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Wi-Fi

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Internet protocol
suite

Layer

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Application

DNS, ENRP,
FTP, HTTP,
IMAP,
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POP3, SIP,
SMTP,
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Session

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TCP,
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…

Network

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…

Link

Ethernet,
Wi-Fi, Token ring, MPLS,
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…

Wi-Fi (also WiFi, Wi-fi, Wifi, or wifi) is
an acronym for
Wireless Fidelity. It 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.

Contrary to popular belief, Wi-Fi did not originally stand for
Wireless-Fidelity. The term "Wi-Fi" was developed by the Wi-Fi
Alliance along with the Interbrand
Corporation (here) to describe WLAN products that are
based on the IEEE 802.11 standards. Phil Belanger of the Wi-Fi Alliance quoted,
"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”. Later, the term "Wireless Fidelity" was coined
with the marketing of a new tag line, "The Standard for Wireless Fidelity." But
that was soon dropped due to confusion among customers and consumers.

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 History

2 Wi-Fi: How it
works

3 Wi-Fi vs.
cellular

4 Commercial Wi-Fi

4.1 Universal
Efforts

5 Free Wi-Fi

6 Wi-Fi vs. Amateur
Radio

7 Advantages of
Wi-Fi

8 Disadvantages of
Wi-Fi

9 Wi-Fi gaming

10 Wi-Fi and free
software

11 Trademark/Certification

12 Unintended and intended
use by outsiders

13 See also

14 External links

[edit]

History

Back in 1991 Wi-Fi was invented by NCR Corporation/AT&T (later
on Lucent &
Agere
Systems) in Nieuwegein, the Netherlands.
Initially meant for cashier systems the first wireless products were brought on
the market under the name WaveLAN with speeds of 1Mbps/2Mbps. Vic
Hayes who is the inventor of Wi-Fi has been named 'father of Wi-Fi' and was
with his team 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 cutting edge, as many
opted for cheaper Wi-Fi solutions. Agere's 802.11abg all-in-one chipset (code
named: WARP) never hit the market, Agere Systems decided to quit the Wi-Fi
market in late 2004.

[edit]

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 broadcasted
every 100ms. The beacons are transmitted at 1Mbps, and are relatively short and
therefore are not of influence on performance. Since 1Mbps is the lowest rate of
Wi-Fi it assures that the client who receives the beacon can communicate at at
least 1Mbps. Based on the settings (i.e. 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 AP's of the same SSID are in range of the
client, the firmware may decide based on signal strength (Signal-to-noise ratio) to which of
the two AP's 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
Windows XP there is a feature called zero configuration which makes the
user show any network available and let the end user connect to it on the fly.
In the future wireless cards will be more and more controlled by the operating
system. Microsoft's newest feature called SoftMAC will take over from
on-board firmware. Having said this, roaming criteria will be totally controlled
by the operating system. 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.

[edit]

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 could compete
with other cellular phone protocols such as GSM, UMTS or CDMA. However, Wi-Fi is ideal for
VoIP applications
like 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 Zyxell,
UT
Starcomm, Samsung, Hitachi and many more are
offering VoIP Wi-Fi phones for reasonable prices.

In 2005 ADSL ISP providers started to offer VoIP services to their customers
(eg. the dutch ISP XS4All). Since calling via VoIP
is low-cost and more often being free, 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. Wi-Fi-only phones have a very
limited range, and so setting up a covering network would be too expensive.
Therefore these kinds of phones may be best reserved for local use such as
corporate networks. However, devices capable of multiple standards may well
compete in the market.

[edit]

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:

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 Pervasive Network philosophy is based
on a nationwide scale.

WiSE Technologies provides commercial
hotspots for airports, universities, and independent cafes in the US;

T-Mobile provides hotspots in
many Starbucks in the U.S, and
UK;

Pacific Century
Cyberworks 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 offers a big network of
hotspots spread over Brazil. Telefónica Speedy WiFi 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

[edit]

Universal Efforts

Another business model seems to be making its way into the news. The idea is
that users will share their bandwidth though 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 though 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.

[edit]

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 [http://www.freenetworks.org/peering.html
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. 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 the Kingdom of Tonga or 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 WiFi Network.

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 also offers Wi-Fi access, often branded 'McInternet'. This was
launched at their flagship restaurant in Oak Brook, Illinois
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
OpenSparknet, a project where people can
name their own wireless access point as a part of Sparknet 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.

[edit]

Wi-Fi vs. Amateur Radio

In the US, 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 two
24 dB gain antennas, an effective radiated power of many hundreds of watts in a
very narrow beam may be used to construct reliable links of over 100 km with
little radio frequency interference to other users.

[edit]

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.

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.

[edit]

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 100 mW limit and one accepts
interference from other sources; including interference which causes your
devices to no longer function. Some believe that Amateur Radio operators
are an exception to the otherwise limited power output ceilings. The claim is
that they may boost power output from their WiFi routers up to the legal maximum
for their Amateur Radio license class, often 100 watts for spread spectrum
operation (roughly 1,000 times that of a normal router).  For operation
in the US, FCC
regulations parts 97.311 and 97.313 seem to support this claim, with the
proviso that they use automatic power control for transmitter power levels
exceeding 1 watt while using spread spectrum modes (e.g., 802.11b). However, Amateur
Radio operators are always required to "use the minimum transmitter power
necessary to carry out the desired communications."

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
WiFi 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.

The 802.11b and 802.11g flavors of Wi-Fi use
the unlicensed 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 that use
microwave frequencies, such as certain types of cellphones, can also cause
degradation in performance. Lots of Wi-Fi cards have Microwave-robustness
algorithms on-board that make the problems in almost all cases non-existent.

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 (caused by weak-key generation). Although most newer wireless
products support the much improved Wi-Fi Protected
Access (WPA) protocol, many first-generation access points cannot be
upgraded in the field and have to be replaced to support it. The adoption of
the 802.11i (aka WPA2) standard in June 2004 makes
available a still further improved security scheme, which is becoming
available on the latest equipment. Both schemes require stronger passwords in
personal mode than most users typically employ. Many enterprises have deployed
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. Range also varies, as WiFi is no exception to the physics of radio
wave propagation, with frequency band. WiFi in the 2.4 GHz frequency block has
better range than WiFi in the 5 GHz frequency block, and less range than the
oldest WiFi (and pre-WiFi) 900 MHz block.

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.

Interoperability issues between brands or deviations in the standard can
cause limited connection or lower throughput speeds.

Free access points (or improperly configured intentionally-private access
points) may be used by the malicious to anonymously initiate an attack that
would be impossible to track beyond the owner of the access point. Also, if
the malicious user transfers a considerable amount of data to or from the
Internet, the supplier of the Internet connection could be charged for this by
his ISP, or if the supplier has a connection which allows him a specified
amount of transfer, this transfer allowance could be used by the malicious
user.

[edit]

Wi-Fi gaming

Wi-Fi is compatible with gaming consoles and handhelds, allowing online
play at any access point.

Iwata, the President of Nintendo announced the Nintendo
Revolution will be Wi-Fi compatible, also saying that titles like Super Smash
Brothers will be playable. The Nintendo DS handheld is
also Wi-Fi compatible.

The Sony
PSP comes with WLAN which can be turned on by the switch of a button to
connect to WI-FI hotspots or wireless connections.

[edit]

Wi-Fi and free software

BSDs (FreeBSD, NetBSD, OpenBSD) have
had support for most adapters since late 1998. Code for Atheros, Prism,
Harris/Intersil and Aironet chips (from assorted WiFi vendors) is mostly
shared among the 3 BSDs. Darwin and Mac OS X, despite their overlap with
FreeBSD, have their own unique implementation. In OpenBSD 3.7, more drivers
for wireless chipsets are available, including RealTek RTL8180L, Ralink
RT25x0, Atmel AT76C50x, and Intel 2100 and 2200BG/2225BG/2915ABG, due to at
least in part of the OpenBSD's effort to push for open source drivers for
wireless chipsets. It is possible that such drivers may be implemented by
other BSDs if they do not already exist. The ndiswrapper is also available for
FreeBSD.

Linux: As of
version 2.6, some Wi-Fi hardware is supported natively in the Linux
kernel. Support for Orinoco, Prism, Aironet and Atmel are included in the
main kernel tree, while ADMtek and Realtek RTL8180L are both supported by
closed source drivers provided by the manufacturer and open source drivers
written by the community. Intel Calexico radios are supported by open sourced
drivers available at Sourceforge. Atheros and Ralink RT2x00 are supported
through open source projects. Otherwise, support for other wireless devices is
available through use of the open source ndiswrapper driver, which
allows Linux running on the Intel x86 architecture to "wrap" a vendor's Windows driver for
direct use. At least one commercial implementation of the idea is also
available. The FSF has some
recommended cards[1] and
more information can be found through the searchable Linux wireless site[2]

[edit]

Trademark/Certification

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.

[edit]

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, instead 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, allowing only 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. It should be
noted that these activities are illegal in many countries, including the United
Kingdom.

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. [3]

[edit]

See also

OSGi Alliance

WiMAX

Liquid
crystal display television with integrated WiFi port

Wikibooks:
Building a Wifi antenna

Wireless mesh
network

Wireless LAN

Wireless security

[edit]

External links

Wikibooks has more about this subject:

Wifi

ndiswrapper is the main WiFi
card support software on Linux - [http://ndiswrapper.sourceforge.net/mediawiki/index.php/List
list of supported cards]

Wifi World Record World Record for
landbased 802.11b wireless internet (Guinness Approved ed. 2005 pg. 112).

First Mile Solutions Free WiFi
internet for developing and developed countries

WiGLE Worldwide database and mapping of wireless
networks.

Wi-Fi Free Spot Directory of free
Wi-Fi locations in the United States.

Wifi-Forum Worldwide discussion forum on
Wi-Fi technology

Man
charged with wireless trespassing

The Mobile Wi-fi Access
Point: Do-it-yourself cheap,
easy Internet... everywhere.

Retrieved from "http://en.wikipedia.org/wiki/Wi-Fi"

Categories:
Wi-Fi | Internet

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This page was last modified 08:42, 24 February 2006.

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