Bluetooth Technology

By Author: johan peter
Total Articles: 45
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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. The Bluetooth baseband protocol is a combination of circuit and packet switching. The technology supports both isochronous and asynchroous services; easy integration of TCP/IP for networking.

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 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. If the address is already known, connection is made by a page message. And if the address is unknown, connection is made by an inquiry message followed by a subsequent page message. In the initial page state, the master unit will send a train of identical page messages on 16 different hop frequencies defined for the device to be paged (slave unit). If there is no response, the master transmits a train of messages on the remaining 16 hop frequencies in the wake-up sequence. The sniff interval is programmable and depends on the application. In the park mode, a device is still synchronised to the piconet but does not participate in the traffic. The Bluetooth baseband technology supports two types of link, synchronous connection oriented (SCO) and asynchronous connectionless (ACL). The SCO link is used primarily for voice, and the ACL for packet data. Different master-slave pairs of the same piconet can use different link types, and the link type may change arbitrarily during a session. Each link type supports up to sixteen different packet types. Four of these are control packets, common to both the SCO and ACL links. Both of these link types use a time division duplex (TDD) scheme for full-duplex transmissions. The SCO link is symmetric and typically supports time-bound voice traffic. SCO packets are transmitted
over reserved intervals. Once the connection is established, both master and slave units may send SCO packets without being polled. One SCO packet type allows both voice and data transmission with only the data portion being retransmitted when corrupted.

Bluetooth devices must be able to recognise each other and load the appropriate software to discover the higher level abilities each device supports. Interoperability at the application level requires identical protocol stacks. Different Bluetooth devices (PCs, handhelds, headsets, cellular telephones) have different compliance requirements. To obtain more functionality, the Bluetooth software framework will reuse existing specifications such as OBEX, vCard/vCalendar, human interface device (HID), and TCP/IP. The Bluetooth specification contemplates interfaces where the radio modules may be integrated into notebook personal computers or attached using PC-card or USB. Bluetooth technology is operating system independent and not tied to any specific operating system. Implementations of the Bluetooth for several commercial operating systems are in development. For notebook computers, the implementation of the Bluetooth in Microsoft Windows 98 and NT 5.0 using WDM and NDIS drivers is being contemplated.

Applications:
Data exchange. Bluetooths ability to penetrate solid objects and its capability for maximum mobility within the piconet allow for many data exchange applications. For example, with Bluetooth a person could synchronise his phone to a PC without taking the phone out of his pocket or purse. The omnidirectional capability of Bluetooth allows synchronisation to start when the phone is brought into the range of the PC. This synchronisation doest require the phone to be in a fixed location. LAN access. Because there are no line-of-sight requirements, Bluetooth is well suited to wirelessly connect a device to a wired network. Also, multipoint capability allows multiple devices to effectively share the media. The primary advantage of Bluetooth is that the user can leave the mobile phone clipped to his belt or in a pocket and walk around for the entire dial-up connection. Voice applications. A native feature of the Bluetooth specification is synchronous voice channels. Bluetooth has the ability to reserve bandwidth for carrying digital voice data. It can support as many as three simultaneous full-duplex voice conversations within a piconet. Security issues. Technology developers Bluetooth technology is being developed through the combined contributions of the members of the
Bluetooth Special Interest Group.

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