Types of wireless access mode

With the rapid development of the Internet and people's increasing demand for broadband, the original fetters people hands and feet single, annoying cable and cable access has been unable to meet the needs of the access mode. At this time, due to the potential of another way of networking has gone into the eyes of the people, and in the new century in the process of alternating the interpretation of a "will go online to the end" of the movement, this is the wireless access technology. With the help of wireless access technology, no matter when, where, people can easily access the Internet. Perhaps, the future Internet access standards will also be born here. This article selected the current domestic and international popular some wireless access technology, and a big review of it, I hope that in the future, we choose wireless access to help.
1. GSM Access Technology
GSM is a kind of mobile communication technology standard originated from Europe, and it is the second generation mobile communication technology. This technology is a common technical representative of personal communication at present. It uses narrow-band TDMA, allowing 8 groups of calls to be made at the same time as a radio frequency  i.e. ' honeycomb '. GSM was launched in 1991. By the end of 1997, it had been operating in more than 100 countries, becoming the de facto standard in Europe and Asia. GSM Digital Network has a strong confidentiality and anti-jamming, sound quality, call stability, and have large capacity, high frequency resource utilization, interface open, powerful and so on. The introduction of this technical standard in China in the early 1990s has been the use of cellular analog mobile technology, that is, the first generation of GSM technology (December 31, 2001 our country closed the analog mobile network). At present, Chinese mobile, China Unicom Each has a GSM network, GSM mobile phone users in the total of 1. More than 400 million, the world's largest mobile communications network.
2. CDMA Access Technology
CDMA is the abbreviation of code-division Multiple access, translated as "CDMA packet data transmission technology", is called the 2nd. 5 Generation mobile communication technology. At present, the market of this technology is mainly in the United States, Japan, Korea and so on, the global user reaches 95 million. CDMA mobile phone with clear voice, not easy to drop words, low transmission power and strong confidentiality characteristics, the launch power only GSM mobile phone launch power 160, known as "Green mobile phone." More importantly, CDMA based on wideband technology makes it possible to use video in mobile communication. CDMA, like GSM, is a relatively mature wireless communication technology. Unlike GSM, which uses time-division multiplexing technology, CDMA does not assign a certain frequency to each caller, but lets each channel use all the spectrum it can provide. Therefore, CDMA Digital Network has the following advantages: Efficient frequency band utilization and greater network capacity, simplified network planning, high quality of call, confidentiality and signal coverage, not easy to drop words and so on. In addition, CDMA system adopts coding technology, its coding is 4. 400 million kinds of digital arrangement, each cell phone's code also changes at any time, this makes the stolen code can only become theoretically possible.
3, GPRS access technology
Compared with the original GSM dialing mode of the circuit Exchange data transmission mode, GPRS is packet switching technology. Because of the use of the "group" technology, users can access the Internet to avoid the pain of disconnection  situation probably with the use of download software netants almost. In addition, the use of GPRS Internet access and WAP and different, with WAP Internet, such as at home, the Internet, the first "dial-up connection", and the Internet can not use the phone line at the same time, but GPRS is more advantageous, download information and call can be carried out simultaneously. Technically speaking, if the simple voice call, it may be possible to continue to use GSM, but if there is data transmission requirements, it is best to use GPRS, it put the application of mobile phones to a higher level. At the same time, the development of GPRS technology is also very "economic", because it only needs to upgrade the existing GSM network. GPRS is widely used, including through the mobile phone to send and receive e-mail, browsing on the internet and so on.
GPRS's biggest advantage lies in: its data transmission speed is not WAP can compare. The current GSM mobile communication network data transmission speed of 9 per second. 6K bytes, and GPRS reaches the 115kbps this speed is twice times the normal 56Kmodem ideal rate. In addition to the speed of the advantages, GPRS and ' Forever online ' features, that is, users at any time to maintain contact with the network.
4, CDPD Access technology
CDPD Access technology is the most important feature of high-speed transmission, the highest communication speed can reach 19. 2kbps. In addition, in the data security, because of the use of RC4 encryption technology, so the security is relatively high, positive and negative channel key asymmetry, key by the Exchange Center Master, mobile terminal login, switching center automatically check the old key to replace the new key once, the implementation of dynamic management. In addition, because the CDPD system is an TCPIP open system, we can easily access the Internet, all applications based on TCPIP protocol can be used without modification, the application software development is simple; the mobile terminal communication number uses the IP address directly. CDPD system also supports user switching and full network roaming, broadcast and group call, support mobile speed up to 100kmh data users, and public wired data network interconnection.
5, Fixed Wireless Broadband (LMDS) Access technology
LMDS's English full name is called the local multipoint distribution services, the Chinese meaning is called the locality multiple point distribution business. This is a microwave broadband technology, due to work in the higher frequency band (24ghz-39ghz), so it can provide a wide bandwidth (up to 1GHz), but also dubbed "Wireless fiber" technology. It can achieve two-way transmission of voice, data images, video, conference TV and other broadband services at a relatively close distance, and support standards such as ATM, TCPIP and MPEG 2. LMDS uses a honeycomb-like service area structure that divides a region that needs to provide a business into a number of services areas, with base stations in each section, and base station equipment that communicates with the client side of the site via point to multicast wireless links. Each service area covers a few kilometres to more than 10 kilometres and can overlap each other.
Because LMDS has the characteristics of higher bandwidth and bidirectional data transmission, it can provide many kinds of broadband interactive data and multimedia service, overcome the bottleneck of traditional local loop, meet the increasing demand of users for high-speed data and image communication, so it is a sharp weapon to solve the problem of communication network access.
6. DBS Satellite Access Technology
DBS technology is also known as Digital live satellite access technology, which utilizes communications satellites located in geosynchronous orbit to send high speed broadcast data to the receiving antenna of the user, so it is also commonly referred to as high orbit satellite communications. Its characteristic is the communication distance, the expense and the distance is independent, the coverage area is not limited by the geographical condition, the bandwidth is wide, the capacity is big, is suitable for the multiple service transmission, may provide the global user with the big span, the wide range, the long-distance roaming and the mobile communication service and so on. In the DBS system, a large number of data by frequency division or time modulation after the use of satellite main station of the high-speed uplink and satellite transponder broadcast, the user through the satellite antenna and satellite receiving modem reception data, the receiving antenna diameter is generally 0. 45m or 0. 53m.
Because of the high reliability of digital satellite system, unlike PSTN network, the use of twisted-pair analog telephones requires more signal error correction, so the download rate can reach 400kbits, and the actual DBS broadcasting rate can reach 12mbits. At present, the United States has been able to provide DBS services, mainly for Internet access, of which the largest DBS network is the Hughes Network system company DIRECTPC. DIRECTPC data transmission is also asymmetric, when the Internet access, download rate is 400kbits, the uplink rate is 33. 6kbits, this rate is much higher than the normal dial-up modem, but it is still not compared with DSL and cable modem technology.
7, Bluetooth technology
The English name of Bluetooth is "Bluetooth", which is actually a protocol for implementing wireless connections between multiple devices. This agreement enables the exchange of information between devices including cellular telephones, handheld computers, laptops, related peripherals, and home units such as the home RF. Bluetooth is used in mobile phone and computer connection, can save the cost of mobile phone, to achieve data sharing, Internet access, wireless hands-free, synchronized data, image transmission and so on.
Although the Bluetooth in the multi-directional transmission has a greater advantage, but if a large number of devices, recognition methods and speed will also have problems; Blue toothbrush has a one-to-many data exchange capability, so it needs a security system to prevent unauthorized access; The basic communication speed of Bluetooth is 750kbitss, However, products with 4mbitssir ports are now very common, and the recent 16mbitss extension has been approved.
8, HomeRF Technology
HomeRF is designed primarily for home networking, designed to reduce the cost of voice data. In order to realize the efficient transmission of packets, the HomeRF adopts the IEEE802. The CSMACA mode in the 11 standard, which is similar to CSMACD, acquires control over the channel in a competitive way, and only one access point can transmit data to the network at a point in time. Unlike other protocols, HomeRF provides a true sense of support for the convection business (stream media). Due to the high priority of the convection business and the use of a priority-prone mechanism, this ensures the bandwidth and low interference and low error rate required for real-time streaming services.
HomeRF works at the 2. 4GHz band  It uses the digital frequency hopping spread spectrum technology, the rate is 50 jumps s a total of 75 bandwidth is 1MHz frequency hopping channel. The modulation mode is a constant envelope of FSK modulation, divided into 2FSK and 4FSK two kinds. FM modulation can effectively restrain the interference and fading in wireless environment. In 2FSK mode, the maximum data transmission rate is 1mbs, in 4FSK mode, the rate can reach 2mbs. The latest version of HomeRF2. X, the use of wbfhwide band frequency hopping technology to increase the width of the jump band, from the original 1MHz to 3MHz, 5MHz, the rate of hopping also increased to 75 jump s, its data peak also up to 10mbs, close. IEEE802. 11b Standard 11mbs, basically can meet the future home broadband communication.
9, WCDMA Access Technology
WCDMA technology can provide users with the highest 2mbits rate of data transmission, under such conditions, now the computer application of any media can be easily passed through the wireless network. The advantage of WCDMA is that the rate of the chip is high, the frequency selectivity diversity and the space receiving and transmitting diversity are used effectively, the multipath problem and the fading problem can be solved, and the Turbo Channel codec is used to provide a higher data transmission rate, and the FDD system can provide wide area full coverage, The downlink base station distinguishes using the unique cell search method, without strict synchronization between base stations. Using continuous pilot technology, can support high-speed mobile terminals.
Compared to the second generation of mobile communication technology, WCDMA has greater system capacity, better voice quality, higher spectral efficiency, faster data rate, stronger resistance to fading, better resistance to multipath, can be applied to the technical advantages of mobile terminals up to 500kmh, and can be smooth transition from GSM system To ensure the investment of operators, providing a good technical basis for 3G operation. WCDMA through the effective use of broadband, not only smooth processing of sound, image data, and the Internet fast Connection, in addition, WCDMA and MPEG-4 technology can also be combined to deal with real dynamic images.
10.3G Communication Technology
The technology is also known as International Mobile Phone 2000, which stipulates that when the mobile terminal is moving at a speed, its transfer data rate is 144kbps, outdoor static or pedestrian speed is 384kbps, and the interior is 2Mbps. But these requirements do not mean that the user can reach 2Mbps, because the room rate will also depend on the detailed frequency planning in the building and the organization and operator collaboration. However, due to the high-speed service speed of wireless LAN is up to 54Mbps, it is difficult to predict the market demand of 2Mbps business when the 3G network is fully rolled out.
11, Wireless LAN
Wireless LAN wireless LAN, referred to as WLAN is a combination of computer network and wireless communication technology products. It is not bound by cable, removable, can solve the problems caused by cable network wiring difficulties, and network flexibility, expansion convenience, and a variety of network standards compatible, widely used and so on. WLAN can not only meet the requirements of all kinds of portable computers, but also can realize remote access of computer LAN, facsimile, e-mail and other functions.
12. Wireless Optical System
Wireless Infrared optical transmission system is the combination of optical communication and wireless communication, through the atmosphere rather than optical fiber to transmit light signals. This technology provides a rate of similar optical fibers, and does not require scarce resources such as the spectrum. The main features are: High transmission rate, high speed data transmission from 2mbs to 622mbs, transmission distance of 200 meters to 6 km range; Due to the work in the infrared light band, the other transmission system will not interfere with the security is strong, signal transmission and reception through optical instruments, no day feeder system, equipment volume is small.