Wi-Fi or WiFi (/ˈwaɪfaɪ/) is a technology for wireless local area
networking with devices based on the
IEEE 802.11 standards.
Wi-Fi is a
trademark of the
Wi-Fi Alliance, which restricts the use of the term
Wi-Fi Certified to products that successfully complete
interoperability certification testing.
Devices that can use
Wi-Fi technology include personal computers,
video-game consoles, phones and tablets, digital cameras, smart TVs,
digital audio players and modern printers.
Wi-Fi compatible devices
can connect to the
Internet via a WLAN and a wireless access point.
Such an access point (or hotspot) has a range of about 20 meters (66
feet) indoors and a greater range outdoors. Hotspot coverage can be as
small as a single room with walls that block radio waves, or as large
as many square kilometres achieved by using multiple overlapping
Depiction of a device sending information wirelessly to another
device, both connected to the local network, in order to print a
Wi-Fi most commonly uses the 2.4 gigahertz (12 cm)
UHF and 5.8
gigahertz (5 cm) SHF ISM radio bands. Anyone within range with a
wireless modem can attempt to access the network; because of this,
Wi-Fi is more vulnerable to attack (called eavesdropping) than wired
Wi-Fi Protected Access
Wi-Fi Protected Access is a family of technologies created
to protect information moving across
Wi-Fi networks and includes
solutions for personal and enterprise networks. Security features of
Wi-Fi Protected Access
Wi-Fi Protected Access constantly evolve to include stronger
protections and new security practices as the security landscape
Wi-Fi ad-hoc mode
IEEE 802.11 standard
4.2 City-wide Wi-Fi
4.3 Campus-wide Wi-Fi
Wi-Fi ad hoc versus
Wi-Fi radio spectrum
6 Service set identifier (SSID)
8.1 Standard devices
8.2 Embedded systems
10 Multiple access points
11 Network security
11.1 Securing methods
11.2 Data security risks
12 Health concerns
13 See also
15 Further reading
IEEE 802.11 § History
ALOHAnet connected the Hawaiian Islands with a
ALOHAnet and the ALOHA protocol were early forerunners
to Ethernet, and later the
IEEE 802.11 protocols, respectively.
A 1985 ruling by the U.S.
Federal Communications Commission
Federal Communications Commission released
ISM band for unlicensed use. These frequency bands are the same
ones used by equipment such as microwave ovens and are subject to
NCR Corporation with AT&T Corporation invented the
precursor to 802.11, intended for use in cashier systems, under the
The Australian radio-astronomer Dr John O'Sullivan with his colleagues
Terence Percival, Graham Daniels, Diet Ostry, and John Deane
developed a key patent used in
Wi-Fi as a by-product of a Commonwealth
Scientific and Industrial Research Organisation (CSIRO) research
project, "a failed experiment to detect exploding mini black holes the
size of an atomic particle". Dr O'Sullivan and his colleagues are
credited with inventing Wi-Fi. In 1992 and 1996, CSIRO obtained
patents for a method later used in
Wi-Fi to "unsmear" the
The first version of the 802.11 protocol was released in 1997, and
provided up to 2 Mbit/s link speeds. This was updated in 1999
with 802.11b to permit 11 Mbit/s link speeds, and this proved to
In 1999, the
Wi-Fi Alliance formed as a trade association to hold the
Wi-Fi trademark under which most products are sold.
Wi-Fi uses a large number of patents held by many different
organizations. In April 2009, 14 technology companies agreed to
pay CSIRO $1 billion for infringements on CSIRO patents. This led
to Australia labeling
Wi-Fi as an Australian invention, though
this has been the subject of some controversy. CSIRO won a
further $220 million settlement for
Wi-Fi patent-infringements in 2012
with global firms in the United States required to pay the CSIRO
licensing rights estimated to be worth an additional $1 billion in
royalties. In 2016, the wireless local area network Test
Bed was chosen as Australia's contribution to the exhibition A History
of the World in 100 Objects held in the National Museum of
The name Wi-Fi, commercially used at least as early as August
1999, was coined by the brand-consulting firm Interbrand. The
Wi-Fi Alliance had hired
Interbrand to create a name that was "a
little catchier than 'IEEE 802.11b Direct Sequence'." Phil
Belanger, a founding member of the
Wi-Fi Alliance who presided over
the selection of the name "Wi-Fi", has stated that
Wi-Fi as a pun upon the word hi-fi.
Interbrand also created the
Wi-Fi logo. The yin-yang
indicates the certification of a product for interoperability.
Wi-Fi Alliance used the nonsense advertising slogan "The Standard
Wireless Fidelity" for a short time after the brand name was
created. The name was, however, never officially "Wireless
Fidelity". Nevertheless, the
Wi-Fi Alliance was also called the
Wireless Fidelity Alliance Inc" in some publications and the
IEEE's own website has stated "WiFi is a short name for Wireless
Wi-Fi technologies intended for fixed points, such as Motorola
Canopy, are usually described as fixed wireless. Alternative wireless
technologies include mobile phone standards, such as 2G, 3G, 4G, and
The name is sometimes written as WiFi, Wifi, or wifi, but these are
not approved by the
Wi-Fi ad-hoc mode
Wi-Fi nodes operating in ad-hoc mode refers to devices talking
directly to each other without the need to first talk to an access
point (also known as base station). Ad-hoc mode was first invented and
realized by Chai K. Toh in his 1996 invention of
Wi-Fi ad-hoc routing,
implemented on Lucent
WaveLAN 802.11a wireless on IBM ThinkPads over a
size nodes scenario spanning a region of over a mile. The success was
recorded in Mobile Computing magazine (1999) and later published
formally in IEEE Transactions on
Wireless Communications, 2002 and
ACM SIGMETRICS Performance Evaluation Review, 2001.
The IEEE does not test equipment for compliance with their standards.
Wi-Fi Alliance was 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 2010[update], the
Wi-Fi Alliance consisted of more
than 375 companies from around the world. The
enforces the use of the
Wi-Fi brand to technologies based on the IEEE
802.11 standards from the IEEE. This includes wireless local area
network (WLAN) connections, device to device connectivity (such as
Wi-Fi Peer to Peer aka
Personal area network (PAN),
local area network (LAN) and even some limited wide area network (WAN)
connections. Manufacturers with membership in the
whose products pass the certification process, gain the right to mark
those products with the
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
IEEE 802.11 draft standards, interaction with cellular-phone
technology in converged devices, and features relating to security
set-up, multimedia, and power-saving.
Wi-Fi device is submitted for certification. The lack of
Wi-Fi certification does not necessarily imply that a device is
incompatible with other
Wi-Fi devices. The
Wi-Fi Alliance may or
may not sanction derivative terms, such as Super Wi-Fi, coined by
Federal Communications Commission
Federal Communications Commission (FCC) to describe proposed
networking in the
UHF TV band in the US.
IEEE 802.11 standard
Wi-Fi router contains dual bands for transmitting the
802.11 standard across the 2.4 and 5 GHz spectrums.
Main article: IEEE 802.11
IEEE 802.11 standard is a set of media access control (MAC) and
physical layer (PHY) specifications for implementing wireless local
area network (WLAN) computer communication in the 2.4, 3.6, 5, and
60 GHz frequency bands. They are created and maintained by the
IEEE LAN/MAN Standards Committee (IEEE 802). The base version of the
standard was released in 1997, and has had subsequent amendments. The
standard and amendments provide the basis for wireless network
products using the
Wi-Fi brand. While each amendment is officially
revoked when it is incorporated in the latest version of the standard,
the corporate world tends to market to the revisions because they
concisely denote capabilities of their products. As a result, in
the market place, each revision tends to become its own standard.
A Japanese sticker indicating to the public that a location is within
range of a
Wi-Fi network. A dot with curved lines radiating from it is
a common symbol for Wi-Fi, representing a point transmitting a
To connect to a
Wi-Fi LAN, a computer has to be equipped with a
wireless network interface controller. The combination of computer and
interface controller is called a station. For all stations that share
a single radio frequency communication channel, transmissions on this
channel are received by all stations within range. The
transmission is not guaranteed to be delivered and is therefore a
best-effort delivery mechanism. A carrier wave is used to transmit the
data. The data is organised in packets on an
Ethernet link, referred
to as "
Wi-Fi technology may be used to provide
Internet access to devices
that are within the range of a wireless network that is connected to
the Internet. The coverage of one or more interconnected access points
(hotspots) can extend from an area as small as a few rooms to as large
as many square kilometres. Coverage in the larger area may require a
group of access points with overlapping coverage. For example, public
Wi-Fi technology has been used successfully in wireless mesh
networks in London, UK. An international example is Fon.
Wi-Fi provides service in private homes, businesses, as well as in
public spaces at
Wi-Fi hotspots set up either free-of-charge or
commercially, often using a captive portal webpage for access.
Organizations and businesses, such as airports, hotels, and
restaurants, often provide free-use hotspots to attract customers.
Enthusiasts or authorities who wish to provide services or even to
promote business in selected areas sometimes provide free Wi-Fi
Routers that incorporate a digital subscriber line modem or a cable
modem and a
Wi-Fi access point, often set up in homes and other
Internet access and internetworking to all devices
connected to them, wirelessly or via cable.
Similarly, battery-powered routers may include a cellular Internet
radio modem and
Wi-Fi access point. When subscribed to a cellular data
carrier, they allow nearby
Wi-Fi stations to access the
2G, 3G, or 4G networks using the tethering technique. Many smartphones
have a built-in capability of this sort, including those based on
Android, BlackBerry, Bada, iOS (iPhone),
Windows Phone and Symbian,
though carriers often disable the feature, or charge a separate fee to
enable it, especially for customers with unlimited data plans.
Internet packs" provide standalone facilities of this type as well,
without use of a smartphone; examples include the MiFi- and
WiBro-branded devices. Some laptops that have a cellular modem card
can also act as mobile
Wi-Fi access points.
Wi-Fi also connects places that normally don't have network access,
such as kitchens and garden sheds.
Google is intending to use the technology to allow rural areas to
enjoy connectivity by utilizing a broad mix of projection and routing
services. Google also intends to bring connectivity to Africa and some
Asian lands by launching blimps that will allow for internet
Further information: Municipal wireless network
Wi-Fi access point
In the early 2000s, many cities around the world announced plans to
Wi-Fi networks. There are many successful examples;
Mysore (Mysuru) became India's first Wi-Fi-enabled city. A
company called WiFiyNet has set up hotspots in Mysore, covering the
complete city and a few nearby villages.
St. Cloud, Florida
St. Cloud, Florida and Sunnyvale, California, became the
first cities in the United States to offer citywide free
Minneapolis has generated $1.2 million in profit
annually for its provider.
In May 2010,
Boris Johnson pledged to have London-wide
Wi-Fi by 2012. Several boroughs including Westminster and
Islington already had extensive outdoor
Wi-Fi coverage at that
Officials in South Korea's capital
Seoul are moving to provide free
Internet access at more than 10,000 locations around the city,
including outdoor public spaces, major streets and densely populated
Seoul will grant leases to KT, LG Telecom and SK
Telecom. The companies will invest $44 million in the project, which
was to be completed in 2015.
Many traditional university campuses in the developed world provide at
Carnegie Mellon University
Carnegie Mellon University built the
first campus-wide wireless
Internet network, called
Pittsburgh campus in 1993 before
originated. By February 1997 the CMU
Wi-Fi zone was fully
operational. Many universities collaborate in providing
to students and staff through the
Eduroam international authentication
Wi-Fi ad hoc versus
Wi-Fi also allows communications directly from one computer to another
without an access point intermediary. This is called ad hoc Wi-Fi
transmission. This wireless ad hoc network mode has proven popular
with multiplayer handheld game consoles, such as the Nintendo DS,
PlayStation Portable, digital cameras, and other consumer electronics
devices. Some devices can also share their
Internet connection using
ad hoc, becoming hotspots or "virtual routers".
Wi-Fi Alliance promotes the specification
for file transfers and media sharing through a new discovery- and
Wi-Fi Direct launched in October 2010.
Another mode of direct communication over
Wi-Fi is Tunneled Direct
Link Setup (TDLS), which enables two devices on the same
to communicate directly, instead of via the access point.
Wi-Fi radio spectrum
Main article: list of WLAN channels
802.11b and 802.11g use the 2.4 GHz ISM band, operating in the United
States under Part 15 Rules and Regulations. Because of this choice of
frequency band, 802.11b and g equipment may occasionally suffer
interference from microwave ovens, cordless telephones, and Bluetooth
Spectrum assignments and operational limitations are not consistent
worldwide: Australia and Europe allow for an additional two channels
(12, 13) beyond the 11 permitted in the United States for the
2.4 GHz band, while Japan has three more (12–14). In the US and
other countries, 802.11a and 802.11g devices may be operated without a
license, as allowed in Part 15 of the FCC Rules and Regulations.
Wi-Fi signal occupies five channels in the 2.4 GHz band. Any
two channel numbers that differ by five or more, such as 2 and 7, do
not overlap. The oft-repeated adage that channels 1, 6, and 11 are the
only non-overlapping channels is, therefore, not accurate. Channels 1,
6, and 11 are the only group of three non-overlapping channels in
North America and the United Kingdom. In Europe and Japan using
Channels 1, 5, 9, and 13 for 802.11g and 802.11n is
802.11a uses the 5 GHz
U-NII band, which, for much of the world,
offers at least 23 non-overlapping channels rather than the
2.4 GHz ISM frequency band, where adjacent channels overlap.
Further information: Electromagnetic interference at 2.4 GHz
Wi-Fi connections can be disrupted or the
Internet speed lowered by
having other devices in the same area. 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.
Wi-Fi pollution, or an
excessive number of access points in the area, especially on the
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
ISM band devices, security cameras,
ZigBee devices, Bluetooth
devices, video senders, cordless phones, baby monitors, and, in
some countries, amateur radio, all of which can cause significant
additional interference. It is also an issue when municipalities
or other large entities (such as universities) seek to provide large
Service set identifier (SSID)
See also: Service set (802.11 network)
In addition to running on different channels, multiple
can share channels.
A service set is the set of all the devices associated with a
Wi-Fi network. The service set can be local, independent,
extended or mesh.
Each service set has an associated identifier, the 32-byte Service Set
Identifier (SSID), which identifies the particular network. The SSID
is configured within the devices that are considered part of the
network, and it is transmitted in the packets. Receivers ignore
wireless packets from networks with a different SSID.
As the 802.11 specifications evolved to support higher throughput, the
bandwidth requirements also increased to support them. 802.11n uses
double the radio spectrum/bandwidth (40 MHz) compared to 802.11a
or 802.11g (20 MHz).76 This means there can be only one 802.11n
network on the 2.4 GHz band at a given location, without
interference to/from other WLAN traffic. 802.11n can also be set to
limit itself to 20 MHz bandwidth to prevent interference in dense
Many newer consumer devices support the latest 802.11ac standard,
which uses the 5 GHz band exclusively and is capable of
multi-station WLAN throughput of at least 1 gigabit per second, and a
single station throughput of at least 500 Mbit/s. In the first quarter
of 2016, The
Wi-Fi Alliance certifies devices compliant with the
802.11ac standard as "
Wi-Fi CERTIFIED ac". This new standard uses
several advanced signal processing techniques such as multi-user MIMO
and 4X4 Spatial
Multiplexing streams, and large channel bandwidth
(160 MHz) to achieve the Gigabit throughput. According to a study
by IHS Technology, 70% of all access point sales revenue In the first
quarter of 2016 came from 802.11ac devices.
Wi-Fi whitelist triggered on an HP laptop
Wi-Fi allows cheaper deployment of local area networks (LANs). Also,
spaces where cables cannot be run, such as outdoor areas and
historical buildings, can host wireless LANs. However, building walls
of certain materials, such as stone with high metal content, can block
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.
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
backward compatible. Unlike mobile phones, any standard
will work anywhere in the world.
An embedded RouterBoard 112 with U.FL-RSMA pigtail and R52 mini PCI
Wi-Fi card widely used by wireless
Internet service providers (WISPs)
in the Czech Republic
OSBRiDGE 3GN – 802.11n Access Point and UMTS/GSM Gateway in one
Wi-Fi adapter with built in
Bluetooth on a Sony
Vaio E series laptop
USB wireless adapter
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
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 built in internal adapters.
Wireless routers integrate a
Wireless Access Point,
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 computer, as
is the case with as Apple's AirPort, which is managed with the AirPort
Utility on macOS and iOS.
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 or for devices which
do not have wireless networking capability (but have wired networking
capability), such as consumer entertainment devices; alternatively, a
wireless bridge can be used to enable a device which supports a wired
connection to operate at a wireless networking standard which is
faster than supported by the wireless network connectivity feature
(external dongle or inbuilt) supported by the device (e.g. enabling
Wireless-N speeds (up to the maximum supported speed on the wired
Ethernet port on both the bridge and connected devices including the
wireless access point) for a device which only supports Wireless-G). A
dual-band wireless bridge can also be used to enable 5 GHz
wireless network operation on a device which only supports
2.4 GHz wireless networking functionality and has a wired
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, as well as from a reduction in the maximum data
throughput that is available. In addition, the effect of additional
users using a network employing wireless range-extenders is to consume
the available bandwidth faster than would be the case where but a
single user migrates around a network employing extenders. For this
reason, wireless range-extenders work best in networks supporting very
low traffic throughput requirements, such as for cases where but a
single user with a
Wi-Fi equipped tablet migrates around the combined
extended and non-extended portions of the total connected network.
Additionally, a wireless device connected to any of the repeaters in
the chain will have a data throughput that is also limited by the
"weakest link" existing in the chain between where the connection
originates and where the connection ends. Networks employing wireless
extenders are also more prone to degradation from interference from
neighboring access points that border portions of the extended network
and that happen to occupy the same channel as the extended network.
The security standard,
Wi-Fi Protected Setup, allows embedded devices
with limited graphical user interface to connect to the
Wi-Fi Protected Setup
Wi-Fi Protected Setup has 2 configurations: The Push Button
configuration and the PIN configuration. These embedded devices are
also called The
Internet of Things and are low-power, battery-operated
embedded systems. A number of
Wi-Fi manufacturers design chips and
modules for embedded Wi-Fi, such as GainSpan.
Increasingly in the last few years (particularly as of 2007[update]),
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.
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.
Wi-Fi modules are designed by OEMs so that implementers need
Wi-Fi knowledge to provide
Wi-Fi connectivity for their
In June 2014, Texas Instruments introduced the first ARM Cortex-M4
microcontroller with an onboard dedicated
Wi-Fi MCU, the SimpleLink
CC3200. It makes embedded systems with
Wi-Fi connectivity possible to
build as single-chip devices, which reduces their cost and minimum
size, making it more practical to build wireless-networked controllers
into inexpensive ordinary objects.
See also: Long-range Wi-Fi
Wi-Fi signal range depends on the frequency band, radio power
output, antenna gain and antenna type as well as the modulation
technique. Line-of-sight is the thumbnail guide but reflection and
refraction can have a significant impact.
An access point compliant with either 802.11b or 802.11g, using the
stock antenna might have a range of 100 m (0.062 mi). The
same radio with an external semi parabolic antenna (15 dB gain)
might have a range over 20 miles.
Higher gain rating (dBi) indicates further deviation (generally toward
the horizontal) from a theoretical, perfect isotropic radiator, and
therefore the further the antenna can project a usable signal, as
compared to a similar output power on a more isotropic antenna.
For example, an 8 dBi antenna used with a 100 mW driver will have
a similar horizontal range to a 6 dBi antenna being driven at
500 mW. Note that this assumes that radiation in the vertical is
lost; this may not be the case in some situations, especially in large
buildings or within a waveguide. In the above example, a directional
waveguide could cause the low power 6 dBi antenna to project much
further in a single direction than the 8 dBi antenna which is not in a
waveguide, even if they are both being driven at 100 mW.
IEEE 802.11n, however, can more than double the range. 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
used by 802.11a (and optionally by 802.11n). On wireless routers with
detachable antennas, it is possible to improve range by fitting
upgraded antennas which have higher gain in particular directions.
Outdoor ranges can be improved to many kilometers through the use of
high gain directional antennas at the router and remote device(s). In
general, the maximum amount of power that a
Wi-Fi device can transmit
is limited by local regulations, such as FCC Part 15 in the US.
Equivalent isotropically radiated power
Equivalent isotropically radiated power (EIRP) in the European Union
is limited to 20 dBm (100 mW).
To reach requirements for wireless LAN applications,
Wi-Fi has fairly
high power consumption compared to some other standards. Technologies
Bluetooth (designed to support wireless personal area network
(PAN) applications) provide a much shorter propagation range between 1
and 100 m 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
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-6)
is not possible or cost-effective. For example, the
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 is designed for applications (such as
where indoor range is more important than mobility.
For the best performance, a number of people only recommend using
wireless networking as a supplement to wired networking.
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
strength for any given area in relation to a transmitter. This
effect does not apply equally to long-range Wi-Fi, since longer links
typically operate from towers that transmit above the surrounding
The 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.[dubious – discuss]
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.
Other wireless technologies are more suitable for communicating with
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. The Swedish Space
Agency transferred data 420 km (260 mi), using 6 watt
amplifiers to reach an overhead stratospheric balloon.
Multiple access points
Increasing the number of
Wi-Fi access points provides network
redundancy, better range, support for fast roaming and increased
overall network-capacity by using more channels or by defining smaller
cells. Except for the smallest implementations (such as home or small
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 use mesh
When multiple access points are deployed they are often configured
with the same SSID [clarification needed] and security settings to
form an "extended service set".
Wi-Fi client devices will typically
connect to the access point that can provide the strongest signal
within that service set.
The main issue with wireless network security is its simplified access
to the network compared to traditional wired networks such as
Ethernet. With wired networking, one must either gain access to a
building (physically connecting into the internal network), or break
through an external firewall. To enable Wi-Fi, one merely needs to be
within the range of the
Wi-Fi network. Most business networks protect
sensitive data and systems by attempting to disallow external access.
Enabling wireless connectivity reduces security if the network uses
inadequate or no encryption.
An attacker who has gained access to a
Wi-Fi network router can
initiate a DNS spoofing attack against any other user of the network
by forging a response before the queried DNS server has a chance to
A common measure to deter unauthorized users involves hiding the
access point's name by disabling the SSID broadcast. While effective
against the casual user, it is ineffective as a security method
because the SSID is broadcast in the clear in response to a client
SSID query. Another method is to only allow computers with known MAC
addresses to join the network, but determined eavesdroppers may be
able to join the network by spoofing an authorized address.
Wired Equivalent Privacy (WEP) encryption was designed to protect
against casual snooping but it is no longer considered secure. Tools
such as AirSnort or
Aircrack-ng can quickly recover WEP encryption
keys. Because of WEP's weakness the
Wi-Fi Alliance approved Wi-Fi
Protected Access (WPA) which uses TKIP. WPA was specifically designed
to work with older equipment usually through a firmware upgrade.
Though more secure than WEP, WPA has known vulnerabilities.
The more secure
Advanced Encryption Standard
Advanced Encryption Standard was introduced
in 2004 and is supported by most new
WPA2 is fully
compatible with WPA. In 2017 a flaw in the
WPA2 protocol was
discovered, allowing a key replay attack, known as KRACK.
A flaw in a feature added to
Wi-Fi in 2007, called
Setup (WPS), allows WPA and
WPA2 security to be bypassed and
effectively broken in many situations. The only remedy as of late 2011
is to turn off
Wi-Fi Protected Setup, which is not always
Virtual Private Networks are often used to secure Wi-Fi.[citation
Data security risks
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The older wireless encryption-standard, Wired Equivalent Privacy
(WEP), has been shown to be easily breakable even when correctly
Wi-Fi Protected Access
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
connecting devices can monitor and record data (including personal
information). Such networks can only be secured by using other means
of protection, such as a VPN or secure Hypertext Transfer Protocol
Transport Layer Security (HTTPS).
Wi-Fi Protected Access
Wi-Fi Protected Access encryption (WPA2) is considered secure,
provided a strong passphrase is used. In 2018,
WPA3 was announced as a
replacement for WPA2, increasing the security.
Main article: Piggybacking (
Further information: Legality of piggybacking
Wi-Fi Protected Setup
Wi-Fi Protected Setup § Physical security
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, particularly since people
on average use only a fraction of their downstream bandwidth at any
Recreational logging and mapping of other people's access points has
become known as wardriving. 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
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. A
Florida court case determined
that owner laziness was not to be a valid excuse.
Piggybacking often occurs unintentionally – a technically
unfamiliar user might not change the default "unsecured" settings to
their access point 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 unsecure
network to log into a website, thereby making the login credentials
available to anyone listening, if the website uses an unsecure
protocol such as plain HTTP without TLS (HTTPS).
An unauthorized user can obtain security information (factory preset
Wi-Fi Protected Setup
Wi-Fi Protected Setup PIN) from a label on a
wireless access point can use this information (or connect by the
Wi-Fi Protected Setup
Wi-Fi Protected Setup pushbutton method) to commit unauthorized and/or
Wireless electronic devices and health
World Health Organization
World Health Organization (WHO) says "no health effects are
expected from exposure to RF fields from base stations and wireless
networks", but notes that they promote research into effects from
other RF sources. Although the WHO's International Agency for
Research on Cancer (IARC) later classified radiofrequency
electromagnetic fields as "possibly carcinogenic to humans (Group
2B)" (a category used when "a causal association is considered
credible, but when chance, bias or confounding cannot be ruled out
with reasonable confidence"), this was based on risks associated
with wireless phone use rather than
The United Kingdom's
Health Protection Agency
Health Protection Agency reported in 2007 that
Wi-Fi for a year results in the "same amount of radiation
from a 20-minute mobile phone call".
A review of studies involving 725 people who claimed electromagnetic
hypersensitivity, "...suggests that 'electromagnetic hypersensitivity'
is unrelated to the presence of EMF, although more research into this
phenomenon is required."
Gi-Fi — a term used by some trade press to refer to faster versions
IEEE 802.11 standards
Indoor positioning system
List of WLAN channels
San Francisco Digital Inclusion Strategy
Super Wi-Fi –
IEEE 802.22 proposal to use television bands
Wireless Broadband Alliance
Wireless network interface controller (WNIC)
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Wireless video and data distribution methods
Digital terrestrial television
Digital terrestrial television (DTT or DTTV)
Digital Video Broadcasting
Multipoint Video Distribution System (
MVDS or DVB-MS)
Television Fixed Service (ITFS; now known as Educational
Broadband Service (EBS))
Local Multipoint Distribution Service (LMDS)
WiMAX (IEEE 802.16e)
Mobile broadband wireless access (IEEE 802.20)
Multichannel Multipoint Distribution Service
Multichannel Multipoint Distribution Service (MMDS; now known as
Radio Service (BRS))
Multimedia Broadcast Multicast Service (3G MMMS)
UWB (IEEE 802.15.3)
Visual sensor network
Wi-Fi (IEEE 802.11)
WiMAX (IEEE 802.16)
WRAN (IEEE 802.22)
Wireless local loop (WLL)
3GPP Long Term Evolution
3GPP Long Term Evolution (LTE)
Cable protection system
Prepay mobile phone
The Telephone Cases
Timeline of communication technology
Undersea telegraph line
Edwin Howard Armstrong
John Logie Baird
Alexander Graham Bell
Jagadish Chandra Bose
Lee de Forest
Erna Schneider Hoover
Charles K. Kao
Alexander Stepanovich Popov
Johann Philipp Reis
Vladimir K. Zworykin
Free-space optical communication
Network switching (circuit
Public Switched Telephone
World Wide Web