Information AboutWlan |
| CATEGORIES ABOUT WIRELESS LAN | |
| local area networks | |
| wireless networking | |
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wireless card.]] A wireless LAN or '''WLAN''' is a s connecting the wireless users to the wired network. 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. METHOD OF COMMUNICATION A Wireless LAN is a Wireless network using Radio Frequencies for Communication between computer devices. The frequency that a particular device transmits on or receives from is designated in two ways: standard and channel. Standard In 1990, the IEEE (Institute of Electrical and Electronic Engineers) formed a group to develop a standard for wireless equipment. On June 26, 1997, a standard was finally developed called 802.11. The standard specified that the upper layers of the OSI model can not be modified, and WLANs must be implemented on the physical and data link layers. This provided the ability to run any operating system or LAN application on a WLAN without any modification. They accomplished this by doing upper layer features on the data link layer. B The original 802.11 standard limited WLAN speed to 2 Mbps, which is not efficient enough for most networking needs. In September of 1999, 802.11b was amended to the original standard. The B standard offered two higher speeds, 5.5 Mbps and 11 Mbps, to the original 1 or 2 Mbps standard. A At the same time B was released, A was also added to the 802.11 standard. 802.11a has a maximum speed of 54 Mbps and supports speeds of 48, 36, 24, 18, 12, 9, and 6 Mbps at a frequency of 5 GHz. 802.11a maintains the same 802.11b data link layer functions, but they are different in the way they operate at the physical layer. The reason that 802.11a is faster than 802.11b is because of its higher frequency, more transmission channels, multiplexed transmissions, and an efficient error-checking scheme. While A and B were released at the same time, A wasn’t implemented until late in 2001. 802.11a was pushed back due to technical problems and the higher cost of implementation. The reason that A is more expensive is because of the semiconductors used. Unlike 802.11b, which uses CMOS (complementary metal oxide semiconductor) as its semiconductor, 802.11a requires a compound like gallium arsenide (GaAs) or silicon germanium (SiGe). These semiconductors are more expensive and require more time to manufacture. G The IEEE then revisited the 802.11 standard one last time to combine the best of both worlds. The new standard would keep the stable and accepted features of 802.11b, and increase the data speed standards so that they are comparable with 802.11a. In late 2001, a draft was proposed called 802.11g. 802.11g runs on the same RF band as B (2.4 GHz) but uses the transmission techniques of A. Like A, the G standard also permits vendors to incorporate proprietary techniques that can potentially push the speeds of G to 108 Mbps. MODES OF OPERATION 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 Network s. 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. 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. See Also: Wireless access point 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. See Also: Wireless Distribution System 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. COMPONENTS OF A WIRELESS LAN Access Point(AP) Access Point s which are two-way Transceiver s that broadcast data into the surrounding environment. Wireless Capture Device Wireless Device s peripherals designed for personal computers. Their purpose is to allow the computer - and therefore its user - to connect to a network through radio waves. These peripherals can be found as PCI cards, or portable USB devices. When activated, they scan their environment for signals from a wireless access point. If one is found, they allow the user to connect to the access point. The wireless capture card can determine if the access point is secured with an encryption method (usually WEP or WPA ) and can still allow the user to connect to it assuming the key or passcode is availible. COSTS FOR WIRELESS LAN Normally you have to pay for a wireless connection. Some people make their wireless routers available for free without registration or password-protection, so everybody near the Hotspot can surf and communicate. Communities can be found here:
Other Hotspots with wireless Lan (WLAN) cost a few dollars per hour. HEALTH CONCERNS Because wireless LAN uses Microwaves similar to those in Mobile Phones , any hypothetical health concerns would be similar. See Also: Wireless electronic devices and health OTHER CONCERNS The frequency which 802.11b operates at is 2.4GHz, which can lead to Interference with Cordless Phone s 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. SEE ALSO
SECURITY See Also: Wireless LAN Security 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 arbitrary 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. 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 . WEP See article on Wired Equivalent Privacy . WPA See article on Wi-Fi Protected Access (WPA) and WPA2. TKIP-PSK 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. There are works in progress for maintaining a List over open wireless networks EXTERNAL LINKS
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