Wi-Fi (pronounced /ˈwaɪfaɪ/) is a trademark A trademark or trade mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or services from those of other entities of the Wi-Fi Alliance The Wi-Fi Alliance is a trade group that owns the trademark Wi-Fi that manufacturers may use to brand certified products that belong to a class of wireless local area network A wireless local area network links devices via a wireless distribution method (typically spread-spectrum or OFDM) and usually provides a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network (WLAN) devices based on the IEEE 802.11 IEEE 802.11 is a set of standards carrying out wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). The base current version of the standard is IEEE 802.11-2007 standards, which is by far the most widespread WLAN class today. Because of the close relationship with its underlying standards, the term Wi-Fi is often used as a synonym for IEEE 802.11 technology.^[1][2]

The Wi-Fi Alliance, a global association of companies, 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. The lack of the Wi-Fi logo does not necessarily imply a device is incompatible with Wi-Fi devices.

As of 2010^[update], IEEE 802.11 devices are installed in many personal computers A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end user, with no intervening computer operator. This is in contrast to the batch processing or time-sharing models which allowed large expensive mainframe, video game consoles A video game console is an interactive entertainment computer or modified computer system that produces a video display signal which can be used with a display device to display a video game. The term "video game console" is used to distinguish a machine designed for consumers to buy and use solely for playing video games from a personal, smartphones A smartphone is a mobile phone that offers more advanced computing ability and connectivity than a contemporary basic 'feature phone'. Smartphones and feature phones may be thought of as handheld computers integrated within a mobile telephone, but while most feature phones are able to run applications based on platforms such as Java ME or BREW, a, printers In computing, a printer is a peripheral which produces a hard copy of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most newer printers, a USB cable to a computer which serves as a document, and other peripherals A peripheral is a device attached to a host computer but not part of it, and is more or less dependent on the host. It expands the host's capabilities, but does not form part of the core computer architecture, and virtually all laptop A laptop is a personal computer designed for mobile use and small and light enough to sit on a person's lap while in use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device , speakers, and usually including a battery, into a single small and light unit. The rechargeable computers.

History

Wi-Fi products use both single-carrier direct-sequence spread spectrum In telecommunications, direct-sequence spread spectrum is a modulation technique. As with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the information signal that is being modulated. The name 'spread spectrum' comes from the fact that the carrier signals occur over the full bandwidth (spectrum) of a radio technology (part of the larger family of spread spectrum Spread-spectrum techniques are methods by which a signal generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference and systems) and multi-carrier orthogonal frequency-division multiplexing Orthogonal frequency-division multiplexing , essentially identical to coded OFDM (COFDM) and discrete multi-tone modulation (DMT), is a frequency-division multiplexing (FDM) scheme utilized as a digital multi-carrier modulation method. A large number of closely-spaced orthogonal sub-carriers are used to carry data. The data is divided into several (OFDM) radio technology. The deregulation of certain radio-frequencies^{[by whom?]} for unlicensed spread spectrum deployment enabled the development of Wi-Fi products, Wi-Fi's onetime competitor HomeRF "HomeRF"was a wireless networking specification for home devices to be connected to each other. It was developed in 1998 by the HomeRF Working Group, a consortium of mobile wireless companies that included Siemens, Motorola, Philips and more than 100 other companies. The group was disbanded in January 2003 after Wi-Fi 802.11b networks, Bluetooth Bluetooth is an open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks (PANs) with high levels of security. Created by telecoms vendor Ericsson in 1994, it was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices,, and many other products such as some types of cordless telephones.

In the US, the FCC The Federal Communications Commission is an independent agency of the United States government, created, directed and empowered by Congressional statute (see 47 U.S.C. § 151 and 47 U.S.C. § 154), and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, first made unlicensed spread spectrum available in rules adopted on May 9, 1985.^[3]

Many other countries later adapted these FCC regulations, enabling use of this technology in all major countries.^{[citation needed]} 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.^[4]

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.^[5] In 1991 NCR Corporation NCR Corporation is a technology company specializing in products for the retail, financial, travel, healthcare, food service, entertainment, gaming and public sector industries. Its main products are self-service kiosks, point-of-sale terminals, automated teller machines, check processing systems, barcode scanners, and business consumables. They/AT&T AT&T Inc. is the largest provider of fixed telephony in the United States, and also provides broadband and subscription television services. AT&T is the second largest provider of mobile telephony service in the United States, with over 85.1 million wireless customers, and more than 210 million total customers (later Lucent Technologies Lucent Technologies was a technology company composed of what was formerly AT&T Technologies, which included Western Electric and Bell Labs. It was spun off from AT&T on September 30, 1996 and Agere Systems Agere Systems Inc. was an integrated circuit components company based in Allentown, Pennsylvania, in the Lehigh Valley region of Pennsylvania, in the United States. Effective April 2, 2007, it was merged into LSI Corporation) invented the precursor to 802.11 / Wi-Fi in Nieuwegein, The Netherlands. The inventors initially intended to use the technology for cashier systems; the first wireless products were brought on the market under the name WaveLAN WaveLAN was originally designed by COMTEN, a subsidiary of NCR Corporation, in 1986-7, and introduced to the market in 1988 as a wireless alternative to Ethernet and Token-Ring. The next year NCR contributed the WaveLAN design to the IEEE 802 LAN/MAN Standards Committee. This led to the founding of the 802.11 Wireless LAN Working Committee which with raw data rates of 1 Mbit/s and 2 Mbit/s. Vic Hayes, who held the chair of IEEE 802.11 for 10 years and has been called the "father of Wi-Fi" was involved in designing the initial 802.11b and 802.11a standards within the IEEE The Institute of Electrical and Electronics Engineers or IEEE is an international non-profit, professional organization for the advancement of technology related to electricity. It has the most members of any technical professional organization in the world, with more than 395,000 members in around 150 countries.

In 1992, the CSIRO The Commonwealth Scientific and Industrial Research Organisation is the national government body for scientific research in Australia. It was founded in 1926 originally as the Advisory Council of Science and Industry obtained a patent in Australia For at least 40,000 years before European settlement in the late 18th century, Australia was inhabited by indigenous Australians, who belonged to one or more of the roughly 250 language groups. After sporadic visits by fishermen from the immediate north and discovery by Dutch explorers in 1606, Australia's eastern half was claimed by the British for their wireless data transfer technology. In 1996, they obtained a patent for the same technology in the US.^[6] WiFi uses the mathematical formula in the patents. In 2000, CSIRO demonstrated the world's first wireless local area network internet connection.^[7]

In April 2009, 14 tech companies including Intel Intel Corporation is a technology company, and the world's largest semiconductor chip maker, based on revenue. It is the inventor of the x86 series of microprocessors, the processors found in most personal computers. Intel was founded on July 18, 1968, as Integrated Electronics Corporation (though a common misconception is that "Intel", Microsoft Microsoft Corporation is a public multinational corporation based in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions. Established on April 4, 1975 to develop and sell BASIC interpreters for the Altair 8800,, HP Hewlett-Packard Company , commonly referred to as HP, is an American multinational information technology corporation headquartered in Palo Alto, California, USA. HP is one of the world's largest information technology companies and operates in nearly every country. HP specializes in developing and manufacturing computing, data storage, and, Dell Dell Inc. is a multinational information technology corporation based in Round Rock, Texas, United States, that develops, sells and supports computers and related products and services. Bearing the name of its founder, Michael Dell, the company is one of the largest technological corporations in the world, employing more than 96,000 people, agreed to pay CSIRO $250 million for their Wi-Fi patent infringements.^[8]

Uses

Internet access

A Wi-Fi enabled device such as a personal computer A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end user, with no intervening computer operator. This is in contrast to the batch processing or time-sharing models which allowed large expensive mainframe, video game console A video game console is an interactive entertainment computer or modified computer system that produces a video display signal which can be used with a display device to display a video game. The term "video game console" is used to distinguish a machine designed for consumers to buy and use solely for playing video games from a personal, mobile phone A mobile phone is an electronic device used for full duplex two-way radio telecommunications over a cellular network of base stations known as cell sites. Mobile phones differ from cordless telephones, which only offer telephone service within limited range through a single base station attached to a fixed land line, for example within a home or, MP3 player A digital audio player, or DAP, usually referred to as an MP3 player, is a consumer electronic device that has the primary function of storing, organizing and playing audio files. Some DAPs are also referred to as portable media players as they have image-viewing and/or video-playing support or personal digital assistant The term PDA was first used on January 7, 1992, by Apple Computer CEO John Sculley at the Consumer Electronics Show in Las Vegas, Nevada, referring to the Apple Newton. In 1996, Nokia introduced the first mobile phone with full PDA functionality, the 9000 Communicator, which has since grown to become the world's best-selling PDA and which spawned can connect to the Internet The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope that are linked by a broad array of electronic and when within range of a wireless network Wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between nodes is implemented without the use of wires. Wireless telecommunications networks are generally implemented with some type of remote information transmission system that uses connected to the Internet. The coverage of one or more (interconnected) access points In computer networking, a wireless access point is a device that allows wireless communication devices to connect to a wireless network using Wi-Fi, Bluetooth or related standards. The WAP usually connects to a router, and can relay data between the wireless devices (such as computers or printers) and wired devices on the network — called hotspots A hotspot is a physical location that offers internet access over a wireless LAN through the use of a shared internet connection and a single router. Hotspots can typically be found in coffee shops and various other public establishments throughout much of North America and Europe — can comprise 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 in wireless mesh networks A wireless mesh network is a communications network made up of radio nodes organized in a mesh topology. Wireless mesh networks often consist of mesh clients, mesh routers and gateways . The mesh clients are often laptops, cell phones and other wireless devices while the mesh routers forward traffic to and from the gateways which may but need not, for example, in London, UK.^[9]

In addition to private use in homes and offices, Wi-Fi can provide public access at Wi-Fi hotspots A hotspot is a physical location that offers internet access over a wireless LAN through the use of a shared internet connection and a single router. Hotspots can typically be found in coffee shops and various other public establishments throughout much of North America and Europe provided either free-of-charge or to subscribers to various commercial services. Organizations and businesses A business is a legally recognized organization designed to provide goods or services, or both, to consumers, businesses and governmental entities. Businesses are predominant in capitalist economies. Most businesses are privately owned. A business is typically formed to earn profit that will increase the wealth of its owners and grow the business - such as those running 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 Commerce is a division of trade or production which deals with the exchange of goods and services from producer to final consumer OR commerce is the exchange of goods and services from the point of production to the point of consumption to satisfy human wants. It comprises the trading of something of economic value such as goods, services, in selected areas sometimes provide free Wi-Fi access. As of 2008^[update] more than 300 metropolitan-wide Wi-Fi (Muni-Fi Municipal wireless network is the concept of turning an entire city into a Wireless Access Zone (WAZ), with the ultimate goal of making wireless access to the Internet a universal service. This is usually done by providing municipal broadband via Wi-Fi to large parts or all of a municipal area by deploying a wireless mesh network. The typical) projects had started.^[10] As of May 2008^[update] the Czech Republic The Czech Republic (pronounced /ˈtʃɛk/ chek; Czech: Česká republika, pronounced [ˈtʃɛskaː ˈrɛpuˌblɪka] ( listen), short form Česko [ˈtʃɛskɔ]) is a country in Central Europe. The country borders Poland to the northeast, Germany to the west and northwest, Austria to the south and Slovakia to the east. The Czech Republic has been a had 879 Wi-Fi based Wireless Internet service providers Wireless Internet Service Providers are Internet service providers with networks built around wireless networking. Technology may include commonplace Wi-Fi wireless mesh networking, or proprietary equipment designed to operate over open 900MHz, 2.4GHz, 4.9, 5.2, 5.4, and 5.8GHz bands or licensed frequencies in the UHF or MMDS bands.^[11][12]

Routers A router is a device that interconnects two or more computer networks, and selectively interchanges packets of data between them. Each data packet contains address information that a router can use to determine if the source and destination are on the same network, or if the data packet must be transferred from one network to another. Where that incorporate a digital subscriber line Digital Subscriber Line is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop. In telecommunications marketing, the term Digital Subscriber Line is widely understood to mean Asymmetric Digital Subscriber Line (ADSL), the most commonly modem or a cable modem A cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a cable television infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high bandwidth of a cable television network. They are and a Wi-Fi access point, often set up in homes and other premises, can provide Internet The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope that are linked by a broad array of electronic and-access and internetworking Internetworking is the practice of connecting a computer network with other networks through the use of gateways that provide a common method of routing information packets between the networks. The resulting system of interconnected networks is called an internetwork, or simply an internet to all devices connected (wirelessly or by cable) to them. One can also connect Wi-Fi devices in ad-hoc mode A wireless ad hoc network is a decentralized wireless network. The network is ad hoc because it does not rely on a preexisting infrastructure, such as routers in wired networks or access points in managed wireless networks. Instead, each node participates in routing by forwarding data for other nodes, and so the determination of which nodes for client-to-client connections without a router. Wi-Fi also connects places that would traditionally not have network access, for example bathrooms, kitchens and garden sheds.

City-wide Wi-Fi

In the early 2000s, many cities around the world announced plans for city-wide Wi-Fi networks. 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.^[13] (As of 2009^[update] few of the Municipal Wi-Fi firms have entered the field of smart grid networks.^{[14][clarification needed]})

In May, 2010, London, UK Mayor Boris Johnson pledged London-wide Wi-Fi by 2012.^[15] Both the City of London, UK^[16] and Islington ^[17] already have extensive outdoor Wi-Fi coverage.

Campus-wide Wi-Fi

Carnegie Mellon University built the first wireless Internet network in the world at their Pittsburgh campus in 1994,^[18] long before Wi-Fi branding originated in 1999. Most campuses now have wireless Internet.

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.

Similarly, the Wi-Fi Alliance promotes a pending specification called Wi-Fi Direct for file transfers and media sharing through a new discovery- and security-methodology.^[19]

Future directions

As of 2010^[update] Wi-Fi technology has spread widely within business and industrial sites. In business environments, just like other environments, increasing the number of Wi-Fi access points provides network 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 "dumb" transceivers. Outdoor applications may utilize mesh topologies. As of 2007 Wi-Fi installations can provide a secure computer networking gateway, firewall, DHCP server, intrusion detection system, and other functions..

Wi-Fi certification

Wi-Fi technology builds 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 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. As of 2009^[update] the Wi-Fi Alliance consisted of more than 300 companies from around the world.^[20][21] Manufacturers with membership in the Wi-Fi Alliance, whose products pass the certification process, gain the right 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.^[22]

The Wi-Fi name

The term Wi-Fi suggests Wireless Fidelity, resembling the long-established audio-equipment classification term high fidelity (in use since the 1930s^[23]) or Hi-Fi (used since 1950^[23]). Even the Wi-Fi Alliance itself has often used the phrase Wireless Fidelity in its press releases^[24][25] and documents;^[26][27] the term also appears in a white paper on Wi-Fi from ITAA.^[28] However, based on Phil Belanger's^[29] statement, the term Wi-Fi was never supposed to mean anything at all.^[30][31]

The term Wi-Fi, first used commercially in August 1999,^[32] was coined by a brand-consulting firm called Interbrand Corporation that the Alliance had hired to determine a name that was "a little catchier than 'IEEE 802.11b Direct Sequence'".^[33][30][31] Belanger also stated that Interbrand invented Wi-Fi as a play on words with Hi-Fi, and also created the yin-yang-style Wi-Fi logo.

The Wi-Fi Alliance initially used an advertising slogan for Wi-Fi, "The Standard for Wireless Fidelity",^[30] 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.^[26][27] There was no official statement related to the dropping of the term.

The yin-yang logo indicates the certification of a product for interoperability.^[26]

Advantages and challenges

Operational advantages

Wi-Fi allows the deployment of local area networks (LANs) 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.

As of 2010^[update] manufacturers are building wireless network adapters into most laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in even more devices.^{[citation needed]} Wi-Fi has become widespread in corporate infrastructures.^{[citation needed]}

Different competitive brands of access points and client network-interfaces can inter-operate at a basic level of service. Products designated as "Wi-Fi Certified" by the Wi-Fi Alliance are backwards compatible. "Wi-Fi" designates a globally operative set of standards: unlike mobile phones, any standard Wi-Fi device will work anywhere in the world.

Wi-Fi operates in more than 220,000 public hotspots and in tens of millions of homes and corporate and university campuses worldwide.^[34] The current version of Wi-Fi Protected Access encryption (WPA2) as of 2010^[update] is considered^{[by whom?]} secure, provided users employ a strong passphrase. 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 do not operate consistently 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^[update], 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. Equivalent isotropically radiated power (EIRP) in the EU is limited to 20 dBm (100 mW).

Reach

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 two times.^[35] 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^[36] in USA.

Due to reach requirements for wireless LAN applications, Wi-Fi has fairly high power-consumption compared to some other standards. Technologies such as Bluetooth (designed to support wireless PAN applications) provide a much shorter propagation range of <10m^[37] and so in general have a lower power-consumption. Other low-power technologies such as ZigBee have fairly long range, but much lower data rate. The high power-consumption of Wi-Fi makes battery life in mobile devices a concern.

Researchers have developed a number of "no new wires" technologies to provide alternatives to Wi-Fi for applications in which Wi-Fi's indoor range is not adequate and where installing new wires (such as CAT-5) is not possible or cost-effective. For example, the ITU-T G.hn standard for high speed Local area networks uses existing home wiring (coaxial cables, phone lines and power lines). Although G.hn does not provide some of the advantages of Wi-Fi (such as mobility or outdoor use), it's designed^{[by whom?]} for applications (such as IPTV distribution) where indoor range is more important than mobility.

Due to the complex nature of radio propagation at typical Wi-Fi frequencies, particularly the effects of signal reflection off trees and buildings, algorithms can only approximately predict Wi-Fi signal strength for any given area in relation to a transmitter.^[38] This effect does not apply equally to long-range Wi-Fi, since longer links typically operate from towers that broadcast above the surrounding foliage.

Mobility

The very limited practical range of Wi-Fi essentially confines mobile use to such applications as inventory-taking machines in warehouses or in retail spaces, barcode-reading devices at check-out stands, or receiving/shipping stations. Mobile use of Wi-Fi over wider ranges is limited, for instance, to uses such as in an automobile moving from one hotspot to another (known as Wardriving). Other wireless technologies are more suitable as illustrated in the graphic.

Data security risks

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) encryption, which became available in devices in 2003, aimed to solve this problem. Wi-Fi access points typically default to an encryption-free (open) mode. Novice users benefit from a zero-configuration device that works out-of-the-box, but this default does not enable any wireless security, providing open wireless access to a LAN. To turn security on requires the user to configure the device, usually via a software graphical user interface (GUI). On unencrypted Wi-Fi networks connecting devices can monitor and record data (including personal information), but such networks may use other means of protection, such as a virtual private network or secure Hypertext Transfer Protocol (HTTPS) and Transport Layer Security.

Population

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.

Channel pollution

Market forces may drive a process of standardization. Interoperability issues between non-Wi-Fi brands or proprietary deviations from the standard can still disrupt connections or lower throughput speeds on all devices within range, including any non-Wi-Fi or proprietary product. Moreover, the usage of the ISM band in the 2.45 GHz range is also common to Bluetooth, WPAN-CSS, ZigBee, and any new system will take its share.

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 other devices' use of other access points, 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 become 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, ZigBee devices, Bluetooth devices and (in some countries) Amateur radio, video senders, cordless phones and baby monitors, all of which can cause significant additional interference. It is also an issue when municipalities^[39] 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.

Hardware

Standard devices

A wireless access point (WAP) connects a group of wireless devices to an adjacent wired LAN. An access point resembles 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. As of 2010^[update], most newer laptop computers come equipped with internal adapters. Internal cards are generally more difficult to install.

Wireless routers integrate a Wireless Access Point, 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 a cable modem or a 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 usually an integrated web server that is accessible 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. A bridge differs from an access point: 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. Strategically placed range-extenders can elongate a signal area or allow for the signal area to reach around barriers such as those pertaining 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 will have a throughput limited by the "weakest link" between the two nodes in the chain from which the connection originates to where the connection ends.

Distance records

Distance records (using non-standard devices) include 382 km (237 mi) in June 2007, held by Ermanno Pietrosemoli and EsLaRed of Venezuela, transferring about 3 MB of data between the mountain-tops of El Águila and Platillon.^[40][41] The Swedish Space Agency transferred data 420 km (260 mi), using 6 watt amplifiers to reach an overhead stratospheric balloon.^[42]

Embedded systems

Increasingly in the last few years (particularly as of 2007^[update]), embedded Wi-Fi modules have become available that incorporate a real-time operating system and provide a simple means of wirelessly enabling any device which has and communicates via a serial port.^[43] This allows the design of simple monitoring devices. An example is a portable ECG device monitoring a patient at home. This Wi-Fi-enabled device can communicate via the Internet.^[44]

These Wi-Fi modules are designed^{[by whom?]} so that implementers need only minimal Wi-Fi knowledge to provide Wi-Fi connectivity for their products.

Network security

The main issue with wireless network security is its simplified access to the network compared to traditional wired networks such as ethernet.^{[citation needed]} With wired networking one must either gain access to a building (physically connecting into the internal network) or break through an external firewall. Most business networks protect sensitive data and systems by attempting to disallow external access. Thus gaining wireless connectivity provides an attack vector, particularly if the network lacks encryption or if the intruder can defeat any encryption.^[45]

Attackers who have gained access to a Wi-Fi network can use DNS spoofing attacks very effectively against any other user of the network, because they can see the DNS requests made, and often respond with a spoofed answer before the queried DNS server has a chance to reply.^[46]

Securing methods

A common but unproductive measure to deter unauthorized users involves suppressing the access point's SSID broadcast, "hiding" it. This is ineffective as a security method because the SSID is broadcast in the clear in response to a client SSID query. Another unproductive method is to only allow computers with known MAC addresses to join the network.^[47] But intruders can defeat this method because they can often (though not always) set MAC addresses with minimal effort (MAC spoofing). If eavesdroppers have the ability to change their MAC address, then they may join the network by spoofing an authorized address.

Wired Equivalent Privacy (WEP) encryption was designed^{[by whom?]} to protect against casual snooping, but is now deprecated. Tools such as AirSnort or Aircrack-ng can quickly recover WEP encryption keys. Once it has seen 5-10 million encrypted packets, AirSnort can determine the encryption password in under a second;^[48] newer tools such as aircrack-ptw can use Klein's attack to crack a WEP key with a 50% success rate using only 40,000 packets.

To counteract this in 2002, the Wi-Fi Alliance approved Wi-Fi Protected Access (WPA) which uses TKIP as a stopgap solution for legacy equipment. Though more secure than WEP, it has outlived its designed lifetime and has known attack vectors.

In 2004, the IEEE ratified the full IEEE 802.11i (WPA2) encryption standards. If used with a 802.1X server or in pre-shared key mode with a strong and uncommon passphrase WPA2 is still considered^{[by whom?]} secure, as of 2009^[update].

Piggybacking

Piggybacking refers to access to a wireless Internet connection by bringing one's own computer within the range of another's wireless connection, and using that service without the subscriber's explicit permission or knowledge.

During the early popular adoption of 802.11, providing open access points for anyone within range to use was encouraged^{[by whom?]} to cultivate wireless community networks,^[49] particularly since people on average use only a fraction of their downstream bandwidth at any given time.

Recreational logging and mapping of other people's access points has become known as wardriving. It is also common for people to use open (unencrypted) Wi-Fi networks as a free service, termed piggybacking. Indeed, many access points are intentionally installed without security turned on so that they can be used as a free service. Providing access to one's Internet connection in this fashion may breach the Terms of Service or contract with the ISP. These activities do not result in sanctions in most jurisdictions; however, legislation and case law differ considerably across the world. A proposal to leave graffiti describing available services was called warchalking^[50]. A Florida court case determined that owner laziness was not to be a valid excuse.^[51]

Piggybacking often occurs unintentionally, most access points are configured^{[by whom?]} without encryption by default, and operating systems can be configured to connect automatically to any available wireless network. A user who happens to start up a laptop in the vicinity of an access point may find the computer has joined the network without any visible indication. Moreover, a user intending to join one network may instead end up on another one if the latter has a stronger signal. In combination with automatic discovery of other network resources (see DHCP and Zeroconf) this could possibly lead wireless users to send sensitive data to the wrong middle-man when seeking a destination (see Man-in-the-middle attack). For example, a user could inadvertently use an insecure network to log in to a website, thereby making the login credentials available to anyone listening, if the website uses an insecure protocol such as HTTP.

See also

• List of WLAN channels
• San Francisco Digital Inclusion Strategy
• Wi-Fi operating system support
• WiMAX
• Wireless electronic devices and health

References

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36. ^ FCC Sec.15.249 Operation within the bands 902–928 MHz, 2400–2483.5 MHz, 5725–5875 MHZ, and 24.0–24.25 GHz.
37. ^ See for example IEEE Standard 802.15.4 section 1.2 scope
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46. ^ Bernstein, Daniel J. (2002). "DNS forgery". http://cr.yp.to/djbdns/forgery.html. Retrieved 2010-03-24. "An attacker with access to your network can easily forge responses to your computer's DNS requests."
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49. ^ NoCat's goal is to bring you Infinite Bandwidth Everywhere for Free
50. ^ "Let's Warchalk" (PDF). Matt Jones. http://www.blackbeltjones.com/warchalking/warchalking0_9.pdf. Retrieved 2008-10-09.
51. ^ See the wikinews article mentioned in this section.

Further reading

• Wireless Networking in the Developing World (PDF book)

External links

• The Wi-Fi Alliance

Categories: Wi-Fi

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• Wi-fi
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