Wireless LAN

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Image:WLAN PCI Card.jpg A wireless LAN or WLAN is a wireless local area network that uses radio waves as its carrier: the last link with the users is wireless, to give a network connection to all users in the surrounding area. Areas may range from a single room to an entire campus. The backbone network usually uses cables, with one or more wireless access points connecting the wireless users to the wired network.

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Standards

A Wireless LAN is a wireless network using radio frequencies for the communication between computer devices and eventually access points which are basically two-way radio transceivers that typically work in the 2.4 GHz (802.11b, 802.11g) or 5 GHz (802.11a) bands.

Most equipment is Wi-Fi-certified, IEEE 802.11b or IEEE 802.11g compliant and offers some level of security like WEP and/or WPA.

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History

WLAN is expected to continue to be an important form of connection in many business areas. The market is expected to grow as the benefits of WLAN are recognized. Frost & Sullivan estimate the WLAN market to have been 0.3 billion US dollars in 1998 and 1.6 billion dollars in 2005. So far WLANs have been installed in universities, airports, and other major public places. Decreasing costs of WLAN equipment has also brought it to many homes. However, in the UK the exorbitant cost of using such connections in public has so far limited use to airports' Business Class lounges, etc. Large future markets are estimated to be in health care, corporate offices and the downtown area of major cities. New York City has even begun a pilot program to cover all five boroughs of the city with wireless internet.

Originally WLAN hardware was so expensive that it was only used as an alternative to cabled LAN in places where cabling was difficult or impossible. Such places could be old protected buildings or classrooms, although the restricted range of the 802.11b (typically 30ft.) limits its use to smaller buildings. WLAN components are now cheap enough to be used in the home, with many being set-up so that one PC (a parent's PC, for example) can be used to share an internet connection with the whole family (whilst retaining access control at the parents' PC).

Early development included industry-specific solutions and proprietary protocols, but at the end of the 1990s these were replaced by standards, primarily the various versions of IEEE 802.11 (Wi-Fi) (see separate articles) and HomeRF (2 Mbit/s, intended for home use, unknown in the UK). An alternative ATM-like 5 GHz standardized technology, HIPERLAN, has so far not succeeded in the market, and with the release of the faster 54 Mbit/s 802.11a (5 GHz) and 802.11g (2.4 GHz) standards, almost certainly never will.

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Security

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At a wired network, one can often, to some degree, restrict the access to the network by physical means. The geographical range of a wireless network will more often than not be significantly greater than the office or home it's meant to cover; any neighbour or arbritrary trespasser may be able to sniff on all the traffic and gain unauthorized access to internal network resources as well as to the Internet, possibly sending spam or doing illegal actions using the owner's IP address, if the security isn't taken seriously.

Some advocates would like to see all access points openly available for the public, with the rationale being that everyone would benefit from being able to get online when on the road.

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Modes of operation

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Peer-to-peer or ad-hoc mode

This mode is a method for wireless devices to directly communicate with each other. Operating in ad-hoc mode allows wireless devices within range of each other to discover and communicate in peer-to-peer fashion without involving central access points.

This is typically used by two PCs to connect to one another, so that one can share the other's Internet connection for example, as well as for wireless mesh networks.

If you have a strength meter for the signal coming from all the other ad-hoc devices the meter will not read the strength accurately, and can be misleading, because it is registering the strength of the strongest signal, such as the closest computer.

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Access Point / Client

The most common is to have access points wired to Internet, and then having wireless clients (typically laptops) accessing Internet through the access point.

Almost any computer with a wireless card and wired connection to Internet can be set up as an Access Point, but today one can buy dedicated boxes cheaply. Those boxes usually look like a hub or router with antenna, bridges a wireless network to a wired Ethernet network. Administration of the access point (like setting SSID, putting up encryption, etc) is usually done through a web interface or telnet.

Home networks would typically have a stand-alone access point wired up i.e. through an ADSL connection, while hotspots and professional networks (i.e. providing wireless coverage in an office building) typically would have multiple access points, placed at strategical points. Template:Main

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Wireless distribution system

When it's difficult to get all the Access Points wired up, it's also possible to put up access points as repeaters. Template:Main

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Monitoring station

Some wireless network cards can be set up to monitor a network without connecting to an access point or revealing itself. This can be used to sniff clear-text activity, or to crack encryption.

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Health concerns

Because wireless LAN uses microwaves similar to those in mobile phones, any hypothetical health concerns would be similar. Template:Main

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Other concerns

The frequency which 802.11b operates at is 2.4GHz, which can lead to interference with cordless phones in the super high frequency range. If one wants to use a cordless telephone on the same premises, one should ensure that the cordless set uses a different frequency, such as 900Mhz or 5.8 Ghz. However, any wireless router has the ability to operate in different channels. Using channel 11 is most often the best situation for a wireless access point.

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See also


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External links

de:Wireless LAN es:WLAN fa:شبکه‌‌ی بی‌سیم fr:Réseau sans fil ko:무선 인터넷 id:Jaringan Lokal Nirkabel it:Wireless local area network nl:Wireless LAN ja:無線LAN no:Trådløst lokalt datanett pl:Sieć bezprzewodowa pt:Rede sem fios fi:WLAN sv:WLAN zh:无线局域网

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