Wlan

Wireless LAN
From Wikipedia, the free encyclopedia
For the radio stations in Lancaster, Pennsylvania, see WLAN (AM) and WLAN-FM.


This notebook computer is connected to a wireless access point using a PC card wireless card.


An example of a Wi-Fi network.
A wireless local area network (WLAN) links two or more devices using some wireless distribution method (typically spread-spectrum orOFDM radio), and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network. Most modern WLANs are based on IEEE 802.11 standards, marketed under the Wi-Fi brand name.
Wireless LANs have become popular in the home due to ease of installation, and in commercialcomplexes offering wireless access to their customers; often for free. Large wireless network projects are being put up in many major cities: New York City, for instance, has begun a pilot program to provide city workers in all five boroughs of the city with wireless Internet access.[1]


An embedded RouterBoard 112 with U.FL-RSMA pigtail and R52 mini PCI Wi-Fi card widely used by wireless Internetservice providers (WISPs)
Contents [hide]
1 History
2 Architecture
2.1 Stations
2.2 Basic service set
2.3 Extended service set
2.4 Distribution system
3 Types of wireless LANs
3.1 Peer-to-peer
3.2 Bridge
3.3 Wireless distribution system
4 Roaming
5 References
[edit]History

Norman Abramson, a professor at the University of Hawaii, developed the world’s first wireless computercommunication network, ALOHAnet, using low-cost ham-like radios. The system included seven computers deployed over four islands to communicate with the central computer on the Oahu Island without using phone lines.[2]
"In 1979, F.R. Gfeller and U. Bapst published a paper in the IEEE Proceedings reporting an experimental wireless local area network using diffused infrared communications. Shortlythereafter, in 1980, P. Ferrert reported on an experimental application of a single code spread spectrum radio for wireless terminal communications in the IEEE National Telecommunications Conference. In 1984, a comparison between infrared and CDMA spread spectrum communications for wireless office information networks was published by Kaveh Pahlavan in IEEE Computer Networking Symposium which appearedlater in the IEEE Communication Society Magazine. In May 1985, the efforts of Marcus led the FCC to announce experimental ISM bands for commercial application of spread spectrum technology. Later on, M. Kavehrad reported on an experimental wireless PBX system using code division multiple access. These efforts prompted significant industrial activities in the development of a new generation ofwireless local area networks and it updated several old discussions in the portable and mobile radio industry.
The first generation of wireless data modems was developed in the early 1980's by amateur communication groups. They added a voice band data communication modem, with data rates below 9600 bps, to an existing short distance radio system such as a walkie talkie. The second generation ofwireless modems was developed immediately after the FCC announcement in the experimental bands for non-military use of the spread spectrum technology. These modems provided data rates on the order of hundreds of Kbps. The third generation of wireless modem now aims at compatibility with the existing LANs with data rates on the order of Mbps. Currently, several companies are developing the thirdgeneration products with data rates above 1 Mbps and a couple of products have already been announced. "[3]


54 Mbit/s WLAN PCI Card (802.11g)
"The first of the IEEE Workshops on Wireless LAN was held in 1991. At that time early wireless LAN products had just appeared in the market and the IEEE 802.11 committee had just started its activities to develop a standard for wireless LANs. The focus of...