Read WIFI wireless network technology in one article

WIFI wireless network in the category of wireless local area network refers to "wireless compatibility certification", which is essentially a kind of commercial authentication, and also a wireless networking technology. Previously connected to a computer through a network cable, and wireless fidelity is through radio waves. Networking; common is a wireless router, then the wireless wave coverage of this wireless router can be wirelessly connected using a wireless fidelity connection. If the wireless router is connected to an ADSL line or other Internet line, it is called It is a hot spot.
A wireless network is a technology that can wirelessly connect terminals such as personal computers and handheld devices (such as PDAs and mobile phones). Wi-Fi is a brand of wireless network communication technology and is owned by the Wi-Fi Alliance. The goal is to improve interoperability between wireless network products based on the IEEE 802.11 standard. Some people use the LAN that uses the IEEE 802.11 family of protocols as wireless fidelity. Even equating wireless fidelity with wireless internet (Wi-Fi is an important component of WLAN)

The main function
WIFIWIFI wireless Internet access can be easily understood as wireless Internet access. Almost all smart phones, tablets and laptops support wireless fidelity Internet access. It is the most widely used wireless network transmission technology. In fact, it is to convert the wired network signal into a wireless signal, just as introduced at the beginning, using a wireless router to support related computers, mobile phones, tablets, etc. to support its technology. If the mobile phone has wireless fidelity function, when there is a Wi-Fi wireless signal, it can not access the Internet through the mobile Unicom network, saving the traffic fee.
Wireless network wireless Internet access is more common in big cities. Although the wireless communication quality transmitted by wireless fidelity technology is not very good, the data security performance is worse than Bluetooth, and the transmission quality needs to be improved, but the transmission speed is very fast, which can reach 54Mbps. Personal and social informatization needs. The main advantage of wireless fidelity is that it does not require wiring and can be free from the restrictions of wiring conditions, so it is very suitable for the needs of mobile office users, and because the transmitted signal power is lower than 100mw, lower than the mobile phone transmit power, so wireless fidelity is relatively It is also the safest and healthiest.
However, the wireless fidelity signal is also provided by the wired network, such as home ADSL, cell broadband, etc., as long as a wireless router is connected, the wired signal can be converted into a wireless fidelity signal. Many developed countries in the world are covered with wireless fidelity signals provided by the government or large companies for residents to use. There are also many places in China that implement the "wireless city" project to promote this technology. In pilot cities where 4G licenses are not issued, many places use 4G to wireless fidelity for the public to try.
Applications Network Media Since the frequency bands of wireless networks do not require any telecom operation licenses worldwide, WLAN wireless devices provide a wireless air interface that can be used worldwide and is extremely inexpensive and has a very high data bandwidth. Users can quickly browse the web in the wireless fidelity coverage area and receive calls anytime, anywhere. Other WLAN-based broadband data applications, such as streaming media and online games, are worthy of user expectations. With wireless fidelity, we make long-distance calls (including international long distance calls), browse the web, send and receive emails, download music, digital photo delivery, etc., without worrying about slow and expensive. Wireless fidelity wireless fidelity technology, like Bluetooth technology, is a short-range wireless technology used in offices and homes.
Handheld devices Wireless networks are becoming more widely used on handheld devices, and smartphones are part of it. Unlike the Bluetooth technology that was applied to mobile phones earlier, wireless fidelity has greater coverage and higher transmission rates, so wireless fidelity mobile phones have become the fashion trend of the mobile communication industry in 2010.
Daily leisure
WIFIWIFI 2010 wireless network coverage is more and more extensive in the country, high-end hotels, luxury residential areas, airports and cafes and other areas have wireless fidelity interfaces. When we travel and work, we can use our handheld devices to surf the web in these places. Manufacturers only need to set up "hot spots" in densely populated areas such as airports, stations, coffee shops, libraries, etc., and connect the Internet to the above places through high-speed lines. In this way, since the "hotspot" emits radio waves that can reach tens of meters to 100 meters from the access point, users can take the wireless-fidelity laptop or PDA or mobile phone or psp or ipodtouch to the area. Inside, you can access the Internet at high speed.
You can also buy a wireless router at home to set up a LAN and then you can go online with great pain.
The difference between wireless network and 3G technology is that 3G transmits better when moving at high speed, but it is enough to use wireless fidelity when it is static.
The commercialization of the scale of wireless networks is a rare success precedent worldwide. The problem is concentrated in two aspects: First, large operators do not recognize this model; second, they lack an effective business model. However, wireless local area networks based on wireless network technology have become increasingly popular, which means that it can be easily applied in the future. Once the public presence of the wireless fidelity network exists, the problem of interoperability, high fees, and roaming of operators is solved, and wireless fidelity will transform from a successful technology to a successful business.
Passenger train
At 14:20 on November 28, 2014, China's first passenger train to open WiFi service - Guangzhou to Hong Kong Kowloon T809 train from Guangzhou East Railway Station, marking the Chinese railway began the era of WiFi (wireless network).
After the train WiFi is opened, not only can you watch the high-definition theater of the internal LAN of the car, play community games, but also directly access the external network, brush microblogs, send e-mails, and connect with the world at a bandwidth speed of 10-50 megabytes. [1]
Originating
WIFIWIFI
The wireless network is a wireless network technology defined by IEEE. When the IEEE officially defined the 802.11 standard in 1999, the IEEE selected and determined that the wireless network technology invented by CSIRO is the best wireless network technology in the world. Therefore, CSIRO's wireless network technology standard, It became the core technical standard for wireless fidelity in 2010.
The wireless network technology was invented by the Australian government research institute CSIRO in the 1990s and successfully applied for wireless network technology patents in the United States in 1996. (US Patent Number 5,487,069)
The inventor is a group of graduates from the University of Sydney engineering graduates led by Dr. John O'Sullivan, a graduate of the University of Sydney's engineering department.
The IEEE has asked the Australian government to abandon its wireless network patents and let the world use wireless fidelity technology for free, but it was rejected.
The Australian government subsequently passed the lawsuit or out-of-court settlement in the United States, collecting patents from almost all electrical telecommunications companies in the world (including Apple, Intel, Lenovo, Dell, AT&T, Sony, Toshiba, Microsoft, Acer, Asus, etc.). fee. In 2010, every time we purchased an electronic device with wireless fidelity technology, the price we paid included the wireless fidelity patent royalty paid to the Australian government.
In 2010, there are an estimated 3 billion electronic devices using wireless network technology every day. By the end of 2013, CSIRO's wireless network patents are expected to increase to 5 billion.
The wireless network has been hailed by the Australian media as the most important technological invention in Australia's history. Its inventor John O'Sullivan was called "the father of Wi-Fi" by the Australian media and won the highest national science award in Australia and many accolades from around the world. Including the European Institutions, the European Patent Office, the European Patent Office (EPO), the European Inventor Award 2012, the 2012 European Inventor Award.
Composition
WIFIWIFI is generally equipped with a wireless network card and an AP. This allows wireless network to share network resources with the existing wired architecture. The cost and complexity of installation is much lower than that of traditional wired networks. If you only have a peer-to-peer network of several computers, you can also do not need an AP. You only need to have a wireless network card for each computer. An AP is an abbreviation of Access Point and is generally translated as a "wireless access point" or a "bridge". It mainly acts as a bridge between wireless workstations and wired local area networks in the media access control layer MAC. With an AP, like a Hub for a typical wired network, a wireless workstation can be quickly and easily connected to the network. Especially for the use of broadband, wireless fidelity is more advantageous. After the cable broadband network (ADSL, residential LAN, etc.) arrives at the home, connect to an AP, and then install a wireless network card in the computer. An ordinary family has an AP enough. Even if the user's neighborhood is authorized, you can access the Internet in a shared way without adding a port.
Hardware Devices With the continuous development and development of wireless networks, the application fields of wireless network modules in 2010 are quite extensive!
However, the wireless fidelity module is a high-frequency product. It is not like ordinary consumer electronics. There are some inexplicable phenomena and problems in the production design, so that some engineers without high-frequency design experience are struggling. Practitioners of relevant experience often also need expensive equipment to assist in the analysis.
For the processing of the wireless network part, there is a design that directly Layouts the wireless fidelity part onto the PCB main board. This design requires courage and technology, because the price of the module itself is not high, and the product corresponding to the main board is expensive, when there is wireless The problem caused by the fidelity part is troublesome for debugging and replacement, and it is a pity to scrap directly; therefore, many designs are willing to adopt the modular wireless fidelity part, which can directly make the Wi-Fi part modular, easy to handle, and the module can be directly disassembled. It also helps the design risk and specific wear and tear of the product.
When the specific hardware design should be consulted with the relevant wireless fidelity module, consider the following aspects:
Communication interface: In 2010, it basically adopts the form of USB interface. PCIE and SDIO also have a small part. The market share of PCIE should be small, the price of all-in-one is expensive, and the practicality is not strong. Many functions of integration will not be used. In fact, it is also a waste.
Power supply: Most of them use 5V direct power supply, and some will also use the power supply sharing in the motherboard design, directly using 3.3V power supply.
Antenna processing: It can have a built-in PCB on-board antenna or ceramic antenna; it can also be connected to the antenna extension cable through the I-PEX connector, and then the antenna can be externally placed.
Specifications and dimensions: This can be based on specific design requirements, the smallest nano model (can directly do nano wireless network card); there can be mini type 12*12 (usually used by external antenna); usually 25 *12 points of design multi-point (basically there are many on-board antennas and ceramic antennas, but also external antenna connectors).
Connection with the motherboard: Direct SMT, or 2.54 pin headers for plug-in connection (this assembly/service is easy).
The debugging of the software should be combined with the specific scheme master. After all, the wireless fidelity part is only a wireless transceiver. Many users are confused when they are consulting! It can be said that the most popular field of wireless fidelity module application in 2013 is the MID market, and some traditional network application markets have also penetrated. For example, some industrial control fields/network broadcasting fields/even some remote control fields are also considered, basically Those who can use the network want to try to wireless!
Network Protocol A wireless fidelity connection point network member and structure station (Station), the most basic component of the network.
The Basic Service Set (BSS) is the most basic service unit of the network. The simplest service unit can consist of only two sites. Sites can be dynamically associated into a basic service unit.
Distribution System (DS). The distribution system is used to connect different basic service units. The medium used by the distribution system is logically separate from the medium used by the basic service unit, although they may physically be the same medium, such as the same wireless band.
Access Point (AP). The access point has both the identity of a normal site and the ability to access the distribution system.
Extended Service Set (ESS). It is a combination of a distribution system and a basic service unit. This combination is logical, not physical - different basic service units may be geographically far apart. A variety of techniques are also available for the distribution system.
Portal is also a logical component. Used to connect a wireless LAN to a wired LAN or other network.
There are three mediums, the wireless medium used by the site, the medium used by the distribution system, and the medium used by other LANs integrated with the wireless LAN. Physically they may overlap each other.
IEEE 802.11 is only responsible for addressing on the wireless medium used by the site. Addressing of distribution systems and other local area networks is outside the scope of wireless local area networks.
IEEE 802.11 does not specifically define the distribution system, but only defines the services that the distribution system should provide. Nine services are defined throughout the WLAN.
The five services belong to the tasks of the distribution system, namely, Association, Disassociation, Distribution, Integration, and Reassociation.
The four services belong to the tasks of the site, namely, Authentication, Deauthenation, Privacy, and MSDU delivery.
Main difference
WIFIWIFI wireless fidelity lifting the issue of re-emphasizing wireless fidelity and Bluetooth technology, the same short-range wireless technology, is a network transmission standard. In daily life, it has been widely used and brought great convenience to people: white-collar workers browse the web in Starbucks, reporters send back manuscripts at the conference site, and ordinary people choose mobile phones or multiple computers in their own homes. Wireless Internet access in laptops, these are inseparable from wireless fidelity.
However, since the Ministry of Industry and Information Technology has banned the support of wireless fidelity-enabled mobile phones to obtain network access licenses in China, foreign brands must remove the wireless fidelity module or block the function in order to enter the Chinese mainland market, becoming a “castration version” that many people have dubbed. "Mobile phone.
"If you enter the Chinese market is the 'castration version' iPhone, then the release date is when I go to buy parallel imports." Many iPhone fans who have been banned from wireless fidelity have expressed similar views.
If you want to understand the important reasons why wireless fidelity is banned in China, you have to mention another standard -- the existence of WAPI. The WAPI standard (full name is WLAN authentication and confidentiality infrastructure) introduced in 2003, as a wireless LAN security technology standard independently developed by China and possessing independent intellectual property rights, is different from wireless fidelity. The biggest difference is security encryption. The technology is different. For the sake of Internet security, China has always strongly recommended recommending WAPI as an independent international standard. The reason why the wireless fidelity function of domestic mobile phones has been canceled is because the Wi-Fi protocol is not officially recognized by mainland China.
Was WAPI victory or wireless fidelity disguised China's intention to enforce the WAPI standard on June 1, 2004, but it was resisted by US companies such as Intel and even the US government until WAPI first won the US, UK, and June 2009. The unanimous consent of more than 10 countries, such as France, will be promoted into an international standard in the form of an independent text.
Many people in the industry still remember the battle between WAPI and wireless fidelity before 2010.
At the end of 2003, the General Administration of Quality Supervision, Inspection and Quarantine and the National Standardization Administration issued an announcement stating that the implementation of the WAPI standard will begin from June 1, 2004. The move was immediately resisted by US companies such as Intel and the US government, and threatened to stop doing wireless business in China, claiming that Western companies are more willing to adopt their own standards than the WAPI standard. On April 22, 2004, China and the United States negotiated, and then Vice Premier Wu Yi of the State Council stated that China agreed to the US request and would not enforce the WAPI standard. In July, China officially submitted the WAPI proposal to the International Standards Organization, but after that, China's WAPI standard encountered an unprecedented blockade, and the WAPI standard became an international standard and was forced to run aground.
Who ever thought that this is five years, until June 2009, things have a major turn. The China WAPI Industry Alliance publicly confirmed that at the 2010 International Standards Organization ISO/IECJTC1/SC6 meeting, WAPI was unanimously agreed by more than 10 members of the US, UK and France, and will be promoted to an international standard in the form of an independent text. Some experts regard this incident as "the first time the US has begun to fulfill the 'significant event of 'promoting WAPI to become an international standard'."
According to the latest policy of the Ministry of Industry and Information Technology in 2010, any mobile phone with WAPI function can be tested and admitted to the network. The principle is that this type of mobile phone can use WAPI access when there is a WAPI network, but not when searching for WAPI. Wireless network access via wireless fidelity, but pure wireless fidelity phones are still not available.
Method of operation
WIFIWIFI and non-wireless fidelity network cooperation If you are a T-Mobile Wi-Fi user, but you are now in the hotspot provided by another operator, you can not use Wi-Fi. In the future, your Wi-Fi device will be able to query the "Extranet (other carriers' wireless network)" service and can be securely connected. Your user identity will roam with you, allowing you to use a variety of different Wi-Fi service.
After the introduction of the 802.11u standard, users will be able to use the wireless network more flexibly. In the future, Wi-Fi will be able to advertise their services as long as you obey its terms. You can access other networks according to your identity. A subset of all or part of the service, in an emergency, you can get the most basic connections and features, the 802.11u standard is scheduled to be finalized in June 2010.
Self-managed clients Wireless fidelity device manufacturers have thought of many ways to make their devices work more intelligently with wireless access points. The management of wireless access points is quite mature, but the management of wireless clients is still blank.
If you use the new Wireless Fidelity Management Protocol at both the access point and the client, the collaboration between them will be more interesting.
Imagine your netbook wireless fidelity adapter, or Wi-Fi VoIP phone, saves power when not sending and receiving wireless signals, or sharing only location data, and access points can redirect Wi-Fi voice conferencing to a better one. On a neighboring access point, or redirect to a lower-loaded access point. A Wi-Fi network can locate a client's location, for example, outside the building, or on the street, and can grant client connection operations based on this data.
The 802.11v standard may be completed by the end of July 2010. There will be many enhancements in Wi-Fi management that will add a counter array for statistics collection, increase power management, improve battery life, and improve location data support.
The Wi-Fi Alliance's Wi-Fi Multimedia Admission Control Specification is also addressing client-side coordination issues, which are under development, allowing wireless networks to negotiate and manage streaming sessions, so high-definition video does not cut off the same access point. Wi-Fi voice sessions, the Wi-Fi Alliance is considering specific Wi-Fi to manage the specification, mainly borrowing several related IEEE standards, and then adding additional wireless management functions.
Improving mobility In the previous standards, RF management was lacking because the access point and the client, and the neighboring wireless devices, usually do not know each other. They only know their own radio wave frequency. This limitation makes it possible to manage RF is also very difficult.
For example, when a Wi-Fi phone enters an access point range, it triggers a blind search process if the client can ask its access point "Who is your neighbor and which one is the best connection access point?" "This allows devices and networks to collaborate better. At the same time, Wi-Fi access points can "see" the client's RF environment, identify weak or insufficient coverage, and then take steps to optimize the connection.
The IEEE 802.11k radio resource management standard, released in 2011, addresses this issue by improving mobility through intelligent RF (radio frequency) management, but Wi-Fi equipment manufacturers have implemented a range of proprietary features to address this challenge, Aruba An example of this is the 2.0 version of the wireless management technology.
At the same time, the Wi-Fi Alliance uses some of its features of 11k to conceive its voice enterprise certification, with the goal of optimizing the quality of large-scale, enterprise-class Wi-Fi voice environments.
Personal area wireless fidelity is an end-to-end connection. In the future wireless fidelity network, your device can be directly connected to other client devices wherever you are. For example, Ozmo devices equipped with low-power chips allow peripheral devices to pass Wi- Fi is directly connected to your laptop.
The Wi-Fi Alliance's latest Wi-Fi Direct (WFD) project will let your wireless fidelity card on your laptop bypass the access point and connect directly to a wireless printer, digital camera, projector, sensor or plasma screen. As an industry specification, WFD will introduce a new protocol implementation in the firmware so that no hardware changes are required.
At the same time, the wireless fidelity access point can also become a point-to-point connection engine through the 802.11z standard (scheduled for July 2010), which will provide extensions for direct connection configuration, and client devices request permission to connect directly from an access point. To another nearby client device, but the data does not pass through the access point, the client is still connected to the access point, and the access point provides a full set of security and management services.
Acceleration method In most cases, the wireless fidelity speed is accelerated by setting a fixed protocol.
The first step is to remove the connected wireless fidelity in the phone, that is, choose not to save! (The differences in the versions are also different.)
In the second step, enter 192.168.1.1 or 192.168.0.1 (local) in the browser to enter the router's control panel and select the setup wizard.
The third step is to change the mode to 11g Only. The default is 11bgn Mixed.
The fourth step is to restart the router and then reconnect the wireless fidelity to the phone.
(Note: The above method is only compatible with the wireless fidelity terminal, it is useless for speed increase, and for the N years ago, the current device can be automatically adapted, no need to make this setting.)
Wireless fidelity sharing method In the absence of wireless fidelity equipment, iPhone, Pad can not use wireless fidelity is a very depressing thing, but you can use the dos command of Win7 system to turn the notebook into a wireless AP transmitter . To provide Internet access to devices such as iPhone and Pad.
Open the Win7 Start menu, find the command prompt option, and run as an administrator.
On the command line, enter netsh wlan set hostednetwork mode=allow ssid=scc_wan key=1*197k51*. This string command starts the virtual wireless network card function that comes with win7 system. "scc_wan" is SSID, "1* 197k51*" is the wireless access password. The mode parameter is used to specify whether to enable the system to bring the virtual wireless network card. If the parameter is set to allow to enable the virtual wireless network card, disallow means disabled.
Return to the control panel, double-click the "Network and Sharing Center" icon, click the Change Adapter Settings button, you will find a "Microsoft Virtual Wi-Fi Adapter" icon, indicating that the virtual wireless AP device has been successfully started.
To share the Internet network, right-click the local adapter property that can access the Internet in the Network Neighborhood property. In the Properties dialog box of the target network connection, click the "Share" tab, and select "Allow other users to pass this computer" in the corresponding settings page. The internet connection is connected to the "etc. option, while selecting the previously configured wireless network in the list, then pressing the OK button.
5. Go back to the command prompt and type netsh wlan start hostednetwork to start the virtual wireless service.
Devices such as the iPhone and Pad can access the Internet via this virtual wireless network.
Feature introduction
WIFIWIFI wireless popularity, Wi-Fi has become a "superstar." Wi-Fi is a "golden helmet armor" that packs itself in eight ways. The following sections analyze the uniqueness of Wi-Fi from bandwidth, signal, power consumption, security, networking, personal services, mobile features, and client-side.
Wider bandwidth Although the IEEE has initiated two projects to increase the 802.11 standard data rate to gigabits or gigabits, it has not yet been drafted.
More practically, the 802.11n standard increases the data rate by one level and can accommodate different functions and devices. All 11n radios support two spatial streams, and two or three antenna combinations can be used to send and receive data. Apple's latest Wi-Fi iPod Touch includes a Broadcom wireless chip that supports the 11n standard.
Soon there will be chips supporting three or four data streams with data rates of 450 Mbps and 600 Mbps, respectively. At the beginning of 2009, Quantenna Communications stated that it has developed a 4x4 chip that can carry high-definition digital TV signal streams.
William Kish, co-founder and CTO of wireless fidelity equipment provider Ruckus Wireless, said: "Although there are not many client devices supporting four spatial streams, as long as the access points are properly designed, the 600 Mbps physical layer data rate can be used to achieve high speed. Wireless backbone network."
You can connect these high-end nodes through the 802.11s standard to form an Internet-like redundant Wi-Fi network.
Stronger RF signal
More optional performance features in 11n will appear in wireless chips, and wireless clients and wireless access points can use these chips to make radio frequency (RF) signals more flexible, stable and reliable, in other words more like a wire.
William McFarland, CTO of wireless chip maker Atheros, said: "The new 11n physical layer technology will make Wi-Fi more powerful, with higher data rates and longer transmission distances in a given range."
These performance features include: low-density parity check code for improved error correction; transmit beamforming, which uses feedback from Wi-Fi clients to allow an access point to centrally process the client's RF signal; space-time block coding (STBC), It uses multiple antennas to improve signal reliability.
McFarland said: "Now you take a Wi-Fi-enabled notebook around the building for a week, you will find that the data rate drops or disappears, but after using STBC, the connection will continue to work."
Wi-Fi power consumption is lower
802.11n has made significant innovations in power consumption and management that not only extend the battery life of Wi-Fi smartphones, but also embed them in other devices such as medical monitoring equipment, building control systems, real-time location tracking tags and consumer electronics. . Data can be continuously monitored and collected, and can be personalized based on the user's identity and location.
Craig Mathias, a blogger at Network World, wrote, "Other modern RF technologies can't do it, and now Wi-Fi can do it."
Atheros' McFarland said: "With the construction of enterprise wireless LANs, these infrastructures are in place, and now only need to add low-power sensors."
The 802.11a wireless communication announced by the Embedded Wi-Fi Wireless Data Communications Manufacturers Summit is available in a variety of plug-ins, allowing devices to use the uncongested 5GHz band. Gainspan offers 11b/g wireless devices with an IP software stack for power consumption. Very low, a standard battery can run for a few years, and Redpine Signals provides a single stream embedded in 11n wireless communication.
Improved security The most devastating impact of the Internet is through theft of identity, denial of service attacks, privacy violations, spying and the lack of appropriate means of trust to harm users, mobile networks make this situation worse, if users Trusting the currently open Wi-Fi connection may expose them to devastating risks.
The IEEE has approved the 802.11w standard, which protects wireless management frames and makes wireless links work better. Matthew Gast, principal analyst at Networks, said: "Wi-Fi clients can now receive and adopt 'landing network' information, This information may have been forged by the hacker who broke the access point using the MAC address, and the 11w standard cut off the attack."
Michael Tennefoss, director of strategic marketing at Aruba Network, said: "Wi-Fi will use identity-based security. In Wi-Fi networks, security policies are associated with users, not ports, so the benefit is that users can be at home. Offices, hotels, branches and public places move, security will not be affected."
Wi-Fi signal map According to the British "Daily Mail" reported on June 19, Luis Hernan, a Ph.D. student at Newcastle University in the United Kingdom, has drawn a series of pictures showing the Wi-Fi connection of invisible networks around humans. These bright beams surrounded by circles are like ghosts.
Hernan first used custom instruments to take photos of Wi-Fi signals to show them. The instrument continuously scans the Wi-Fi network and turns the signal strength into a color LED. Hernan eventually got entangled curled colored light stripes.
Technical parameters
The types of certifications announced by the WIFIWIFI pre-Wi-Fi Alliance are:
*WPA/WPA2: WPA/WPA2 is a test program based on IEEE802.11a, 802.11b, 802.11g single-mode, dual-mode or dual-band products. The content includes verification of communication protocols, verification of wireless network security mechanisms, and network transmission performance and compatibility testing.
*WMM (Wi-Fi MultiMedia): How to verify whether the bandwidth guarantee mechanism works normally when audio and video multimedia is transmitted through the wireless network. It is the purpose of WMM test on different wireless network devices and different security settings. .
* WMM Power Save: How to extend the battery life by managing the standby time of the wireless network device when the audio and video multimedia is transmitted through the wireless network, without affecting its functionality, can be verified by the WMM Power Save test.
*WPS (Wi-Fi Protected Setup): This is a certification that was released in early 2007 to allow consumers to set up wireless network devices in an easier way and to ensure a certain level of security. The current WPS allows the wireless network device to be set by means of Pin Input Config (PIN), Push Button Config (PBC), USB Flash Drive Config (UFD), and Near Field Communication, and Contactless Token Config (NFC).
*ASD (Application Specific Device): This is for wireless network devices with special applications other than wireless network access points (Access Point) and stations (Station), such as DVD players, projectors, printers, etc.
*CWG (Converged Wireless Group): Mainly for the test procedure of the RF part measurement of Wi-Fi mobile converged devices.
Channel frequency channel frequency (MHz)
1 2412
2 2417
3 2422
4 2427
5 2432
6 2437
7 2442
8 2447
9 2452
10 2457
11 2462
12 2467
13 2472
14 2484

Development prospects fold fusion 3G
WIFIWIFI
Since 2003, the hotspots of China's mobile communication technology and market have been concentrated on the timing of the introduction of 3G and the discussion of what standards should be adopted by 3G.
Although the level of attention to 3G has reached unprecedented heights with the promotion of domestic and foreign equipment manufacturers, publicity and government support, we should be more aware of the current status of China's 3G development: its technology maturity and lack of killer business. , construction costs, operating license fees and poor development of the European market and other factors, China's mobile communications market has been slow to start, operators, equipment manufacturers, chip manufacturers, research institutes, content providers have a common expectation The rise of 3G has not yet been realized.
From the perspective of China's 3G market in the future, voice services will not help mobile operators to increase revenue, and because of the increase in the number of mobile operators, the ARPU brought by voice services will inevitably decline. Therefore, providing more data multimedia services will help the mobile operators to maintain user loyalty, improve network utilization, increase service added value, and maximize profits. This is also the pre-deployment of 3G operators. The issues that must be considered. In contrast, with the joint promotion of chip manufacturers, PC manufacturers, Wi-Fi Alliance members, and operators, WLAN has made substantial progress in deployment. China Telecom, China Netcom, China Mobile and China Unicom are all implementing their own hotspot coverage plans. In the previous period, there was even a WLAN instead of 3G. However, from the comprehensive analysis of coverage, transmission rate, basic service category, mobile speed, forward expansion, and evolution, 3G and WLAN are not a competitive relationship that can replace each other, but a complementary relationship that can foster strengths and avoid weaknesses. . Currently, the promotion and certification of WLAN is mainly done by the industry standard organization Wi-Fi Alliance, so WLAN technology is often called Wi-Fi.
For GPRS, CDMA1x, 1xRTT, EV-DO, EV-DV and other technologies, the symmetry of uplink and downlink data services is a clear advantage of wireless fidelity. For 2Mbit data rate in 3G indoors, wireless fidelity also has an absolute advantage. It currently uses the 802.11b standard, and the theoretical data rate can reach 11Mbit. The actual physical layer data rate supports 1, 2, 5.5, and 11Mbit adjustable. The range is from 100-300m. With the development and improvement of technologies and protocol standards such as 802.11g/a, 802.16e, 802.11i, WiMAX, and the rapid response of the wireless fidelity alliance to the market, Wi-Fi is entering a stage of rapid development. Among them, 802.16 (WiMAX Worldwide Interoperability for Microwave Access), which is the successor to 802.11b development, has been officially approved in January 2003, although it uses a different frequency band than 802.11b (10-66GHz). )，但是作为一项无线城域网(WMAN)技术，它可以和802.11b/g/a无线接入热点互为补充，构筑一个完全覆盖城域的宽带无线技术。 Wi-Fi/WiMAX作为Cable和DSL的无线扩展技术，它的移动性与灵活性为移动用户提供了真正的无线宽带接入服务，实现了对传统宽带接入技术的带宽特性和QoS服务质量的延伸。
纵观2013年全球市场趋势，固网运营商和有线电视运营商的Wi-Fi部署需求保持了稳定增长，移动运营商的Wi-Fi部署需求则实现了爆发式的增长，这使得2013年运营商级Wi-Fi市场整体保持了强劲的增长势头。移动运营商已经有能力把20%~30%的移动宽带流量承载于Wi-Fi网络上。
全球运营商级Wi-Fi设备收入2013年全年达到7.13亿美元，相比2012年增幅高达47%。预计全球运营商级Wi-Fi设备收入在2014年全年有望达到12亿美元，相比2013年同比增长64%，2018年将达到31亿美元，近5年的复合年增长率将高达34.2%。
在Wi-Fi应用标准方面，802.11n设备仍然是2013年Wi-Fi市场绝对的主流，少数运营商开始关注802.11ac设备的采购。随着802.11ac第二波技术的不断成熟以及802.11ac终端的普及，预计2015年开始802.11ac的设备将逐渐成为主流。
对于无线保真技术而言，漫游、切换、安全、干扰等方面都是运营商组网时需考虑的重点。随着骨干传输网容量和传输速率的提高，无论采用平面或者两层的架构都不会影响到用户的宽带快速接入；随着IAPP以及MobileIP技术的完善、IPv6的发展也可以最终解决漫游和切换的问题；802.11i标准的产生将提供更多的包括WPA2、多媒体认证等安全策略；不断成熟的组网方案和干扰预检测机制都可以减少频率资源开发带来的干扰。
事实上，不同的标准化组织的工作与各类标准的制订，正是NGN发展进程中各方加强合作与标准融合工作的体现。Wi-Fi/WiMAX的市场目标是成为宽带无线接入城域网技术，基本目标是要提供一种城域网领域点对多点的多厂商环境下可有效地互操作的宽带无线接入手段，以实现满足3G标准的以无线广域网WWAN为基本模式、以公众语音及多媒体数据为内容、在全球范围内漫游的个人手机终端的基本市场定位。Wi-Fi/WiMAX也可以作为3G无线广域/城域、多点基站互联支持手段的补充。
按NGN概念演进的下一代移动网，以终端、应用、服务为主导将成为市场发展的重要驱动力也是运营商赢利的关键。其互操作性和后向兼容性将成为不同标准化组织的工作考虑的一个重点。如果进行无生命力的重覆，其产品和技术终将为市场所淘汰，其唯一出路是在NGN及3G演进的基本概念上彼此融合，共同作出贡献。而且随着Wi-Fi/WiMAX接入技术成本的逐步下降，电信运营商选择Wi-Fi/WiMAX技术为消费者提供VoWLAN语音服务将成为可能。
综上所述，Wi-Fi/WiMAX的发展方向包括：
*网络技术，覆盖更大的范围，从热点到热区到整个城市；
*Wi-Fi手持终端和VoWLAN业务必然成为潜在的应用模式；WIFIWIFI
*基于IP的Wi-Fi/WiMAX的交换技术和开放的业务平台，将使WLAN网络更智能、更易管理；
*基于多层次的安全策略(WEP、WPA、WPA2、AES、VPN等）提供不同等级的安全方案，将使企业、个人用户可以根据不同的性价比来选择满足自己需要的安全策略。
1.基于全IP的网络架构 不管是商用的还是正在试验的(CDMA2000/WCDMAR99/R4/TD-SCDMA）3G标准都不是基于全IP的网络，比如CDMA2000是基于ANSI-41；WCDMA99/TD-SCDMA是基于传统的GSM-MAP、R4软交换的承载和控制分离方式，而直到R5引入了IMS才实现全IP的核心网。显然全IP的核心网络也是3G发展的方向，采用基于全IP的核心网不但可以与无线接入方式独立地发展，还可以支持包括Wi-Fi/WiMAX、WCDMA、Bluetooth等多种无线接入方式。在3G的R6中已经开始把WLAN和3G一同考虑了。
2.共用开放的业务平台和运营支撑系统
Wi-Fi/WiMAX和3G不同的承载特性（吞吐量、延时、QoS、对称性等）为用户享受语音、数据、多媒体业务提供更多的接入方式选择；它们可通过共用开放的业务平台融合不同的业务引擎实现网络间互通；根据网络服务区内的性能，用户可以手工或者自动选择接入那个网络；同时支持WLAN和3G网络的运营支撑系统，可以对双网实现统一的运营管理、计费、甚至用户身份认证，最大限度降低网络建设、维护成本。
应用的互补 两种网络技术在移动通信技术发展中将实现局部的融合，各自发挥优势、扬长避短，互补趋势集中体现在以下几个方面：
1. 语音和VoWLAN
相对于满足大话务量、多用户数的3G技术，基于IP技术的WLAN网络更适合开展广播式的语音业务(PTT、
多方会议、长途通话、广告发布等。
2. 广域覆盖和区域覆盖下的数据业务 相对于3G技术覆盖范围大、快速移动时仍能保持144kbit的数据速率的特点，WLAN技术在特定区域内满足用户高速数据传输的需求具有绝对优势。
3. 无线信道资源的利用
3G分配的频率资源是有限的，而数据业务对信道的占用率极高，影响其同时接入的语音用户数量。如果规划特定区域（比如商业中心人群密集区）内把数据业务转移到Wi-Fi/WiMAX的公共数据通道无疑将大大提高3G无线网络资源利用率。
4. 手持终端和Laptop/PDA结合 传输数据速率高、AlwaysOnLine和低使用费的Laptop/PDA可以满足商业用户大信息量的需求：携带更为方便、小巧的3G手持终端可以满足个人用户对快速消息的需求。
5. 手机和电脑连接再也不用有线了，无线全能搞定。
商业运作
WIFIWIFI当前不少智能手机与多数平板电脑都支持无线保真上网，无线保真是当前大部分人所希望能随时搜索到的。它不仅是无线宽带接入服务的补充，同时还是运营商创新运营的重要一环。从全球无线保真业务发展上看，只依靠提供单一的无线宽带接入实现盈利的方式，基本上都无法支撑Wi-Fi业务的发展。面对这种情况，迫切需要一种新的盈利模式来为无线保真的发展提供强有力的支撑，保证投入的同时能有所回报。Wi-Fi广告模式，显然是当前比较成熟和可经营的模式，并且，Wi-Fi广告模式的探索正呈现出以下几个新方向。
方向1：区域电子地图 以Wi-Fi登录Portal页面的区域电子地图为基础进行的广告模式，即基于热点的不同位置，Wi-Fi用户会看到当前所在热点及其周围区域的电子地图，运营商可利用区域地图对热点周围商家继续进行广告宣传和标注。Wi-Fi门户的地图上注有鼠标停留短语，用户在区域地图上移动鼠标会显示不同商家的最新信息和链接，当点击任一广告，便进入这一商户的网页界面，商家可在后台更新自己的商家信息，运营商负责页面的维护和统一管理。这一模式对于用户来说，不仅可以找到离自己最近的商家、餐馆、自动取款机、加油站、电影院、医院等周边生活信息，以及使用地图导航、查询移动黄页等业务，而且还能找到诸如“最近的电影院即将上演的影片”或“该餐馆的消费水平、饭菜口味如何”等更深层的信息。
对广告主的好处：Wi-Fi电子地图广告可将广告推广和先进安全的无线网络技术合二为一，使商家广告宣传结合信息完备的地图，贴近距离最近的潜在客户，使热点上网的顾客能够就近方便地找到商家的地理位置。
对运营商的好处：利用顾客喜欢就近购买、省时方便的消费行为，使Wi-Fi单个热点变成一个个商圈，热点越多，其广告的商业价值就越大。
方向2：个性化Portal页面 在Wi-Fi账号登录页面及登录后弹出页面上放置商家个性化广告或市场调研选项，也可以为每个热点的商家独立设置其个性化Portal页面，收取广告定制及发布费。这种模式的主要特点是，运营商拥有页面的控制权，商家可以利用其特定页面发布广告信息。
对广告主的好处：特定个性化广告页面直达Wi-Fi用户，让用户在上网第一时间接触到商家的广告或市场调研选项，既凸显商家的形象，又是进行市场调研的一种好方法。
对运营商的好处：利用账号登录页面及登录后弹出页面这一特有资源，可以为Portal定制“VLAN+端口+IP地址”的个性化认证页面，同时可以在Portal页面上开展广告业务，内置服务选择和信息发布等内容，进行业务拓展，实现Wi-Fi网络的运营。
方向3：地理位置定位 利用Wi-Fi热点地理位置可定位的特点来开展广告服务，广告主通过选择特定的地域和热点来推送广告，使广告主的广告能吸引最有可能购买其产品的潜在客户。同时，广告主还可以针对不同地理区域制定相应的特价促销或优惠活动方案，使广告的投放更加精准，更有针对性，能将定制化的信息推送到Wi-Fi用户，进行有效的广告宣传。例如，旅游服务类的广告主可针对机场Wi-Fi热点目标客户群，推送它们的广告，咖啡行业的广告主可以在咖啡吧等特定的Wi-Fi热点通过推送选项式广告去了解和发现目标客户群的习惯。
对广告主的好处：此模式能够根据商家的意愿和爱好，通过不同热点或地理位置，有意识地选择需要投放广告的客户群，从而能够精准，有效地进行广告营销。
对运营商的好处：Wi-Fi运营商能通过IP和VLAN对不同热点进行区隔，可有效细分客户群，使不同热点、不同场景的客户群呈现不同的消费特征，从而满足广告主对目标客户群精确投放的要求。
方向4：广告换取Wi-Fi免费
Wi-Fi的上网接入一般都是通过输入账号付费来实现的，而“通过观看广告可以免费上网”的运营模式将改变这单一的状况，转变成“后向付费”的运营模式，即前向用户使用Wi-Fi接入上网时是“零付费”。所谓“后向付费”是指由后向的广告主付费，而使用无线网络的用户则不用支付网络服务费。这一模式的典型使用场景是：上网者在登录Wi-Fi网络之前，需要观看登录页面上的广告，或者点击市场调查选项按钮等，用户只要选择并提交后就可免费上网。时间可由运营商设定，如30分钟，用户上网30分钟后，页面又会自动回到新的一组广告页面，只要用户再去看广告或继续点选，才可以再免费30分钟上网。
对广告主的好处：由于浏览广告或点选按钮是用户免费上网的必经之路，所以，商家广告的浏览量就有了保证，商家的市场调查也有了广泛的基础，在Wi-Fi上做广告就变得有价值。比如：在人口集中的街道、广场、咖啡馆、酒吧、餐馆、地铁等区域布设热点(可以以免费帮助商户设立热点的方式进行)，并对外销售广告，广告主甚至可以指定某一区域的热点显示广告。
对运营商的好处：这种模式会降低Wi-Fi上网的门槛，增加用户数量。用户数量增加，则Wi-Fi使用量增加，广告的价值也就提升了。这种模式与付费模式要有一定的区隔，如付费用户会享受比免费用户更高的带宽，这样，才会不影响用户体验。
方向5：共建“吸引力”内容
Wi-Fi运营商与合作伙伴在Wi-Fi门户上共建“Wi-Fi Zone”内容区，“Wi-Fi Zone”里有能够吸引用户的“吸引力”内容，“吸引力”内容包括：精彩电影播放、音乐下载、优惠促销信息、活动信息、体验信息、网上冲印等，商家的广告穿插在相应的内容中，依靠“吸引力”内容被用户浏览。
对广告主的好处：通过“吸引力”内容，使广告浏览量增加，效果得到强化，同时有些商家的品牌促销广告也可以是“吸引力”内容的一部分。如在星巴克的用户，在消费的同时，可以收到店内各种优惠销售的信息 对运营商的好处：运营商与商家合作建立“Wi-Fi Zone”内容，可以吸引更多用户上网浏览其内容，创立优秀的内容品牌，并能与合作伙伴建立长久稳定的关系。同时，运营商也可以与商家合作推出诸如“Wi-Fi Zone”卡等产品，卡内既含账号密码信息，用户又可以持卡享受到“Wi-Fi Zone”的商家优惠，这一共赢模式会吸引商家在“Wi-Fi Zone”进行广告投入。
由此可见，在网络迅猛发展的今天，运营商可以通过尝试Wi-Fi商业模式的创新来探索Wi-Fi发展新的经营之道；目前国内的Wi-Fi商业模式主要是广告，根据这一模式国内领先的Wi-Fi服务商witown开发出了一套Wi-Fi营销系统，将中小企业的闲置Wi-Fi改造成商用营销型Wi-Fi；不仅有企业级的路由功能，还可以通过Wi-Fi展示企业品牌0成本全天候推送广告等功能，相信不久会在国内的中小企业中刮起一股旋风。随着Wi-Fi网络建设的加速，热点会越来越多，基于无线上网的Wi-Fi创新应用也一定会有更大的市场空间。
构建物联
WIFIWIFI
5G嵌入式Wi-Fi模块应用车联网 物联网等信息化技术是建设智慧城市的手段和工具，是承载智慧城市建设的基础设施。在互联网技术日益发达的今天，云计算、物联网、车联网等新技术层出不穷，这些新技术也反哺互联网，让互联网技术本身获得史无前例的快速发展。
而车联网的出现或许能够改变在互联网冲击下的通信产业的当前现状，如果传统运营商抓住时代所赋予的先机，对于通信业，焕发第二春不是不无可能，夺回行业话语权也将指日可待。
车辆是城市的重要组成部分，中国的机动车总保有量已经达到2.33亿辆，仅次于美国，基于这个庞大的汽车保有量，“车联网”应运而生。如此可观的数字后面，带来的是多种问题，如交通堵塞、环境污染等，车联网作为中国打造智慧城市的重要动力;而客户增多和需求上升，为车联网的发展提供商业市场。
据美国科技媒体报道，这个史无前例的项目由密歇根大学交通研究中心(UMTRI)管理，在未来12个月内，约3000辆车将列入计划。司机都是特别招聘的，因为他们经常在AnnArbor四分之一圆范围内活动。每辆车通过专用短程通信通道连接，这个技术类似于你在家或是咖啡馆使用的Wi-fi网络。
所有的数据都将被记录，所以研究者可以确定警告的准确性，知道哪种类型的警告最能帮助司机远离危险。眼下还没有自动驾驶车辆，但是车辆被安装了更多的传感器。大部分汽车是参与者自己的，汽车制造商也提供了64辆车，这些车辆配备了嵌入式通信设备连接汽车的机载计算机网络，安装了汽车制造商的定制警告界面和多个摄像机。
这个项目是美国交通运输部门、汽车制造商以及密歇根大学交通研究中心历经10年努力的成果。项目已经投入了2500万美元，80%的资金由美国交通运输部门提供。八大汽车制造商(Ford，GeneralMotors，Honda，Hyundai-Kia，Mercedes-Benz，Nissan，ToyotaandVolkswagen)通过合作协议的方式对研究提供支持。
来自美国国家公路交通安全管理局的数字显示，美国平均每年有34000人死于交通事故，需要约2400亿美元维护公路交通安全。而该项目如果未来大规模推广，无疑将有效的减少交通事故，避免人员伤亡。
连接车辆减少交通事故 据不完全统计，每年全世界因交通事故死亡的人数超过100万WIFIWIFI。尽管科技日新月异，但是几十年过去了这个世界性难题依然难以解决。之前我们也介绍过隐形自行车头盔、Google无人驾驶汽车等等。
美国密歇根州运输研究所(UMTRI)联合汽车厂家和各种机构，准备推出一个基于专用短程通讯(DSRC)的云平台，利用类似Wi-Fi的技术连接车载电脑和远程交通安全管理平台，在汽车有可能发生事故前发出警告信息，提醒司机注意安全驾驶，从而减少交通事故的发生。
未来一年内将有超过3000辆车参与到这个项目，工作人员将为每辆汽车配备车载电脑、通信设备、若干传感器和多个摄像头，车载电脑会在车辆行驶时的各种实时信号传给交通安全管理平台。
每当有危险情况发生，例如汽车超速行驶或逆向行驶，安全平台就会即刻察觉并通过车载电脑发出语音或震动警告。这个平台除了提供安全警告，还有其他应用，例如可以设置提醒功能，下班记得接孩子放学等等，也支持开发者为其开发各种应用。
当前已有八大汽车制造商加入了这个试验，包括福特、通用、本田、现代、奔驰、日产、丰田和大众。密歇根州这个项目眼下只是一个试点，但仍要花费25亿美元。如果在全美推广的话每年要花费240亿美元，但考虑到美国每年有3.4万人死于交通事故，生命无价，这笔投入还是可以接受的。
覆盖全球 让全世界每个角落都覆盖无线网，听上去好像是个美丽的设想，不过美国一家科技公司打算把它变成现实。这家公司预计在2015年6月前向近地轨道发射数百颗迷你卫星，这些卫星面向地球持续释放无线网络信号，覆盖世界各地，使用任何电子终端都能连接上无线网。
2014年2月26日，美国一家充满雄心壮志的公司，名叫媒体发展投资基金公司，他们推出的项目叫“Outernet”。这家公司正在与美国航天局联系，希望获得帮助，在国际空间站进行信号释放测试，后期还需要美国航天局帮忙把数百颗Cube-Sats迷你卫星送入指定轨道。按照设想，进入预定轨道后的卫星能够接收来自地面基站释放的网络数据，卫星需要对这些数据进行解析，并转换成无线网络释放到地球上。
另据站长之家报道，据外媒消息，美科技创业者们欲通过一个名为Outernet的“科技乌托邦”项目来达到将无线网络信号覆盖全世界的目的。据悉，该项目是通过将数百颗微型人造卫星CubeSats发射至近地轨道，而这些人造卫星便是免费wifi 的“发源地”。
实际上，Outernet 计划仍无法提供完善的无线网络，准确的说，这项计划主要是为了广泛的传播高质量的新闻以及息息相关的教育信息。Outernet计划中的通信方式更趋向于一种多通道无线规划形式。
技术优点
WiFi技术无线电波的覆盖范围广：WiFi的半径则可达100米，适合办公室及单位楼层内部使用。而蓝牙技术只能覆盖l5米内。
WiFi技术速度快，可靠性高：802．1lb无线网络规范是IEEE802．1 l网络规范的变种，最高带宽为1Mbps，在信号较弱或有干扰的情况下，带宽可调整为5．5Mbps、2Mbps和1Mbps，带宽的自动调整，有效地保障了网络的稳定性和可靠性。
WiFi技术无需布线：WiFi最主要的优势在于不需要布线，可以不受布线条件的限制，因此非常适合移动办公用户的需要，具有广阔市场前景。目前它已经从传统的医疗保健、库存控制和管理服务等特殊行业向更多行业拓展开去，甚至开始进入家庭以及教育机构等领域。
WiFi技术健康安全：IEEE802．1规定的发射功率不可超过100毫瓦，实际发射功率约6O～70毫瓦，手机的发射功率约200毫瓦至1瓦间，手持式对讲机高达5瓦，而且无线网络使用方式并非像手机直接接触人体，是绝对安全的。
研发产品 火车wifi火车wifi火车wifi
2014年3月6日，记者从交通运输方面专家和相关通信开发公司了解到，正在研发“火车WiFi”系统，并且在不久的将来就会在成渝动车上实现WiFi覆盖。
WiFi不会影响动车通信
2014年3月6日晚上，西南交通大学信息科学与技术学院通信工程系主任方旭明教授接受天府早报记者采访时介绍，王梦恕误解了地铁通信和动车通信的概念，动车上使用WiFi的频率不会影响动车通信。
为保证列车运营、调度的正常进行，铁路通信如GSM-R频率为800-900MHz左右，属于专门的通信频段，受到专门的保护。铁路系统的通信是沿着铁路线专门覆盖和优化的，信号质量得以保障。WiFi和地铁使用的通信频率属于公共频段，频率在2.4GHz，医疗等公共机构都可以使用这个频段。
由于地铁和WiFi的通信频率相同，在地铁上使用WiFi可能影响地铁通信。但铁路部门的通信系统和WiFi系统两者使用不同的网络，在频段和系统制式上都不同，“两个系统之间不会产生影响”。
适时公布“火车WiFi”进展情况 西南交通大学信息科学与技术学院通信工程系与北京某通信公司目前正在研制“火车WiFi”系统，春运期间曾经在成渝动车组上进行测试运行。
同步播报：WiFi信号不影响成都地铁运行 成都市无线电管理委员会相关负责人表示，地铁上使用WiFi不会影响地铁运行。
在成都地铁规划之初，成都市无线电管理委员会办公室就对成都地铁公司1、2号线800MHz数字集群通信系统组织召开了专家评审会，对成都地铁公司的通信系统设计问题进行了调研，证实其安全可靠。
其次，地铁开通之前，市无委还组织了成都市无线电监测站对成都地铁1、2号线所有站点进行了电磁环境测试，保证了指配频率的安全性。同时建立了定期联络沟通机制，成立了应急领导小组，并与电子政府应急网络接通，一旦地铁在地下运行出现问题，地面能及时知道情况。
安全风险 央视曝光危险WiFi
2014年6月，央视“危险的WiFi”为题的节目揭露了在无线网络存在巨大的安全隐患，公共场所的免费WiFi热点有可能就是钓鱼陷阱，而家里的路由器也可能被恶意攻击者轻松攻破。网民在毫不知情的情况下，就可能面临个人敏感信息遭盗取，访问钓鱼网站，甚至造成直接的经济损失。
WIFI危险无处不在：
危险一：WiFi钓鱼陷阱 许多商家为招揽客户，会提供WiFi接入服务，客人发现WiFi热点，一般会找服务员索要连接密码。黑客就提供一个名字与商家类似的免费WiFi接入点，吸引网民接入。
一旦连接到黑客设定的WiFi热点，上网的所有数据包，都会经过黑客设备转发，这些信息都可以被截留下来分析，一些没有加密的通信就可以直接被查看。
危险二：WiFi接入点被偷梁换柱 除了伪装一个和正常WiFi接入点雷同的WiFi陷阱，攻击者还可以创建一个和正常WiFi名称完全一样的接入点。
方法是这样的：你在喝咖啡，另一个人在你附近也在喝咖啡，由于咖啡厅的无线路由器信号覆盖不够稳定，你的手机会自动连接到攻击者创建的WiFi热点。在你完全没有察觉的情况下，又一次掉落陷阱。
危险三：黑客主动攻击 这是最讨厌的，也是最危险的，属于明显带有敌意。黑客可以使用黑客工具，攻击正在提供服务的无线路由器，干扰连接，家用型路由器抗攻击的能力较弱的网络连接就这样断线，继而连接到黑客设置的无线接入点。
危险四：攻击家用路由器 这种危险与以上三种不同，攻击者首先会使用各种黑客工具破解家用无线路由器的连接密码，如果破解成功，黑客就成功连接你的家用路由器，共享一个局域网。
攻击者并不甘心免费享用网络带宽，有些人还会进行下一步，尝试登录你的无线路由器管理后台。由于市面上存在安全隐患的无线路由器相当常见，黑客很可能破解你的家用路由器登录密码。
315曝光
2015年央视315晚会曝光了黑客利用虚假WiFi盗取用户照片、邮箱账号等隐私信息的全过程，让观众们对公共WiFi上网安全产生严重怀疑，因为谁都不知道在遍布酒店、商场中的WiFi后面是否也躲着“黑客”。
据315晚会报道，黑客可利用搭设虚假WiFi网络的方式骗取用户接入，从而盗取用户隐私信息。而据安全专家分析，虚假WiFi钓鱼是当前免费WiFi的主要安全风险。
防范措施 五大wifi安全防范方法
1、更改信道 更改信道能够避免由其他设备引起的干扰。虽然如今的路由器已经具备了更强的信道选择能力，但你也可以手动选择以提升速度和稳定性。
你可以使用Acrylic Wi-Fi和Netgear Wi-Fi Analytics等免费工具来查看家里哪个信道最繁忙，然后将路由器所使用的信道更改成状态最佳的。
2、优先设备 市面上一些更新或更高端的路由器都支持为特定应用或设备提供优先权，让它们拥有更多的带宽。当你在玩在线游戏或播放在线视频时，这一功能可带来明显不同。
这项技术一般被称作Qos或WMM，不同路由器的执行方式都不尽相同，你可以根据自己的需要为设备设定优先级。
3、切换到最高速度 大多数路由器都可以处理现有几乎所有的Wi-Fi标准，比如最老的802.11a和最新最快的802.11ac。如果你家里的笔记本和智能手机都支持最新802.11ac标准，那你可以让路由器专注于提供最快的速度，而不是去照顾更老的设备。
4、隐藏SSID
路由器在默认状态下会广播自己的SSID(服务集标识符)，好让新设备可以快速加入其网络。如果你将其隐藏，那么就只

Reading Glasses

Reading Glasses,Adjustable Reading Glasses,Stylish Reading Glasses,Rimless Reading Glasses

Danyang Hengshi Optical Glasses Co., Ltd. , https://www.hengshi-optical.com