Wi-Fi (/ˈwaɪfaɪ/) is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point (or hotspot) has a range of about 20 meters (65 ft) indoors and a greater range outdoors. Multiple overlapping access points can cover large areas.
“Wi-Fi” is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11 family of standards. Wi-Fi is used by over 700 million people. There are over four million hotspots (places with Wi-Fi Internet connectivity) around the world, and about 800 million new Wi-Fi devices are sold every year. Wi-Fi products that complete Wi-Fi Alliance interoperability certification testing successfully may use the “Wi-Fi CERTIFIED” designation and trademark.
To connect to a Wi-Fi LAN, a computer has to be equipped with a wireless network interface controller. The combination of computer and interface controller is called a station. All stations share a single radio frequency communication channel. Transmissions on this channel are received by all stations within range. The hardware does not signal the user that the transmission was delivered and is therefore called a best-effort delivery mechanism. A carrier wave is used to transmit the data in packets, referred to as “Ethernet frames”. Each station is constantly tuned in on the radio frequency communication channel to pick up available transmissions.
Internet access
A Wi-Fi-enabled device, such as a personal computer, video game console, smartphone or digital audio player, can connect to the Internet when within range of a wireless network connected to the Internet. The coverage of one or more (interconnected) access points—called hotspots—comprises an area as small as a few rooms or as large as many square miles. Coverage in the larger area may depend on a group of access points with overlapping coverage. Wi-Fi technology has been used successfully in wireless mesh networks in London, UK, for example.
Wi-Fi provides service in private homes and offices as well as in public spaces at Wi-Fi hotspots set up either free-of-charge or commercially. Organizations and businesses, such as airports, hotels, and restaurants, often provide free-use hotspots to attract or assist clients. Enthusiasts or authorities who wish to provide services or even to promote business in selected areas sometimes provide free Wi-Fi access. As of 2008 more than 300 city-wide Wi-Fi projects had been created. As of 2010 the Czech Republic had 1150 Wi-Fi based wireless Internet service providers.
Routers that incorporate a digital subscriber line modem or a cable modem and a Wi-Fi access point, often set up in homes and other buildings, provide Internet access and internetworking to all devices tuned into them, wirelessly or via cable. With the emergence of MiFi and WiBro (a portable Wi-Fi router) people can easily create their own Wi-Fi hotspots that connect to Internet via cellular networks. Now iPhone, Android, Bada and Symbian phones can create wireless connections.
One can also connect Wi-Fi devices in ad-hoc mode for client-to-client connections without a router. Wi-Fi also connects places normally without network access, such as kitchens and garden sheds.
City-wide Wi-Fi
In the early 2000s, many cities around the world announced plans to construct city-wide Wi-Fi networks. Doing so proved to be more difficult than envisioned, and as a result most of these projects were either cancelled or placed on indefinite hold. A few were successful; for example, in 2005 Sunnyvale, California, became the first city in the United States to offer city-wide free Wi-Fi, and Minneapolis has generated $1.2 million in profit annually for its provider.
In May 2010, London, UK, Mayor Boris Johnson pledged to have London-wide Wi-Fi by 2012. Islington in London already has extensive outdoor Wi-Fi coverage.
In 2010 Mysore became India’s first Wi-fi-enabled city and second in the world after Jerusalem. A company called WiFiyNet has set up hotspots in Mysore, covering the complete city and a few nearbly villages.
Campus-wide Wi-Fi
Many traditional college campuses provide at least partial wireless Wi-Fi Internet coverage. Carnegie Mellon University built the first campus-wide wireless Internet network, called Wireless Andrew at its Pittsburgh campus in 1993 before Wi-Fi branding originated.
In 2000, Drexel University in Philadelphia became the United States’s first major university to offer completely wireless Internet access across its entire campus.
Direct computer-to-computer communications
Wi-Fi also allows communications directly from one computer to another without an access point intermediary. This is called ad hoc Wi-Fi transmission. This wireless ad hoc network mode has proven popular with multiplayer handheld game consoles, such as the Nintendo DS, digital cameras, and other consumer electronics devices.
The disadvantage of this method is that vendors must not implement speeds greater than 11 Mbit/s(802.11b) and only WEP encryption is available, not WPA(2).
Similarly, the Wi-Fi Alliance promotes a specification called Wi-Fi Direct for file transfers and media sharing through a new discovery- and security-methodology. Wi-Fi Direct launched in October 2010.
Some devices can share their Internet connection, becoming hotspots or “virtual routers”.
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