The so-called Bluetooth technology is actually a short-range radio technology. The use of "Bluetooth" technology can effectively simplify the communication between mobile communication terminal devices such as handheld computers, notebook computers, and mobile phones. Communication can also successfully simplify the communication between the above devices and the Internet, thereby making the data transmission between these modern communication devices and the Internet faster and more efficient, broadening the path for wireless communication. To put it more simply, Bluetooth technology enables some modern mobile communication devices and computer devices that are easily portable to be connected to the Internet without the use of cables, and can access the Internet wirelessly. Its practical application scope can also be expanded to various home appliances and consumer electronics. Products and information appliances such as cars form a huge wireless communication network. "Bluetooth" technology is a short-distance, low-cost wireless connection technology. It is an open solution that can realize wireless transmission of voice and data. Therefore, the current wireless communication "Bluetooth" has just begun to show its buds, but it has already It has attracted close attention from the global communications industry and users.
2. The origin of Bluetooth
Bluetooth is named after a Scandinavian king who unified Denmark and Sweden in the 10th century AD. It breeds quite magical prospects: for mobile phones, there is no need to connect to headphones; for personal computers, the host and the keyboard, monitor and printer can get rid of the messy connections; on a larger scale, Refrigerators, microwave ovens and other household appliances can be connected to computer networks to achieve intelligent operation.
The inventor of Bluetooth technology was Swedish telecommunications giant Ericsson. Because this technology has very promising application prospects, in May 1998, five of the world's top communications/computer companies: Ericsson, Nokia, Toshiba, IBM and Intel jointly established the Bluetooth SIG after consultations. ), with the purpose of accelerating its development, promotion and application. After this wireless communication technology was announced, it quickly gained unanimous support from a large number of companies including Motorola, 3Com, Lucent, Compaq, Siemens, etc. To date, more than 2,000 companies have joined the Bluetooth SIG, including many of the world's most famous companies. Companies in the fields of computers, communications, and consumer electronics, and even manufacturers and manufacturers of automobiles and cameras. The fact that an open technical specification has received such widespread attention and support from the industry shows that products based on this Bluetooth technology will have broad application prospects and a huge potential market. The Bluetooth Alliance Interest Group has now been renamed the Bluetooth Promotion Group.
3. Technical content of Bluetooth
Bluetooth technology products use low-energy radio communication technology to realize voice, data and video transmission, with a maximum transmission rate of 1Mb/s per second. , full-duplex communication is performed in a time-division manner, and the communication distance is about 10 meters. The communication distance can be further increased by configuring a power amplifier.
Bluetooth products use frequency hopping technology to resist signal fading; use fast frequency hopping and short packet technology to effectively reduce co-channel interference and improve communication security; use forward error correction coding technology to reduce the interference of random noise during long-distance communication; use the 2.4GHz ISM (ie Industrial, Scientific, Medical) frequency band to save the trouble of applying for a dedicated license; use FM modulation to make the equipment more Simple and reliable; "Bluetooth" technology products send a synchronous packet at a frequency hopping frequency, and each group occupies one time slot, which can also be increased to 5 time slots; "Bluetooth" technology supports an asynchronous data channel, or 3 concurrent A synchronous voice channel, or a channel that carries both asynchronous data and synchronous voice. Each voice channel of "Bluetooth" supports 64Kbps synchronous voice. The asynchronous channel supports an asymmetric connection with a maximum rate of 721Kbps and a reverse response rate of 57.6Kbps, or a symmetric connection of 432.6Kbps.
The communication between Bluetooth technology products and the Internet enables devices at home and in the office to interconnect without cables, greatly improving office and communication efficiency. Therefore, "Bluetooth" will become the new favorite in the field of wireless communications and will provide great convenience to the majority of users.
4. Bluetooth technical indicators and system parameters
The currently announced Bluetooth technical parameters are shown in Table 1. (2001.5)
Table 1 Bluetooth technical parameters
Working frequency band ISM frequency band, 2.402~2.480GHz
Duplex mode full duplex, TDD time division duplex
The service type supports circuit switching and packet switching services
Data rate 1Mb/s
Asynchronous channel rate asymmetric connection 721/57.6kb/s, symmetric connection 432.6kb/s
Synchronization channel rate 64Kb/s
Power US FCC requires <0dbm (1mW), other countries can be expanded to 100mW
Frequency hopping frequency 79 frequency points/MHz
Frequency hopping rate 1600 times/s
Working mode PARK/HOLD/SNIFF
The data connection method is oriented to the connection business SCO, Connectionless business ACL
Error correction method 1/3FEC, 2/3FEC, ARQ
Authentication uses reactive logic arithmetic
Channel encryption uses 0 bits, 40 bit, 60-bit key
Voice coding method continuously variable slope modulation CVSD
The transmission distance can generally reach 10~10cm, and can reach 100m with increased power
5. Terminology in Bluetooth technology
Piconet is a network composed of devices using Bluetooth technology in a specific way. The establishment of a piconet begins with the connection of two devices (such as a laptop computer and a cell phone) and can consist of up to eight devices. All Bluetooth devices are peers and work in the same way. However, when a piconet is established, there is only one master device and the others are slave devices, and this situation will remain as long as the piconet exists.
A distributed network (Scatternet) is formed by multiple independent, asynchronous piconets.
Master unit means that in a piconet, if the clock and frequency hopping sequence of a certain device are used to synchronize other devices, it is called the master device. Slave unit means that all devices that are not master devices are slave devices.
MAC address (MAC address) is a 3-bit address used to distinguish devices in the piconet. Parked units are devices that only participate in synchronization in the piconet but do not have a MAC address. Sniff and Hold mode refers to the two low-power working modes of slave devices in the piconet.