Wireless LAN(Wireless LAN) An industry standard for wireless network communications defined for IEEE (IEEE802.11).
The first version of the wireless LAN was published in 1997, which defines the media access access control layer (MAC layer) and the physical layer. The physical layer defines two wireless frequency modulation methods and one infrared transmission method that operates on the 2.4GHz ISM band, with the total data transmission rate designed to be 2Mbit/s. Communication between two devices can be performed freely (ad hoc) or under the coordination of a base station (B as station, BS) or an access point (Access Point, AP).
Two additional versions were added in 1999: 802.11a defines a physical layer with data transmission rates up to 54Mbit/s on the 5GHz ISM band, and 802.11b defines a physical layer with data transmission rates up to 11Mbit/s on the 2.4GHz ISM band. The 2.4GHz ISM frequency band is universal to most countries in the world, so 802.11b has been widely used. Apple named the 802.11 standard it developed by itself AirPort. In 1999, the industry established the Wi-Fi Alliance, committed to solving the production and equipment compatibility issues of products that comply with the 802.11 standard. 802.11 Standards and Supplements.
- 802.11, 1997, original standard (2Mbit/s works at 2.4GHz).
- 802.11a, 1999, Physical layer supplement (54Mbit/s working at 5GHz).
- 802.11b, 1999, physical layer supplement (11Mbit/s work at 2.4GHz).
- 802.11c, 802.1D-compliant Media Access Control Layer (MAC) Bridge (MAC Layer Bridge).
- 802.11d, adjustments made according to radio regulations of each country.
- 802.11e, support for service level (QS).
- 802.11f, Interoperability of base stations.
- 802.11g, physical layer supplement (54Mbit/s working at 2.4GHz).
- 802.11h, adjustment of wireless coverage radius, indoor and outdoor channels (5GHz band).
- 802.11i, Supplement to security and authentication.
In addition to the above IEEE standard, there is another technology called IEEE802.11b+, which provides a data transmission rate of 22Mbit/s based on IEEE802.11b (2.4GHz frequency band) through PBCC technology (Packet Binary Convolutional Code). But this is actually not an IEEE public standard, but a technology with private ownership (the property rights belong to Texas Instruments, USA).
Technical brief description
Network members and structures
- Site (Station), the most basic component of the network.
- Basic Service Set (BSS). The most basic service unit of the network. The simplest service unit can consist of only two sites. The site can be dynamically associated into the basic service unit.
- Distribution System (DS). The allocation system is used to connect different basic service units. The media used by the allocation system are logically distinct from the media used by the basic service unit, although they may physically be the same medium, such as the same wireless frequency band.
- Access Point (AP). The access point has the identity of an ordinary site and the function of accessing to the allocation system.
- Extended Service Set (ESS). It is composed of a combination of distribution system and basic service units. This combination is logically, not physically - different basic service units may be geographically far apart. The distribution system can also use a variety of techniques.
- Portal is also a logical component. Used to connect wireless LANs to wired LANs or other networks.
There are three types of media here: wireless media used by the site, media used by the distribution system, and media used by other LANs integrated with the wireless LAN. Physically they may overlap with each other. IEEE802.11 is only responsible for addressing on wireless media used by the site. The addressing of the allocation system and other LANs does not fall within the scope of the wireless LAN.
IEEE802.11 does not specifically define the allocation system, but only defines the services (Service) that the allocation system should provide. The entire wireless LAN defines 9 services.
- The five types of services belong to the tasks of the allocation system, namely, Association, End-up connection, Distribution, Integration, and Reassociation.
- The four types of services belong to the tasks of the site, namely, authentication (authentication), end authentication (deauthentication), privacy (Privacy), and MAC data transmission (MSDU delivery).