Bluetooth technology is an open global wireless data and voice communication standard. Based on low-cost short-distance wireless connection, it establishes a special connection for the communication environment of fixed and mobile devices. This program is written in a 9×9 mm microchip.
For example, if Bluetooth technology is introduced into mobile phones and laptops, the annoying connection line between mobile phones and laptops can be removed and communication can be established wirelessly. Printers, PDA's, desktop computers, fax machines, keyboards, joysticks and all other digital devices can be part of the Bluetooth system. In addition, Bluetooth wireless technology also provides a universal interface for existing digital networks and peripheral devices, so as to form a group of personal dedicated connection devices far away from fixed networks.
Bluetooth works in the global 2.4GHz ISM (industrial, scientific and medical) frequency band. The data rate of Bluetooth is 1 MB/s ... Time division duplex transmission scheme is used to realize full duplex transmission.
ISM band is open to all radio systems, so using one of the bands will encounter unpredictable interference sources. For example, some household appliances, cordless phones, garage door openers, microwave ovens, etc. , may be interference. For this reason, Bluetooth has specially designed a fast acknowledgement and frequency hopping scheme to ensure the stability of the link. Frequency hopping technology divides the frequency band into several frequency hopping channels. In a connection, the radio transceiver constantly "hops" from one channel to another according to a certain code sequence (that is, a certain law, technically called "pseudo-random code", that is, "false" random code). Only the transmitter and receiver communicate according to this law, and other interferences cannot interfere according to the same law. The instantaneous bandwidth of frequency hopping is very narrow, but this narrow bandwidth is expanded to a hundred times of broadband by spread spectrum technology, which makes the possible impact of interference very small.
Compared with other systems operating in the same frequency band, Bluetooth has faster frequency hopping and shorter data packets, which makes Bluetooth more stable than other systems. The use of FEC (Forward Error Correction) suppresses the random noise of long-distance links. Frequency hopping transceiver using binary frequency modulation (FM) technology is used to suppress interference and prevent fading.
Bluetooth baseband protocol is a combination of circuit switching and packet switching. Synchronous data packets can be transmitted in reserved time slots, and each data packet is sent at a different frequency. A data packet nominally occupies one time slot, but in fact it can be extended to occupy five time slots. Bluetooth can support asynchronous data channels, up to three simultaneous voice channels, and can also use one channel to transmit asynchronous data and synchronous voice simultaneously. Each voice channel supports 64kb/s synchronous voice link. Asynchronous channels can support asymmetric connections with a maximum rate of 72 1kb/s at one end and 57.6kb/s at the other end, or symmetric connections with a rate of 43.2 kb/s. ..
Bluetooth system consists of the following functional units:
Wireless unit
Link control unit
Link management
Software function definition
Bluetooth technology supports point-to-point and point-to-multipoint connections. Several piconets can be connected together, and each piconet can be identified by frequency hopping sequence. All users of the same piconet are synchronized with this frequency hopping sequence. Its topological structure can be described as a "multi-piconet" structure. In the "multi-piconet" structure, in the case of 10 full-load independent piconet, the full-duplex data rate exceeds 6 MB/s.
The voice channel adopts continuous variable slope incremental modulation (CVSD) voice coding scheme, and never retransmits voice packets. CVSD coding is good at dealing with lost and damaged speech samples. Even if the bit error rate reaches 4%, the voice encoded by CVSD can still be heard.
The Bluetooth air interface is based on an antenna level of 0dBm. The air interface follows the ISM band standard of FCC (Federal Communications Commission), and the level is 0dBm. If the global level is above 100mW, you can use the spread spectrum function to add some supplementary services. The spectrum spreading function is realized by 79 frequency hopping points, starting frequency is 2.402, ending frequency is 2.480, and the interval is 1MHz. Due to some local regulations, Japan, France and Spain all reduced their bandwidth. The maximum frequency hopping rate is 1660 hops/second. The ideal connection range is 10 cm- 10 m, but the distance can be extended to 100 m by improving the transmission level.
Bluetooth devices need to support some basic interoperability requirements. For some devices, this requirement involves wireless module, air protocol, application layer protocol and object exchange format. But for other devices, such as headphones, this requirement is much simpler. Bluetooth devices must be able to recognize each other and load corresponding software to support a higher level of device performance.
Bluetooth has different requirements for different levels of equipment (such as PC, handset, mobile phone, earphone, etc.). For example, you can't expect a Bluetooth headset to provide an address book. However, mobile phones, mobile phones and laptops need more functional features.
Bluetooth profile interface can be directly integrated into notebook computer, or connected through PC card or USB interface.
The usage modes of notebook computers include:
Connect to a remote network through a Bluetooth phone.
Use Bluetooth mobile phone as speaker
Business card transactions among Bluetooth laptops, mobile phones and mobile phones
Time Synchronization among Bluetooth Laptop, Mobile Phone and Mobile Phone
Bluetooth is an independent operating system and does not depend on any operating system. Bluetooth profiles of several different commercial operating systems are being improved.
Bluetooth mode interface can be directly integrated into the cellular phone or connected through other devices. The usage modes of the mobile phone include (optional):
Realize the hands-free function of mobile phone through Bluetooth wireless headset.
Wireless connection with laptop and mobile phone
Trade with business cards of other Bluetooth phones, laptops and mobile phones.
Automatically synchronize the address book with a trusted Bluetooth laptop or mobile phone.
Usage patterns of other Bluetooth devices include:
earphone
Mobile phones and other portable devices
Man-machine interface equipment
Data and voice access points
1. What is Bluetooth technology?
The so-called Bluetooth technology is actually a short-range radio technology, which can effectively simplify PDA, notebook computer and mobile phone.
The communication between mobile communication terminal devices such as telephones and mobile phones can also successfully simplify the communication between these devices and the Internet, thus making these modern communications
Data transmission between devices and the Internet becomes faster and more efficient, which broadens the way of wireless communication. To put it bluntly, Bluetooth technology makes some modern people easy to carry.
Mobile communication equipment and computer equipment can be networked without cables, and can be wirelessly connected to the Internet. Its practical application can also be extended to various household appliances.
Consumer electronic products such as automobiles and information appliances constitute a huge wireless communication network. "Bluetooth" technology belongs to a short-distance, low-cost wireless connection technology, which is a kind of
It can realize the open scheme of voice and data wireless transmission. Therefore, the "Bluetooth" of wireless communication has just sprouted, but it has aroused the global communication industry and
Users pay close attention to it.
Second, the origin of Bluetooth
Bluetooth was named after the Scandinavian king who unified Denmark and Sweden in the 10 century. It has given birth to a rather magical prospect: for mobile phones, it is no longer wearing headphones.
Need to connect; In personal computer, the host can get rid of the messy connection with keyboard, monitor and printer; On a larger scale, refrigerators, microwave ovens and other household appliances
It can be connected with computer network to realize intelligent operation.
The inventor of Bluetooth technology is Swedish telecom giant Ericsson. Because this technology has a very gratifying application prospect, in May 1998, the top five communication/computer companies in the world:
Ericsson, Nokia, Toshiba, IBM and Intel jointly established Bluetooth SIG through negotiation, aiming at accelerating its development, promotion and application.
After the publication of this wireless communication technology, it quickly won the unanimous support of a large number of companies including Motorola, 3Com, Lucent, Compaq and Siemens. , has joined Bluetooth SIG so far.
There are more than 2,000 companies here, including many of the most famous enterprises in the fields of computer, communication and consumer electronics, and even manufacturers and students of cars and cameras.
Manufacturer. An open technical specification can get such extensive attention and support from the industry, which shows that products based on this Bluetooth technology will have broad application prospects and great potential.
Potential market. Bluetooth * * * The same interest group is now renamed Bluetooth Promotion Group.
Third, the technical content of Bluetooth.
Bluetooth technology products use low-energy radio communication technology to realize voice, data and video transmission, with the highest transmission rate of 1Mb/s and full duplex in time division.
Communication, the communication distance is about 10 meter, and the configuration of power amplifier can further increase the communication distance. Bluetooth products adopt frequency hopping technology, which can resist signal fading; choose
Adopting fast frequency hopping and short packet technology can effectively reduce co-frequency interference and improve communication security; Forward error correction coding technology is adopted to reduce the random noise in long-distance communication.
Interference; Adopt 2.4GHz ISM (industrial, scientific and medical) frequency band, saving the trouble of applying for special license; Adopt FM modulation mode to make the equipment more simple and reliable; "
Bluetooth technology products send a synchronization packet with a frequency hopping, and each group occupies one time slot, which can also be increased to five time slots; Bluetooth technology supports asynchronous data communication.
Channel, or three synchronous voice channels, or channels that simultaneously transmit asynchronous data and synchronous voice. Each voice channel of Bluetooth supports synchronous voice at 64Kbps.
Asynchronous channels support asymmetric connections with a maximum rate of 72 1Kbps and a reverse response rate of 57.6Kbps, or symmetric connections with a rate of 432.6Kbps.
The communication between Bluetooth technology products and the Internet enables home and office equipment to be interconnected without cables, which greatly improves the efficiency of office and communication.
Therefore, "Bluetooth" will become the new favorite in the field of wireless communication, which will provide great convenience for users and be favored.