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Details of Wi-Fi

Wi-Fi is a wireless technology brand owned by the Wi-Fi Alliance intended to improve the interoperability of wireless local area network products based on the IEEE 802.11 standards. Common applications for Wi-Fi include Internet and VoIP phone access, gaming, and network connectivity for consumer electronics such as televisions, DVD players, and digital cameras.

The Wi-Fi Alliance is a consortium of separate and independent companies agreeing to a set of common interoperable products based on the family of IEEE 802.11 standards. The Wi-Fi Alliance certifies products via a set of established test procedures to establish interoperability. Those manufacturers that are members of Wi-Fi Alliance whose products pass these interoperability tests can mark their products and product packaging with the Wi-Fi logo.

Wi-Fi technologies have gone through several generations since their inception in 1997. Wi-Fi is supported to different extents under Microsoft Windows, Apple Mac OS X and open source Unix and Linux operating systems.

Uses

A Wi-Fi enabled device such as a PC, game console, cell phone, MP3 player or PDA can connect to the Internet when within range of a wireless network connected to the Internet. The area covered by one or more interconnected access points is called a hotspot. Hotspots can cover as little as a single room with wireless-opaque walls or as much as many square miles covered by overlapping access points. Wi-Fi has been used to create mesh networks, for example, in London. Both architectures are used in community networks.

In addition to restricted use in homes and offices, Wi-Fi is publicly available at Wi-Fi hotspots provided either free of charge or to subscribers to various providers. Free hotspots are often provided by businesses such as hotels, restaurants, and airports who offer the service to attract or assist clients. Sometimes free Wi-Fi is provided by enthusiasts, or by organizations or authorities who wish to promote business in their area. Metropolitan-wide WiFi (Muni-Fi) already has more than 300 projects in process.

Wi-Fi also allows connectivity in peer-to-peer (wireless ad-hoc network) mode, which enables devices to connect directly with each other. This connectivity mode is useful in consumer electronics and gaming applications.

When the technology was first commercialized there were many problems because consumers could not be sure that products from different vendors would work together. The Wi-Fi Alliance began as a community to solve this issue so as to address the needs of the end user and allow the technology to mature. The Alliance created the branding Wi-Fi CERTIFIED to show consumers that products are interoperable with other products displaying the same branding.

Many consumer devices use Wi-Fi. Amongst others, personal computers can network to each other and connect to the Internet, mobile computers can connect to the Internet from any Wi-Fi hotspot, and digital cameras can transfer images wirelessly.

Routers which incorporate a DSL or cable modem and a Wi-Fi access point are often used in homes and other premises, and provide Internet access and internetworking to all devices connected wirelessly or by cable into them. Devices supporting Wi-Fi can also be connected in ad-hoc mode for client-to-client connections without a router.

Business and industrial Wi-Fi is widespread as of 2007. In business environments, increasing the number of Wi-Fi access points provides redundancy, support for fast roaming and increased overall network capacity by using more channels or creating smaller cells. Wi-Fi enables wireless voice applications (VoWLAN or WVOIP). Over the years, Wi-Fi implementations have moved toward 'thin' access points, with more of the network intelligence housed in a centralized network appliance, relegating individual Access Points to be simply 'dumb' radios. Outdoor applications may utilize true mesh topologies. As of 2007 Wi-Fi installations can provide a secure computer networking gateway, firewall, DHCP server, intrusion detection system, and other functions.

Advantages

Wi-Fi allows LANs to be deployed without cabling for client devices, typically reducing the costs of network deployment and expansion. Spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs.

As of 2007 wireless network adapters are built into most modern laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in even more devices. Wi-Fi has become widespread in corporate infrastructures, which also helps with the deployment of RFID technology that can piggyback on Wi-Fi.

Different competitive brands of access points and client network interfaces are inter-operable at a basic level of service. Products designated as "Wi-Fi Certified" by the Wi-Fi Alliance are backwards inter-operable. Wi-Fi is a global set of standards. Unlike mobile telephones, any standard Wi-Fi device will work anywhere in the world.

Wi-Fi is widely available in more than 250,000 public hotspots and tens of millions of homes and corporate and university campuses worldwide. WPA is not easily cracked if strong passwords are used and WPA2 encryption has no known weaknesses. New protocols for Quality of Service (WMM) make Wi-Fi more suitable for latency-sensitive applications (such as voice and video), and power saving mechanisms (WMM Power Save) improve battery operation.

Disadvantages

Spectrum assignments and operational limitations are not consistent worldwide. Most of Europe allows for an additional 2 channels beyond those permitted in the U.S. for the 2.4 GHz band. (1-13 vs. 1-11); Japan has one more on top of that (1-14). Europe, as of 2007, is now essentially homogeneous in this respect. A very confusing aspect is the fact a Wi-Fi signal actually occupies five channels in the 2.4 GHz band resulting in only three non-overlapped channels in the U.S.: 1, 6, 11, and four in Europe: 1, 5, 9, 13.

Some countries, such as Italy, formerly required a 'general authorization' for any Wi-Fi used outside an operator's own premises, or require something akin to an operator registration. Equivalent isotropically radiated power (EIRP) in the EU is limited to 20 dBm (0.1 W).

Power consumption is fairly high compared to some other low-bandwidth standards, such as Zigbee and Bluetooth, making battery life a concern.

The most common wireless encryption standard, Wired Equivalent Privacy or WEP, has been shown to be easily breakable even when correctly configured. Wi-Fi Protected Access (WPA and WPA2), which began shipping in 2003, aims to solve this problem and is now available on most products. Wi-Fi Access Points typically default to an "open" (encryption-free) mode. Novice users benefit from a zero-configuration device that works out of the box, but this default is without any wireless security enabled, providing open wireless access to their LAN. To turn security on requires the user to configure the device, usually via a software graphical user interface (GUI). Wi-Fi networks that are open (unencrypted) can be monitored and used to read and copy data (including personal information) transmitted over the network, unless another security method is used to secure the data, such as a VPN or a secure web page. (See HTTPS/Secure Socket Layer.)

Many 2.4 GHz 802.11b and 802.11g Access points default to the same channel on initial startup, contributing to congestion on certain channels. To change the channel of operation for an access point requires the user to configure the device.

Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or 802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m (300 ft) outdoors. Range also varies with frequency band. Wi-Fi in the 2.4 GHz frequency block has slightly better range than Wi-Fi in the 5 GHz frequency block. Outdoor range with improved (directional) antennas can be several kilometres or more with line-of-sight.

Wi-Fi performance also decreases exponentially as the range increases.

Wi-Fi pollution, or an excessive number of access points in the area, especially on the same or neighboring channel, can prevent access and interfere with the use of other access points by others, caused by overlapping channels in the 802.11g/b spectrum, as well as with decreased signal-to-noise ratio (SNR) between access points. This can be a problem in high-density areas, such as large apartment complexes or office buildings with many Wi-Fi access points. Additionally, other devices use the 2.4 GHz band: microwave ovens, security cameras, Bluetooth devices and (in some countries) Amateur radio, video senders, cordless phones and baby monitors can cause significant additional interference. General guidance to those who suffer these forms of interference or network crowding is to migrate to a WiFi 5 GHz product, (802.11a or the newer 802.11n IF it has 5GHz/11a support) as the 5 GHz band is relatively unused and there are many more channels available. This also requires users to set up the 5 GHz band to be the preferred network in the client and to configure each network band to a different name (SSID).

It is also an issue when municipalities, or other large entities such as universities, seek to provide large area coverage. This openness is also important to the success and widespread use of 2.4 GHz Wi-Fi.

Interoperability issues between non WiFi brands or proprietary deviations from the standard can disrupt connections or lower throughput speeds on all user's devices that are within range, to include the non-WiFi or proprietary product.

Standard devices

Wireless access points connects a group of wireless devices to an adjacent wired LAN. An access point is similar to a network hub, relaying data between connected wireless devices in addition to a (usually) single connected wired device, most often an ethernet hub or switch, allowing wireless devices to communicate with other wired devices.

Wireless adapters allow devices to connect to a wireless network. These adapters connect to devices using various external or internal interconnects such as PCI, miniPCI, USB, ExpressCard, Cardbus and PC card. Most newer laptop computers are equipped with internal adapters. Internal cards are generally more difficult to install.

Wireless routers integrate a WAP, ethernet switch, and internal Router firmware application that provides IP Routing, NAT, and DNS forwarding through an integrated WAN interface. A wireless router allows wired and wireless ethernet LAN devices to connect to a (usually) single WAN device such as cable modem or DSL modem. A wireless router allows all three devices (mainly the access point and router) to be configured through one central utility. This utility is most usually an integrated web server which serves web pages to wired and wireless LAN clients and often optionally to WAN clients. This utility may also be an application that is run on a desktop computer such as Apple's AirPort.

Wireless network bridges connect a wired network to a wireless network. This is different from an access point in the sense that an access point connects wireless devices to a wired network at the data-link layer. Two wireless bridges may be used to connect two wired networks over a wireless link, useful in situations where a wired connection may be unavailable, such as between two separate homes.

Wireless range extenders or wireless repeaters can extend the range of an existing wireless network. Range extenders can be strategically placed to elongate a signal area or allow for the signal area to reach around barriers such as those created in L-shaped corridors. Wireless devices connected through repeaters will suffer from an increased latency for each hop. Additionally, a wireless device connected to any of the repeaters in the chain throughput that is limited by the weakest link between the two nodes in the chain from which the connection originates to where the connection ends.

History

Wi-Fi uses both single carrier direct-sequence spread spectrum radio technology (part of the larger family of spread spectrum systems) and multi-carrier OFDM (Orthogonal Frequency Division Multiplexing) radio technology. These regulations then enabled the development of Wi-Fi, its onetime competitor HomeRF, and Bluetooth.

Unlicensed spread spectrum was first made available in the US by the Federal Communications Commission in 1985 and these FCC regulations were later copied with some changes in many other countries enabling use of this technology in all major countries. The FCC action was proposed by Michael Marcus of the FCC staff in 1980 and the subsequent regulatory action took 5 more years. It was part of a broader proposal to allow civil use of spread spectrum technology and was opposed at the time by main stream equipment manufacturers and many radio system operators.

The precursor to Wi-Fi was invented in 1991 by NCR Corporation/AT&T (later Lucent & Agere Systems) in Nieuwegein, the Netherlands. It was initially intended for cashier systems; the first wireless products were brought on the market under the name WaveLAN with speeds of 1 Mbit/s to 2 Mbit/s. Vic Hayes, who held the chair of IEEE 802.11 for 10 years and has been named the 'father of Wi-Fi,' was involved in designing standards such as IEEE 802.11b, and 802.11a.

Origin and meaning of the term "Wi-Fi"

Despite the similarity between the terms "Wi-Fi" and "Hi-Fi", statements reportedly made by Phil Belanger of the Wi-Fi Alliance contradict the conclusion that "Wi-Fi" stands for "Wireless Fidelity". According to Belanger, the Interbrand Corporation developed the brand "Wi-Fi" for the Wi-Fi Alliance to use to describe WLAN products that are based on the IEEE 802.11 standards. In Belanger's words,

Wi-Fi and the yin yang style logo were invented by Interbrand. We [the founding members of the Wireless Ethernet Compatibility Alliance, now called as the Wi-Fi Alliance] hired Interbrand to come up with the name and logo that we could use for our interoperability seal and marketing efforts. We needed something that was a little catchier than 'IEEE 802.11b Direct Sequence'.

The Wi-Fi Alliance themselves invoked the term "Wireless Fidelity" with the marketing of a tag line "The Standard for Wireless Fidelity," but later removed the tag from their marketing. The Wi-Fi Alliance now seems to discourage the propagation of the notion that "Wi-Fi" stands for "Wireless Fidelity", but it has been referred to as such by the Wi-Fi Alliance in White Papers currently held in their knowledge base: "... a promising market for wireless fidelity (Wi-Fi) network equipment." and "A Short History of WLANs." The association created the Wi-Fi (Wireless Fidelity) logo to indicate that a product had been certified for interoperability.