Wednesday, April 2, 2008

BLUE TOOTH

Bluetooth is a standard and communications protocol primarily designed for low power consumption, with a short range (power-class-dependent: 1 meter, 10 meters, 100 meters) based on low-cost transceiver microchips in each device.[1]
Bluetooth enables these devices to communicate with each other when they are in range. The devices use a radio communications system, so they do not have to be in line of sight of each other, and can even be in other rooms, as long as the received transmission is powerful enough.
Class
Maximum Permitted PowermW(dBm)
Range(approximate)
Class 1
100 mW (20 dBm)
~100 meters
Class 2
2.5 mW (4 dBm)
~10 meters
Class 3
1 mW (0 dBm)
~1 meter
In most cases the effective range of class 2 devices is extended if they connect to a class 1 transceiver, compared to pure class 2 network. This is accomplished by the higher sensitivity and transmission power of Class 1 devices.
Version
Data Rate
Version 1.2
1 Mbit/s
Version 2.0 + EDR
3 Mbit/s
WiMedia Alliance(proposed)
53 - 480 Mbit/s

[edit] Bluetooth profiles
Main article: Bluetooth profile
In order to use Bluetooth, a device must be compatible with certain Bluetooth profiles. These define the possible applications and uses of the technology.

[edit] List of applications

A typical Bluetooth mobile phone headset
More prevalent applications of Bluetooth include:
Wireless control of and communication between a mobile phone and a hands-free headset. This was one of the earliest applications to become popular.
Wireless networking between PCs in a confined space and where little bandwidth is required.
Wireless communications with PC input and output devices, the most common being the mouse, keyboard and printer.
Transfer of files between devices with OBEX.
Transfer of contact details, calendar appointments, and reminders between devices with OBEX.
Replacement of traditional wired serial communications in test equipment, GPS receivers, medical equipment, bar code scanners, and traffic control devices.
For controls where infrared was traditionally used.
Sending small advertisements from Bluetooth enabled advertising hoardings to other, discoverable, Bluetooth devices.
Two seventh-generation game consoles, Nintendo's Wii[2] and Sony's PlayStation 3 use Bluetooth for their respective wireless controllers.
Dial-up internet access on personal computer or PDA using a data-capable mobile phone as a modem.

[edit] Bluetooth vs. Wi-Fi in networking

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Bluetooth and Wi-Fi have slightly different applications in today's offices, homes, and on the move: setting up networks, printing, or transferring presentations and files from PDAs to computers. Both are versions of unlicensed spread spectrum technology.
Bluetooth differs from Wi-Fi in that the latter provides higher throughput and covers greater distances, but requires more expensive hardware and higher power consumption. They use the same frequency range, but employ different modulation techniques. While Bluetooth is a replacement for a variety of applications, Wi-Fi is a replacement only for local area network access. Bluetooth can be thought of as wireless USB[citation needed], whereas Wi-Fi is wireless Ethernet[citation needed], both operating at much lower bandwidth[citation needed] than cable networking systems. However, this analogy is not entirely accurate since any Bluetooth device can, in theory, host any other Bluetooth device—something that is not universal to USB devices, therefore it would resemble more a wireless FireWire.

[edit] Bluetooth
Bluetooth exists in many products, such as phones, printers, modems and headsets. The technology is useful when transferring information between two or more devices that are near each other in low-bandwidth situations. Bluetooth is commonly used to transfer sound data with phones (i.e. with a Bluetooth headset) or byte data with hand-held computers (transferring files).
Bluetooth simplifies the discovery and setup of services between devices. Bluetooth devices advertise all of the services they provide. This makes using services easier because there is no longer a need to setup network addresses or permissions as in many other networks.

[edit] Wi-Fi
Wi-Fi is more like a traditional Ethernet network, and requires configuration to set up shared resources, transmit files, and to set up audio links (for example, headsets and hands-free devices). It uses the same radio frequencies as Bluetooth, but with higher power resulting in a stronger connection. Wi-Fi is sometimes called "wireless Ethernet." This description is accurate as it also provides an indication of its relative strengths and weaknesses. Wi-Fi requires more setup, but is better suited for operating full-scale networks because it enables a faster connection, better range from the base station, and better security than Bluetooth.

[edit] Computer requirements

A typical Bluetooth USB dongle, shown here next to a metric ruler

An internal notebook Bluetooth card (14×36×4 mm)
A personal computer must have a Bluetooth adapter in order to be able to communicate with other Bluetooth devices (such as mobile phones, mice and keyboards). While some desktop computers and most recent laptops come with a built-in Bluetooth adapter, others will require an external one in the form of a dongle.
Unlike its predecessor, IrDA, which requires a separate adapter for each device, Bluetooth allows multiple devices to communicate with a computer over a single adapter.

[edit] Operating system support
For more details on this topic, see Bluetooth stack.
Apple has supported Bluetooth since Mac OS X v10.2 released in 2002.[3]
For Microsoft platforms, Windows XP Service Pack 2 and later releases have native support for Bluetooth. Previous versions required users to install their Bluetooth adapter's own drivers, which were not directly supported by Microsoft.[4] Microsoft's own Bluetooth dongles (packaged with their Bluetooth computer devices) have no external drivers and thus require at least Windows XP Service Pack 2.
Linux provides two Bluetooth stacks, with the BlueZ [5] stack included with most Linux kernels. It was originally developed by Qualcomm and Affix. BlueZ supports all core Bluetooth protocols and layers. FreeBSD features Bluetooth support since its 5.0 release. NetBSD features Bluetooth support since its 4.0 release. Its Bluetooth stack has been ported to OpenBSD as well.
 
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