Bluetooth technology detailed
The world of boiling figures and information is constantly injective, while Bluetooth is open to the door of voice, text and image, and the new field of communication of mobile communications is blocked. Even if Bluetooth still has many details, it is urgent to solve, but when Bluetooth technology is relatively perfect, the new world of wireless communications is also coming! This article provides you with information may just be part of Bluetooth, will be more exciting in the future! Not?
Name Origin:
Bluetooth is the name of a Danish Emperor of a thousand years ago. He has a unified contribution to the four-point five-cracked Sweden, Finland, and Denmark. The Ericsson, Sweden, for this city, will become a global wireless technology, may have a general meaning of the world (why not call Genghis Khan?). Its original meaning may not be able to know, but according to the translation of English is "Bluetooth" has been accepted by everyone, it is a huge little teeth, or it will be swallowed on the blue sky, which takes the other wireless sky, we have to wait and see.
Introduction:
Bluetooth is a new wireless communication agreement, I heard that Bluetooth will gradually replace the IRDA infrared technology in the second half of this year, and will replace existing serial ports (which is Serial Port), (but Bluetooth really replaces IRDA? Suspetent! Click here to download Irda's discussion - English). Bluetooth is an open standard for wireless data and voice transmission, which is mainly a short-range wireless connection, generally ten centimeters to
Ten meters
The range is currently an increase in power or plus certain peripherals to reach a distance of one hundred meters, such as an Optional AMPLIFIER. Bluetooth adopts 2.402-2.480GHz high frequency wireless frequency, the center frequency is 2.45GHz, which is higher than the existing GSM1800, and the effective Bluetooth data rate is 721kbps when the transmitter frequency is 1MHz. Perhaps relative WAP, it standardizes more specific hardware and frequency applications. WAP is also a wireless communication agreement. From understanding meaning, it may be a wireless access protocol or directly call a wireless Internet protocol, standardize the browsing format and communication protocols of the web page, such as TCP / IP. "The Bluetooth protocol enables information exchange between cellular phones, handheld, laptops, related peripherals, and home HUBs including home RF. Bluetooth broadband protocol combines circuit switches and packet switches, applicable to voice and data transmission Each channel supports 64KB synchronization (voice) links per second. The asynchronous channel supports either direction to 721KB of asymmetric links per second and the backhaul direction of 57.6KB per second. So, it can quickly deal with the cellular system Very large data ratio (this paragraph comes from here) "The left picture is a better sections of Bluetooth, the left end of the figure is antenna and filter, and the right end is an electronic component of the single-chip implanted Bluetooth (using standard) BGA package), the actual size is small than the buttons in the sustain. Therefore, it is easy to apply in electronic products.
member:
In Ericsson, the Special Interest Group made with Intel, IBM, NOKIA, and TOSHIBA created Bluetooth technology, and now 1667 companies have added, including Motorola, Simens, Alcatel, CANON, ACER and other computers and communications. manufacturer. And the number is still growing. Perhaps most of the products will be implanted into Bluetooth to make wireless connections.
Application: 1) The phone is connected to the computer:
At present, most of the IRDA infrared or RS232 serial lines are connected, and Bluetooth is replaced, it is not only convenient and the speed of data is transferred is not worried. (Some situations, the speed of Irda is faster). Perhaps the connectors under the future mobile phone will also disappear or become more simplified - don't forget to charge it (Hey, the battery development, what is the day)!
2) Save mobile phone costs:
Built-in Bluetooth chip's mobile phone, can be used as a cordless phone at home, do not need two-way charge, do not have to have many silver every minute. Of course, you will automatically switch to the wireless network base station after you leave the house!
3) Data sharing, the office is simpler:
Whether mobile phones, computers, PDAs, printers, or digital cameras, MP3 players, D player ... all can use Bluetooth to intermittent, text, images, files ... Spider mesh conference room will not exist , Whiteboard record instruments, projectors, etc., can use Bluetooth to simplify operations.
4) Internet access:
Notebook computers or mobile phones in built-in Bluetooth chips, not only using PSTN (Published Switch Telephone Network, ISDN (Integrated Services Digital Network), LAN (Local Area Net LAN), XDSL (X) User lines such as ADSL, ie asymmetric digital user lines), and cellular mobile networks can be high-speed connections.
5) Wireless hands-free:
The laptop has a microphone and a speaker (speaker), using Bluetooth to connect the future mobile phone (perhaps broadband network), multi-person video conference is not a dream. And hands-free phones are no longer a car.
6) Synchronous information
Back to the office or home, through Bluetooth and the appropriate procedure, you can synchronize your Notebook, mobile phone or PDA, etc. Of course, Email can also receive and walk into the computer, and your email can also be completed on the plane, and automatically issued by it after pressing machine, ...
7) Image transfer
It is a bit similar to the NOKIA9110 video transmission method, but it will be more simple, with a digital camera with Bluetooth function, after you shoot, you can send it directly to any corner of the world, the reporter seems to have this feature! - Faile more trouble, and the format used by fax is TIF file is not very good, and slowly! Of course, you can also send images directly into the printer, ready to shoot.
8) Wireless
Everything is in the wireless, Bluetooth can be applied to include keyboard, mouse, home network, high speed wireless internal network, electronic business card ... maybe lack is just our more imagination ...
Baixi has an omission
Bluetooth may still exist in many details, such as:
Although it is better than the multi-directional transmission of IRDA, it is also necessary to prevent misreading and intercepting information, each device has a different frequency.
Bluetooth provides licenses and security features in its Baseband protocol. Authorization utilizes a key (password or pin), each device can be authorized to other devices, then encrypted the content.
At present, IEEE802.11 agreement also take this band, how will they solve this problem? If you take a Bluetooth device to an Equipment IEEE802.11 wireless network card, it will cause interference. Is there a distinctive way to solve it? Bluetooth has a full range of features. If there are many equipment, it is futuristic, and it is futile, and it is problematic and speed? Maybe the user can force the selected appropriate device from the device list (eg, according to its 48-bit address or username).
Bluetooth has a pair of multi-point exchange data capabilities, so it requires security systems to prevent unauthorized access.
Bluetooth's communication speed is 750kbits / s, with only 1 Mbps of bandwidth. And now the products with 4MBITS / SIR ports are all, and the expansion of the recent 16MBITS / S has also been approved. What does this mean?
Bluetooth - short-range wireless communication technology
The current development of mobile communications is very fast. The existing GSM, NCDMA and other technologies are red-fired, and the third generation mobile communication system (
3G
) Has also been put on a agenda and will be put into commercial use. These technologies can achieve long-distance communication. But people may not not notice that wireless communication is also required in the same room or in the place of the feet. Therefore, another requirement is thereon: a low price, low power consumption, can replace the cable's wireless data and voice links. It is desirable to provide various services for mobile and commercial users through a small, short-range wireless network.
Currently, the connection between the close-to-distance portable devices is the most infrared link (IRDA). Applying IRDA although there is still a lot of inconveniences using the wires or cable connections: connection distance is limited to 1
2
Meter
And must be directly aligned on the line of sight, there is no barrier in the middle; it is limited to connection between the two devices, and more devices cannot be connected.
"Bluetooth" plan
In May 1998, five world famous big companies such as Ericsson, Nokia, Toshiba, IBM and Intel announced a plan called "Bluetooth" and created Bluetooth Special Interest Group. They strive to develop an open industrial standards, and is based on short-range wireless communication technologies for replaceable cables applied to mobile and commercial markets. After this plan announced, quickly got Motorola, Lucent, Kangbo, Siemens, Gao Tong,
3C
Many manufacturers of many manufacturers, such as OM, TDK.
1999
year
12
month
1
day
Microsoft, Lucent,
3C
OM and Motorola four company plus people to the founder, making the Bluetooth Special Interest Group have become jointly leaders from 9 companies. By June 2000, there were 18,82 companies in the world, and institutions joined this group.
1999
year
12
month
1
day
The Bluetooth Special Interest Group released the latest version of the Bluetooth standard, that is, 1.ob version. The "Bluetooth" standard is mainly defined by the underlying protocol, and has some high-level protocols and related compatibility. interface.
For its industrial implementation, the "Bluetooth" standard can be divided into two parts of hardware and software. The hardware part includes RF / Radio Protocol, baseband / link controller protocol, and link manager protocol, which is generally made into a chip. The software part includes logical key control and adaptation protocols and all parts above. The hardware and software are connected between HCI, that is, HCI is in hardware and software, and both provide the same interface for communication.
Typical application of "Bluetooth" technology
In general, "Bluetooth" technology is suitable for short-range wireless connections in the following three aspects:
1) Data and voice access points;
2) Alternative wires and cables;
3) A network containing hardware, software, and interoperability needs. For users, the following scenarios may be implemented in the near future: all devices - including laptops, mouse, printers, access points, mobile phones, and microphones, etc., all use "Bluetooth" protocol wireless connection. Together, the exchange of voice and data, while also connecting to the outside through wireless or wired access points such as PSTN, ISDN, LAN, XDSL).
Several typical applications for "Bluetooth" technology are as follows:
(1) Three-in-one call. "Bluetooth" technology allows a mobile phone mobile phone to use within a variety of occasions: in the office, this phone is internal phone, no phone bill; at home, it is a cordless phone, fixed telephone fee; go out, is a Ministry mobile phone, press the phone bill for mobile phones.
(2) Internet bridge. "Bluetooth" technology allows the laptop to enter the Internet through mobile phones anywhere, and to the Internet to "surf" anytime, anywhere.
(3) Interactive conference. In the conference, "Bluetooth" technology can quickly make your information via the 便 排 电脑, mobile phones, and PDA, etc. are shared by other participants.
(4) The door briefcase. The laptop also received an external email in the bag, and the user's mobile phone will sound, remind the user "computer has received email". At this time, users don't have to open the computer, and you can browse the received email on your phone.
(5) Wireless transmission of images in digital cameras. "Bluetooth" technology sends images in digital cameras to other digital cameras or PCs, PDAs, and the like.
(6) Remote control and home appliance network of various household equipment.
latest progress
In terms of product, Ericsson issued a wireless headset based on "Bluetooth" technology, and launched a mobile phone mobile phone mobile phone module built-in "Bluetooth" transceiver signal module; Motorola will showcase Internet access and synchronous services at the Consumer Electronics Exhibition. ELSA provides "Bluetooth" ISDN products. "Bluetooth" PCMCIA card and modems are coming soon. In addition, more and more companies have announced that all kinds of products based on "Bluetooth" technology are produced.
In terms of chips, relevant vendors have developed a variety of "Bluetooth" special integrated circuit (ASIC), and issued a corresponding development kit that makes it earlier to produce applications more easily and more easily produce application products.
In terms of software, many companies have also developed the corresponding "Bluetooth" mid money. It is particularly worth mentioning that the headquarters developed the IVT company in Beijing to achieve the "Bluetooth" protocol with C code and SDL. Stack, you can develop a corresponding software development package for different operating systems.
Bluetooth technology connects various portable computers, mobile phones, and household appliances, and combines computer and communication more closely, so that people can exchange and transfer data information anytime, anywhere. People believe that "Bluetooth" The technology will set off the revolution of wireless connection and communication. Therefore, the telecommunications industry, computer industry, and home appliance industry have attached great importance to "Bluetooth" technology. It is considered that "Bluetooth" technology will have a huge promotion of future wireless mobile data communication services. In recent years, the wireless data communication business will grow rapidly. "Bluetooth" technology is considered to be one of the most important progress of wireless data communication.
Bluetooth goal
Bluetooth is a low-cost, short-range wireless connection technology standard. It is a global wirelessly advocated by 5 world-class computers and communications companies, ie, Ericsson, International Commercial Machine (IBM), Intel (INTEL), Nokia and Toshiba 5 companies. technical standard. Has been in 1999
year
Seduce
month
26
day
The Bluetooth Technical Specification 1.0 version is launched. "Bluetooth" is a king name in the 10th century Denmark, used to name this new technical standard, intended to be unified. Therefore, the Bluetooth Sig, which is established, has adopted a strategy for transferring the patent technology to the entire industry to achieve its global unified standards. The original intention of blue bud technology is to connect smart mobile phones, handheld, and external devices of various digital information, thereby forming a network of personal surrounding fields, making various information within their scope. Both mobile portable devices can achieve seamless resource sharing. Since the establishment of the Blue Bud Special Interest, the company has built more than 1,800, including AMD, Compaq, Dell, HP, Texas Instruments, Qualcomm and Casio, Philips, Samsung, LG, Seiko Many of the world's most famous computers, communications, and consumer electronics fields in Sharp, and even manufacturers and manufacturers of cars and cameras. A open global unified technical specification has been rare in the past, which is rare in the industry. This shows that the product based on this blue bud technology will have broad application prospects and huge potential markets. Recently, the US software giant micro-software company no longer adheres to the attitude of watching, officially announced the company's special interest group, and has become a Group's interest group with 3COM, Lucent, Motorola and the original 5 companies. 9 leadership members are jointly committed to promoting this wireless technical standard in a global scale. According to foreign authorities forecast, after a few years, hundreds of millions of digital mobile phones, PCs, and various information devices will embed this blue bud technology.
The ultimate goal of Blue Bud Technologies is to establish a global unified wireless connection standard, which makes various mobile computing and portable equipment produced by different manufacturers. It can be easily connected to the cable in close range. Share with data. This way of blue bud wireless connection can be said to be very novel, users don't have to learn how to install, how to set it. Any device embedded in blue buds can automatically contact and confirm, using the corresponding control software, no user intervention can automatically establish connection transfer data. With blue bud technology, portable information devices such as mobile phones, laptops, and handheld computers can share data such as the same database, phone thin, email and electronic secretary; whether in the hand, you can play Telephone, read emails, but don't worry about which device is stored on. Digital mobile phones embedded in Blue Bud Techniques will enable one machine and truly realize the functionality of personal communication. In the office, it can be used as an internal wireless group phone. After going home, it can be used as a cord phone, and the cost of expensive mobile phones can not be paid. On the way outdoors or ride, it is still combined as a mobile phone or a personal digital assistant PDA, and can go to the Internet to surf the Internet, which will go to the Internet, anytime, anytime, anywhere, by embedding the LAN for blue buds. Life is more convenient and fast. Bluetooth technology represents a new challenge for traditional communication and computer terminal equipment. If this technological cost is low and widely used (it is reported that with the improvement of integration, the cost of the Blue Bud Technique is expected to fall to $ 5), then it will bring our work and communication. huge change.
Bluetooth Technology and Personal LAN (PAN) In recent years, with the development of various short-range wireless communication technology, people have put forward a new concept, that is, Personal Area Network, PAN. PAN core thinking is to replace traditional cable cables with radio or infrared, to achieve intelligent interconnection of personal information terminals, and form a personalized information network. From the perspective of a computer network, the PAN is a local area network; and from the perspective of the telecommunications network, the PAN is an access network.
PAN is located in the application of the family and small offices, and its main applications include voice communication gateways, data communication gateways, information appliances, and information automatic exchange.
The implementation technology of PAN has: Bluetooth, Irda, Home RF and UWB (Ultra-Wideband Radio). Among them, Bluetooth technology is a support point-to-point, point-to-multi-point voice, data service short-range wireless communication technology, Bluetooth technology has greatly promoted the development of PAN technology, and IEEE has set up IEEE802. 15 groups are responsible for studying PAN technology based on Bluetooth. Let us first look at what is some of Bluetooth technology and Bluetooth technology.
I. Concept of Bluetooth technology
Bluetooth is an open, short-range wireless communication technology standard, which can be used to implement a fixed device and network interconnection between the mobile device in a smaller range, and can be between various digital devices Realize voice and data communication of flexible, safe, low cost, small power consumption. Because Bluetooth technology can be easily embedded in a single CMOS chip, it is especially suitable for small mobile communication devices.
Second, the Bluetooth protocol
The Bluetooth communication protocol also uses a hierarchical structure. The hierarchy makes its equipment with maximum possible versatility and flexibility. According to the communication protocol, various Bluetooth devices can find other Bluetooth devices from manual or automatic queries, and to form various functions provided by manual or automatic query, which makes various functions provided by the system. Convenience. Figure 1 is the hierarchy of the Bluetooth protocol stack, where:
* Bluetooth Radio is a transceiver responsible for transmitting and receiving modulating radio signals in the Bluetooth device. For compatibility, the use of Bluetooth wireless devices should have a determined wireless transceiver feature.
* Baseband (baseband) The Bluetooth Physical layer is responsible for managing physical channels and links, but does not include incorrect corrections, data processing, frequency hopping, and Bluetooth security.
* ACL is an Asynchronous Connection-Less physical link that transmits data on a physical channel. The ACL link provides a packet switched connection between the main unit (Master) and all other slave units (SLAVE).
The SCO is synchronous connection (Synchronous connection-oriented) physical link, which is mainly used for information transmission such as voice communication. The SCO is the primary unit and the symmetry link of point-to-point between the unit. It is very similar to the circuit switched connection.
* Link Manager mainly handles tasks such as link establishment, link security, and link control. It provides services for authentication, encryption control, power control, and QoS capabilities. Link management can also manage devices under different modes (Park, Hold, Sniff, and Active).
* L * L
2C
AP is the logical link control and adaptation layer protocol (Logical Link Control and Adaptation Layer Protocol). It is located in the data link layer, providing multiplexed, segment, reorganization, and group abstraction, etc. L
2C
AP allows high-level protocols and applications to send up lengths of up to 64 kB in length.
2C
AP packet.
* SDP, Service Discovery Protocol, application uses this protocol to find out which services are available and determine the features of these available services.
The serial simulation protocol (RFCMM) is a simple transport protocol that can be in L
2C
The simulation RS-232 (EITIA-232-E) serial port is simulated, so it is actually a cable alternative protocol. The RFComm protocol supports up to 60 concurrent connections between two Bluetooth devices.
TCP (Transmission Control Protocol: Transmission Control Protocol) The reliable connection between the transport layer is established in the transport layer in the network layer with IP protocol.
The IP protocol provides protocol multiplexing and connection based on IP addresses.
* Jini technology provides a simple mechanism that uses this mechanism to combine device combines to form an instant group - no plan, installation, or artificial interference. Each device provides services they can use by other devices in the group. These devices provide their own interface to ensure their reliability and compatibility. Compared with the on-site Bluetooth, JINI runs at a higher level. WAP is a Wireless Application Protocol, which provides standard protocols for Internet communication and advanced telephone services for mobile phones, pagers, PDAs, and other wireless terminals.
Third, key technology in Bluetooth
The following mainly introduces some of the theoretical and techniques involved in the Bluetooth implementation.
Sweugue technology
Bluetooth carrier frequency is globally universal
2.45g
HZ ISM band, due to
2.45g
The frequency band of Hz is a frequency band that is open to all radio systems, so any of the bands use may encounter unpredictable interference sources. It is an effective measure to avoid interference. The frequency hopping technology is to divide the frequency band into several frequency hop channels. In a connection, the radio transceiver will continue to jump from one channel from a channel in a certain code sequence, and only the transceivers are communicating according to this law, while others The interference is impossible to interfere with the same law. The transient bandwidth of frequency hopping is narrow, but the narrow band is extended to a broadband band by extending spectrum technology to make the influence of the interference possible.
According to the specific situation of all countries,
2.45g
Hz is the center frequency, up to 79
1M
HZ bandwidth channel. In the emitted bandwidth
1M
When Hz, its effective data rate is 721kb / s and is transmitted using low power time division multiplexing. Bluetooth technology ideal connection range
10
cm
-
10
Meter
However, the distance can be extended by increasing the transmit power.
100
Meter
. Frequency hopping sputum technology is one of the key technologies for Bluetooth. Corresponding to a single-slot packet, the Bluetooth frequency hopping rate is 1600 hops / second; corresponding to the slot package, the frequency hopping rate is reduced; but is increased to 3200 jumps per second when establishing a link. With such a high frequency hopping rate, the Bluetooth system has sufficiently high anti-interference capabilities. It uses a mapping scheme with multi-stage butterfly operation as a core, compared with other programs, and has a simple and superior performance of the 79/23 frequency band, and the frequency hopping sequences of various states use a unified circuit. To achieve the characteristics. Compared with other systems that work in the same frequency band, Bluetooth hopping is faster and the packet is shorter, so more stable.
2. Micro and Distributive Network
When the two Bluetooth devices have successfully established the link, a piconet is formed, and the communication between the two is accomplished by radio waves in 79 channels.
The micro network channel is defined by a main unit identifier (providing frequency hopping sequence) and system clock (providing frequency hopping phase), and other slave units. Each Bluetooth wireless system has a local clock without a usual timing reference. When the micro network is established, the clock compensation is performed from the unit, so that the main unit is synchronized, after the micro-network is released, the compensation is also canceled, but can be stored for reuse. A general micro-network channel has an amount of 8 (1 main 7), ensuring effective addressing and massive communication between cells. In fact, the number of internet devices in a piconet is not limited, but only 8 can be activated at the same time, one of which is the main, and 7 are from. On the basis of peer communication, the Bluetooth system is based on peer communication, the master is only valid within the micro-network survival period. When the micro-net is canceled, the master is canceled with the master. Each unit can be a main / slave unit, which can define a unit of units for establishing a pico-network. In addition to the definition of the micro-net, the main unit also controls the information traffic of the piconet, and manages access. Bluetooth provides a specific jump mode to each piconet, so it allows a large number of picoons to exist at the same time, and the interconnection of multiple picoons in the same area forms a dispersion network. Different micro network channels have different main units, thereby present different jump modes. The Bluetooth system is optimized to dozens of pico-run operations in the same area without significant performance degradation. The Bluetooth slot connection uses a packet-based communication that allows different piconoms to interconnect. Want to connect the unit to different piconnia, but only the wireless signal can only be modulated to a single hopping carrier, one moment unit can only communicate in a minor network. By adjusting the micro-network channel parameters (ie, the main unit flag and the main unit clock), the unit can jump from a micro-net to another micro network, and can change the task. For example, at the main unit of the piconet at a certain moment, another time is from the unit in another piconet. Since the main unit parameter indicates the jump mode of the micro network channel, a unit cannot be the main unit in different piconics. The frequency hopping selection mechanism should be designed to allow mutual communication between the micro-network, entered the selection mechanism by changing the flag and clock, and the new micro network can immediately select new frequency hopping. In order to make the frequency hopping between the different piconets, there is no protection time in the data stream system to prevent the difference in time slots in different picoons. In the Bluetooth system, the retention mode is introduced, allowing a single unit to be temporarily left a micro-micro-net to access another piconet.
3. Multiple Access (TDMA) modulation technology
In the 1.0 version of the technical standard, Bluetooth baseband bit rate is
1M
B / S, use TDD scheme to achieve full duplex transmission, so a baseband frame of Bluetooth includes two packets, first and foremost, the packet is transmitted, and then the packet is received. The Bluetooth system supports circuit exchange and supporting packet exchange, supporting real-time synchronous orientation coupling (SCO) and non-real-time asynchronous unpacked coupling (ACL).
The SCO link is a link between a single main unit and a single slave unit in a piconet. The main unit can maintain the SCO link in a manner that reserves the time slot (circuit switch type) in accordance with the specified interval. The main unit can support up to three concurrent SCO links, and from the unit, two or three SCO links can be supported, and the packets on the SCO link will not re-transfer. The SCO link is mainly used for voice transmission of 64 kb / s.
The ACL link is a multi-point link between the main unit and all from the unit. In the case where the time slot is not reserved for the SCO link, the main unit can establish an ACL link on an arbitrary slave unit, which includes the case where the slave unit has used a SCO link (packet Exchange type). For most ACL packets, you can apply data packs. The ACL link is mainly data-based and can be transmitted at any time slot.
4. Addressing technology
Bluetooth has 4 basic types of equipment addresses:
* Bd_addr: bd_addr is a 48-bit long address that is in line with the IEEE802 standard, which can be divided into LAP (24-bit address low-end portion), UAP (8-bit address high-end portion) and NAP (16-bit meaningful address part) three parts . * AM_ADDR: AM_ADDR is a 3-digit active member address, all 0 information am_addr is used to broadcast messages.
* PM_ADDR: PM_ADDR is an 8-bit long member address, assigned to a slave unit used.
* Ar_addr: ar_addr is an access request address (Access Request Address), which is paused with this address to determine the access window within the access window, transmitting access messages by it.
Any Bluetooth device can get a unique 48bit BD_ADDR according to the IEEE 802 standard. It is an open address code that can be queried by manual or automatically. Based on BD_ADDR, a variety of confidentiality and security codes can be obtained using some performance algorithms, thereby ensuring the uniqueness of the device identification code (ID) in the world, as well as the security confidentiality of the equipment in the communication process.
5. Security
Bluetooth technology wireless transmission features make it very easy to attack, so security mechanisms are especially important in Bluetooth technology. Although the frequency hopping technology used by the Bluetooth system has provided a certain security, the Bluetooth system still requires security management of link layers and application layers. In the link layer, the Bluetooth system uses functions such as authentication, encryption, and key management. In the application layer, the user can use the personal identification code (PIN) to perform single bidirectional authentication.
6, error correction technology
The error correction mechanism of the Bluetooth system is divided into FEC and packages. FEC supports 1/3 rate and 2/3 rate FEC code. 1/3 rate is only used to repeat the encoding with 3 digits, and most of the receiving end decisions can be used in both the data clamp, and can also be used for the package load of the SCO connection. 2/3 rate code uses a shortened Hamming code, and the error captures for decoding, which can be used for the SCO connection synchronization package load, or the asynchronous packet load of the ACL connection. In the ACL connection, the ARQ structure can be used. In this configuration, if the receiver does not respond, the origin will be loaded. Each load contains a CRC for detecting the error. The ARQ structure is divided into: stop waiting for ARQ, backward N ARQ, repeats the ARQ and mixing structure.
In order to reduce complexity, the overhead and ineffective retransmitted to the smallest, Bluetooth perform fast ARQ structure: the transmitting end is retranscate in the TX slot, and the packet is received in the Rx slot prompt package. If the 2/3 rate FEC code is added, the result of the mixing ARQ structure of the class I is obtained. The ACK / NACK information is loaded in the header of the returning package, and in the structural exchange time of the RX / TX, it is determined whether the receiving package is correct. In the header of the returning package, generate the ACK / NACK domain, and the ACK / NACK domain that receives the package header can indicate whether the previous load is properly received, decide whether to retransmit or send the next package. Due to the short processing time, when the package is received, the decoding selection is performed in the idle time, and simplifies the FEC coding structure to speed up the processing speed. The fast ARQ structure is similar to the ARQ structure, but the delay is the smallest, which is not actually an additional delay caused by the ARQ structure. This structure is more efficient than the rear N ARQ and the same efficiency is the same as repeated selection, but due to the resend of the package that is exposed, it can reduce overhead. In the fast ARQ structure, only one serial number is sufficient (two packets) in order to filter out errors in the ACK / NACK domain.
Fourth, Bluetooth system composition
The Bluetooth system is typically composed of an antenna unit, a link control (firmware) unit, the link management (software) unit, and the Bluetooth software (protocol stack) unit. Antenna unit
Bluetooth antenna part is very small, light weight, belongs to the microstrip antenna. The Bluetooth air interface is based on the antenna level is 0dB. The air interface follows the standard of the ISM band of the FCC related to 0 dB. If the global level reaches
100M
We can use extended spectrum functions to add some additional services.
2. Link Control (Hardware) Unit
The current Bluetooth product link control hardware unit includes three integrated chips: connecting controllers, baseband processors, and RF transmission / receivers, and 3-5 separate tuning elements are used. The baseband link controller is responsible for handling baseband protocols and other low-level regular protocols.
3. Link Management (Software) Unit
Link Management (LM) Software Module Carrys the link data settings, authentication, link hardware configuration, and other protocols. LM can discover other far-end LMs and communicate through the LMP (Link Management Protocol). The LM module provides the following services: sending and receiving data, request name, link address query, establishing connection, authentication, link mode negotiation, and establishment, determining the type of frame.
4. Software (protocol stack) unit
Bluetooth software (protocol stack) is an independent operating system that is not bundled with any operating system, which meets the Bluetooth specification that has been developed. The Bluetooth specification includes two parts: the first part is the core part, to specify components such as radio frequency, baseband, connection management, business discovery, transport layer, and interoperability between different communication protocols; the second part is the application specification Part of the section to specify the protocols and processes required for different Bluetooth applications. Complete the filtering and transmission, frequency hopping, and data frame transmission, the establishment of the connection, the connection, the control of the link, the service quality (QoS), the multiplexing of the data, and the differentiation of the data.
Bluetooth devices rely on dedicated Bluetooth microchips to enable the device to send radio signals within a short range to find another Bluetooth device. Once found, communication is started with each other. Currently, the developers of Bluetooth mainly seek its ASIC solutions, including RF and baseband parts. There are now many solutions that make baseband ASIC circuits and RF ASIC circuits into a circuit module, and it is expected to come into batches of mass production. Most of the Bluetooth system communication protocols can be implemented, and can be operated in the Flash RAM.
Five, Bluetooth technology and PAN
The concept of Bluetooth system and PAN complements, in fact, Bluetooth system is already a prototype of PAN. In the Bluetooth 1.o version of the Bluetooth 1.o version released in December 1999, a variety of applications including the use of WAP protocols are connected to the Internet are defined. It can add new features to existing networks such as cellular telephone systems, cordless communication systems, wireless local area networks, and the Internet to add wireless transmission and networking capabilities to all kinds of computers, fax machines, printer devices, automated family and office, home entertainment, E-commerce, wireless briefcase application, various types of digital electronic equipment, industrial control, intelligent construction, etc. have opened up a broad application.
