Introduction:
Wi-Fi (pronounced /ˈwaɪfaɪ/) is a trademark of the Wi-Fi Alliance for certified products based on the IEEE 802.11 standards. This certification warrants interoperability between different wireless devices.
In some countries (and in this article) the term Wi-Fi[1][2] is often used by the public as a synonym for IEEE 802.11-wireless LAN (WLAN).
Not every IEEE 802.11 compliant device is certified by the Wi-Fi Alliance, which may be because of certification costs that must be paid for each certified device type. The lack of the Wi-Fi logo does not implythat a device is incompatible to certified Wi-Fi-devices.
Wi-Fi is used by most personal computer operating systems, many video game consoles, laptops,smartphones, printers, and other peripherals.
Uses:
A Wi-Fi enabled device such as a PC, video game console, mobile phone, MP3 player or PDA 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 a hotspot — can comprise an area as small as a single room with wireless-opaque walls or as large as many square miles covered by overlapping access points. Wi-Fi technology has served to set up mesh networks, for example, in London. Both architectures can operate in community networks.
In addition to restricted use in homes and offices, Wi-Fi can make access publicly available at Wi-Fi hotspots provided either free of charge or to subscribers to various providers. Organizations and businesses such as airports, hotels and restaurants often provide free hotspots to attract or assist clients. Enthusiasts or authorities who wish to provide services or even to promote business in a given area sometimes provide free Wi-Fi access. There are already more than 300 metropolitan-wide Wi-Fi (Muni-Fi) projects in progress. There were 879 Wi-Fi based Wireless Internet service providers in the Czech Republic as of May 2008.
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 can prove useful in consumer electronics and gaming applications.
When wireless networking technology first entered the market many problems ensued for consumers who could not rely on products from different vendors working together. The Wi-Fi Alliance began as a community to solve this issue — aiming to address the needs of the end-userand to allow the technology to mature. The Alliance created the branding Wi-Fi CERTIFIED to reassure consumers that products willinteroperate 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-modem or a cable-modem and a Wi-Fi access point, often set up in homes and other premises, provideInternet-access and internetworking to all devices connected (wirelessly or by cable) to them. One can also connect Wi-Fi devices in ad hoc mode for client-to-client connections without a router. Wi-Fi also enables places which would traditionally not have network to be connected, for example bathrooms, kitchens and garden sheds.
As of 2007 Wi-Fi technology had spread widely within business and industrial sites. In business environments, just like other 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 by defining 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 the role of mere "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.
Naming
The term Wi-Fi suggests Wireless Fidelity, compared with the long-established audio recording term High Fidelity or Hi-Fi. Wireless Fidelity has often been used in an informal way, even by the Wi-Fi Alliance itself, but officially the term Wi-Fi does not mean anything.
The term Wi-Fi, first used commercially in August 1999, was coined by a brand consulting firm called Interbrand Corporation that had been hired by the Alliance to determine a name that was "a little catchier than 'IEEE 802.11b Direct Sequence'." Interbrand invented Wi-Fias a play on words with Hi-Fi, and also created the yin yang-style Wi-Fi logo.
The Wi-Fi Alliance initially complicated matters by stating that it "actually stood for" Wireless Fidelity, as with the advertising slogan, "The Standard for Wireless Fidelity,"] but later removed the phrase from their marketing. The Wi-Fi Alliance's early White papers still held on their website say: "…a promising market for wireless fidelity (Wi-Fi) network equipment."and "A Short History of WLANs." The yin yang logo indicates that a product had been certified for interoperability.
The Alliance has since downplayed the connection to Hi-Fi. Their official position now is that it is merely a brand name that stands for nothing in particular, and they now discourage the use of the term Wireless Fidelity.
Limitations
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, was essentially homogeneous in this respect. A very confusing aspect is the fact that 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 three or four in Europe: 1, 5, 9, 13 can be used if all the equipment on a specific area can be guaranteed not to use 802.11b at all, even as fallback or beacon. Equivalent isotropically radiated power(EIRP) in the EU is limited to 20 dBm (100 mW).
