03-10-2012, 01:37 PM
Wi-Fi (wireless fidelity)
Wi-Fi.docx (Size: 672.28 KB / Downloads: 33)
INTRODUCTION
Wi-Fi is a popular technology that allows an electronic device to exchange data wirelessly (using radio waves) over a computer network, including high-speed Internet Connections. Since most modern WLANs are based on these standards, the term "Wi-Fi" is used in general English as a synonym for "WLAN".
A device using Wi-Fi, such as a personal computer, video game console, smartphone, tablet, or digital audio player, can connect to a network resource such as the Internet via a wireless network access point. Such an access point (or hotspot) has a range of about 20 meters (65 ft) indoors and a greater range outdoors.
"Wi-Fi" is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11 family of standards. Only Wi-Fi products that complete Wi-Fi Alliance interoperability certification testing successfully may use the "Wi-Fi CERTIFIED" designation and trademark.
Wi-Fi has had a checkered security history. Its earliest encryption system, WEP, proved easy to break. Much higher quality protocols, WPA and WPA2, were added later. However, an optional feature added in 2007,called Wi-Fi Protected Setup (WPS), has a flaw that allows a remote attacker to recover the router's
USES
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
1A Wi-Fi-enabled device 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.
City-Wide Wi-Fi
In the early 2000s, many cities around the world announced plans to construct city-wide Wi-Fi networks. There are many successful examples; 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 2004, Mysore became India's first Wi-Fi enabled city and second in the world after Jerusalem.
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 in1993 before Wi-Fi branding originated.
In 2000, Drexel University in Philadelphia became the United State’s first major university to offer completely wireless Internet access across its entire campus.
HISTORY
Wi-Fi would certainly not exist without a decision taken in 1985 by the Federal Communications Commission (FCC), America's telecoms regulator, to open several bands of wireless spectrum, allowing them to be used without the need for a government license. This was an unheard-of move at the time; other than the ham-radio channels, there was very little unlicensed spectrum
These so-called “garbage bands”, at 900MHz, 2.4GHz and 5.8GHz, were already allocated to equipment that used radio-frequency energy for purposes other than communications: microwave ovens, for example, which use radio waves to heat food. The FCC made them available for communications purposes as well, on the condition that any devices using these bands would have to steer around interference from other equipment. They would do so using “spread spectrum” technology, originally developed for military use, which spreads a radio signal out over a wide range of frequencies, in contrast to the usual approach of transmitting on a 1single, well-defined frequency.
THE NAME Wi-Fi
The term Wi-Fi suggests Wireless Fidelity, resembling the long-established audio-equipment classification term Hi-Fi (used since 1950 or high fidelity (in use since the 1930s). Even the Wi-Fi Alliance itself has often used the phrase Wireless Fidelity in its press releases and documents.
The yin-yang Wi-Fi logo indicates the certification of a product for interoperability.
Non-Wi-Fi technologies intended for fixed points such as Motorola Canopy are usually described as fixed wireless. Alternative wireless technologies include mobile phone standards such as 2G, 3G or 4G.
Wi-Fi.docx (Size: 672.28 KB / Downloads: 33)
INTRODUCTION
Wi-Fi is a popular technology that allows an electronic device to exchange data wirelessly (using radio waves) over a computer network, including high-speed Internet Connections. Since most modern WLANs are based on these standards, the term "Wi-Fi" is used in general English as a synonym for "WLAN".
A device using Wi-Fi, such as a personal computer, video game console, smartphone, tablet, or digital audio player, can connect to a network resource such as the Internet via a wireless network access point. Such an access point (or hotspot) has a range of about 20 meters (65 ft) indoors and a greater range outdoors.
"Wi-Fi" is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11 family of standards. Only Wi-Fi products that complete Wi-Fi Alliance interoperability certification testing successfully may use the "Wi-Fi CERTIFIED" designation and trademark.
Wi-Fi has had a checkered security history. Its earliest encryption system, WEP, proved easy to break. Much higher quality protocols, WPA and WPA2, were added later. However, an optional feature added in 2007,called Wi-Fi Protected Setup (WPS), has a flaw that allows a remote attacker to recover the router's
USES
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
1A Wi-Fi-enabled device 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.
City-Wide Wi-Fi
In the early 2000s, many cities around the world announced plans to construct city-wide Wi-Fi networks. There are many successful examples; 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 2004, Mysore became India's first Wi-Fi enabled city and second in the world after Jerusalem.
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 in1993 before Wi-Fi branding originated.
In 2000, Drexel University in Philadelphia became the United State’s first major university to offer completely wireless Internet access across its entire campus.
HISTORY
Wi-Fi would certainly not exist without a decision taken in 1985 by the Federal Communications Commission (FCC), America's telecoms regulator, to open several bands of wireless spectrum, allowing them to be used without the need for a government license. This was an unheard-of move at the time; other than the ham-radio channels, there was very little unlicensed spectrum
These so-called “garbage bands”, at 900MHz, 2.4GHz and 5.8GHz, were already allocated to equipment that used radio-frequency energy for purposes other than communications: microwave ovens, for example, which use radio waves to heat food. The FCC made them available for communications purposes as well, on the condition that any devices using these bands would have to steer around interference from other equipment. They would do so using “spread spectrum” technology, originally developed for military use, which spreads a radio signal out over a wide range of frequencies, in contrast to the usual approach of transmitting on a 1single, well-defined frequency.
THE NAME Wi-Fi
The term Wi-Fi suggests Wireless Fidelity, resembling the long-established audio-equipment classification term Hi-Fi (used since 1950 or high fidelity (in use since the 1930s). Even the Wi-Fi Alliance itself has often used the phrase Wireless Fidelity in its press releases and documents.
The yin-yang Wi-Fi logo indicates the certification of a product for interoperability.
Non-Wi-Fi technologies intended for fixed points such as Motorola Canopy are usually described as fixed wireless. Alternative wireless technologies include mobile phone standards such as 2G, 3G or 4G.