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In the process of our exposure to the wireless industry, we often encounter some professional terms. Today I will tell you about 802.11, which I often hear. What is 802.11 and what is its content? a bit.
The 802.11 protocol cluster is a standard developed by the International Institute of Electrical and Electronics Engineering (IEEE) for wireless local area networks. Although WI-FI uses 802.11's media access control layer (MAC) and physical layer (PHY), the two are not exactly the same. In the following standards, the most used should be the 802.11n standard, working in the 2.4GHz or 5GHz frequency band, up to 600Mbps (theoretical value).
Detailed agreement
802.11:
A wireless LAN standard originally formulated by IEEE is mainly used to solve the wireless access between users and user terminals in office LANs and campus networks. The business is mainly limited to data access, and the rate can only reach 2Mbps. Because it cannot meet people's needs in terms of speed and transmission distance, the IEEE team has launched two new standards, 802.11b and 802.11a.
802.11a:
The 802.11a standard operates in the 5GHz U-NII frequency band, with a physical layer rate up to 54Mbps and a transmission layer rate up to 25Mbps. Can provide 25Mbps wireless ATM interface and 10Mbps Ethernet wireless frame structure interface, and TDD / TDMA air interface; support voice, data, image services; a sector can access multiple users, each user can bring multiple User terminal.
Wireless transmission can also reduce the data rate to 48, 36, 24, 18, 12, 9, or 6 Mb / s as needed. 802.11a has 12 non-overlapping channels, 8 for indoor use, and 4 for point-to-point transmission. It cannot interoperate with 802.11b unless it uses equipment that uses both standards.
Data rate (Mbit / s)
Modulation
Coding rate
Ndbps
1472 byte transfer time (µs)
6
BPSK
1/2
twenty four
2012
9
BPSK
3/4
36
1344
12
4-QAM
1/2
48
1008
18
4-QAM
3/4
72
672
twenty four
16-QAM
1/2
96
504
36
16-QAM
3/4
144
336
48
64-QAM
2/3
192
252
54
64-QAM
3/4
216
224
Although the 2003 World Radiocommunication Conference made it easier to apply 802.11a globally, different countries still have different regulations to support it. Relevant regulations for 802.11a have already appeared in the United States and Japan, but in other regions, such as the European Union, regulatory agencies have considered using the European HIPERLAN standard, and banned the use of 802.11a in Europe in mid 2002. In the United States, the decision of the Federal Communications Commission in mid-2003 may provide more spectrum for 802.11a. However, 802.11a products began to sell in 2001, which is later than 802.11b products, because the 5GHz components in the product were developed too slowly. Since 802.11b has been widely adopted, 802.11a has not been widely adopted. Coupled with some weaknesses of 802.11a, and regulations in some places, it makes its scope of use narrower.
In order to cope with this lack of market, 802.11a equipment manufacturers have improved the technology (802.11a and 802.11b are similar in many features), and developed technologies that can use more than one 802.11 standard. There are already dual-band, dual-mode or triple-mode wireless network cards that can support both 802.11a and b, or a, b, and g. They can automatically select standards according to the situation. Similarly, there have been mobile adapters and access devices that can support all of these standards simultaneously.
802.11b:
IEEE802.11b is a standard for wireless local area networks. The carrier frequency is 2.4GHz and the transmission speed is 11Mbit / s. IEEE802.11b is well-known among all wireless local area network standards, and it is also a widely used standard. It is sometimes incorrectly labeled as Wi-Fi. In fact, Wi-Fi is a trademark of the Wireless Local Area Network Alliance (WLANA). The trademark only guarantees that the products using the trademark can cooperate with each other, and has nothing to do with the standard itself. A total of 14 channels with a bandwidth of 22MHz are available in the 2.4-GHz-ISM band. The successor standard of IEEE802.11b is IEEE802.11g, and its transmission speed is 54 Mbit / s.
802.11c:
802.11c was extended at the level of media access control / link connection control (MAC / LLC), aiming to formulate wireless bridge operation standards, but later the standard was added to the existing 802.1 and became 802.1d.
802.11d:
Like 802.11c, it extends at the MAC / LLC level, corresponding to the 802.11b standard, and solves the problem of countries that cannot use the 2.4GHz band.
802.11e:
802.11e is a WLAN standard developed by IEEE to meet the quality of service (Qos) requirements. Qos is a very important indicator in the transmission of some voices and videos. At the 802.11MAC layer, 802.11e adds the Qos function. Its distributed control mode can provide stable and reasonable service quality, and the centralized control mode can flexibly support multiple service quality strategies, allowing video and audio transmission to be timely, quantitative, and ensuring multimedia. For smooth application, the WIFI Alliance refers to this as WMM (wi-fimultimedia).
802.11f:
802.11f adds IAPP (inter-access point protocol) agreement to ensure that the user terminal roams between different access points, allowing the user terminal to smoothly and invisibly switch the access area. The 802.11f standard determines the login of access points within the same network and the exchange of information when users switch from one access point to another.
802.11g:
In July 2003, IEEE 802.11g passed the third modulation standard. The carrier frequency is 2.4GHz (same as 802.11b), the original transmission speed is 54Mbit / s, and the net transmission speed is about 24.7Mbit / s (same as 802.11a). 802.11g devices are compatible with 802.11b. 802.11g is a standard formulated to improve the higher transmission rate. It uses the 2.4GHz band, uses JS and 802.11b for backward compatibility, and it also uses OFDM technology for data streams up to 54Mbit / s. The bandwidth provided is 1.5 times of 802.11a. From 802.11b to 802.11g, you can find the trajectory of the continuous development of WLAN standards: 802.11b is the cornerstone of the evolution of all WLAN standards. In the future, many systems will need to be backward compatible with 802.11b. Not backward compatible with 802.11b, but using OFDM JS, supports data streams up to 54Mbit / s, providing high-speed channels several times that of 802.11b / g, such as 802.11b / g providing 3 non-overlapping channels up to 8-12 It can be seen that there is a gap in Wi-Fi compatibility between 802.11g and 802.11a. For this reason, a dual-band JS bridging this gap—dual mode (dual band) 802.11a + g (= b), it better integrates 802.11a / g technology, works in two frequency bands of 2.4GHz and 5GHz, complies with standards such as 802.11b / g / a, and is backward compatible with 802.11b, allowing users to easily connect to the current It is possible or future 802.11 network becomes possible.
802.11h:
It is a revised standard in coordination with HiperLAN2 in Europe. There is a difference in the planning and application of the 5GHz band between the United States and Europe. The purpose of this standard is to reduce interference to radars that are also in the 5GHz band. There is also 802.16 (WIMAX), of which 802.16B was developed for coordination with Wireless HUMAN. 802.11h involves two technical JS, one is dynamic frequency selection (DFS), that is, the access point constantly scans the radar on the channel, the access point and related base stations change the frequency at any time, greatly reduce interference, and evenly distribute WLAN traffic; another type of JS is transmission power control (TPC), the total transmission power or interference will be reduced by 3dB.
802.11i:
IEEE802.11i is an amendment made by IEEE to make up for 802.11's fragile security encryption function (WEP, Wired Equivalent Privacy), which was completed in July 2004. It defines the new encryption protocol CCMP (CTR with CBC-MAC Protocol) based on AES, and the encryption protocol TKIP (Temporal Key Integrity Protocol) which is forward compatible with RC4.
It takes quite a long time for the security problems in the wireless network to be exposed and finally solved, and the communication chip manufacturers of the major manufacturers obviously cannot accept that nothing will be sold during this period, so the eager Wi-Fi manufacturers adopt draft 3 of 802.11i as a blueprint Designed a series of communication equipment, which was later called WPA (Wi-Fi Protected Access) support; later said that the communication equipment that supports 802.11i final protocol is called WPA2 (Wi-Fi Protected Access 2) support.
802.11j:
It is a standard customized to adapt to the different applications of Japan above 5GHz. Japan started to use it at 4.9GHz. At the same time, their powers are also different. For example, the same frequency band is 5.15-5.25GHz. Europe allows 200MW power, Japan only allows 160MW.
802.11k:
802.11k provides standards for how wireless local area networks should perform channel selection, roaming services, and transmission power control. He provides wireless resource management, allowing frequency bands (BAND), channels (CHANNEL), carrier (CARRIER), etc. to be more flexibly and dynamically adjusted and scheduled, so that the limited frequency bands can be improved in the overall operational efficiency. In a wireless local area network, each device is usually connected to an access point that provides a strong signal. This kind of management may sometimes lead to excessive demand for one access point and reduce the utilization rate of other access points, resulting in reduced performance of the entire network, which is mainly determined by the number of access users and geographic location. In a network that complies with the 802.11k specification, if an access point with a strong signal is loaded with its large capacity and a wireless device is connected to an access point with a low utilization rate, in this case, even if its signal may be It is relatively weak, but the overall throughput is still relatively large. This is because the network resources are more effectively used.
802.11l:
Because (11L) is easily confused with (11i) of the safety specification and is very similar to (111), it is abandoned for programming.
802.11m:
802.11m mainly maintains, revises, and improves the 802.11 family specifications, as well as provides explanation documents. The m in 802.11m stands for Maintenance.
802.11n:
IEEE802.11n, in January 2004, IEEE announced the formation of a new unit to develop new 802.11 standards. The data transmission speed is estimated to reach 475Mbps (a higher speed transmission rate needs to be generated at the physical layer). This new standard should be 45 times faster than 802.11b and about 8 times faster than 802.11g. 802.11n will also transmit to longer distances than previous wireless networks.
There are two proposals for competing with each other in 802.11n:
WWiSE (World-Wide Spectrum Efficiency) is supported by some manufacturers led by Broadcom.
TGn Sync is supported by Intel and Philips.
802.11n adds a standard for MIMO (multiple-input multiple-output). MIMO uses multiple transmit and receive antennas to allow higher data transmission rates. MIMO also uses Alamouti coding coding schemes to increase the transmission range.
802.11o:
Developed for VOWLAN (Voice over WLAN), faster unlimited cross-zone handover, and reading voice (voice) have higher transmission priority than data (Data).
802.11p:
80211p is a standard released for the special environment of automobile communication. The initial design is to have a transmission speed of 6Mbps within a distance of 300M. It works in the 5.9GHz frequency band and has a transmission distance of 1000 feet and a data rate of 6Mbps. 802.11p will be used in many areas such as toll collection, car security business, and e-commerce through cars. From the technical JS point of view, 802.11p has made a number of improvements to 802.11 for special environments such as cars, such as more advanced switching between hotspots, more support for mobile environments, enhanced security, and enhanced identity authentication.
802.11q:
Establish a mechanism to support VLAN (virtual LAN, virtual local area network).
802.11r:
The 802.11r standard focuses on reducing the time required for authentication while roaming, which will help support real-time applications such as voice. Mobile users using wireless technology JS must be able to quickly disconnect from one access point and reconnect to another access point. The delay time during this switching process should not exceed 50 milliseconds, because this is the time interval that the human ear can feel. But the average delay of the 802.11 network when roaming is a few hundred milliseconds, which directly leads to intermittent transmission, resulting in connection loss and voice quality degradation. So for widely used 802.11-based wireless voice communications, faster switching is critical. 802.11r improves the handover process when mobile client devices move between access points. The protocol allows a wireless client to establish a safe and QoS state with a new access point before switching, which reduces connection loss and call interruption to a minimum.
802.11s:
Formulate and implement the current advanced MESH network, providing self-configuring, self-healing and other capabilities. A wireless mesh network can connect multiple wireless LANs to cover a university campus or the entire city. When a new access point is added, it can automatically complete the security and quality of service settings. The data packets of the entire mesh network will automatically avoid busy access points and find good routing lines. There are 15 proposals on this standard. IEEE may formally recognize the standard in 2008.
802.11t:
Provides methods for improving the consistency of radio broadcast link characteristics evaluation and measurement standards to measure wireless network performance.
802.11u:
Interactivity with other networks. In the future, more products will have both Wi-Fi and other wireless protocols, such as GXXXXXX, Edge, EV-DO, etc. The working group is developing methods for transferring information between different networks to simplify network exchange and roaming.
802.11v:
Wireless network management. Working Group V is a newly formed group whose tasks will be based on the results achieved by 802.11k. 802.11v mainly faces operators, and is committed to enhancing the services provided by Wi-Fi networks.
802.11ac:
The version of the protocol being developed by mainstream manufacturers (Qualcomm, Broadcom, Intel, etc.) uses the 5GHz frequency band (also can be said to be the 6GHz frequency band) and adopts: wider baseband (high expansion to 160Mhz), more MIMO, high density Modulation and demodulation (256 QAM). In theory, 11ac can provide 1Gbit of bandwidth for multiple site services or 500Mbit of transmission bandwidth for a single connection.
The world's first router using 802.11ac wireless technology JS was launched on November 15, 2011 by the American startup Quantenna. On January 5, 2012, industry giant Broadcom released its first chip supporting 802.11ac.
802.11ad:
802.11ad works in the 57-66 GHz frequency band, evolved from 802.15.3c, and the standard is still under discussion. The 802.11ad draft shows that it will support nearly 7GBit of bandwidth.
Due to the limitations of carrier characteristics, this standard will mainly meet the requirements of the personal area network (PAN) for ultra-high bandwidth. A possible application will be the close-range transmission of wireless high-definition audio and video signals.
802.11ax:
802.11ax is an 802.11 wireless local area network (WLAN) communication standard that transmits over the 5G frequency band and is a subsequent upgraded version of 802.11ac.
One of the primary goals of the 802.11ax standard is to increase the wireless speed of independent network clients by 4 times. The domestic manufacturer Huawei has revealed (the IEEE 802.11ax standard working group has its engineers) that the 802.11ax standard can bring up to 10.53Gbps Wi-Fi connection speed in the 5GHz band.
It will be able to improve the Wi-Fi performance in multi-user environments (such as hotspots in public places), which is mainly achieved by improving spectrum efficiency, better managing crosstalk, and enhancing the underlying protocols (such as media access control data communication). The new standard should make public Wi-Fi hotspots faster and more stable.
Orthogonal Frequency Division Multiple Access (OFDMA) will also be used to increase the amount of data that the router can transmit. Just like orthogonal frequency division multiplexing technology (OFDM) technology JS, OFDMA encodes data on multiple sub-carriers-that is, more data is loaded in the same spatial area. OFDMA's "multiple access" describes a way to allocate a subset of these subcarrier frequencies to individual users.
Performance parameter
protocol
Release date
frequency band
Large transmission speed
802.11
1997
2.4-2.5 GHz
2 Mbps
802.11a
1999
5.15-5.35 / 5.47-5.725 / 5.725-5.875 GHz
54 Mbps
802.11b
1999
2.4-2.5 GHz
11 Mbps
802.11g
2003
2.4-2.5 GHz
54 Mbps
802.11n
2009
2.4GHz or 5GHz
600 Mbps (40MHz * 4 MIMO)
802.11ac
2011.2
5GHz
433Mbps, 867Mbps, 1.73 Gbps, 3.47 Gbps, 6.93 Gbps (8 MIMO, 160MHz)
802.11ad
2012.12 (Draft)
60GHz
up to 7000Mbps
802.11ax
2015.5
5GHz
10Gbps
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