【正文】 rovides segmentation and reassembly of onair packets. In Basic mode, L2CAP provides packets with a payload configurable up to 64kB, with 672 bytes as the default MTU, and 48 bytes as the minimum mandatory supported MTU. In Retransmission amp。 2/3 FEC is used in ACL link. In unnumbered ARQ, the data send in a time slot must receive a confirmation of receipt in the next time slot. Only when the data is checked to be without mistake after header error detection and CRC at receiver will the confirmation sent to sender, or an error message will be sent back. RANGE Range is application specific and although a minimum range is mandated by the Core Specification, there is not a limit and manufacturers can tune their implementation to support the use case they are enabling. Range may vary depending on class of radio used in an implementation: ? Class 3 radios – have a range of up to 1 meter or 3 feet ? Class 2 radios – most monly found in mobile devices , have a range of 10 meters or 33 feet ? Class 1 radios – used primarily in industrial use cases , have a range of 100 meters or 300 feet POWER In order to make a Bluetooth equipment can also be in connection even in a very low power state, Bluetooth stipulates three energy saving state: Park state, Hold state and Sniff state. The energy saving efficiency of these states declines one l by one. The most monly used radio is Class 2 and users of power. Bluetooth technology is designed to have very low power consumption. This is reinforced in the specification by allowing radios to be powered down when inactive. The Generic Alternate MAC/PHY in Version HS enables the discovery of remote AMPs for high speed devices and tums on the radio only when needed for data transfer giving a power optimization benefit as well as aiding in the security of the radios. Bluetooth low energy technology, optimized for devices requiring maximum battery life instead of a high data transfer rate, consumers between 1/2 and 1/100 the power of classic Bluetooth technology. SECURITY Mobility and open of Bluetooth system makes safety problems extremely important. Although the frequency modulation technique used by Bluetooth system has already provided a certain security, but Bluetooth system still need safety management to link layer and application layer. In link layer, Bluetooth system provides authentication, encryption and key management, and other functions. Each user has a Personal Identification Number (PIN), which will be translated into 128 bit link key for oneway or bothway certification. Once the authentication finished, link will use encryphon key to encrypt. The link layer security mechanism provides a great deal of certification schemes and a flexible encryption scheme (means allow the consultation of the length of password). This mechanism is very important when the equipments in munication are from different countries, because some countries will specify maximum password length. Bluetooth system will select the smallest maximum allowable password length of all equipments in the pico. Bluetooth system also supports the high level of protocol stack in different applications of special security mechanisms. Bluetooth security mechanism builds trust relationship between devices relying on pins. Once this relationship established, these pins can be stored in the equipment, in order to connection more quickly the next time. Application The Bluetooth application can be divided into 4 main aspects: Home, Work, En route and Entertainment. Home Modern family home is so different with pervious. With the seamless improvement of modern technology, more and more people start home office, living more freely and efficiently. Moreover, they also extend the technology to other aspects more than family office, such as family life. By using the products of Bluetooth technology, people are able to get rid of the cables around the home office. Mouse, keyboard, printer, laptop, puter, earphone and speakers can be used in a PC environment wireless, which not only l increase the office area of beauty, but also for interior decoration and to provide more creative freedom. In addition, with mobile devices and home PC to be synchronous and share calendar information, uses can access the latest information everywhere, at all times. Bluetooth devices can not only make the home office easier, but also make home entertainment more convenient: You don’t have to put aside the guests, left alone to choose the music. Users can store 30 feet wireless control on a PC or Apple iPod audio files. Bluetooth technology can also be used in the adapter, allowing people share with friends by sending photos to the TV Bluetooth Headset from cameras, mobile phone and laptop. BT GO of ASUS is an perfect example of the Bluetooth technology which has the function of file sharing backup, puter performance realtime adjustment Bluetooth(BT Turbo Remote), Bluetooth mobile puters to share Inter access(BT to Net), listening to music, remote control, synchronization scheduling personal management. Work previously, the office is usually in chaos for various wires tangled. Power cable for the device, connection between the puter and the keyboard, printer, mouse, and cables of PDA, all of them make a disorder work environment. In some cases, this will increase the risk of the office, such as the employee may be tripping over wires or cables around. However, with Bluetooth wireless technology, the office no longer exist messy wires, the whole office is like a machine, like an orderly and efficient operation. PDA can be synchronized with the puter sharing calendars and contact lists, puter peripheral devices can directly municate with employees through a Bluetooth headset when walking in the office answer the phone, all without wires. Not limited to the use of Bluetooth technolog