Shulou(Shulou.com)06/01 Report--

Wireless local area network (WLAN) has been developed for more than 20 years since the 1890s, in which there are many protocol versions and revised versions. Here is a brief overview for everyone to understand.

The earliest wireless local area network (WLAN), which appeared in the 1870s, was developed by the University of Hawaii and was named "ALOHAnet". It was mainly used to transfer data between the Hawaiian islands. IEEE began to prepare for the development of standards for wireless Lans in 1991. In 1997, the first 802.11 standard was approved. Become the original standard of 802.11. Since then, IEEE has been revising and improving the WLAN standard to enable it to provide faster and better services. Here is a chronological introduction to the development of infinite local area networks:

In the 1970s, an infinite local area network prototype appeared at the University of Hawaii for data communication between the Hawaiian islands.

In 1997, the original 802.11 standard was approved as IEEE Std 802.11-1997, which uses IR,FHSS or DSSS for data transmission in the 2.4GHz band at the transmission rates of 1Mbps and 2Mbps.

In 1999, the 802.11b protocol was approved as 802.11b-1999, which uses HR-DSSS for data transmission over 2.4GHz at a transmission rate of 1Mbps, 2Mbps5.5Mbps and 11Mbps.

In 1999, the 802.11a protocol was approved as 802.11a-1999, which uses OFDM for data transmission over 5GHz, and the transmission rate is increased to 54Mbps.

In 2003, the 802.11g protocol was approved as 802.11g-2003, which uses ERP-OFDM for data transmission over 2.4GHz, and the transmission rate is increased to 54Mbps.

In 2007, the 802.11n protocol was approved as 802.11n-2007, which transmits data over 2.4GHz and 5GHz. According to different antenna matching, the transmission data is increased to 150Mbps, 300Mbps, 450Mbps or 600Mbps (40MHz). 802.11n uses a variety of methods to improve the transmission rate, such as MIMO,SGI,channel-bonding and so on. It will be described in more detail later.

In 2013, the 802.11ac protocol was approved as 802.11ac-2013, which transmits data over 5GHz. Depending on the matching of different antennas, the data transmission is increased to 433.3 Mbps, 866.7 Mbps, or 1300 Mbps (80MHz). 802.11ac can be seen as an improved version of 802.11n, which will be described in more detail later.

The above is what we often come into contact with in the 802.11 agreement. In fact, IEEE also defines a number of protocols. Here is a brief introduction:

802.11d-2001, adding 802.11 devices for specifications in other countries (Europe, the United States and later countries in Japan), such as Contry Code information, will be included in Beacons and Probe Response frames.

802.11h-2003, which defines the behavior of DFS (dynamic Frequency change) and TPC (Transmission Power Control). The main purpose is to enable the 802.11 equipment running in 5G to automatically detect radar signals and avoid the channels used by radar to prevent interference with the use of radar equipment.

802.11i-2004, the three key parts of wireless security solution: data privacy (encryption), data integrity (prevent tampering), and authentication (authentication). The familiar WPA2 security standard is defined by this protocol.

802.11j-2004 to solve the problems related to the use of 4.9GHz and 5GHz frequencies in Japan.

802.11e-2005, the specification defines the relevant requirements of QoS, as well as WMM (multimedia) related matters

802.11r-2008, mainly to help solve problems related to roaming

802.11k-2008, which defines how Transmit Power Control (TPC) is used in bands other than 5GHz. 5GHz TPC is defined by 802.11h-2003.

802.11w-2009 provides a secure way to transmit management frames to prevent them from being eavesdropped. 802.11w frames are also known as robust management frames.

802.11p-2010, strengthen the 802.11 standard specification to support Intelligent Transportation Systems (ITS) applications. In order to better support data transmission under high-speed mobile.

802.11z-2010, mainly solving problems related to Direct Link Setup (DLS)

802.11u-2011 mainly solves the problems between the 802.11 network and other external networks.

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