Wi-Fi (pronounced /ˈwaɪfaɪ/) is a trademark of the Wi-Fi Alliance that may be used with certified products that belong to a class of wireless local area network (WLAN) devices based on the IEEE 802.11 standards. Because of the close relationship with its underlying standard, the term Wi-Fi is often used as a synonym for IEEE 802.11 technology.
The Wi-Fi Alliance is a global, non-profit association of companies that promotes WLAN technology and certifies products if they conform to certain standards of interoperability. Not every IEEE 802.11-compliant device is submitted for certification to the Wi-Fi Alliance, sometimes because of costs associated with the certification process and the lack of the Wi-Fi logo does not imply a device is incompatible with Wi-Fi devices.
Today, an IEEE 802.11 device is installed in many personal computers, video game consoles, smartphones, printers, and other peripherals, and virtually all laptop or palm-sized computers.
ternet access
A roof mounted Wi-Fi antenna
A Wi-Fi enabled device such as a personal computer, video game console, mobile phone, MP3 player or personal digital assistant 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 few rooms or as large as many square miles covered by a group of access points with overlapping coverage. Wi-Fi technology has been used in wireless mesh networks, for example, in London.[3]
In addition to private use in homes and offices, Wi-Fi can provide public access at Wi-Fi hotspots provided either free of charge or to subscribers to various commercial services. 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 selected areas sometimes provide free Wi-Fi access. As of 2008 there are more than 300 metropolitan-wide Wi-Fi (Muni-Fi) projects in progress.[4] There were 879 Wi-Fi based Wireless Internet service providers in the Czech Republic as of May 2008.[5][6]
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 premises, provide Internet-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 that would traditionally not have network to be connected, for example bathrooms, kitchens and garden sheds.
Airport Wi-Fi
In September of 2003, Pittsburgh International Airport became the first airport to allow and offer free Wi-Fi throughout its terminal.[7] It is now commonplace.
City-wide Wi-Fi
Further information: Municipal wireless network
Wikibooks has a book on the topic of
Nets, Webs and the Information Infrastructure
A municipal wireless antenna in Minneapolis
In the early 2000s, many cities around the world announced plans for a city wide Wi-Fi network. This proved to be much more difficult than their promoters initially envisioned with the result that most of these projects were either canceled 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.[8] Few of the Municipal Wi-Fi firms have now entered into the field of Smart grid networks.[9][clarification needed]
Campus-wide Wi-Fi
Carnegie Mellon University built the first wireless Internet network in the world at their Pittsburgh campus in 1994, long before the Wi-Fi standard was adopted.[10]
Direct computer-to-computer communications
Wi-Fi also allows communications directly from one computer to another without the involvement of an access point. This is called the ad-hoc mode of 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. A similar method is a new specification called Wi-Fi Direct which is promoted by the Wi-Fi Alliance for file transfers and media sharing through a new discovery and security methodology.[11]
Future directions
As of 2010 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.
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 orthogonal frequency-division multiplexing (OFDM) radio technology. The deregulation of certain radio-frequencies for unlicensed spread spectrum deployment enabled the development of Wi-Fi products, its onetime competitor HomeRF, Bluetooth, and many other products such as some types of cordless telephones.
Unlicensed spread spectrum was first made available in the US by the FCC in rules adopted on May 9, 1985[12] 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 mainstream equipment manufacturers and many radio system operators.
Half-size ISA 2.4 GHz WaveLAN card by AT&T
Wi-Fi technology has its origins in a 1985 ruling by the U.S. Federal Communications Commission that released several bands of the radio spectrum for unlicensed use.[14] The precursor to the common Wi-Fi system was invented in 1991 by NCR Corporation/AT&T (later Lucent Technologies & 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.
Key portions of the IEEE 802.11 technology underlying Wi-Fi (in its a, g, and n varieties) were determined to be infringing on U.S. Patent 5,487,069, which was filed in 1993[15] by CSIRO, an Australian research body. The patent has been the subject of protracted and ongoing legal battles between CSIRO and major IT corporations. In 2009, the CSIRO settled with 14 companies, including Hewlett-Packard, Intel, Dell, Toshiba, ASUS, Microsoft and Nintendo, under confidential terms. The revenue arising from these settlements to October 2009 is approximately AU$200 million. [16][17][18][19][20][21]
Europe leads overall in uptake of wireless-phone technology but the US leads in Wi-Fi systems partly because they lead in laptop usage. As of July 2005, there were at least 68,643 Wi-Fi locations worldwide, a majority in the US, then the UK and Germany. The US and Western Europe make up about 80% of the worldwide Wi-Fi users. Plans are underway in areas of the US to provide public Wi-Fi coverage as a public free service. Even with these large numbers and more expansion, the extent of actual Wi-Fi usage is lower than expected. Jupiter Research found that only 15% of people have used Wi-Fi and only 6% in a public place.[22]
Wi-Fi certification
Main article: Wi-Fi Alliance
Wi-Fi technology is based on IEEE 802.11 standards. The IEEE develops and publishes these standards, but does not test equipment for compliance with them. The non-profit Wi-Fi Alliance was formed in 1999 to fill this void — to establish and enforce standards for interoperability and backward compatibility, and to promote wireless local area network technology. Today the Wi-Fi Alliance consists of more than 300 companies from around the world.[23][24] Manufacturers with membership in the Wi-Fi Alliance, whose products pass the certification process, are permitted to mark those products with the Wi-Fi logo.
Specifically, the certification process requires conformance to the IEEE 802.11 radio standards, the WPA and WPA2 security standards, and the EAP authentication standard. Certification may optionally include tests of IEEE 802.11 draft standards, interaction with cellular phone technology in converged devices, and features relating to security set-up, multimedia, and power saving.
The Wi-Fi name
The term Wi-Fi suggests Wireless Fidelity, compared with the long-established audio equipment certification term High Fidelity or Hi-Fi. Wireless Fidelity has often been used, even by the Wi-Fi Alliance itself in its press releases[26][27] and documents;[28][29] the term may also be found in a white paper on Wi-Fi from ITAA.[30] However, based on Phil Belanger's[31] statement, the term Wi-Fi was never supposed to mean anything at all.[32][33]
The term Wi-Fi, first used commercially in August 1999,[34] 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'."[35][32][33] Mr Belanger also said, Interbrand invented Wi-Fi as a play on words with Hi-Fi, and also created the yin yang-style Wi-Fi logo. The term Wireless Fidelity was used later as an explanation of what Wi-Fi means.
The Wi-Fi Alliance initially used an advertising slogan for Wi-Fi, "The Standard for Wireless Fidelity",[32] but later removed the phrase from their marketing. Despite this, some documents from the Alliance dated 2003 and 2004 still contain the term Wireless Fidelity.[28][29] There was also no official statement for dropping the term.
The yin yang logo indicates that a product had been certified for interoperability.[28]
Advantages and challenges
A keychain size Wi-Fi detector.
Operational advantages
Wi-Fi allows local area networks (LANs) to be deployed without wires 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.
Wireless network adapters are now built into most 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.
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 compatible. Wi-Fi is a global set of standards. Unlike mobile phones, any standard Wi-Fi device will work anywhere in the world.
Wi-Fi is widely available in more than 220,000 public hotspots and tens of millions of homes and corporate and university campuses worldwide.[36] The current version of Wi-Fi Protected Access encryption (WPA2) is considered secure, provided a strong passphrase is used. 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.
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).
Reach
See also: Long-range Wi-Fi
Large satellite dish modified for long-range Wi-Fi communications in Venezuela
Wi-Fi networks have limited range. A typical wireless 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. The new IEEE 802.11n however, can exceed that range by more than double.[citation needed] 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 ranges - through use of directional antennas - can be improved with antennas located several kilometres or more from their base. In general, the maximum amount of power that a Wi-Fi device can transmit is limited by local regulations, such as FCC Part 15[37] in USA.
Wi-Fi performance decreases roughly quadratically[citation needed] as distance increases at constant radiation levels.
Due to reach requirements for wireless LAN applications, power consumption is fairly high compared to some other standards. Technologies such as Bluetooth, that are designed to support wireless PAN applications, provide a much shorter propagation range of <10m>
The Wi-Fi Alliance is a global, non-profit association of companies that promotes WLAN technology and certifies products if they conform to certain standards of interoperability. Not every IEEE 802.11-compliant device is submitted for certification to the Wi-Fi Alliance, sometimes because of costs associated with the certification process and the lack of the Wi-Fi logo does not imply a device is incompatible with Wi-Fi devices.
Today, an IEEE 802.11 device is installed in many personal computers, video game consoles, smartphones, printers, and other peripherals, and virtually all laptop or palm-sized computers.
ternet access
A roof mounted Wi-Fi antenna
A Wi-Fi enabled device such as a personal computer, video game console, mobile phone, MP3 player or personal digital assistant 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 few rooms or as large as many square miles covered by a group of access points with overlapping coverage. Wi-Fi technology has been used in wireless mesh networks, for example, in London.[3]
In addition to private use in homes and offices, Wi-Fi can provide public access at Wi-Fi hotspots provided either free of charge or to subscribers to various commercial services. 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 selected areas sometimes provide free Wi-Fi access. As of 2008 there are more than 300 metropolitan-wide Wi-Fi (Muni-Fi) projects in progress.[4] There were 879 Wi-Fi based Wireless Internet service providers in the Czech Republic as of May 2008.[5][6]
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 premises, provide Internet-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 that would traditionally not have network to be connected, for example bathrooms, kitchens and garden sheds.
Airport Wi-Fi
In September of 2003, Pittsburgh International Airport became the first airport to allow and offer free Wi-Fi throughout its terminal.[7] It is now commonplace.
City-wide Wi-Fi
Further information: Municipal wireless network
Wikibooks has a book on the topic of
Nets, Webs and the Information Infrastructure
A municipal wireless antenna in Minneapolis
In the early 2000s, many cities around the world announced plans for a city wide Wi-Fi network. This proved to be much more difficult than their promoters initially envisioned with the result that most of these projects were either canceled 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.[8] Few of the Municipal Wi-Fi firms have now entered into the field of Smart grid networks.[9][clarification needed]
Campus-wide Wi-Fi
Carnegie Mellon University built the first wireless Internet network in the world at their Pittsburgh campus in 1994, long before the Wi-Fi standard was adopted.[10]
Direct computer-to-computer communications
Wi-Fi also allows communications directly from one computer to another without the involvement of an access point. This is called the ad-hoc mode of 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. A similar method is a new specification called Wi-Fi Direct which is promoted by the Wi-Fi Alliance for file transfers and media sharing through a new discovery and security methodology.[11]
Future directions
As of 2010 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.
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 orthogonal frequency-division multiplexing (OFDM) radio technology. The deregulation of certain radio-frequencies for unlicensed spread spectrum deployment enabled the development of Wi-Fi products, its onetime competitor HomeRF, Bluetooth, and many other products such as some types of cordless telephones.
Unlicensed spread spectrum was first made available in the US by the FCC in rules adopted on May 9, 1985[12] 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 mainstream equipment manufacturers and many radio system operators.
Half-size ISA 2.4 GHz WaveLAN card by AT&T
Wi-Fi technology has its origins in a 1985 ruling by the U.S. Federal Communications Commission that released several bands of the radio spectrum for unlicensed use.[14] The precursor to the common Wi-Fi system was invented in 1991 by NCR Corporation/AT&T (later Lucent Technologies & 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.
Key portions of the IEEE 802.11 technology underlying Wi-Fi (in its a, g, and n varieties) were determined to be infringing on U.S. Patent 5,487,069, which was filed in 1993[15] by CSIRO, an Australian research body. The patent has been the subject of protracted and ongoing legal battles between CSIRO and major IT corporations. In 2009, the CSIRO settled with 14 companies, including Hewlett-Packard, Intel, Dell, Toshiba, ASUS, Microsoft and Nintendo, under confidential terms. The revenue arising from these settlements to October 2009 is approximately AU$200 million. [16][17][18][19][20][21]
Europe leads overall in uptake of wireless-phone technology but the US leads in Wi-Fi systems partly because they lead in laptop usage. As of July 2005, there were at least 68,643 Wi-Fi locations worldwide, a majority in the US, then the UK and Germany. The US and Western Europe make up about 80% of the worldwide Wi-Fi users. Plans are underway in areas of the US to provide public Wi-Fi coverage as a public free service. Even with these large numbers and more expansion, the extent of actual Wi-Fi usage is lower than expected. Jupiter Research found that only 15% of people have used Wi-Fi and only 6% in a public place.[22]
Wi-Fi certification
Main article: Wi-Fi Alliance
Wi-Fi technology is based on IEEE 802.11 standards. The IEEE develops and publishes these standards, but does not test equipment for compliance with them. The non-profit Wi-Fi Alliance was formed in 1999 to fill this void — to establish and enforce standards for interoperability and backward compatibility, and to promote wireless local area network technology. Today the Wi-Fi Alliance consists of more than 300 companies from around the world.[23][24] Manufacturers with membership in the Wi-Fi Alliance, whose products pass the certification process, are permitted to mark those products with the Wi-Fi logo.
Specifically, the certification process requires conformance to the IEEE 802.11 radio standards, the WPA and WPA2 security standards, and the EAP authentication standard. Certification may optionally include tests of IEEE 802.11 draft standards, interaction with cellular phone technology in converged devices, and features relating to security set-up, multimedia, and power saving.
The Wi-Fi name
The term Wi-Fi suggests Wireless Fidelity, compared with the long-established audio equipment certification term High Fidelity or Hi-Fi. Wireless Fidelity has often been used, even by the Wi-Fi Alliance itself in its press releases[26][27] and documents;[28][29] the term may also be found in a white paper on Wi-Fi from ITAA.[30] However, based on Phil Belanger's[31] statement, the term Wi-Fi was never supposed to mean anything at all.[32][33]
The term Wi-Fi, first used commercially in August 1999,[34] 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'."[35][32][33] Mr Belanger also said, Interbrand invented Wi-Fi as a play on words with Hi-Fi, and also created the yin yang-style Wi-Fi logo. The term Wireless Fidelity was used later as an explanation of what Wi-Fi means.
The Wi-Fi Alliance initially used an advertising slogan for Wi-Fi, "The Standard for Wireless Fidelity",[32] but later removed the phrase from their marketing. Despite this, some documents from the Alliance dated 2003 and 2004 still contain the term Wireless Fidelity.[28][29] There was also no official statement for dropping the term.
The yin yang logo indicates that a product had been certified for interoperability.[28]
Advantages and challenges
A keychain size Wi-Fi detector.
Operational advantages
Wi-Fi allows local area networks (LANs) to be deployed without wires 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.
Wireless network adapters are now built into most 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.
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 compatible. Wi-Fi is a global set of standards. Unlike mobile phones, any standard Wi-Fi device will work anywhere in the world.
Wi-Fi is widely available in more than 220,000 public hotspots and tens of millions of homes and corporate and university campuses worldwide.[36] The current version of Wi-Fi Protected Access encryption (WPA2) is considered secure, provided a strong passphrase is used. 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.
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).
Reach
See also: Long-range Wi-Fi
Large satellite dish modified for long-range Wi-Fi communications in Venezuela
Wi-Fi networks have limited range. A typical wireless 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. The new IEEE 802.11n however, can exceed that range by more than double.[citation needed] 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 ranges - through use of directional antennas - can be improved with antennas located several kilometres or more from their base. In general, the maximum amount of power that a Wi-Fi device can transmit is limited by local regulations, such as FCC Part 15[37] in USA.
Wi-Fi performance decreases roughly quadratically[citation needed] as distance increases at constant radiation levels.
Due to reach requirements for wireless LAN applications, power consumption is fairly high compared to some other standards. Technologies such as Bluetooth, that are designed to support wireless PAN applications, provide a much shorter propagation range of <10m>
