The origin of Bluetooth
Bluetooth was named after a Scandinavian king who unified Denmark and Sweden in the 10th century. It is pregnant with quite magical prospects: for cell phones, and headphones no longer need to connect the wires; in personal computers, the host computer and the keyboard, monitor and printer can be rid of the messy wires between; in a wider range, refrigerators, microwave ovens and other household appliances can be connected to a computer network, to achieve intelligent operation.
The invention of Bluetooth technology is the 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 after consultations, jointly established the Bluetooth *** with the interests of the group (Bluetooth SIG), in order to accelerate its development, promotion and application. After the announcement of this wireless communication technology, it quickly got including Motorola, 3Com, Lucent, Compaq, Siemens and a large number of companies unanimously embraced, so far to join the Bluetooth SIG has reached more than 2,000 companies, including many of the world's most famous computers, communications, and consumer electronics field of the enterprise, and even automobile and camera manufacturers and manufacturers. An open technical specification can get so much attention and support from the industry, which indicates that the products based on this Bluetooth technology will have broad application prospects and huge potential market. The Bluetooth *** Same Interest Group is now known as the Bluetooth Promotion Group.
Three, the technical content of the Bluetooth
Bluetooth technology products is the use of low-energy radio communications technology to achieve voice, data and video transmission, the transmission rate of up to 1Mb / s per second to time division for full-duplex communication, communication distance of about 10 meters, the configuration of power amplifiers can be used to make the communication distance to further increase.
Bluetooth products use frequency-hopping technology to resist signal degradation; the use of fast frequency-hopping and short packet technology can effectively reduce the same frequency interference and improve the security of communications; the use of forward error correction coding technology to reduce the interference of random noise in long-distance communication; the use of 2.4GHz ISM (industrial, scientific, medical) band to save the trouble of applying for a special license FM modulation, making the device more simple and reliable; "Bluetooth" technology products a frequency hopping rate to send a synchronized packet, each group of a packet occupies a time slot, can also be increased to five time slots; "Bluetooth" technology supports an asynchronous Bluetooth" technology supports one asynchronous data channel, or three concurrent synchronous voice channels, or a channel that transmits asynchronous data and synchronous voice at the same time. "Each Bluetooth voice channel supports 64Kbps synchronous voice, and the asynchronous channel supports asymmetric connections with a maximum rate of 721Kbps and an inverse response rate of 57.6Kbps, or symmetric connections with a rate of 432.6Kbps.
Bluetooth technology products and the Internet Internet communication, so that the home and office equipment does not require cables can be realized without interoperability interconnection, greatly improving the office and communication efficiency. Therefore, "Bluetooth" will become the new favorite in the field of wireless communications, will provide great convenience for the majority of users and favored.
Four, Bluetooth technical indicators and system parameters
The current published Bluetooth technical parameters shown in Table 1. (2001.5)
Table 1 Bluetooth Technical Parameters
Operating Frequency Band ISM band, 2.402~2.480GHz
Duplexing Mode Full-duplex, TDD time-division duplexing
Service Types Circuit-switched and Packet-switched Services Supported
Data Rate 1Mb/s
Unsynchronized Channel Rate 721/57.6kb/s for asymmetric connection, 432.6kb/s for symmetric connection
Synchronous channel rate 64Kb/s
Power US FCC requirement <0dbm (1mW), other countries can be extended to 100mW
Frequency hopping frequency number 79 frequencies/MHz
Frequency hopping frequency rate 1600times/s <
Operating modes PARK/HOLD/SNIFF
Data connectivity modes SCO for connection-oriented services, ACL for connectionless services
Error correction modes 1/3 FEC, 2/3 FEC, ARQ
Authentication Reactive logic arithmetic
Channel encryption 0-bit, 40-bit, 60-bit keys
Speech coding method Continuous Variable Slope Modulation CVSD
Transmission distance Generally up to 10~10cm, and up to 100m in case of increased power
V. Nomenclature in Bluetooth technology
PicoNet (Piconet) is a network composed of devices using Bluetooth technology in a specific way. The establishment of a Piconet starts with the connection of two devices (e.g., portable computers and cellular phones) and consists of up to eight devices. All Bluetooth devices are peer-to-peer and work in the same way. However, when a micro-mini network is established, only one device is the master and all others are slaves, and this will remain the case for the duration of a micro-mini network's existence.
A distributed network (Scatternet) is formed by a number of independent, asynchronous micronets.
Master unit (Master unit) refers to a device that is said to be the master if its clock and frequency hopping sequence is used to synchronize other devices in the Scatternet. Slave unit (Slave unit) means that any device that is not the master unit is a slave unit.
MAC address (MAC address) is an address expressed in 3 bits, used to distinguish between devices in the micro-micro network. Dormant devices (Parked units) are devices that participate only in synchronization in a micro-micro network, but do not have a MAC address. Listen and Hold mode (Sniff and Hold mode) refers to the two low-power operating modes of the slave devices in the micro-micro network.