Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, personal computers, printers, digital cameras, and video game consoles over a secure, globally unlicensed short-range radio frequency. The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group.
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.
Uses
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.
It has to be noted that 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 higher sensitivity and transmitter power of the Class 1 device. The higher transmitter power of Class 1 device allows higher power to be received by the Class 2 device. Furthermore, higher sensitivity of Class 1 device allows reception of much lower transmitted power of the Class 2 devices. Thus, allowing operation of Class 2 devices at much higher distances.
Bluetooth 1.0 and 1.0B
Versions 1.0 and 1.0B had many problems, and manufacturers had difficulties making their products interoperable. Versions 1.0 and 1.0B also had mandatory Bluetooth hardware device address (BD_ADDR) transmission in the Connecting process, rendering anonymity impossible at a protocol level, which was a major setback for certain services planned to be used in Bluetooth environments.
Bluetooth 1.1
* Ratified as IEEE Standard 802.15.1-2002.
* Many errors found in the 1.0B specifications were fixed.
* Added support for non-encrypted channels.
* Received Signal Strength Indicator (RSSI).
Bluetooth 1.2
This version is backward-compatible with 1.1 and the major enhancements include the following:
* Faster Connection and Discovery
* Adaptive frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence.
* Higher transmission speeds in practice, up to 721 kbit/s, as in 1.1.
* Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets.
* Host Controller Interface (HCI) support for three-wire UART.
* Ratified as IEEE Standard 802.15.1-2005.
Bluetooth 2.0
This version, specified on November 10, 2004, is backward-compatible with 1.1. The main enhancement is the introduction of an Enhanced Data Rate (EDR) of 3.0 Mbit/s. This has the following effects:
* Three times faster transmission speed—up to 10 times in certain cases (up to 2.1 Mbit/s).
* Lower power consumption through a reduced duty cycle.
* Simplification of multi-link scenarios due to more available bandwidth.
The practical data transfer rate is 2.1 megabits per second and the basic signalling rate is about 3 megabits per second.The "Bluetooth 2.0 + EDR" specification given at the Bluetooth Special Interest Group (SIG) includes EDR and there is no specification "Bluetooth 2.0" as used by many vendors. The HTC TyTN pocket PC phone, shows "Bluetooth 2.0 without EDR" on its data sheet.In many cases it is not clear whether a product claiming to support "Bluetooth 2.0" actually supports the EDR higher transfer rate.
Bluetooth 2.1
Bluetooth Core Specification Version 2.1 is fully backward-compatible with 1.1, and was adopted by the Bluetooth SIG on July 26, 2007.This specification includes the following features:
* Extended inquiry response: provides more information during the inquiry procedure to allow better filtering of devices before connection. This information includes the name of the device, a list of services the device supports, as well as other information like the time of day, and pairing information.
* Sniff subrating: reduces the power consumption when devices are in the sniff low-power mode, especially on links with asymmetric data flows. Human interface devices (HID) are expected to benefit the most, with mouse and keyboard devices increasing the battery life by a factor of 3 to 10.
* Encryption Pause Resume: enables an encryption key to be refreshed, enabling much stronger encryption for connections that stay up for longer than 23.3 hours (one Bluetooth day).
* Secure Simple Pairing: radically improves the pairing experience for Bluetooth devices, while increasing the use and strength of security. It is expected that this feature will significantly increase the use of Bluetooth.
* NFC cooperation: automatic creation of secure Bluetooth connections when NFC radio interface is also available. For example, a headset should be paired with a Bluetooth 2.1 phone including NFC just by bringing the two devices close to each other (a few centimeters). Another example is automatic uploading of photos from a mobile phone or camera to a digital picture frame just by bringing the phone or camera close to the frame.
source:en.wikipedia.org
cell phone Bluetooth
