Technical principle of wireless WiFi
What is the wireless network in the wireless LAN category? Wireless compatibility certification? In essence, it is a business authentication and wireless network technology. In the past, computers were connected by network cables, while Wi-Fi was connected by radio waves. Wireless router is common, so within the effective range of radio wave coverage of this wireless router, Wi-Fi connection can be used for networking. If a wireless router is connected to an ADSL line or other Internet access line, it is also called a hotspot.
The main functions of wireless WiFi
Wireless Internet access can be simply understood as wireless Internet access. Almost all smartphones, tablets and laptops support Wi-Fi access, which is the most widely used wireless network transmission technology today. In fact, it is to convert wired network signals into wireless signals, as introduced at the beginning, using wireless routers to receive related computers, mobile phones, tablets and so on that support its technology. If the mobile phone has Wi-Fi function, it can surf the Internet without using the mobile Unicom network when there is Wi-Fi wireless signal, thus saving the traffic fee.
Wireless Internet access is widely used in big cities. Although the wireless communication quality transmitted by Wi-Fi technology is not very good, the data security performance is worse than that of Bluetooth, and the transmission quality needs to be improved, but the transmission speed is very fast, reaching 54Mbps, which meets the needs of personal and social informatization. The main advantage of Wi-Fi is that it does not need wiring and is not limited by wiring conditions, which is very suitable for the needs of mobile office users. Moreover, because the transmitted signal power is lower than 100mw, which is lower than the transmitted power of mobile phones, Wi-Fi surfing the Internet is relatively the safest and healthiest.
But Wi-Fi signals are also provided by wired networks, such as ADSL and residential broadband at home. Wired signals can be converted into Wi-Fi signals as long as a wireless router is connected. Many cities in foreign developed countries have covered the Wi-Fi signals provided by the government or large companies for residents, and many places in China have also implemented them? Wireless city? This project popularized this technology. In pilot cities that have not yet issued 4G licenses, many places use 4G to Wi-Fi for citizens to try.
Application field of wireless WiFi
network media
Because the frequency band of wireless network does not need any telecom license worldwide, WLAN wireless equipment provides a wireless air interface that can be used worldwide with extremely low cost and extremely high data bandwidth. Users can browse the web quickly in the Wi-Fi coverage area, and answer and make calls anytime and anywhere. Other broadband data applications based on WLAN, such as streaming media and online games, are worthy of users' expectation. With the Wi-Fi function, we can make long-distance calls (including international calls), browse the web, send and receive emails, download music and transmit digital photos. Don't worry about slow speed and high cost. Wi-Fi technology, like Bluetooth technology, belongs to short-distance wireless technology used in offices and homes.
handheld device
Wireless networks are widely used in handheld devices, and smart phones are one of them. Different from the Bluetooth technology used in early mobile phones, Wi-Fi has a wider coverage and higher transmission rate, so Wi-Fi mobile phones have become a fashion trend in the 20 10 mobile communication industry.
Daily leisure
20 10 domestic wireless network coverage is more and more extensive, and high-end hotels, luxury residential areas, airports and cafes all have Wi-Fi interfaces. When we travel and work, we can surf the Internet in these places with our handheld devices. Manufacturers only need to be located in airports, railway stations, cafes, libraries and other crowded places? Hot spot? And access the internet to the above places through high-speed lines. So, because? Hot spot? The emitted radio waves can reach a radius of tens of meters to 100 meters from the access point. Users can surf the Internet at high speed as long as they bring a laptop with Wi-Fi function, PDA, mobile phone, psp or ipodtouch into this area.
You can also buy a wireless router to set up a local area network at home, and then you can surf the Internet wirelessly.
The difference between wireless network and 3G technology is that 3G has better transmission quality when it is moving at high speed, but it is enough to surf the Internet with Wi-Fi when it is stationary.
The large-scale commercial application of wireless network is rare in the world. The problem is concentrated in two aspects: first, large operators do not recognize this model; Second, the lack of an effective business model. However, wireless LAN based on wireless network technology has become more and more popular, which means that it can be applied very conveniently in the future. Once the Wi-Fi network exists in public places, it solves the problems of interconnection, high cost and roaming of operators, and Wi-Fi will be transformed from a successful technology to a successful service in the future.
passenger train
201165438 In 2004+10/October 28th 14: 20, the first passenger train in China, the T809 through train from Guangzhou to Kowloon, Hong Kong, started from guangzhou east railway station, marking the beginning of the WiFi (wireless network) era of China railway.
After the train WiFi is opened, you can not only watch high-definition cinemas and play community games on the local area network inside the train, but also directly access the external network, brush Weibo and send emails, and connect with the world at the bandwidth speed of 10-50 megabytes.
Public toilet
Free WIFI in public toilets
20 public toilets with free WIFI function will be built in 20 16, Nan 'an District, Chongqing.
Background of wireless WiFi
Wireless network is a wireless network technology defined by IEEE. When IEEE formally defined the standard of 802. 1 1 in 1999, IEEE selected and recognized the wireless network technology invented by CSIRO as the best wireless network technology in the world, so the wireless network technology standard of CSIRO became the core technology standard of Wi-Fi in 20 10.
The wireless network technology was invented by CSIRO, a research institute under the Australian government, in the 1990s, and successfully applied for the wireless network technology patent in the United States on 1996. (U.S. Pat. No.5,487,069) The inventor is a research group composed of engineering graduates from the University of Sydney, led by Dr. john O'Sullivan, a graduate of the University of Sydney. IEEE once asked the Australian government to give up the wireless network patent and let the world use Wi-Fi technology for free, but it was rejected. The Australian government subsequently won the lawsuit or settled out of court in the United States, and incorporated almost all electrical and telecommunications companies in the world (including Apple, Intel, Lenovo, Dell, AT & amp； T, Sony, Toshiba, Microsoft, Acer, ASUS, etc. ) 20 10/0 Every time we buy an electronic device with Wi-Fi technology, the price paid includes the patent fee paid to the Australian government.
In 20 10, it is estimated that 3 billion electronic devices will use wireless network technology every day in the world. By the end of 20 13, that is, after the expiration of CSIRO's wireless network patent, this number is expected to increase to 5 billion.
Wireless network was praised by Australian media as the most important scientific and technological invention in Australian history, and its inventor john O'Sullivan was called by Australian media? The father of Wi-Fi It has won the highest national science award in Australia and many praises around the world, including the European Inventor Award 20 12 awarded by the European Union, the European Patent Office and the European Patent Office (EPO).
Composition structure of wireless WiFi
Generally speaking, the basic equipment for building a wireless network is the wireless network card and AP, so it can share the network resources with the existing wired architecture in a wireless way, and the construction cost and complexity are much lower than the traditional wired network. If it's just a point-to-point network of several computers, you don't need an AP, just equip each computer with a wireless network card. AP is short for access point. Wireless access point? , or? Bridge? . It mainly acts as a bridge between wireless workstation and wired LAN in MAC of media access control layer. With AP, wireless workstations can connect to the network quickly and conveniently, just like hubs in general wired networks. Especially for the use of broadband, Wi-Fi has more advantages. After the wired broadband network (ADSL, local area network, etc.). ) connect to your home, you can connect an AP, and then install a wireless network card in your computer. It is enough for ordinary families to have an AP. Even after the user's block is authorized, you can surf the Internet in a * * * way without adding a port.
Hardware equipment
With the continuous rise and development of wireless network, the application field of 20 10 wireless network module is quite extensive!
However, Wi-Fi module is a high-frequency product after all. Different from ordinary consumer electronic products, there will be some inexplicable phenomena and problems in production and design, which will make some engineers who have no experience in high-frequency design very entangled, while employees with relevant experience often need expensive equipment to assist in analysis.
For the wireless network part, one design is to lay the Wi-Fi part directly on the PCB motherboard. This design requires courage and technology, because the module itself is not expensive, and the products corresponding to the motherboard are expensive. When there is a problem with the Wi-Fi part, debugging and replacement are very troublesome, and it is a pity to scrap it directly. Therefore, many designs are willing to use the modular Wi-Fi part, which can directly modularize the Wi-Fi part, which is convenient to handle, and the module can be directly disassembled, which is also very helpful for the design risk and specific loss of the product.
Consult relevant Wi-Fi modules for specific hardware design, and consider the following aspects clearly:
Communication interface: 20 10 basically adopts USB interface, and there are a few PCIE and SDIO. The market share of PCIE should be small, and the all-in-one machine is expensive and not practical. Many integrated functions will not be used, which is actually a waste.
Power supply: Most of them use 5V direct power supply, and some will use the power supply in the motherboard design to directly use 3.3V power supply.
Antenna processing form: there can be built-in PCB onboard antenna or ceramic antenna; You can also connect the antenna extension cable through the I-PEX connector, and then make the antenna external.
Specifications and dimensions: this can be based on specific design requirements, and the smallest one is the nano model (which can be directly used as a nano wireless network card); There are probably 12* 12 that can be miniaturized (generally using external antennas); Usually the design is around 25* 12 (basically there are many onboard antennas and ceramic antennas, as well as external antenna connectors).
Connection form with motherboard: SMT directly or plug-in connection through 2.54 pin arrangement (which is convenient for assembly/maintenance).
Software debugging should be combined with specific master control. After all, the Wi-Fi part is just a wireless transceiver. Many users are easily confused when consulting! It can be said that the most popular field of Wi-Fi module application in 20 13 years is the MID market. At the same time, some traditional network application markets have also penetrated, such as some industrial control fields/network broadcasting fields/even some remote control fields. Basically, everyone who can use the network wants to try wireless!
Network protocol of wireless WiFi
Wi-Fi connection point network members and structure stations are the most basic parts of the network.
Basic service set (BSS) is the most basic service unit in the network. The simplest service unit can only contain two sites. Sites can be dynamically associated with basic service units.
Distribution system. The power distribution system is used to connect different basic service units. The media used by the distribution system is logically different from the media used by the basic service unit, although they may be physically the same media, such as the same radio frequency band.
Access point (AP). The access point not only has the identity of an ordinary station, but also has the function of accessing the distributed system.
Extended Service Set (ESS). It consists of distribution system and basic service unit. This combination is logical, not physical-different basic service units may be geographically far apart. The distribution system can also use various technologies.
The gateway is also a logical component. Used to connect wireless LAN and wired LAN or other networks.
There are three kinds of media, the wireless media used by the site, the media used by the distribution system, and the media used by other LANs integrated with the wireless LAN. They may overlap each other physically.
IEEE802. 1 1 is only responsible for addressing on the wireless medium used by the site. The addressing of distribution system and other local area networks is beyond the scope of wireless local area networks.
IEEE802. 1 1 does not specifically define the distribution system, but only defines the services that the distribution system should provide. The whole WLAN defines 9 services, among which 5 services belong to the tasks of distributed system, namely, association, disassociation, distribution, integration and reassociation.
Four services belong to the tasks of the site, namely authentication, verification, privacy and MAC data transmission.
Authentication type of wireless WiFi
The certification categories announced by the former Wi-Fi Alliance are:
* wpa/wpa2: wpa/wpa2 is a test program based on IEEE802. 1 1a, 802.1b, 802. 1 1g single-mode, dual-mode or dual-band products. The content includes the verification of communication protocol, the verification of wireless network security mechanism, the performance and compatibility test of network transmission.
*WMM(Wi-Fi Multimedia): When audio-visual multimedia is transmitted through wireless network, the purpose of WMM test is to verify whether the bandwidth guarantee mechanism works normally under different wireless network devices and different security settings.
* WMM power saving: How to extend the battery life without affecting its function by managing the standby time of wireless network equipment when transmitting audio-visual multimedia through wireless network can be verified by WMM power saving.
*WPS(Wi-Fi Protected Setup): This certification was issued in early 2007, aiming at enabling consumers to set up wireless network equipment in a simpler way and ensuring certain security. At present, WPS allows setting wireless network devices through Pin input configuration (PIN), button configuration (PBC), USB flash drive configuration (UFD), near field communication and contactless token configuration (NFC).
*ASD(Application Specific Device): This refers to wireless network devices with special applications except wireless network access points and stations, such as DVD players, projectors, printers, etc.
*CWG (Converged Wireless Group): It is mainly the test procedure for measuring the RF part of Wi-Fi mobile convergence equipment.
Development prospect of wireless WiFi
Convergence 3G
From the comprehensive analysis of coverage, transmission rate, basic service category, mobile rate, forward expansion and evolution trend, 3G and WLAN are complementary.
For GPRS, CDMA 1x, 1xRTT, EV-DO, EV-DV and other technologies, the symmetry of uplink and downlink data services is an obvious advantage of Wi-Fi. Wi-Fi also has an absolute advantage for the data rate of 2Mbit in 3G rooms. At present, the standard of 802. 1 1b is adopted, the theoretical data rate can reach 1/mbit, and the actual physical layer data rate supports1,2, 5.5 and 165438. With the development and perfection of 802. 1 1g/a, 802. 16e, 802.1I, WiMAX and other technologies and protocol standards, as well as the rapid response ability of Wi-Fi alliance to the market, Wi-Fi Among them, as the successor standard of 802. 1 1b, 802. 16 (WiMAX worldwide interoperability for microwave access) was officially approved in June 2003. Although it uses a different frequency band (10-66GHz) from 802.1b, as a wireless metropolitan area network (WMAN) technology, it can complement 802. 1 1b/g/a wireless access hotspot. Wi-Fi/WiMAX, as a wireless extension technology of wired and DSL, provides real wireless broadband access service for mobile users with its mobility and flexibility, which extends the bandwidth characteristics and QoS quality of traditional broadband access technology.
For Wi-Fi technology, roaming, handover, security, interference and other aspects are the key points that operators need to consider when networking. With the increase of the capacity and transmission rate of backbone transmission network, whether using plane or two-layer architecture, it will not affect the fast broadband access of users; With the continuous improvement of IAPP and MobileIP technologies and the development of IPv6, roaming and handover problems will be finally solved. 802. The emergence of11I standard will provide more security policies, including WPA2 and multimedia authentication. Mature networking scheme and interference pre-detection mechanism can reduce the interference caused by frequency resource development.
The market goal of Wi-Fi/WiMAX is to become the broadband wireless access technology of metropolitan area network, and the basic goal is to provide a broadband wireless access mode that can effectively interoperate in the multi-vendor environment of metropolitan area network, and realize the basic market positioning of personal mobile phone terminals that conform to 3G standards, take WWAN as the basic mode, take public voice and multimedia data as the content, and roam around the world. Wi-Fi/WiMAX can also be used as a supplement to 3G wireless wide area/metropolitan area and multipoint base station interconnection support means.
The development direction of Wi-Fi/WiMAX includes: network technology, covering a wider range, from hot spots to hot spots to the whole city; Wi-Fi handheld terminal and VoWLAN service will inevitably become potential application modes; Wi-Fi/WiMAX switching technology based on IP and open service platform will make WLAN network more intelligent and easy to manage. Multi-level security policies (WEP, WPA, WPA2, AES, etc. Providing different levels of security schemes will enable enterprises and individual users to choose security strategies that meet their own needs according to different cost performance.
1. Network architecture based on all IP
Neither commercial nor experimental (CDMA 2000/WCDMA 99/R4/TD-SCDMA) 3G standard is an all-IP network. For example, CDMA 2000WCDMA99/TD-SCDMA based on ANSI-4 1 is based on traditional GSM-MAP and R4 softswitch, and it was not until R5 introduced IMS that the all-IP core network was realized. Obviously, the all-IP core network is also the development direction of 3G. All-IP-based core network can not only develop independently from wireless access modes, but also support various wireless access modes including Wi-Fi/WiMAX, WCDMA and Bluetooth. In R6 of 3G, WLAN and 3G are considered together.
2.*** Use an open business platform and operation support system.
Wi-Fi/WiMAX and 3G have different bearer characteristics (throughput, delay, QoS, symmetry, etc.). ) provide users with more access options and enjoy voice, data and multimedia services. They can integrate different business engines through an open business platform to realize inter-network interoperability; According to the performance in the network service area, users can manually or automatically choose which network to access; The operation support system that supports both WLAN and 3G networks can realize unified operation management, billing and even user identity authentication of dual networks, and minimize the cost of network construction and maintenance.