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Explain what is 802.11?
In the process of our contact with the wireless industry, we often meet some professional terms. Today we talk about 802.11 that we often hear about. So what exactly is 802.11? What is its content? a bit.
The 802.11 protocol suite is a standard developed by the International Institute of Electrical and Electronics Engineers (IEEE) for wireless local area networks. Although WI-FI uses the media access control layer (MAC) and physical layer (PHY) of 802.11, the two are not exactly the same. Among the following standards, the most used ones should be the 802.11n standard, which operates in the 2.4 GHz or 5 GHz band and can reach 600 Mbps (theoretical value).
Detailed agreement
802.11 :
A wireless local area network standard originally set by the IEEE is mainly used to solve the wireless access of users and user terminals in office LANs and campus networks. The business is mainly limited to data access, and the maximum speed can only reach 2 Mbps. Because it can not meet people's needs in terms of speed and transmission distance, the IEEE team has successively introduced two new 802.11b and 802.11a standards.
802.11a :
The 802.11a standard operates in the 5GHz U-NII band, with physical layer rates of up to 54Mbps and transmission layer rates up to 25Mbps. Provides 25Mbps wireless ATM interface and 10Mbps Ethernet wireless frame structure interface, as well as TDD/TDMA air interface; supports voice, data, image services; a sector can access multiple users, each user can bring multiple User terminal.
According to needs, the data rate can also be reduced to 48, 36, 24, 18, 12, 9, or 6 Mb/s. 802.11a has 12 channels that do not overlap, 8 are for indoor use, and 4 are for point-to-point transmission. It cannot interoperate with 802.11b unless the device used for both standards is used.
Data rate (Mbit/s) modulation coding rate Ndbps 1472 bytes transmission time (μs)
6BPSK1/2242012
9BPSK3/4361344
124-QAM1/2481008
184-QAM3/472672
2416-QAM1/296504
3616-QAM3/4144336
4864-QAM2/3192252
5464-QAM3/4216224
Although the 2003 World Radiocommunication Conference made it easier for 802.11a to be used globally, different countries still have different regulations and support. The United States and Japan have already adopted regulations that recognize 802.11a. However, in other regions, such as the European Union, the 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 2003 Federal Communications Commission decision may provide more spectrum for 802.11a. However, 802.11a products began to be sold in 2001, which is later than 802.11b products. This is because the development of 5GHz components in the products is too slow. Since 802.11b has been widely adopted, 802.11a has not been widely adopted. Coupled with some of the weaknesses of 802.11a, and the restrictions imposed by some places, it makes its use more narrow. 802.11a equipment vendors have improved their technology in response to such market failures (802.11a technology is similar to 802.11b in many features) and developed technologies that can use more than one 802.11 standard. Already there are dual-band, dual-mode or tri-mode wireless network cards that can support both 802.11a and b, or a, b, and g, and they can automatically select the 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. Its carrier frequency is 2.4GHz and transmission speed is 11Mbit/s. IEEE802.11b is the most famous and widely-accepted standard in all wireless LAN standards. It is also sometimes mistakenly labeled as Wi-Fi. In fact, Wi-Fi is a trademark of the Wireless Local Area Network Alliance (WLANA). This trademark only guarantees that products using the trademark can cooperate with each other, and that it is not actually related to the standard itself. In the 2.4-GHz-ISM band, a total of 14 channels with a frequency of 22 MHz are available. The successor to IEEE802.11b is IEEE802.11g, which has a transmission speed of 54 Mbit/s.
802.11c :
802.11c expands at the media access control/link connection control (MAC/LLC) level to develop wireless bridging operation standards, but later adds the standard to the existing 802.1, becoming 802.1d.
802.11d :
He is expanding at the media access control/link connection control (MAC/LLC) level like 802.11c, and corresponds to the 802.11b standard, solving the problem of using the 2.4 GHz band countries.
802.11e :
802.11e is a WLAN standard developed by IEEE to meet the requirements of Quality of Service (Qos). Qos is a very important indicator in the transmission of some voice and video. In 802.11 MAC layer, 802.11e joins Qos function, its distributed control mode can provide stable and reasonable service quality, and centralized control mode can flexibly support multiple service quality strategies, allowing video and audio transmission to be timely, quantitative, and ensure multimedia. Smooth application, the WIFI Alliance calls this WMM (wi-fi multimedia).
802.11f :
802.11f adds an inter-access point protocol (IAPP) to ensure that the user's roaming between different access points allows the user to smoothly and invisibly switch the access area. The 802.11f standard determines the login of access points in the same network and the exchange of information when the user switches from one access point to another.
802.11g :
IEEE 802.11g passed the third modulation standard in July 2003. The frequency of its carrier 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 developed to increase higher transmission rates. It uses the 2.4GHz band, uses CCK technology for backward compatibility with 802.11b, and it supports data flows up to 54Mbit/s by using OFDM technology. Bandwidth is 1.5 times that of 802.11a. From 802.11b to 802.11g, we 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. 802.11a is a non-global standard. Incompatibility with 802.11b backwards, but using OFDM technology, supporting data flow 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 between Wi-Fi compatibility between 802.11g and 802.11a. For this reason, there is a dual-band technology that bridges this gap - dual band 802.11a+g. (=b) It is a well-integrated 802.11a/g technology that operates in the 2.4 GHz and 5 GHz bands, obeys standards such as 802.11b/g/a, and is backward compatible with 802.11b, allowing users to easily connect to existing networks. There are or may be future 802.11 networks possible.
802.11h :
In order to coordinate with European HiperLAN2, the United States and Europe have different plans and applications in the 5GHz band. The purpose of this standard is to reduce the interference to the same radar in the 5GHz band. Similar to 802.16 (WIMAX), 802.16B is designed to coordinate with Wireless HUMAN. 802.11h involves two technologies, one is dynamic frequency selection (DFS), that is, the access point constantly scans the radar on the channel, the access point and the related base station change the frequency at any time, minimizes interference, and evenly allocates WLAN. Traffic; Another technique is Transmission Power Control (TPC), which reduces the total transmission power or interference by 3dB.
802.11i :
IEEE802.11i is an amendment made by IEEE to compensate for the 802.11 vulnerable security encryption function (WEP, Wired Equivalent Privacy) and was completed in July 2004. Among them, the new encryption protocol CCMP (CTR with CBC-MAC Protocol) based on AES and the TKIP (Temporal Key Integrity Protocol) compliant with RC4 are defined.
The security problems in wireless networks have experienced considerable time from exposure to eventual resolution. The major chip makers in the telecommunications industry obviously cannot accept that they will not sell anything during this period. Therefore, the Wi-Fi vendors who can't wait to adopt Draft 3 of 802.11i as a blueprint A series of communication devices were designed, which were later called WPA (Wi-Fi Protected Access); later, the communication devices that support the 802.11i final protocol were said to support WPA2 (Wi-Fi Protected Access 2).
802.11j :
It is a standard that is tailored to Japan's different applications above 5GHz. Japan began to use 4.9GHz, and their power is also different. For example, the same frequency band of 5.15-5.25GHz, Europe allows 200MW power, Japan only allows 160MW.
802.11k :
802.11k provides a standard for how wireless LANs should perform channel selection, roaming service, and transmission power control. He provides radio resource management, allowing more flexible and dynamic adjustments and scheduling of bands, channels, and carriers (CARRIER), so that the limited frequency bands can be used to improve overall application efficiency. In a wireless LAN, each device is usually connected to the access point that provides the strongest signal. This type of management can sometimes lead to excessive demands on one access point and reduce the utilization of other access points, resulting in reduced overall network performance, which is primarily determined by the number of access users and geographic location. In a network that complies with the 802.11k specification, if the access point with the strongest signal is loaded at its maximum capacity and a wireless device is connected to a less-utilized access point, in this case, even if its signal It may be weak, but the overall throughput is still relatively large, because at this time, network resources have been used more effectively.
802.11l :
Since (11L) is confusingly confusing with (11i), and is much like (111), it is abandoned for use.
802.11m :
802.11m is mainly to maintain, revise, improve, and provide interpretation files for the 802.11 family specification. m in 802.11m stands for Maintenance.
802.11n :
IEEE802.11n, January 2004 The IEEE announced the formation of a new unit to develop the new 802.11 standard. The data transmission speed is estimated to be 475 Mbps (requiring higher transmission rates at the physical layer). The new standard should be 45 times faster than 802.11b and about 8 times faster than 802.11g. 802.11n will also be transmitted farther than the previous wireless network.
There are two proposals in 802.11n competing with each other:
WWiSE (World-Wide Spectrum Efficiency) is supported by some vendors led by Broadcom.
TGn Sync is supported by Intel and Philips.
802.11n increases the standard for multiple-input multiple-output (MIMO). MIMO uses multiple transmit and receive antennas to allow higher data rates. MIMO uses Alamouti coding coding schemes to increase the transmission range.
802.11o :
Developed for VOWLAN (Voice over WLAN), faster infinity handover, and read voice (voice) have higher transmission priority than data (Data).
802.11p :
The 80211p is a standard that has been released for the special environment of automotive communications. The initial setup was to have a 6Mbps transmission speed within a 300M distance. It operates in the 5.9GHz band and has a 1000-foot transmission distance and a 6Mbps data rate. 802.11p will be able to be used for toll collection stations, automotive safety business, automotive e-commerce and many other aspects. From a technical point of view, 802.11p has made many improvements to 802.11 for special environments such as automobiles, such as more advanced switching between hotspots, more support for mobile environments, enhanced security, and enhanced authentication.
802.11q :
Develop a mechanism for supporting virtual LANs (virtual LANs).
802.11r :
The 802.11r standard focuses on reducing the time required for authentication when roaming, which will help support real-time applications such as voice. Mobile users using wireless telephony must be able to quickly disconnect from one access point and reconnect to another access point. The delay time in this handoff process should not exceed 50 milliseconds, because this is the interval that the human ear can feel. However, the average delay of an 802.11 network when roaming is a few hundred milliseconds, which directly leads to the interruption of the transmission process, resulting in loss of connection and degradation of voice quality. So for the widely used 802.11-based wireless voice communications, faster switching is critical. 802.11r improves the handoff process when mobile client devices move between access points. The protocol allows a wireless client to establish a secure and QoS-neutral state with the new access point before switching is implemented, which minimizes connection loss and call disruption.
802.11s :
Develop and implement the most advanced X-Mesh network, providing self-configuring and self-healing capabilities. Wireless mesh networks can connect multiple wireless LANs to cover a university campus or the entire city. When a new access point joins in, it can automatically complete security and quality of service settings. The entire mesh network will automatically avoid busy access points and find the best route. There are 15 proposals for this standard. The IEEE may formally endorse this standard in 2008.
802.11t :
Provides a consistent methodological standard for improving the evaluation and measurement of radio broadcast link characteristics to measure wireless network performance.
802.11u :
Interactivity with other networks. In the future, more products will have Wi-Fi and other wireless protocols, such as GXXXXXX, Edge, EV-DO, etc. The working group is developing ways to transfer information between different networks to simplify network switching and roaming.
802.11v :
Wireless network management. V Working Group is the newly established group, and its task will be based on the achievements of 802.11k. 802.11v is mainly faced by operators and is dedicated to enhancing services provided by Wi-Fi networks.
802.11ac :
A version of the protocol being developed by mainstream vendors (Qualcomm, Broadcom, Intel, etc.) that uses the 5GHz band (or 6GHz band), using: wider baseband (up to 160Mhz), more MIMO, higher density Modem (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 was launched on November 15, 2011 by US startup Quantenna. On January 5, 2012, the industry giant Broadcom released its first chip that supports 802.11ac.
802.11ad :
802.11ad operates in the 57-66 GHz band and evolved from 802.15.3c. The standard is still being discussed. The 802.11ad draft shows that it will support nearly 7GBit of bandwidth.
Due to the limitation of carrier characteristics, this standard will mainly satisfy the demand for ultra-high bandwidth of personal area network (PAN). The most likely 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 band and is a follow-on upgrade to 802.11ac.
One of the primary goals of the 802.11ax standard is to increase the wireless speed of an independent network client by a factor of four. Huawei, a domestic manufacturer, has disclosed that (the IEEE 802.11ax standard working group has their engineers), and the 802.11ax standard can bring up to 10.53 Gbps Wi-Fi connection speed in the 5GHz band.
Will improve the Wi-Fi performance in multi-user environments (such as hotspots in public places), which is mainly achieved by improving spectral efficiency, better managing crosstalk, and enhancing 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) is also used to increase the amount of data that the router can transmit. Just like Orthogonal Frequency Division Multiplexing (OFDM) technology, OFDMA encodes data on multiple subcarriers—that is, loads more data in the same spatial area. The "multiple access" of OFDMA describes a way to assign subsets of these subcarrier frequencies to individual users.
Performance parameters
Protocol release date band maximum transmission speed
802.1119972.4-2.5 GHz2 Mbps
802.11a19995.15-5.35/5.47-5.725/5.725-5.875 GHz54 Mbps
802.11b19992.4-2.5 GHz11 Mbps
802.11g20032.4-2.5 GHz54 Mbps
802.11n20092.4GHz or 5GHz600 Mbps (40MHz*4 MIMO)
802.11ac2011.25GHz433Mbps, 867Mbps, 1.73 Gbps, 3.47 Gbps, 6.93 Gbps (8 MIMO, 160 MHz)
802.11ad2012.12 (draft) 60 GHz up to 7000 Mbps
802.11ax2015.5
5GHz10Gbps