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1、BluetoothFrom Wikipedia, the free encyclopediaBluetoothis awirelesstechnology standard for exchanging data over short distances (using short-wavelength radiotransmissionsin theISM band from 24002480MHz) from fixed and mobile devices, creatingpersonal area networks(PANs) with high levels of security.
2、 Created by telecom vendorEricssonin 1994,it was originally conceived as a wireless alternative toRS-232data cables. It can connect several devices, overcoming problems of synchronization.Bluetooth is managed by theBluetooth Special Interest Group, which has more than 18,000 member companies in the
3、areas of telecommunication, computing, networking, and consumer electronics.Bluetooth was standardized asIEEE 802.15.1, but the standard is no longer maintained. The SIG oversees the development of the specification, manages the qualification program, and protects the trademarks.To be marketed as a
4、Bluetooth device, it must bequalifiedto standards defined by the SIG.A network ofpatentsis required to implement the technology, which is licensed only for that qualifying device.The word Bluetooth is ananglicizedversion of the ScandinavianBltand/Bltann, theepithetof the tenth-century kingHarald I o
5、f Denmarkand parts ofNorway who united dissonant Danish tribes into a single kingdom. The idea of this name was proposed byJim Kardachwho developed a system that would allow mobile phones to communicate with computers (at the time he was readingFrans Gunnar Bengtssons historical novelThe Long Shipsa
6、bout Vikings and king Harald Bluetooth).The implication is that Bluetooth does the same with communications protocols, uniting them into one universal standard.A master Bluetooth device can communicate with a maximum of seven devices in apiconet(an ad-hoc computer network using Bluetooth technology)
7、, though not all devices reach this maximum. The devices can switch roles, by agreement, and the slave can become the master (for example, a headset initiating a connection to a phone will necessarily begin as master, as initiator of the connection; but may subsequently prefer to be slave).The Bluet
8、ooth Core Specification provides for the connection of two or more piconets to form ascatternet, in which certain devices simultaneously play the master role in one piconet and the slave role in another.At any given time, data can be transferred between the master and one other device (except for th
9、e little-used broadcast mode). The master chooses which slave device to address; typically, it switches rapidly from one device to another in around-robinfashion. Since it is the master that chooses which slave to address, whereas a slave is (in theory) supposed to listen in each receive slot, being
10、 a master is a lighter burden than being a slave. Being a master of seven slaves is possible; being a slave of more than one master is difficult.The specification is vague as to required behavior in scatternets.Many USB Bluetoothadaptersor dongles are available, some of which also include anIrDAadap
11、ter. Older (pre-2003) Bluetooth dongles, however, have limited capabilities, offering only the Bluetooth Enumerator and a less-powerful Bluetooth Radio incarnation.Such devices can link computers with Bluetooth with a distance of 100 meters, but they do not offer as many services as modern adapters
12、do.To use Bluetooth wireless technology, a device has to be able to interpret certain Bluetooth profiles, which are definitions of possible applications and specify general behaviors that Bluetooth enabled devices use to communicate with other Bluetooth devices. These profiles include settings to pa
13、rametrize and to control the communication from start. Adherence to profiles saves the time for transmitting the parameters anew before the bi-directional link becomes effective. There are a wide range of Bluetooth profiles that describe many different types of applications or use cases for devices.
14、Bluetooth exists in many products, such as telephones, tablets, media players,Lego Mindstorms NXT,PlayStation 3,PS Vita, the NintendoWii, and some high definitionheadsets,modems, and watches.The technology is useful when transferring information between two or more devices that are near each other i
15、n low-bandwidth situations. Bluetooth is commonly used to transfer sound data with telephones (i.e., with a Bluetooth headset) or byte data with hand-held computers (transferring files).Bluetooth protocols simplify the discovery and setup of services between devices. Bluetooth devices can advertise
16、all of the services they provide.This makes using services easier because more of the security, network address and permission configuration can be automated than with many other network types.A personal computer that does not have embedded Bluetooth can be used with a Bluetooth adapter that will enable the PC to communicate with other Bluetooth devices (such as mobile phones,mouseandkeyboards). While some
