as the Instrumentation, Scientific, and Medical (ISM) band. This band provides license-free operation in the United States, Europe, Japan, and most industrialized nations worldwide.

Power transmitted by the Bluetooth:

In the Bluetooth specification there are three classes of radios, which are characterized by their output power. Class 1 is specified to have a maximum transmit power of +20 dBm (100 milliwatts). Class 2 has a maximum transit power of +4 dBm (2.5 milliwatts). Class 3 has a maximum transmit power of 0 dBm (1 milliwatt). The Bluetooth specification limits the radio output power exactly to that actually required. For instance, if the receiving radio indicates that it is only a few meters away, the transmitter immediately modifies its signal strength to suit the exact range. This feature dramatically reduces the radio's power consumption as well as its radio interference. Furthermore, the radio chip automatically shifts to a low-power mode as soon as traffic volumes becomes low or stops. The low-power mode is only interrupted by very short signals with the purpose of verifying the established connection.

The radio with Bluetooth wireless technology consumes less than a few percent of the power consumed with a modern mobile phone. The transmission mode is only used as necessary, and always for the shortest possible period of time.

Supported Bluetooth Profiles:

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