Wifi

Wifi (also WiFi, Wi-fi or wifi), is a brand originally licensed by the Wi-Fi Alliance to describe the underlying technology of wireless local area networks (WLAN) based on the IEEE 802.11 specifications.

A person with a Wi-Fi device, such as a computer, telephone, or personal digital assistant (PDA) can connect to the Internet when in proximity of an access point. The region covered by one or several access points is called a hotspot. Hotspots can range from a single room to many square miles of overlapping hotspots. Wi-Fi can also be used to create a Wireless mesh network. Both architectures are used in Wireless community network, municipal wireless networks like Wireless Philadelphia [1], and metro-scale networks like M-Taipei [2].

Wi-Fi also allows connectivity in peer-to-peer mode, which enables devices to connect directly with each other. The Wi-Fi Alliance began as a community to solve this issue so as to address the needs of the end user and allow the technology to mature. The Alliance created another brand "Wi-Fi CERTIFIED" to denote products are interoperable with other products displaying the "Wi-Fi CERTIFIED" brand.

Wi-Fi uses both single carrier direct-sequence spread spectrum radio technology, part of the larger family of spread spectrum systems and multi-carrier OFDM (Orthogonal Frequency Division Multiplexing) radio technology. The precursor to Wi-Fi was invented in 1991 by NCR Corporation/AT&T (later Lucent & 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 was the primary inventor of Wi-Fi and has been named the 'father of Wi-Fi,' was involved in designing standards such as IEEE 802.11b, 802.11a and 802.11g. Agere Systems suffered from strong competition in the market even though their products were high quality, as many opted for cheaper Wi-Fi solutions. Agere's 802.11a/b/g all-in-one chipset (code named: WARP) never made it to market, and Agere Systems decided to quit the Wi-Fi market in late 2004.

Origin and meaning of the term "Wi-Fi"

Despite the similarity between the terms "Wi-Fi" and "Hi-Fi", statements reportedly [3] made by Phil Belanger of the Wi-Fi Alliance contradict the popular conclusion that "Wi-Fi" stands for "Wireless Fidelity".

According to Mr. Belanger, the Interbrand Corporation developed the brand "Wi-Fi" for the Wi-Fi Alliance to use to describe WLAN products that are based on the IEEE 802.11 standards. In Mr. Belanger's words, "Wi-Fi and the yin yang style logo were invented by Interbrand. The Wi-Fi Alliance themselves invoked the term "Wireless Fidelity" with the marketing of a tag line, "The Standard for Wireless Fidelity," but later removed the tag from their marketing. The Wi-Fi Alliance now seems to discourage propagation of the notion that "Wi-Fi" stands for "Wireless Fidelity" but includes it in their knowledge base:

To understand the value of Wi-Fi Certification, you need to know that Wi-Fi is short for "Wireless Fidelity," and it is the popular name for 802.11-based technologies that have passed Wi-FI certification testing. Wi-Fi: How it works

The typical Wi-Fi setup contains one or more Access Points (APs) and one or more clients. Also the firmware running on the client Wi-Fi card is of influence. The Wi-Fi standard leaves connection criteria and roaming totally open to the client. This is a strength of Wi-Fi, but also means that one wireless adapter may perform substantially better than the other. Since Wi-Fi transmits in the air, it has the same properties as a non-switched ethernet network. Channels

Wi-Fi vs. cellular

Some argue that Wi-Fi and related consumer technologies hold the key to replacing cellular telephone networks such as GSM. Since calling via VoIP is free or low-cost, VoIP enabled ISPs have the potential to open up the VoIP market. GSM phones with integrated Wi-Fi & VoIP capabilities are being introduced into the market and have the potential to replace land line telephone services.

Currently it seems unlikely that Wi-Fi will directly compete against cellular in areas that have only sparse Wi-Fi coverage. Wi-Fi-only phones have a very limited range, so setting up a covering network would be too expensive. Many current Wi-Fi devices and drivers do not support roaming yet and connect to only one access point at a time. Opportunities for mobile operators to offer differentiated pricing and services

Commercial Wi-Fi

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

T-Mobile provides hotspots in many Starbucks.

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.

restaurant chain Panera provides free Wi-Fi access at its restaurants.

The objective: to construct a wireless metropolitan network with full Wi-Fi coverage of Paris. als@tis One of the largest Wireless Internet Service Provider for rural areas in France.

GlobeQUEST, under Globe Telecom, provides for prepaid Wi-Fi services for nearly all cafes in the Philippines

Vex offers a big network of hotspots spread over Brazil. Telefónica Speedy Wi-Fi has started its services in a new and growing network distributed over the state of São Paulo.

FatPort is Canada's oldest independent Wi-Fi HotSpot operator with coverage from coast to coast.

It aims to become the largest network of hotspots in the world by the end of 2006 with 30 000 access points. The users are divided into three categories: linus share Internet access for free; bills sell their personal bandwidth; and aliens buy access from bills. 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 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 (see Mu-Fi). 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.

Wireless Leiden developed their own routing software under the name LVrouteD for community wi-fi networks that consist of a completely wireless backbone. Some smaller countries and municipalities already provide free Wi-Fi hotspots and residential Wi-Fi internet access to everyone. Examples include Estonia which have already a large number of free Wi-Fi hotspots throughout their countries.

In Paris, France, OzoneParis offers free Internet access for life to anybody who contributes to the Pervasive Network’s development by making their rooftop available for the Wi-Fi Network.

A private company, Annapolis Wireless Internet, will administrate the network. Users will only see local advertisements upon accessing the network. [4]

Unwire Jerusalem is a project to put free Wi-Fi access points at the main shopping centers of Jerusalem.

Many universities provide free Wi-Fi internet access to their students, visitors, and anyone on campus. Similarly, some commercial entities such as Panera Bread and Culver's offer free Wi-Fi access to patrons. McDonald's Corporation also offers Wi-Fi access, often branded 'McInternet'. Recently commercial Wi-Fi providers have built free Wi-Fi hotspots and hotzones. These providers hope that free Wi-Fi access would equate to more users and significant return on investment.

Wi-Fi vs. Amateur radio

In the US, (and Australia) the 2.4 GHz Wi-Fi radio spectrum is also allocated to amateur radio users. FCC Part 15 rules govern non-licenced operators (i.e. most Wi-Fi equipment users). Under Part 97, licensed amateur operators may construct their own equipment, use very high-gain antennas, and boost output power to 100 watts on frequencies covered by Wi-Fi channels 2-6. Advantages of Wi-Fi

Wi-Fi silicon pricing continues to come down, making Wi-Fi a very economical networking option and driving inclusion of Wi-Fi in an ever-widening array of devices.

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. Products designated as Wi-Fi CERTIFIED by the Wi-Fi Alliance are interoperable and include WPA2 security.

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.

Wi-Fi is a global set of standards. Unlike cellular carriers, the same Wi-Fi client works in different countries around the world.

New protocols for Quality of Service (WMM) and power saving mechanisms (WMM Power Save) make Wi-Fi even more suitable for latency-sensitive applications (such as voice and video) and small form-factor devices.

Disadvantages of Wi-Fi

Wi-Fi Access Points typically default to an open (encryption-free) mode. WPA Wi-Fi Protected Access which began shipping in 2003 aims to solve these problems and is now generally available, but adoption rates remain low.

Wi-Fi networks have limited range. Range also varies with frequency band, as Wi-Fi is no exception to the physics of radio wave propagation. Wi-Fi in the 2.4 GHz frequency block has better range than Wi-Fi in the 5 GHz frequency block, and less range than the oldest Wi-Fi (and pre-Wi-Fi) 900 MHz block. Wi-Fi pollution, meaning interference of a closed or encrypted access point with other open access points in the area, especially on the same or neighboring channel, can prevent access and interfere with the use of other open access points by others caused by overlapping channels in the 802.11g/b spectrum as well as with decreased signal-to-noise ratio (SNR) between access points. This is a widespread problem in high-density areas such as large apartment complexes or office buildings with many Wi-Fi access points.

This openness is also important to the success and widespread use of Wi-Fi, but makes Part 15 (US) unsuitable for "must have" public service functions.

Wi-Fi networks can be monitored and used to read and copy data (including personal information) transmitted over the network when no encryption such as VPN is used.

Wi-Fi Alliance programs test devices for interoperability and designate devices which pass testing as Wi-Fi CERTIFIED.