Wednesday, January 5, 2011
Weak current College】 【Bluetooth and infrared difference】.
Prior to this, the wireless communications sector leader is to become familiar with infra-red transmission. But the IR has a fatal flaw is a must in the Visual range, the infrared interface transmission technology to work. The existence of a disadvantage to the Bluetooth development provides new opportunities.
In addition, when using the scope aspect, the difference between infrared and Bluetooth is still very clear. Infrared technology is generally suitable for low cost, cross-platform, point-to-point high-speed data connectivity, particularly in embedded systems, such as devices, gateway, etc. While Bluetooth is a different matter, Bluetooth technology is used as a substitute for the "cable" technology for development to today has evolved into a personal information network platform. It mainly has the following three main purposes: voice/data access, peripherals, Internet and personal area networks.
1974 invention of infrared brings us a new connection, and more importantly, it brings us a new concept, we are a wireless fresh. In 1998 the Bluetooth technology to the fore, with its strong advantage to attract me, and great coverage in the infrared, Bluetooth protocol and Infrared Transfer Protocol are the differences?
Bluetooth (BLUETOOTH), in 1998 launched a new wireless transmission mode, you replace the data cable of short-range wireless communication technologies, through low-bandwidth radio point-to-point or point-to-multipoint connection between the exchange of information. The network mode is also called private space network (PAN, PersonalAreaNetwork), is more than one micro-network or exquisite Bluetooth master/adnexal built mini Web-based, each micro-network consists of eight active device and 255 ancillary installations, and multiple micro-network connection up and expansion of the network was formed to facilitate and speed of implementation of various communication between devices. It is the voice and data wireless transmission of open specification, is a low-cost, short-range wireless connectivity technology.
2. technical characteristics:
Bluetooth technology's features include: the use of frequency hopping technology, signal fading; the use of fast frequency-hopping and short packet technology, reducing the co-channel interference, guaranteed transmission reliability; the use of forward error correction coding technology, reduce long-distance transmission of random noise effects; use 2.4GHz ISM band, shall not be required to apply for a license; the use of FM modulation mode, reducing the complexity of the device. The technical design of the transmission rate to the 1MHz time division duplex mode, its baseband Protocol is a circuit-switched and packet-switched. A frequency hopping frequency sends a synchronization group, each group uses a time slot, also scales up to 5 time slot. Bluetooth support 1 asynchronous data channel or 3 concurrent synchronization voice channels, or 1 transmit asynchronous data and synchronize voice channel. Each voice channel support 64kb/s synchronous voice; asynchronous channel support maximum rate for 721kb/s, reverse response rate for 57.6kb/s for asymmetric connections or 432.6kb/s symmetrical connection.
(1) to establish a connection
Establishment in Pico-mesh, all devices are in the ready state. In this State, not connected to the device every time the message 1.28s listens, the device once it is awake, predefined 32-hopping frequency monitoring information. FH number varies by region, but 32-hopping frequency is used by the vast majority of countries. Connection process by master device initialization. If a device address known, adopt page information (Pagemessage) to establish the connection; if the address is unknown, it uses the following pages of information query information (Inquirymessage) establish the connection. In a slight net, no data transmission equipment to power-saving state. The primary device can be set to keep from the device, in this case, only the internal timer; from the device can also request to maintain. Equipment by way of keeping out, you can immediately resume data transfer. Connect a few slight net or manage a low-power devices, often used to maintain. Listen mode and sleep mode is the addition of two low-power mode. Bluetooth baseband technology supports two types of connection: connection-oriented (SCO), mainly for voice transmission; no way connect (ACL), which is mainly used for grouping the data transfer.
(2) error control
Baseband controller with 3 kinds of error detection and correction mode: 1/3 forward error correction coding (FEC); 2/3 forward error correction coding; automatic retransmission request (ARQ).
(3) authentication and encryption
Authentication and encryption services provided by the physical layer. Authentication using password-answer mode, the connection process, you may need one or two authentication or no authentication. Certification on any one of the Bluetooth system are important components that allow users to add trusted Bluetooth device, for example, only the user's own laptop can pass the user's own cell phone to communicate. Bluetooth security mechanism is intended to provide an appropriate level of protection, if the user has a higher level of confidentiality requirements, you can use valid transport layer and application layer security mechanism.
(4) software structure
Bluetooth devices should be interoperable, for some devices, from radio compatible modules and air interfaces, until the application layer protocol and object Exchange format, is to achieve interoperability; on the other device (such as a headset device, etc.) requirements are relaxed. Bluetooth program goal is to ensure that any device with a Bluetooth mark can be interchangeable. Software interoperability began in the link-level protocol multiplexing, device and service discovery, and the grouping of segmentation and reassembly. Bluetooth device must be able to recognize each other, and install the appropriate software to identify each other in support of the high level functions. Interoperability requires use of the same application-layer protocol stack. Different types of Bluetooth device for compatibility with different requirements, the user cannot expect headset device contains an address book. Bluetooth compatibility means it has a radio compatibility, the ability to send and receive voice and discover other Bluetooth devices, more featuresBy mobile phones, handheld devices and notebook computers.