Wi-Fi

Wi-Fi (or Wi-fi, WiFi, Wifi, wifi), short for "Wireless Fidelity", is a set of product compatibility standards for wireless local area networks (WLAN) based on the IEEE 802.11 specifications. New standards beyond the 802.11 specifications, such as 802.16(WiMAX), are currently in the works and offer many enhancements, anywhere from longer range to greater transfer speeds.

Wi-Fi was intended to be used for mobile devices and LANs, but is now often used for Internet access. It enables a person with a wireless-enabled computer or personal digital assistant (PDA) to connect to the Internet when in proximity of an access point. The geographical region covered by one or several access points is called a hotspot.

Certified products can use the official Wi-Fi logo, which indicates that the product is interoperable with any other product also showing the logo.

Contents

1 Wi-Fi vs. cellular 2 Commercial Wi-Fi 3 Free Wi-Fi 4 Advantages of Wi-Fi 5 Disadvantages of Wi-Fi 6 Wi-Fi and free software 7 Trademark 8 Unintended and Intended use by outsiders 9 See also 10 External links

Wi-Fi vs. cellular

Some argue that Wi-Fi and related consumer technologies hold the key to replacing cellular telephone networks such as GSM. Some obstacles to this happening in the near future are missing roaming and authentication features (see 802.1x, SIM cards and RADIUS), the narrowness of the available spectrum and the limited range of Wi-Fi. Despite such problems, companies like Zyxel, SocketIP and Symbol Technologies are already offering telephony platforms (Central Office replacements and terminals (phones)) that use Wi-Fi transport.

Many operators are now selling mobile internet products that link cellular wireless and Wi-Fi radio system in a more or less transparent way to take advantage of the benefits of both systems. Future wireless systems are expected to routinely switch between a variety of radio systems.

The term 4G is occasionally used for Wi-Fi, the implication being that the bandwidth and capabilities offered are already greater than those promised by the 3G cellular telephone standards.

The main difference between cellular and Wi-Fi is that the cellular system uses the licensed spectrum, and Wi-Fi is implemented in unlicensed bands. The economic basis for its implementation is therefore completely different. The success of Wi-Fi has made many people look to the unlicensed spectrum as the future of wireless access, rather than the spectrum licensed and controlled by large corporations.

Commercial Wi-Fi

Commercial Wi-Fi services are available in places such as Internet cafes, coffee houses and airports around the world (commonly called Wi-Fi-cafés), although coverage is patchy in comparison with cellular:

• WiSE Technologies (http://www.wisezone.net) provides commercial hotspots for airports, universities, and independent cafes in the US;
• T-Mobile provides hotspots in many Starbucks in the U.S;
• Pacific Century Cyber Works provides hotspots in Pacific Coffee shops in Hong Kong;
• a Columbia Rural Electric Association subsidiary offers 2.4 GHz Wi-Fi service across a 3,700 mi² (9,500 km²) region within Walla Walla and Columbia counties in Washington and Umatilla County, Oregon;
• Other large hotspot providers in the U.S. include Boingo, Wayport and iPass;
• Sify, an Indian internet service provider, has set up 120 wireless access points in Bangalore, India in hotels, malls and government offices.
• Vex (http://www.pointernetworks.com.br) offers a big network of hotspots spread over Brazil. Telefónica Speedy WiFi (http://www.speedywifi.com.br) has started its services in a new and growing network distributed over the state of São Paulo.
• Link repository on Wi-Fi topics at AirHive Net (http://www.airhive.net/modules.php?name=Web_Links)

Free Wi-Fi

While commercial services attempt to move existing business models to Wi-Fi, many groups, communities, cities, and individuals have set up free Wi-Fi networks, often adopting a common peering agreement (http://www.freenetworks.org/peering.html) in order that networks can openly share with each other. Free wireless mesh networks are often considered the future of the internet.

Many municipalities have joined with local community groups to help expand free Wi-Fi networks. Some community groups have built their Wi-Fi networks entirely based on volunteer efforts and donations.

For more information, see wireless community network, where there is also a list of the free Wi-Fi networks one can find around the globe.

OLSR is one of the protocols used to set up free networks. Some networks use static routing; other, such as Wireless Leiden rely completely on OSPF. Most networks rely heavily on open source software, or even publish their setup under an open source license.

Some smaller countries and municipalities already provide free Wi-Fi hotspots and residential Wi-Fi internet access to everyone. Examples include the Kingdom of Tonga or Estonia which have already a large number of free Wi-Fi hotspots throughout their countries.

Many universities provide free WiFi internet access to their students, visitors, and anyone on campus. Similarly, some commercial entities such as Panera Bread offer free Wi-Fi access to patrons. McDonald's Corporation may be offering Wi-Fi access soon, and currently has Wi-Fi access at their flagship restaurant in Oak Brook, Illinois.

However, there is also a third subcategory of networks set up by certain communities such as universities where the service is provided free to members and guests of the community such as students, yet used to make money by letting the service out to companies and individuals outside. An example of such a service is Sparknet (http://www.sparknet.fi/) in Finland. Sparknet also supports OpenSparknet (https://open.sparknet.fi/), a project where people can name their own wireless access point as a part of Sparknet in return for certain benefits.

Advantages of Wi-Fi

• Unlike packet radio systems, Wi-Fi uses unlicensed radio spectrum and does not require regulatory approval for individual deployers.
• Allows LANs to be deployed without cabling, potentially 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.
• Wi-Fi products are widely available in the market. Different brands of access points and client network interfaces are interoperable at a basic level of service.
• Competition amongst vendors has lowered prices considerably since their inception.
• Many Wi-Fi networks support roaming, in which a mobile client station such as a laptop computer can move from one access point to another as the user moves around a building or area.
• Many access points and network interfaces support various degrees of encryption to protect traffic from interception.
• Wi-Fi is a global set of standards. Unlike cellular carriers, the same Wi-Fi client works in different countries around the world.

Disadvantages of Wi-Fi

• Use of the 2.4 GHz Wi-Fi band does not require a license in most of the world provided that one stays below the 100mWatt limit and one accepts interference from other sources; including interference which causes your devices to no longer function. It is alleged that Amateur Radio operators have license to boost the power on their routers up to the legal maximum for their license class, which tends to be 1500 watts (roughly 15,000 times that of a normal router).
• Legislation is not consistent worldwide; most of Europe allows for an additional 2 channels; Japan has one more on top of that - and some countries, like Spain, prohibit use of the lower-numbered channels. Furthermore some countries, such as Italy, used to require a 'general authorization' for any WiFi used outside the owned premises; or required something akin to an operator registration. For Europe; consult http://www.ero.dk for an annual report on the additional restriction each European country imposes.
• The 802.11b and 802.11g flavors of Wi-Fi use the 2.4 GHz spectrum, which is crowded with other devices such as Bluetooth, microwave ovens, cordless phones (900 MHz or 5.8 GHz are, therefore, alternative phone frequencies one can use if one has a Wi-Fi network), or video sender devices, among many others. This may cause a degradation in performance. Other devices which use microwave frequencies such as certain types of cell phones can also cause degradation in performance.
• Power consumption is fairly high compared to other standards, making battery life and heat a concern.
• The most common wireless encryption standard, Wired Equivalent Privacy or WEP, has been shown to be easily breakable even when correctly configured. Although newer wireless products are slowly providing support for the Wi-Fi Protected Access (WPA) protocol, many older access points will have to be replaced to support it. The adoption of the 802.11i (aka WPA2) standard in June 2004 makes available a rather better security scheme for future use — when properly configured. In the meantime, many enterprises have had to deploy additional layers of encryption (such as VPNs) to protect against interception.
• Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or 802.11g might have a range of 45 m (150 ft) indoors and 90 m (300 ft) outdoors.
• Interference of a closed or encrypted access point with other open access points on the same or a neighboring channel can prevent access to the open access points by others in the area. This can pose a problem in high-density areas such as large apartment buildings where many residents are operating Wi-Fi access points.
• Access points could be used to steal personal information transmitted from Wi-Fi users.
• Free access points (or improperly configured access points) may be used by a hacker to anonymously initiate an attack that would be impossible to track beyond the owner of the access point.

Wi-Fi and free software

• BSD (FreeBSD, NetBSD, OpenBSD) have had support for most adapters since late 1998. Code for Atheros, Prism, Harris/Intersil and Aironet is mostly shared between the 3 BSDs. Darwin and Mac OS X, despite their overlap with FreeBSD, have their own unique implementation.
• Linux: As of version 2.6, little Wi-Fi hardware is supported natively by the Linux kernel. However, support for most wireless devices is available through use of the ndiswrapper driver, which allows Linux compiled for the Intel x86 architecture to "wrap" a windows driver for direct use.

Trademark

Wi-Fi is a trademark of the Wi-Fi Alliance (formerly the Wireless Ethernet Compatibility Alliance), the trade organization that tests and certifies equipment compliance with the 802.11x standards.

Unintended and Intended use by outsiders

The default configuration of most Wi-Fi access points provides no protection from unauthorized use of the network. Many business and residential users do not intend to secure their access points by leaving them open to users in the area. It has become etiquette to leave access points open for others to use just as one can expect to find open access points while on the road.

Measures to deter unauthorized users include suppressing the AP's service set identifier (SSID) broadcast, only allowing computers with known MAC addresses to join the network, and various encryption standards. Older access points frequently do not support adequate security measures to protect against a determined attacker armed with a packet sniffer and the ability to switch MAC addresses. Recreational exploration of other people's access points has become known as wardriving, and the leaving of graffiti describing available services as warchalking.

However, it is also common for people to unintentionally use others' Wi-Fi networks without authorization. Operating systems such as Windows XP and Mac OS X automatically connect to an available wireless network, depending on the network configuration. 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's signal is stronger. In combination with automatic discovery of other network resources (see DHCP and Zeroconf) this can lead wireless users to send sensitive data to the wrong destination, as described by Chris Meadows in the February 2004 RISKS Digest. [1] (http://catless.ncl.ac.uk/Risks/23.16.html#subj4)

See also

• OSGi Alliance
• WiMAX
• Liquid crystal display television with integrated WiFi port
• Wikibooks: Building a Wifi antenna
• Wireless mesh network
• Wireless LAN

External links

• WiFi Tutorial (http://www.tutorial-reports.com/wireless/wlanwifi/) Includes information on Architecture, Standards, Security and Comparisons
• JiWire (http://www.jiwire.com) The Largest Directory Of Public Hotspots Worldwide
• Total Hotspots - The Global Wi-Fi Hotspots Directory (http://www.totalhotspots.com) Quality hotspot search engine with street level mapping and proximity search functionality.
• Wireless Libraries (http://wirelesslibraries.blogspot.com)
• Flash/audio (http://www.airhive.net/modules.php?name=Web_Links&l_op=visit&lid=1475) showing how to configure a Linksys Wi-Fi router to share your broadband connection.
• FreeNetworks (http://www.freenetworks.org) A volunteer association dedicated to education, collaboration, and advocacy for the creation of free WiFi networks
• First Mile Solutions (http://www.firstmilesolutions.com) Free WiFi internet for developing and developed countries
• LocustWorld (http://locustworld.com) WiFi mesh networking projects
• WiFiMaps.com (http://www.WiFiMaps.com) Maps of Wi-Fi installations across the US submitted by users' findings
• WEP Cracking, the FBI Way (http://primary0.blogspot.com/2005/06/wep-cracking-fbi-way.html) A brief guide in cracking WEP enabled networks as demonstrated by the FBI.
• WiGLE (http://wigle.net) Worldwide database and mapping of wireless networks.cs:Wi-Fi

de:Wi-Fi es:Wi-Fi fr:Wi-Fi it:Wi-Fi ms:Wifi nl:Wi-fi ja:Wi-Fi pl:WiFi sk:Wi-Fi he:Wi-Fi