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.
Wi-Fi was intended to be used for mobile computing devices, such as laptops, in LANs, but is now often used for increasingly more applications, including Internet and VoIP phone access, gaming, and basic connectivity of consumer electronics such as televisions and DVD players. There are even more standards in development that will allow Wi-Fi to be used by cars in highways in support of an Intelligent Transportation System to increase safety, gather statistics, and enable mobile commerce IEEE 802.11p.
for detailed operation:
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. This connectivity mode is useful in consumer electronics and gaming applications.
When the technology was first commercialized there were many problems because consumers could not be sure that products from different vendors would work together. 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.
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 OFDM (Orthogonal Frequency Division Multiplexing) radio technology. Unlicensed spread spectrum was first authorized by the Federal Communications Commission in 1985 and these FCC regulations were later copied with some changes in many other countries enabling use of this technology in all major countries. These regulations then enabled the development of Wi-Fi, its onetime competitor HomeRF, and Bluetooth.
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. In 2003, Vic retired from Agere Systems. 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. We (the founding members of the Wireless Ethernet Compatibility Alliance, now called the Wi-Fi Alliance) hired Interbrand to come up with the name and logo that we could use for our interoperability seal and marketing efforts. We needed something that was a little catchier than 'IEEE 802.11b Direct Sequence'."
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. This includes IEEE 802.11a, 802.11b, 802.11g and upcoming 802.11 technologies.
Wi-Fi: How it works
The typical Wi-Fi setup contains one or more Access Points (APs) and one or more clients. An AP broadcasts its SSID (Service Set Identifier, "Network name") via packets that are called beacons, which are broadcast every 100 ms. The beacons are transmitted at 1 Mbit/s, and are of relatively short duration and therefore do not have a significant influence on performance. Since 1 Mbit/s is the lowest rate of Wi-Fi it assures that the client who receives the beacon can communicate at least 1 Mbit/s. Based on the settings (e.g. the SSID), the client may decide whether to connect to an AP. Also the firmware running on the client Wi-Fi card is of influence. Say two APs of the same SSID are in range of the client, the firmware may decide based on signal strength to which of the two APs it will connect. 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. Even collisions can therefore appear like in non-switched ethernet LAN's.
Channels
Except for 802.11a, which operates at 5 GHz, Wi-Fi uses the spectrum near 2.4 GHz, which is standardized and unlicensed by international agreement, although the exact frequency allocations vary slightly in different parts of the world, as does maximum permitted power. However, channel numbers are standardized by frequency throughout the world, so authorized frequencies can be identified by channel numbers.
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. It is more likely that WiMax will compete with other cellular phone protocols such as GSM, UMTS or CDMA. However, Wi-Fi is ideal for VoIP applications e.g. in a corporate LAN or SOHO environment. Early adopters were already available in the late '90s, though not until 2005 did the market explode. Companies such as Zyxel, UT Starcomm, Samsung, Hitachi and many more are offering VoIP Wi-Fi phones for reasonable prices.
In 2005 ADSL ISP started to offer VoIP services to their customers (eg. the Dutch ISP XS4All). 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. Additionally, cellular technology allows the user to travel while connected, bouncing the connection from tower to tower (or "cells") as proximity changes, all the while maintaining one solid connection to the user. Many current Wi-Fi devices and drivers do not support roaming yet and connect to only one access point at a time. In this case, once you are out of range of one "hotspot", the connection will drop and will need to be re-connected to the next one each time.
For these reasons, Wi-Fi phones are still best suited for local use such as corporate or home networks. However, devices capable of multiple standards, called converged devices, (using SIP or UMA) may well compete in the market. Top-tier handset manufacturers have announced converged dual-radio handsets. Converged handsets present several compelling advantages to mobile carriers:
Efficient spectrum allocation, as more data-intensive services come online and bandwidth demands increase
Improved in-building coverage in markets such as the US, where dropped calls are still a major cause of customer dissatisfaction
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.
In the US:
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.
WiSE Technologies provides commercial hotspots for airports, universities, and independent cafes in the US;
Boingo Wireless has over 45,000 hotspots worldwide, including most major airports in the U.S.
restaurant chain Panera provides free Wi-Fi access at its restaurants.
Other large hotspot providers include Wayport, iPass, and iBahn.
There are also a number of aggregators of Wi-Fi, the main one being BOZII, they allow users access to over 250 networks including BT Openzone and Orange France, all with one username and password for a flat fee and no roaming charges.
In the UK:
T-Mobile provides hotspots in many Starbucks in the UK too.
BT Openzone provides many hotspots across the United Kingdom, notably in most McDonalds restaurants, and have roaming agreements with T-Mobile UK and ReadyToSurf. Their customers are also able to access hotspots managed by The Cloud.
In France:
Ozone and OzoneParis In France, in September 2003, Ozone started deploying the OzoneParis network across the City of Lights. The objective: to construct a wireless metropolitan network with full Wi-Fi coverage of Paris. Ozone is also deploying its network in Brussels (Belgium) and other cities in France like Rennes. Ozone Pervasive Network philosophy is based on a nationwide scale.
als@tis One of the largest Wireless Internet Service Provider for rural areas in France.
In other places:
GlobeQUEST, under Globe Telecom, provides for prepaid Wi-Fi services for nearly all cafes in the Philippines
Pacific Century Cyberworks provides hotspots in Pacific Coffee shops in Hong Kong;
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.
Netstop provides hotspots in New Zealand;
FatPort is Canada's oldest independent Wi-Fi HotSpot operator with coverage from coast to coast.
Universal Efforts
Another business model seems to be making its way into the news. The idea is that users will share their bandwidth through their personal wireless routers, which are supplied with specific software. An example is FON, a Spanish start-up created in November 2005. 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. Thus the system can be described as a peer-to-peer sharing service, which we usually relate to software.
Although FON has received some financial support by companies like Google and Skype, it remains to be seen whether the idea can actually work. There are three main challenges for this service at the moment. The first is that it needs much media and community attention first in order to get through the phase of "early adoption" and into the mainstream. Then comes the fact that sharing your Internet connection is often against the terms of use of your ISP. This means that in the next few months we can see ISPs trying to defend their interests in the same way music companies united against free MP3 distribution. And third, the FON software is still in Beta-version and it remains to be seen if it presents a good solution of the imminent security issues.
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.
OLSR is one of the protocols used to set up free networks. Some networks use static routing; others rely completely on OSPF. Wireless Leiden developed their own routing software under the name LVrouteD for community wi-fi networks that consist of a completely wireless backbone. 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 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.
Annapolis, Maryland is in the early phases (as of April 2006) of a pilot program to provide free, advertisement-financed Wi-Fi to all its residents. 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'. This was launched at their flagship restaurant in Oak Brook, Illinois, USA, and is also available in many branches in London, UK.
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 in Finland. Sparknet also supports OpenSpark, a project where people can share their own wireless access point and become as a part of Sparknet and OpenSpark community in return for certain benefits.
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). Amateur operators retain what the FCC terms "primary status" on the band under a distinct set of rules (Part 97). 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. However, Part 97 rules mandate using only the minimum power necessary for communications, forbid obscuring the data, and require station identification every 10 minutes. Therefore, expensive automatic power-limiting circuitry is required to meet regulations, and the transmission of any encrypted data (for example https) is questionable.
In practice, microwave power amplifiers are expensive and decrease receive-sensitivity of link radios. On the other hand, the short wavelength at 2.4 GHz allows for simple construction of very high gain directional antennas. Although Part 15 rules forbid any modification of commercially constructed systems, amateur radio operators may modify commercial systems for optimized construction of long links, for example. Using only 200 mW link radios and high gain directional antennas, a very narrow beam may be used to construct reliable links with minimal radio frequency interference to other users.
Advantages of Wi-Fi
Allows LANs to be deployed without cabling, 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.
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.
Widely available in more than 250,000 public hot spots and millions of homes and corporate and university campuses worldwide.
As of 2006, WPA and WPA2 encryption are not easily crackable if strong passwords are used
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
Spectrum assignments and operational limitations are not consistent worldwide; most of Europe allows for an additional 2 channels beyond those permitted in the US; 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 Wi-Fi used outside an operator's own premises, or require something akin to an operator registration. For Europe; consult http://www.ero.dk for an annual report on the additional restrictions each European country imposes.
EIRP in the EU is limited to 20dbm.
Power consumption is fairly high compared to some 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 breakable even when correctly configured.
Wi-Fi Access Points typically default to an open (encryption-free) mode. Novice users benefit from a zero configuration device that works out of the box but might not intend to provide open wireless access to their LAN. 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.
Many 2.4 GHz 802.11b and 802.11g Access points default to the same channel, contributing to congestion on certain channels.
Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or 802.11g with a stock antenna might have a range of 45 m (150 ft) indoors and 90 m (300 ft) outdoors. 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. Outdoor range with improved antennas can be several kilometres or more with line-of-sight.
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.
It is also an issue when municipalities or other large entities such as universities seek to provide large area coverage. Everyone is considered equal when they use the band (except for amateur radio operators who are the primary licensee); often this causes contention when one user seeks to claim priority in this unlicensed band. 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.
Interoperability issues between brands or deviations from the standard can disrupt connections or lower throughput speeds on other user's devices within range. Wi-Fi Alliance programs test devices for interoperability and designate devices which pass testing as Wi-Fi CERTIFIED.
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