【正文】 work where devices integrate and synchronize their frequencyhopping to keep in touch with each other.With the use of a specific evice addresses in Bluetooth capable devices, it is possible to create multiple picos or personal area works within the same area. This means that since a cordless phone base unit and handset municate with each other using a specific address range range, they will not interfere with Bluetoothcapable devices in the same room. The Bluetooth work ignores any transmission from devices outside of its assigned address range. The addresses of these devices and the program that instructs these devices to listen and respond using a specific address range are programmed by the manufacturer to lessen interference and increase the efficiency in data transmission of Bluetooth devices.Since each device in a pico is synchronized in frequencyhopping, the risk of two picos interfering with each other by being in the same frequency at the same time is very minimal. Moreover, since the picos change frequencies 1600 times every second, a collision between two picos will last only a fraction of a second. Corrective software in these Bluetooth devices will also correct any interferenceconsequent errors, thereby increasing the efficiency of work munication.Bluetooth Power ClassesBluetooth provides three types of power classes, although class 3 devices are not in general availability.Type Power Level Operating RangeClass 3 Devices 100mW Up to 100 metersClass 2 Devices 10mW Up to 10 metersClass 1 Devices 1mW metersBluetooth SecurityBluetooth security is based upon device authentication, not user authentication. Each device is either trusted or untrusted. Bluetooth devices are identified by unique 48bit identifiers, much like Ether MAC addresses.Bluetooth Security ModesBluetooth features three security modes.Mode Name Description1 Nonsecure No security is implemented2Servicelevel securityAccess is granted to individual services3 Linklevel securitySecurity is enforced at a mon level for all applications at the beginning of the connectionBluetooth Security LevelsBluetooth features three possible security levels.Mode Description3 No authentication or authorization is required2 Authentication is required。 authorization is not required1 Authorization and authentication are requiredBluetooth Security WeaknessesBluetooth weakness include:The Bluetooth challengeresponse key generation is weak. This scheme may use a static number or a number for a period of time, which can reduce the effectiveness of the authentication.Bluetooth39。s challengeresponse is simplistic. A oneway challenge for authentication is susceptible to maninthemiddle attacks. Mutual authentication via user verification should be used.The keys used by Bluetooth are weak. The initialization key needs to be more robust and the unit key is a publicgenerated key that can be reused. A set of keys should be used instead.The master key is shared between Bluetooth connections. This key is a broadcast and should have a better scheme than what is used.The encryption algorithm scheme utilized in Bluetooth uses a single algorithm and allows repeat authentication. A more robust method that limits authentication and increases the encryption should be used.Authentication encryption should be increased.Bluetooth implementations normally imit the PIN number range. A PIN number is usually only four digits and the scalability for large environments is difficult.Additional Sources of Information on Bluetooth SecurityFor more information on Bluetooth security, read Bluetooth Security at BlueTomorrow, Bluetooth Protocol and Security Architecture Review by Korak Dasgupta, or Overview of Ad Hoc and Bluetooth Networks.Bluetooth versus Infrared1The major advantages of the Bluetooth technology over other munication technologies are its being cheap, wireless and automatic.1A data transmission technology parable to Bluetooth is IrDA or infrared munication much like what your remote control devices use to control the TV, stereo, air conditioner etc. The big drawback of this type of technology, however, is the requirement that the two devices establishing a connection must be within sight of one another for transmission to take place. You can only control infrared devices by pointing the remote directly at the device or lining up the infrared ports of both IR capable devices.1Bluetooth devices can municate with one another even when they are not in the same room. In fact, even in its low power setting, a Bluetooth device can municate with another device that is within its tenmeter radius regardless of walls, windows, or other physical obstructions.1Infrared technology limits the device munications to one on one. Thus, an IR remote control can control only one electronic device at a time. On the other hand, Bluetooth devices are capable of municating with multiple devices at any given time.1Infrared devices, however, are less susceptible to interference than Bluetooth devices. This means that you can be sure that the data will be sent to the intended recipient without any distortion or inaccuracies. Improvements in the Bluetooth technology however minimizes this problem by enabling the Bluetooth devices to hop frequencies and municate within a specific frequency range. Therefore, although there is still risk of interference, the chances of it happening are very minimal. If such occurs, it will happen only in a very brief period of time and a software will be available to correct any consequent distortion.From：藍　牙藍牙技術(shù)又叫哈拉藍牙，是以1900年的丹麥國王的名字命名的，寓意鞏固丹麥和挪威的統(tǒng)一。對于這項技術(shù)名稱的選擇，是本地區(qū)的中環(huán)公司的電信行業(yè)的影響力為表現(xiàn)。藍牙是不依賴于用戶控制或大量電能的一種網(wǎng)絡(luò)技術(shù)。藍牙通過保持以極低的發(fā)射功率設(shè)置（1mv），是手機電池供電設(shè)備的理想選擇。此外，藍牙不依賴于用戶，因為它可以自動檢測并與其他藍牙設(shè)備無需任何用戶輸入。藍牙技術(shù)依賴兩個方面，無線射頻技術(shù)和協(xié)議軟件，使其能夠?qū)?shù)據(jù)