What is Bluetooth?
First, the origin of the Bluetooth name
The name of Bluetooth comes from Danish King Harald Blatand in the 10 century. In the preparatory stage of the trade association, an expressive name is needed to name this high-tech. Industry organizers, after a night of discussion about the history of Europe and the infinite development of science and technology in the future, some people think that it is most appropriate to name it after King Blatter. King Blatter unified Norway, Sweden and Denmark. Just like this upcoming technology, technology will be defined as allowing coordination between different industrial fields, such as computing, mobile phones and automobile industries. So the name is decided.
In Jelling, Denmark, there is a monument in the church. This monument was erected to commemorate the achievements of King Blatin and his father, the first Danish king "Old Golm". Interestingly, this special stone was lost after a war between harald and his son Sven Fokbeard. No one has seen this stone for nearly 600 years. Sven won (and exiled his father), because this stone engraved with ancient Nordic characters is the glory of harald, so Sven buried it. Until recent years, a farmer became curious about this big mound on his farm and finally found this stone.
This logo was originally designed by Scandinavian companies when the business association announced it. The logo retains the traditional features of its name, including the ancient Nordic letter "H", which looks very similar to the asterisk and "B". You can see both carefully on the trademark.
Second, the introduction of Bluetooth technology.
Bluetooth was originally the name of the king who unified Denmark in the tenth century. Now take the meaning of "unification" to name Bluetooth technology, aiming at unifying the wireless LAN communication standard. Bluetooth technology is a wireless network technology jointly launched by Ericsson and IBM in 1998. Subsequently, the Bluetooth Special Interest Group (SIG) was established to be responsible for the development of this technology and the formulation of technical agreements. At present, more than 65,438+0,800 companies around the world have joined this organization. Recently, Microsoft officially joined and became one of the main members of SIG.
Bluetooth is an open standard for wireless data and voice transmission, which wirelessly connects various communication devices, computers and their terminal devices, various digital data systems and even household appliances. Its transmission distance is 10 cm ~ 10 m, and it can reach 100m if the power is increased or some peripherals are added. It adopts 2.4GHz ISM band, frequency modulation and frequency hopping technology, and uses directional error correction coding, ARQ, TDD and baseband protocols. TDMA is 0.625μs per time slot, baseband coincidence rate is 1mb/s, and bluetooth supports 64kb/s real-time voice transmission and data transmission. The voice coding is CVSD, and the transmission power is 1mW, 2.5mW and 100mW respectively, using the globally unified 48-bit equipment identification code. Because Bluetooth uses wireless interface instead of wired cable connection, it is portable and suitable for many occasions. In addition, the technology has the advantages of low power consumption, little harm to human body, simple application, easy realization and easy popularization.
Bluetooth technology
On July 26th, 1999, SIG released the Bluetooth technical specification 1.0. The architecture of Bluetooth technology is divided into three parts: the bottom hardware module, the middle protocol layer and the high-level application. The underlying hardware includes radio frequency hopping (RF), baseband (BB) and link management (LM). The wireless frequency hopping layer filters and transmits the data bit stream through the 2.4GHz unauthorized ISM band microwave. This layer protocol mainly defines the conditions that Bluetooth transceiver needs to meet in this frequency band. Baseband is responsible for frequency hopping and transmission of Bluetooth data and information frames. Link management is responsible for connecting, establishing and dismantling links, and carrying out security control.
Bluetooth technology combines the characteristics of circuit switching and packet switching, which can carry out asynchronous data communication, support at most three simultaneous voice channels, and can also transmit asynchronous data and synchronous voice simultaneously with one channel. 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. ..
The intermediate protocol layer includes logical link control and adaptation protocol, service discovery protocol, serial port simulation protocol and telephone communication protocol. Logical link control and adaptation protocol has the functions of completing data disassembly, controlling service quality and multiplexing protocol, and is the basis of other protocols. The service discovery protocol layer provides a mechanism for the upper application to discover the available services and their characteristics in the network. The serial port simulation protocol layer has the function of simulating a 9-pin RS232 serial port. The telephone communication protocol layer provides call control instructions for voice and data between Bluetooth devices.
Host Control Interface Layer (HCI) is the interface between hardware and software in Bluetooth protocol, which provides a unified command interface for calling hardware such as baseband, link management, status and control registers. When communicating between Bluetooth devices, the protocol software entities above HCI run on the host, while the functions below HCI are completed by Bluetooth devices, and they interact through the transport layer transparent to both ends.
At the top of the Bluetooth protocol stack are various advanced application frameworks. Among them, dial-up network, earphone, LAN access, file transfer and so on are typical, corresponding to an application mode respectively. Various applications can realize wireless communication through their corresponding application modes. Dial-up network applications can access piconets through analog serial ports, and data devices can also access traditional local area networks. Users can realize the wireless transmission of audio streams in mobile phones and earplugs through the audio layer in the protocol stack. You can transfer files and enjoy information quickly and flexibly without any connection between multiple PCs or laptops, and you can also synchronize multiple devices.
In a word, the whole Bluetooth protocol has a simple structure, uses retransmission mechanism to ensure the reliability of the link, and can realize various hierarchical security mechanisms in baseband, link management and application layer, and eliminates the interference of other wireless devices in the network environment through frequency hopping technology.
Application prospect
Bluetooth technology is widely used in various data and voice devices in LAN, such as PC, dial-up network, notebook computer, printer, fax machine, digital camera, mobile phone and high-quality headphones. Bluetooth wireless communication mode connects the above devices into a piconet, and multiple piconets can also be interconnected to realize communication between various devices anytime and anywhere. The typical application environment of Bluetooth technology includes wireless office environment, automobile industry, information appliances, medical equipment, school education and factory automatic control. At present, the initial products of Bluetooth have come out, and some chip manufacturers have begun to improve the chips with Bluetooth function. At the same time, some powerful software companies either launch their own protocol stack software or cooperate with chip manufacturers to launch specific solutions for Bluetooth technology. However, in order to truly popularize Bluetooth technology, the following problems need to be solved: First, reduce the cost; Secondly, it should be convenient and practical, and bring tangible benefits and benefits to people; Third, we must work safely, stably and reliably; Fourth, authoritative international standards should be issued as soon as possible. Once the above problems are solved, Bluetooth will quickly change people's way of life and work and greatly improve people's quality of life.
What is Bluetooth?
Bluetooth is a technical standard for short-range wireless data communication proposed by Toshiba, Ericsson, IBM, Intel and Nokia in May 1998. It can realize wireless data and sound transmission from single point to multipoint within the radius of 10 meter, and the data transmission bandwidth can reach 1Mbps. The communication medium is electromagnetic wave with frequency between 2.402GHz and 2.480GHz.
Characteristics of Bluetooth communication technology
■ Bluetooth works in the globally open 2.4GHz ISM (i.e. industrial, scientific and medical) frequency band;
The frequency band is divided into several frequency hopping channels by using frequency hopping spread spectrum technology. In a connection, the radio transceiver constantly "hops" from one channel to another according to a certain code sequence;
■ One Bluetooth device can establish connection with seven other Bluetooth devices at the same time;
■ The data transmission rate can reach1mbit/s;
■ Low power consumption and good communication security;
■ It can be connected across obstacles within an effective range without special communication angle and direction requirements;
■ Support voice transmission;
■ Networking is simple and convenient
The Use of Bluetooth Communication Technology
Bluetooth technology is a new technology and has not been widely used. At present, many Bluetooth devices are still in the laboratory testing stage. But what is certain is that in the future, most devices with infrared wireless data communication function can use Bluetooth technology to realize wireless connection. At the same time, the network characteristics and voice transmission technology of Bluetooth technology enable it to realize some specific functions that infrared technology cannot, such as wireless telephone and networking of multiple devices.
Recognition by manufacturers and consumers
Bluetooth technology has been responded by more than 2000 enterprises, so it has great development and production capacity. Bluetooth has a high popularity and consumers are very interested in this technology.
Implantation cost
At present, Bluetooth devices on the market are still relatively rare. Bluetooth adapters with USB interface, Bluetooth PC cards and Bluetooth mobile phones have been marketed with higher prices. It can be seen that the implantation cost of Bluetooth in the early stage of development is still relatively high. However, it is estimated that the implantation cost after mass production can be below $30. In the mature period of Bluetooth technology, the implantation cost should be controlled within 10 USD.
disadvantaged
Bluetooth is a technology that is not yet fully mature. Although the description is attractive, it still needs strict inspection in actual use. The communication speed of Bluetooth is not very high, and it may also affect its development in today's era of data explosion.
At present, the mainstream software and hardware platforms do not provide support for Bluetooth, which makes the application cost of Bluetooth higher and the popularization more difficult.
ISM band is an open band, which may be interfered by microwave ovens, cordless phones, scientific research instruments, industrial or medical equipment.