Wi-Fi

Wi-Fi (/ˈwaɪfaɪ/)[1] is a family of radio technologies that is commonly used for the wireless local area networking (WLAN) of devices which is based around the IEEE 802.11 family of 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.[2][3] Wi-Fi uses multiple parts of the IEEE 802 protocol family and is designed to seamlessly interwork with its wired sister protocol Ethernet.

Devices that can use Wi-Fi technologies include desktops and laptops, video game consoles, smartphones and tablets, smart TVs, printers, digital audio players, digital cameras, cars and drones. Compatible devices can connect to each other over Wi-Fi through a wireless access point as well as to connected Ethernet devices and may use it to access the Internet. 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 access points.

Wi-Fi
Depiction of a device sending information wirelessly to another device, both connected to the local network, in order to print a document

The different versions of Wi-Fi are specified by various IEEE 802.11 protocol standards, with the different radio technologies determining the ranges, radio bands, and speeds that may be achieved. Wi-Fi most commonly uses the 2.4 gigahertz (12 cm) UHF and 5 gigahertz (6 cm) SHF ISM radio bands; these bands are subdivided into multiple channels. Each channel can be time-shared by multiple networks. These wavelengths work best for line-of-sight. Many common materials absorb or reflect them, which further restricts range, but can tend to help minimise interference between different networks in crowded environments. At close range, some versions of Wi-Fi, running on suitable hardware, can achieve speeds of over 1 Gbit/s.

Wi-Fi is potentially more vulnerable to attack than wired networks because anyone within range of a network with a wireless network interface controller can attempt access. Wi-Fi Protected Access (WPA) 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 WPA have included stronger protections and new security practices as the security landscape has changed over time.

Wi-Fi
WiFi Logo
The old Wi-Fi Alliance logo
IntroducedSeptember 1998
Compatible hardwarePersonal computers, gaming consoles, televisions, printers, mobile phones

History

In 1971, ALOHAnet connected the Hawaiian Islands with a UHF wireless packet network. 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 released the ISM band for unlicensed use.[4] These frequency bands are the same ones used by equipment such as microwave ovens and are subject to interference.

In 1991, NCR Corporation with AT&T Corporation invented the precursor to 802.11, intended for use in cashier systems, under the name WaveLAN.

The Australian radio-astronomer Dr John O'Sullivan with his colleagues Terence Percival, Graham Daniels, Diet Ostry, and John Deane[5] 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".[6] Dr O'Sullivan and his colleagues are credited with inventing Wi-Fi.[7][8] In 1992 and 1996, CSIRO obtained patents[9] for a method later used in Wi-Fi to "unsmear" the signal.[10]

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 be popular.

In 1999, the Wi-Fi Alliance formed as a trade association to hold the Wi-Fi trademark under which most products are sold.[11]

Wi-Fi uses a large number of patents held by many different organizations.[12] In April 2009, 14 technology companies agreed to pay CSIRO $1 billion for infringements on CSIRO patents.[13] This led to Australia labeling Wi-Fi as an Australian invention,[14] though this has been the subject of some controversy.[15][16] 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.[13][17][18] 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 Australia.[19]

Etymology and terminology

The name Wi-Fi, commercially used at least as early as August 1999,[20] 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'."[21][22] Phil Belanger, a founding member of the Wi-Fi Alliance who presided over the selection of the name "Wi-Fi", has stated that Interbrand invented Wi-Fi as a pun on the word hi-fi (high fidelity), a term for high-quality audio technology.[23]

The name Wi-Fi has no further meaning, and was never officially a shortened form of "Wireless Fidelity".[24] Nevertheless, the Wi-Fi Alliance used the advertising slogan "The Standard for Wireless Fidelity" for a short time after the brand name was created,[21][25][26] and the Wi-Fi Alliance was also called the "Wireless Fidelity Alliance Inc" in some publications.[27]

Interbrand also created the Wi-Fi logo. The yin-yang Wi-Fi logo indicates the certification of a product for interoperability.[25]

Non-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 LTE.

The name is sometimes written as WiFi, Wifi, or wifi, but these are not approved by the Wi-Fi Alliance. IEEE is a separate, but related, organization and their website has stated "WiFi is a short name for Wireless Fidelity".[28][29]

Au wifi
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 signal.[30]

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 controllers is called a station.

A service set is the set of all the devices associated with a particular 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.

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 Keong Toh in his 1996 invention[31] 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)[32] and later published formally in IEEE Transactions on Wireless Communications, 2002[33] and ACM SIGMETRICS Performance Evaluation Review, 2001.[34]

Wi-Fi certification

The IEEE does not test equipment for compliance with their standards. The non-profit 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, the Wi-Fi Alliance consisted of more than 375 companies from around the world.[35][36] The Wi-Fi Alliance 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 Wi-Fi Direct), Personal area network (PAN), local area network (LAN) and even some limited wide area network (WAN) connections. Manufacturers with membership in the Wi-Fi Alliance, whose products pass the certification process, gain the right to mark those products with the Wi-Fi logo.

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 tests of IEEE 802.11 draft standards, interaction with cellular-phone technology in converged devices, and features relating to security set-up, multimedia, and power-saving.[37]

Not every 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.[38] The Wi-Fi Alliance may or may not sanction derivative terms, such as Super Wi-Fi,[39] coined by the US Federal Communications Commission (FCC) to describe proposed networking in the UHF TV band in the US.[40]

Versions

There are many different versions of Wi-Fi: 802.11a, 802.11b, 802.11g, 802.11n (Wi-Fi 4[41]), 802.11h, 802.11i, 802.11-2007, 802.11-2012, 802.11ac (Wi-Fi 5[41]), 802.11ad, 802.11af, 802.11-2016, 802.11ah, 802.11ai, 802.11aj, 802.11aq, 802.11ax (Wi-Fi 6[41]), 802.11ay.

Generation IEEE Standard Maximum Linkrate
Wi‑Fi 6 802.11ax 600–9608 Mbit/s
Wi‑Fi 5 802.11ac 433–6933 Mbit/s
Wi‑Fi 4 802.11n 72–600 Mbit/s

Equipment frequently support multiple versions of Wi-Fi. To communicate, devices must use a common Wi-Fi version. The versions differ between the radio wavebands they operate on, the radio bandwidth they occupy, the maximum data rates they can support and other details. In general, lower frequencies have better range but have less capacity. Some versions permit the use of multiple antennas, which permits greater speeds as well as reduced interference.

Historically, equipment has simply listed the versions of Wi-Fi using the name of the IEEE standard that it supports. The Wi-Fi alliance has standardised generational numbering so that equipment can indicate that it supports Wi-Fi 4 (if the equipment supports 802.11n), Wi-Fi 5 (802.11ac) and Wi-Fi 6 (802.11ax). These generations have a high degree of backward compatibility with previous versions. The alliance have stated that the generational level 4, 5, or 6 can be indicated in the user interface when connected, along with the signal strength.[41]

Uses

Internet access

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 outdoor Wi-Fi technology has been used successfully in wireless mesh networks in London. 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 access.

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 buildings, provide 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 Internet over 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 Internet 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 connection with Wi-Fi technology.[42]

City-wide Wi-Fi

Metro Wireless Node
An outdoor Wi-Fi access point

In the early 2000s, many cities around the world announced plans to construct citywide Wi-Fi networks. There are many successful examples; in 2004, 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.[43]

In 2005, St. Cloud, Florida and Sunnyvale, California, became the first cities in the United States to offer citywide free Wi-Fi (from MetroFi).[44] Minneapolis has generated $1.2 million in profit annually for its provider.[45]

In May 2010, London mayor Boris Johnson pledged to have London-wide Wi-Fi by 2012.[46] Several boroughs including Westminster and Islington[47][48] already had extensive outdoor Wi-Fi coverage at that point.

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 residential areas. 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.[49]

Campus-wide Wi-Fi

Many traditional university campuses in the developed world provide at least partial Wi-Fi coverage. Carnegie Mellon University built the first campus-wide wireless Internet network, called Wireless Andrew, at its Pittsburgh campus in 1993 before Wi-Fi branding originated.[50][51][52] By February 1997, the CMU Wi-Fi zone was fully operational. Many universities collaborate in providing Wi-Fi access to students and staff through the Eduroam international authentication infrastructure.

Wi-Fi ad hoc versus Wi-Fi direct

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".[53]

Similarly, the Wi-Fi Alliance promotes the specification Wi-Fi Direct for file transfers and media sharing through a new discovery- and security-methodology.[54] Wi-Fi Direct launched in October 2010.[55]

Another mode of direct communication over Wi-Fi is Tunneled Direct Link Setup (TDLS), which enables two devices on the same Wi-Fi network to communicate directly, instead of via the access point.[56]

WiFi-detector
A keychain-size Wi-Fi detector

Wi-Fi radio spectrum

The 802.11 standard provides several distinct radio frequencies ranges for use in Wi-FI communications: 900 MHz, 2.4 GHz, 5 GHz, 5.9 GHz, and 60 GHz bands.[57][58][59] Each range is divided into a multitude of channels. Countries apply their own regulations to the allowable channels, allowed users and maximum power levels within these frequency ranges. The ISM band ranges are also often used.[60]

802.11b/g/n can use the 2.4 GHz ISM band, operating in the United States under Part 15 Rules and Regulations. In this frequency band equipment may occasionally suffer interference from microwave ovens, cordless telephones, USB 3.0 hubs, and Bluetooth devices.

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.

A standard speed 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. However, channels that are four apart interfere a negligible amount, much less than reusing channels.[61] In Europe and Japan where channel 13 is available, using Channels 1, 5, 9, and 13 for 802.11g and 802.11n is recommended.

802.11a/h/j/n/ac/ax can use the 5 GHz U-NII band, which, for much of the world, offers at least 23 non-overlapping 20 MHz channels rather than the 2.4 GHz ISM frequency band, where the channels are only 5MHz wide. The 5GHz bands are more strongly absorbed by common building materials, and usually give shorter range.

As the 802.11 specifications evolved to support higher throughput, the bandwidth requirements also increased to support them. 802.11n can use double the radio spectrum/bandwidth (40 MHz- 8 channels) compared to 802.11a or 802.11g (20 MHz). 802.11n can also be set to limit itself to 20 MHz bandwidth to prevent interference in dense communities.[62] In the 5 GHz band, 20, 40, 80 and 160 Mhz bandwidth signals are permitted with some restrictions, giving much faster connections.

Communication stack

Wi-Fi is a technology considered to operate at the physical and data link layers of the OSI model, as part of the IEEE 802 protocol family. The data is organized into 802.11 frames that are very similar to Ethernet frames at the data link layer, but with extra address fields. MAC addresses are used as network addresses.[63]

Wi-Fi's MAC and physical layer (PHY) specifications are defined by IEEE 802.11 for modulating and receiving one or more carrier waves to transmit the data in the infrared, and 2.4, 3.6, 5, or 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 many 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.[64] As a result, in the market place, each revision tends to become its own standard.

In addition to 802.11 the IEEE 802 protocol family has specific provisions for Wi-Fi. These are required because Ethernet's cable-based media are not usually shared, whereas with wireless all transmissions are received by all stations within range that employ that radio channel.[65] While Ethernet has essentially negligible error rates, wireless communication media are subject to significant interference. Therefore accurate transmission is not guaranteed so delivery is therefore a best-effort delivery mechanism. Because of this, for Wi-Fi, the Logical Link Control (LLC) specified by IEEE 802.2 employs Wi-Fi's media access control (MAC) protocols to manage retries without relying on higher levels of the protocol stack.

Performance

Wifi point to point
Parabolic dishes transmit and receive the radio waves only in particular directions and can give much greater range than omnidirection antennas
Yagi-Uda antenna for Wi-Fi on Router
Yagi-Uda antennas, widely used for television reception, are relatively compact at Wi-Fi wavelengths

Wi-Fi operational range depends on factors such as the frequency band, radio power output, receiver sensitivity, antenna gain and antenna type as well as the modulation technique. In addition, propagation characteristics of the signals can have a big impact.

At longer distances, and with greater signal absorption, speed is usually reduced.

Transmitter power

Compared to cell phones and similar technology, Wi-Fi transmitters are low power devices. 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 (EIRP) in the European Union is limited to 20 dBm (100 mW).

To reach requirements for wireless LAN applications, Wi-Fi has higher power consumption compared to some other standards designed to support wireless personal area network (PAN) applications. For example, Bluetooth provides a much shorter propagation range between 1 and 100m[66] 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 Wi-Fi makes battery life in some mobile devices a concern.

Antenna

An access point compliant with either 802.11b or 802.11g, using the stock omnidirectional antenna might have a range of 100 m (0.062 mi). The same radio with an external semi parabolic antenna (15 dB gain) with a similarly equipped receiver at the far end 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 antenna can project a usable signal further in particular directions, as compared to a similar output power on a more isotropic antenna.[67] 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.

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).

MIMO (multiple-input and multiple-output)

Netgear-Nighthawk-AC1900-WiFi-Router
This Netgear Wi-Fi router contains dual bands for transmitting the 802.11 standard across the 2.4 and 5 GHz spectrums and supports MIMO.

Some standards, such as IEEE 802.11n and IEEE 802.11ac for Wi-Fi allow a device to have multiple antennas. Multiple antennas enable the equipment to focus on the far end device, reducing interference in other directions, and giving a stronger useful signal. This greatly increases range and network speed without exceeding the legal power limits.

IEEE 802.11n can more than double the range.[68] 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).

Under optimal conditions, IEEE 802.11ac can achieve communication rates of 1Gbit/s.

Radio propagation

With Wi-Fi signals line-of-sight usually works best, signals can transmit, absorb, reflect, and diffract through and around structures.

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 Wi-Fi signal strength for any given area in relation to a transmitter.[69] This effect does not apply equally to long-range Wi-Fi, since longer links typically operate from towers that transmit above the surrounding foliage.

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 moving vehicles.

Distance records

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.[70][71] The Swedish Space Agency transferred data 420 km (260 mi), using 6 watt amplifiers to reach an overhead stratospheric balloon.[72]

Radio bands

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.[73]

Interference

Wi-Fi connections can be disrupted or the Internet speed lowered by having other devices in the same area. Wi-Fi protocols are designed to share channels reasonably fairly, and will often work with little to no disruption. However, 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, can prevent access and interfere with other devices' use of other access points as well as with decreased signal-to-noise ratio (SNR) between access points. In addition interference can be caused by overlapping channels in the 802.11g/b spectrum. These issues can become a problem in high-density areas, such as large apartment complexes or office buildings with many Wi-Fi access points. Wi-Fi 6 has greatly improved power control, and suffers less from interference in congested areas.

Other devices use the 2.4 GHz band: microwave ovens, ISM band devices, security cameras, ZigBee devices, Bluetooth devices, video senders, cordless phones, baby monitors,[74] and, in some countries, amateur radio, all of which can cause significant additional interference. It is also an issue when municipalities[75] or other large entities (such as universities) seek to provide large area coverage.

To minimise collisions with Wi-Fi and non Wi-Fi devices, Wi-Fi employs Carrier-sense multiple access with collision avoidance (CSMA/CA), where transmitters listen before transmitting, and delay transmission of packets if they detect that other users are active on the channel. Nevertheless Wi-Fi networks are still susceptible to the hidden node and exposed node problem.[76]

These bands are allowed to be used with low power transmitters, without requiring a license and with few restrictions. However, while unintended interference is common, users that have been found to knowingly cause deliberate interference to other users (particularly for attempting to locally monopolise these bands for commercial purposes) have been handed large fines.[77]

Throughput

Throughputenvelope80211g
Graphical representation of Wi-Fi application specific (UDP) performance envelope 2.4 GHz band, with 802.11g
ThroughputEnvelope11n
Graphical representation of Wi-Fi application specific (UDP) performance envelope 2.4 GHz band, with 802.11n with 40 MHz

Various layer 2 variants of IEEE 802.11 has different characteristics. Across all flavours of 802.11, maximum achievable throughputs are either given based on measurements under ideal conditions or in the layer 2 data rates. This, however, does not apply to typical deployments in which data are being transferred between two endpoints of which at least one is typically connected to a wired infrastructure and the other endpoint is connected to an infrastructure via a wireless link.

This means that typically data frames pass an 802.11 (WLAN) medium and are being converted to 802.3 (Ethernet) or vice versa.

Due to the difference in the frame (header) lengths of these two media, the packet size of an application determines the speed of the data transfer. This means that an application which uses small packets (e.g. VoIP) creates a data flow with a high overhead traffic (e.g. a low goodput).

Other factors which contribute to the overall application data rate are the speed with which the application transmits the packets (i.e. the data rate) and the energy with which the wireless signal is received. The latter is determined by distance and by the configured output power of the communicating devices.[78][79]

The same references apply to the attached throughput graphs which show measurements of UDP throughput measurements. Each represents an average throughput of 25 measurements (the error bars are there, but barely visible due to the small variation), is with a specific packet size (small or large), and with a specific data rate (10 kbit/s – 100 Mbit/s). Markers for traffic profiles of common applications are included as well. This text and measurements do not cover packet errors but information about this can be found at the above references. The table below shows the maximum achievable (application specific) UDP throughput in the same scenarios (same references again) with various different WLAN (802.11) flavours. The measurement hosts have been 25 meters apart from each other; loss is again ignored.

Multiple access points

Increasing the number of Wi-Fi access points for a network provides 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 office networks), 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 topologies.

An Extended Service Set may be formed by deploying multiple access points that are configured with the same SSID and security settings. Wi-Fi client devices will typically connect to the access point that can provide the strongest signal within that service set.

Hardware

RouterBoard 112 with U.FL-RSMA pigtail and R52 miniPCI Wi-Fi card
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
3GN
OSBRiDGE 3GN – 802.11n Access Point and UMTS/GSM Gateway in one device

Wi-Fi allows wireless 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 Wi-Fi signals.

Since the early 2000s, 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.[80]

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 Wi-Fi device will work anywhere in the world.

Access point

Apple-Airport-Extreme-80211g-WiFi-Card
An AirPort wireless G Wi-Fi adapter from an Apple MacBook.

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 devices.

Wireless adapter

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, most newer laptop computers come equipped with built in internal adapters.

Router

Wireless routers integrate a Wireless Access Point, Ethernet switch, 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, DSL modem or optical 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.[81]

Bridge

Wireless network bridges can act to connect two networks to form a single network at the data-link layer over Wi-Fi. The main standard is the wireless distribution system (WDS).

Wireless bridging can connect a wired network to a wireless network. A bridge differs from an access point: an access point typically connects wireless devices to one wired network. Two wireless bridge devices 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 Ethernet port.

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, and there may be a reduction in the maximum available data throughput. 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 whereby a single user migrates around a network employing extenders. For this reason, wireless range-extenders work best in networks supporting low traffic throughput requirements, such as for cases whereby a single user with a Wi-Fi equipped tablet migrates around the combined extended and non-extended portions of the total connected network. Also, a wireless device connected to any of the repeaters in the chain will have a data throughput that is limited by the "weakest link" existing in the chain between where the connection originates and where the connection ends. Networks employing wireless extenders are 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.

Embedded systems

Ezurio wism2 small
Embedded serial-to-Wi-Fi module

The security standard, Wi-Fi Protected Setup, allows embedded devices with limited graphical user interface to connect to the Internet with ease. 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.[82]

Increasingly in the last few years (particularly as of 2007), embedded 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.[83] 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.[84]

Wireless network interface controller Gigabyte GC-WB867D-I - front and back - 2018-05-15
Wireless network interface controller Gigabyte GC-WB867D-I.
Antenna of wireless network interface controller Gigabyte GC-WB867D-I - 2018-05-18
Antenna of wireless network interface controller Gigabyte GC-WB867D-I.

These Wi-Fi modules are designed by OEMs so that implementers need only minimal Wi-Fi knowledge to provide Wi-Fi connectivity for their products.

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.

Network security

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.[85][86][87]

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 reply.[88]

Securing methods

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,[89] 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.[90] 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 WPA2 using Advanced Encryption Standard was introduced in 2004 and is supported by most new Wi-Fi devices. WPA2 is fully compatible with WPA.[91] In 2017, a flaw in the WPA2 protocol was discovered, allowing a key replay attack, known as KRACK.[92][93]

A flaw in a feature added to Wi-Fi in 2007, called Wi-Fi Protected 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,[94] which is not always possible.

Virtual Private Networks are often used to secure Wi-Fi.

Data security risks

The older wireless encryption-standard, Wired Equivalent Privacy (WEP), has been shown to be easily breakable even when correctly configured. 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 Wi-Fi networks 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 over Transport Layer Security (HTTPS).

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 security;[95] it rolled out on June 26.[96]

Piggybacking

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 to cultivate wireless community networks,[97] particularly since people on average use only a fraction of their downstream bandwidth at any given time.

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 Internet connection 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.[98]

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.

An unauthorized user can obtain security information (factory preset passphrase and/or 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 pushbutton method) to commit unauthorized and/or unlawful activities.

Health concerns

The 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.[99] Although the WHO's International Agency for Research on Cancer (IARC) later classified radio-frequency electromagnetic fields (EMFs) as "possibly carcinogenic to humans (Group 2B)"[100] (a category used when "a causal association is considered credible, but when chance, bias or confounding cannot be ruled out with reasonable confidence"),[101] this classification was based on risks associated with wireless phone use rather than Wi-Fi networks.

The United Kingdom's Health Protection Agency reported in 2007 that exposure to Wi-Fi for a year results in the "same amount of radiation from a 20-minute mobile phone call".[102]

A review of studies involving 725 people who claimed electromagnetic hypersensitivity, "...suggests that 'electromagnetic hypersensitivity' is unrelated to the presence of an EMF, although more research into this phenomenon is required."[103]

Alternatives

A number of other "wireless" technologies provide alternatives to Wi-Fi in some cases:

  • Bluetooth, short distance network
  • Bluetooth Low Energy, a low-power variant
  • Zigbee, low-power, low data rate, and close proximity
  • Cellular networks, as used by smartphones
  • WiMax, provide wireless internet connection from outside individual homes

Some alternatives are "no new wires", re-using existing cable:

There are also several wired technologies for computer networking which in some cases will be viable alternatives, in particular:

See also

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Further reading

  • The WNDW Authors (1 March 2013). Butler, Jane (ed.). Wireless Networking in the Developing World (Third Edition). ISBN 978-1-4840-3935-9.
AirDrop

AirDrop is an ad-hoc service in Apple Inc.'s macOS and iOS operating systems, introduced in Mac OS X Lion (Mac OS X 10.7) and iOS 7, which enables the transfer of files among supported Macintosh computers and iOS devices over Wi-Fi and Bluetooth, without using mail or a mass storage device.Prior to OS X Yosemite (OS X 10.10), and under OS X Lion, Mountain Lion, and Mavericks (OS X 10.7–10.9, respectively) the AirDrop protocol in macOS was different from the AirDrop protocol of iOS, and the two were therefore not interoperable with each other. OS X Yosemite and later support the iOS AirDrop protocol, which is used for transfers between a Mac and an iOS device as well as between two 2012 or later Mac computers, and which uses both Wi-Fi and Bluetooth. Legacy mode for the old AirDrop protocol (which only uses Wi-Fi) between two 2012 or older Mac computers is also available.There is no restriction on the size of the file which AirDrop will accommodate.

Amazon Kindle

The Amazon Kindle is a series of e-readers designed and marketed by Amazon. Amazon Kindle devices enable users to browse, buy, download, and read e-books, newspapers, magazines and other digital media via wireless networking to the Kindle Store. The hardware platform, developed by Amazon subsidiary Lab126, began as a single device in 2007 and now comprises a range of devices, including e-readers with E Ink electronic paper displays and Kindle applications on all major computing platforms. All Kindle devices integrate with Kindle Store content, and as of March 2018, the store has over six million e-books available in the United States.

Electromagnetic hypersensitivity

Electromagnetic hypersensitivity (EHS) is a claimed sensitivity to electromagnetic fields, to which negative symptoms are attributed. EHS has no scientific basis and is not a recognised medical diagnosis. Claims are characterized by a "variety of non-specific symptoms, which afflicted individuals attribute to exposure to electromagnetic fields".Those who are self-described with EHS report adverse reactions to electromagnetic fields at intensities well below the maximum levels permitted by international radiation safety standards. The majority of provocation trials to date have found that such claimants are unable to distinguish between exposure and non-exposure to electromagnetic fields. A systematic review of medical research in 2011 found no convincing scientific evidence for symptoms being caused by electromagnetic fields. Since then, several double-blind experiments have shown that people who report electromagnetic hypersensitivity are unable to detect the presence of electromagnetic fields and are as likely to report ill health following a sham exposure as they are following exposure to genuine electromagnetic fields, suggesting the cause in these cases to be the nocebo effect.As of 2005 the WHO recommended that people presenting with claims of EHS be evaluated to determine if they have a medical condition that may be causing the symptoms the person is attributing to EHS, that they have a psychological evaluation, and that the person's environment be evaluated for issues like air or noise pollution that may be causing problems. Cognitive behavioral therapy may be helpful in managing the condition.Some people who feel they are sensitive to electromagnetic fields may seek to reduce their exposure or use alternative medicine. Government agencies have enforced false advertising claims against companies selling devices to shield against EM radiation.

Hotspot (Wi-Fi)

A hotspot is a physical location where people may obtain Internet access, typically using Wi-Fi technology, via a wireless local area network (WLAN) using a router connected to an internet service provider.

Public hotspots may be created by a business for use by customers, such as coffee shops or hotels. Public hotspots are typically created from wireless access points configured to provide Internet access, controlled to some degree by the venue. In its simplest form, venues that have broadband Internet access can create public wireless access by configuring an access point (AP), in conjunction with a router and connecting the AP to the Internet connection. A single wireless router combining these functions may suffice.Private hotspots may be configured on a smartphone or tablet with a mobile network data plan to allow Internet access to other devices via Bluetooth pairing or if both the hotspot device and the device/s accessing it are connected to the same Wi-Fi network.

IEEE 802.11

IEEE 802.11 is part of the IEEE 802 set of LAN protocols, and specifies the set of media access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) Wi-Fi computer communication in various frequencies, including but not limited to 2.4, 5, and 60 GHz frequency bands.

They are the world's most widely used wireless computer networking standards, used in most home and office networks to allow laptops, printers, and smartphones to talk to each other and access the Internet without connecting wires. They are created and maintained by the Institute of Electrical and Electronics Engineers (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 marketplace, each revision tends to become its own standard.

The protocols are typically used in conjunction with IEEE 802.2, and are designed to interwork seamlessly with Ethernet, and are very often used to carry Internet Protocol traffic.

Although IEEE 802.11 specifications list channels that might be used, the radio frequency spectrum availability allowed varies significantly by regulatory domain.

IEEE 802.11ac

IEEE 802.11ac is a wireless networking standard in the 802.11 set of protocols (which is part of the Wi-Fi networking family), providing high-throughput wireless local area networks (WLANs) on the 5 GHz band. The standard was developed in the IEEE Standards Association from 2008 (PAR approved 2008-09-26) through 2013 and published in December 2013 (ANSI approved 2013-12-11). The standard has been retroactively labelled as Wi-Fi 5 by Wi-Fi Alliance.The specification has multi-station throughput of at least 1 gigabit per second and single-link throughput of at least 500 megabits per second (500 Mbit/s). This is accomplished by extending the air-interface concepts embraced by 802.11n: wider RF bandwidth (up to 160 MHz), more MIMO spatial streams (up to eight), downlink multi-user MIMO (up to four clients), and high-density modulation (up to 256-QAM).Wi-Fi Alliance separated the introduction of ac wireless products into two phases ("wave"), named "Wave 1" and "Wave 2". From mid-2013, the alliance started certifying Wave 1 802.11 ac products ships by manufacturers, based on the IEEE 802.11ac Draft 3.0 (the IEEE standard was not finalized until later that year). Subsequently in year 2016, Wi-Fi Alliance introduced the Wave 2 certification, which include additional features like MU-MIMO, 160MHz channel width support, support for more 5GHz channels, and four spatial streams (with four antennas; compares to three in Wave 1 and 802.11n, and eight in IEEE's 802.11ac specification). It means Wave 2 products would have higher bandwidth and capacity than Wave 1 products.

IEEE 802.11ax

IEEE 802.11ax, marketed as Wi-Fi 6 by Wi-Fi Alliance, is one of the two Wi-Fi specifications standards, of IEEE 802.11, both expecting full deployment late 2019; the other is ay. They can be thought of as High Efficiency Wireless.

802.11ax is designed to operate in all band spectrums between 1 and 7 GHz when they become available in addition to the 2.4 and 5 GHz already existing. Devices presented at CES 2018 showed a top speed of 11 Gbit/s. For dense deployments, throughput speeds are 4× higher than IEEE 802.11ac, even though the nominal data rate is just 37% faster at most. Latency is also down 75%.To improve spectrum efficient utilization, the new version introduces better power control methods to avoid interference with neighbouring networks, OFDMA modulation, higher order 1024-QAM modulation, and uplink direction added with the downlink of MIMO and MU-MIMO to further increase throughput, as well as dependability improvements of power consumption and security protocols such as Target Wake Time and WPA3.

IPad

iPad ( EYE-pad) is a line of tablet computers designed, developed and marketed by Apple Inc., which run the iOS mobile operating system. The first iPad was released on April 3, 2010; the most recent iPad models are the iPad (2018), released on March 27, 2018; the fifth-generation iPad mini, released on March 18, 2019; the third-generation iPad Air, released on March 18, 2019; and the 11-inch (280 mm) and third-generation 12.9-inch (330 mm) iPad Pro, released on November 7, 2018.

As of May 2017, Apple has sold more than 360 million iPads, though sales peaked in 2013. It is the most popular tablet computer by sales as of the second quarter of 2018.The user interface is built around the device's multi-touch screen, including a virtual keyboard. All iPads can connect via Wi-Fi; some models also have cellular connectivity. iPads can shoot video, take photos, play music, and perform Internet functions such as web-browsing and emailing. Other functions – games, reference, GPS navigation, social networking, etc. – can be enabled by downloading and installing apps. As of March 2016, the App Store has more than million apps for the iPad by Apple and third parties.

There have been eight versions of the iPad. The first generation established design precedents, some of which have persisted through all models. The 2nd-generation iPad (iPad 2) introduced a new thinner design, a dual-core Apple A5 processor, and VGA front-facing and 720p rear-facing cameras designed for FaceTime video calling. The third generation added a Retina Display, the new Apple A5X processor with a quad-core graphics processor, a 5-megapixel camera, HD 1080p video recording, voice dictation, and 4G (LTE). The fourth generation added the Apple A6X processor and replaced the 30-pin connector with an all-digital Lightning connector. The iPad Air added the Apple A7 processor and the Apple M7 motion coprocessor, and reduced the thickness for the first time since the iPad 2. The iPad Air 2 added the Apple A8X processor, the Apple M8 motion coprocessor, an 8-megapixel camera, and the Touch ID fingerprint sensor; and further reduced the thickness. The iPad introduced in 2017 added the Apple A9 processor, while sacrificing some of the improvements the iPad Air 2 introduced in exchange for a lower launch price.

There have been five versions of the iPad Mini, all of which have a screen size of 7.9 inches (20 cm). The first generation has similar internal specifications to the iPad 2 but uses the Lightning connector instead. The iPad Mini 2 added the Retina Display, the Apple A7 processor, and the Apple M7 motion coprocessor, closely matching the internal specifications of the iPad Air. The iPad Mini 3 added the Touch ID fingerprint sensor. The iPad Mini 4 features the Apple A8 and the Apple M8 motion coprocessor. The 5th generation features the Apple A12 SoC.

There have been three generations of the iPad Pro. The first generation came with 9.7" and 12.9" screen sizes, while the second came with 10.5" and 12.9" sizes, and the third with 11" and 12.9" sizes. The iPad Pros have unique features such as the Smart Connector, which are exclusive to this series of iPads.

IPad (3rd generation)

The third-generation iPad (marketed as The new iPad, colloquially referred to as the iPad 3) is a tablet computer, developed and marketed by Apple Inc. The third device in the iPad line of tablets, it added a Retina Display, the new Apple A5X chip with a quad-core graphics processor, a 5-megapixel camera, HD 1080p video recording, voice dictation, and support for LTE networks in North America. It shipped with iOS 5, which also provides a platform for audio-visual media, including electronic books, periodicals, films, music, computer games, presentations and web content.In the United States and Canada, nine variations of the third-generation iPad were offered, compared to six in the rest of the world, although some countries had only the Wi-Fi only model. Each variation was available with black or white front glass panels, with options for 16, 32, or 64 GB of storage. In North America, connectivity options were Wi-Fi only, Wi-Fi + 4G (LTE) on Verizon, AT&T, Telus, Rogers, or Bell. For the rest of the world outside North America, connectivity options are Wi-Fi only (on the Wi-Fi model) or Wi-Fi + 3G (on the Wi-Fi + Cellular model), with the latter unavailable in some countries, as 4G (LTE) connectivity for the device is not available outside North America. The Wi-Fi + Cellular model includes GPS capability.

Initially, the cellular version was titled and marketed worldwide as the "Wi-Fi + 4G" model, but due to regional differences in classification of 4G (LTE) connectivity outside of North America, Apple later rebranded and altered their marketing to call this the "Wi-Fi + Cellular" model.The tablet was released in ten countries on March 16, 2012. It gained mostly positive reviews, earning praise for its Retina display, processor and 4G (LTE) capabilities. However, controversy arose when the LTE incompatibilities became known. Three million units were sold in the first three days.After only seven months (221 days) of official availability, the third-generation iPad was discontinued on October 23, 2012, following the announcement of the fourth-generation iPad. The third-generation iPad had the shortest lifespan of any iOS product. It is also the last iPad to support the 30-pin dock connector, as the fourth-generation iPad and later use the Lightning connector.

IPad Mini

The iPad Mini family (branded and marketed as iPad mini) is a line of mini tablet computers designed, developed, and marketed by Apple Inc. It is a sub-series of the iPad line of tablets, with a reduced screen size of 7.9 inches, in contrast to the standard 9.7 inches. The first generation iPad Mini was announced on October 23, 2012, and was released on November 2, 2012, in nearly all of Apple's markets. It features similar internal specifications to the iPad 2, including its display resolution.

The second generation iPad Mini, with a faster processor and a Retina Display, was announced on October 22, 2013 and released on November 12, 2013. The third generation iPad Mini was announced on October 16, 2014 and was released on October 22, 2014; it features the same external hardware as the Mini 2 and the addition of a Touch ID fingerprint sensor compatible with Apple Pay. On September 9, 2015, Apple released the iPad Mini 4. On March 18, 2019, Apple released the 5th generation iPad Mini.

IPad Pro

The iPad Pro family is a line of iPad tablet computers designed, developed, and marketed by Apple Inc., that runs the iOS mobile operating system. Its current generation is available in two screen sizes, 11-inch (28 cm) and 12.9-inch (33 cm), each with four options for internal storage capacities: 64, 256, 512 GB, or 1 TB.

The first iPad Pro, the 12.9-inch version, was announced on September 9, 2015 and released on November 11, 2015. It is larger than all previous iPad models and the first iPad tablet to feature LPDDR4 RAM. The 12.9-inch tablet was later followed by the smaller 9.7-inch version, which was announced on March 21, 2016, and released on March 31 that same year.On June 5, 2017, the second generation iPad Pro was announced, which features A10X Fusion processors, with basic storage of 64 GB, and optional 512 GB. Upgraded displays include a new 10.5-inch version to replace the 9.7-inch model, while the 12.9-inch version was refreshed. Following this announcement, both models of the first generation iPad Pro were discontinued.

The third generation of iPad Pro was announced on October 30, 2018. It is available in two screen sizes: 11-inch (28 cm) and 12.9-inch (33 cm). They feature full screen displays, with the 11-inch model replacing the 10.5-inch model of the previous generation. They also feature up to 1 TB of storage and Face ID which works in both vertical and horizontal orientations, a feature that does not apply to iPhones with Face ID. The third generation does not feature a home button.

IPod Touch

The iPod Touch (stylized and marketed as iPod touch) is a brand of iOS-based all-purpose mobile devices designed and marketed by Apple Inc. with a touchscreen-controlled user interface. It connects to the Internet only through Wi-Fi base stations, does not use cellular network data, and is therefore not a smartphone. Similarly to an iPhone, it can be used as a music player, digital camera, web browser, note-logger, and handheld gaming device. As of May 2013, 100 million iPod Touch units had been sold since 2007.iPod Touch models are sold by storage space and color, with all models of the same generation typically offering otherwise identical features, processors, and performance, in addition to available operating system upgrades; an exception was the fifth generation, as the low-end (16 GB) model was initially sold without a rear-facing camera. The current iPod touch is the sixth-generation model, released on July 15, 2015.

The iPod Touch is currently the only product in Apple's iPod product line, following the discontinuation of the iPod Nano and iPod Shuffle on July 27, 2017. Following the discontinuation, Apple revised the storage and pricing for the iPod Touch with 32 and 128 GB of storage.

Nintendo Wi-Fi Connection

Nintendo Wi-Fi Connection (Japanese: ニンテンドーWi-Fiコネクション, Hepburn: Nintendō Wi-Fi Konekushon) (commonly abbreviated WFC) was an online multiplayer gaming service run by Nintendo to provide free online play in compatible Nintendo DS and Wii games. The service included the company's Wii Shop Channel and DSi Shop game download services. It also ran features for the Wii and Nintendo DS systems.

Games designed to take advantage of Nintendo Wi-Fi Connection offered Internet play integrated into the game. When promoting this service, Nintendo emphasized the simplicity and speed of starting an online game. For example, in Mario Kart DS, an online game was initiated by selecting the online multiplayer option from the main menu, then choosing whether to play with friends, or to play with other gamers (either in the local region or worldwide) at about the same skill level. After a selection was made, the game started searching for an available player.

On January 26, 2012, it was announced by Nintendo during an investors' meeting that the Nintendo Wi-Fi Connection service will be succeeded by and absorbed into Nintendo Network. This new online system will eventually unify the 3DS and Wii U platforms and replace Friend Codes, while providing paid downloadable content, an online community style multiplayer system, and personal accounts. Nintendo Network is fully supported on the Nintendo 3DS and on the Wii U, whilst still continuing providing partial legacy support for both Wii and Nintendo DS under the Nintendo Wi-Fi Connection brand. Specifically, the Wii U can boot to Wii mode and then access the Wii Message Board messages which have been recorded by the gameplay progress of compatible local games, but it cannot send Wii Message Board messages remotely between different machines.

The Nintendo Wi-Fi Connection service was terminated on May 20, 2014 at 10.30 PM (EST) for all Wii and DS games; online play features incorporated into these games are no longer available without homebrew. The shutdown is connected to the shutdown of multiplayer services by GameSpy, who was acquired by Glu Mobile in 2012. 3DS and Wii U games are not affected by the shutdown because their multiplayer platform uses Nintendo's own infrastructure instead of a third-party service. The Wii Shop Channel, third-party video services, and the Pay & Play variants will remain active for the moment.The shutdown had an immediate effect on all Nintendo-published Wii and Nintendo DS titles, however it may not necessarily apply to certain third-party titles, which could have separate servers running their own games' online functions. For example, Electronic Arts revealed that some of the games they published on the Wii and Nintendo DS had their online support terminated on June 30, 2014.A small selection of online-enabled Wii games, such as newer FIFA games as well as Call of Duty games (except World at War) and Dragon Quest X, which by happenstance are not branded under the Nintendo Wi-Fi Connection, may continue using their online functions normally. Starting in 2015, various Wii and Nintendo DS titles were digitally re-released, including titles which formerly supported Nintendo Wi-Fi Connection. However, like their physical counterparts post-shutdown date, the digital versions are only playable offline, despite faithfully retaining online features.

Nintendo Wi-Fi USB Connector

The Nintendo Wi-Fi USB Connector is a wireless game adapter, developed jointly by Nintendo and Buffalo Technology, which allows Nintendo DSi and Wii users without a Wi-Fi connection or compatible Wi-Fi network to establish one via a broadband-connected PC. Inserted into the host PC's USB port, the connector functions with the Nintendo DS, Wii, and DSi, permitting the user to connect to the Internet to play Nintendo Wi-Fi Connection games and access various other online functionality. The product was the best selling Nintendo accessory to date, according to the official Nintendo site on 15 November 2007, but was discontinued in the same month until further notice. On September 8, 2008, Nintendo announced the Nintendo Wi-Fi Network Adapter, an 802.11g wireless router/bridge which serves a similar purpose.

Wi-Fi Alliance

Wi-Fi Alliance is a non-profit organization that promotes Wi-Fi technology and certifies Wi-Fi products for conformity to certain standards of interoperability. Not every IEEE 802.11-compliant device is submitted for certification to the Wi-Fi Alliance, sometimes because of costs associated with the certification process. The lack of the Wi-Fi logo does not necessarily imply a device is incompatible with Wi-Fi devices.

The Wi-Fi Alliance owns the Wi-Fi trademark. Manufacturers may use the trademark to brand certified products that have been tested for interoperability.

Wi-Fi Direct

Wi-Fi Direct, initially called Wi-Fi P2P, is a Wi-Fi standard enabling devices to easily connect with each other without requiring a wireless access point. Wi-Fi Direct allows two devices to establish a direct Wi-Fi connection without requiring a wireless router. Hence, Wi-Fi Direct is single radio hop communication, not multihop wireless communication, unlike wireless ad hoc networks and mobile ad hoc networks. Wi-Fi ad hoc mode, however, supports multi-hop radio communications, with intermediate Wi-Fi nodes as packet relays.

Wi-Fi becomes a way of communicating wirelessly, much like Bluetooth. It is useful for everything from internet browsing to file transfer, and to communicate with one or more devices simultaneously at typical Wi-Fi speeds. One advantage of Wi-Fi Direct is the ability to connect devices even if they are from different manufacturers. Only one of the Wi-Fi devices needs to be compliant with Wi-Fi Direct to establish a peer-to-peer connection that transfers data directly between them with greatly reduced setup.

Wi-Fi Direct negotiates the link with a Wi-Fi Protected Setup system that assigns each device a limited wireless access point. The "pairing" of Wi-Fi Direct devices can be set up to require the proximity of a near field communication, a Bluetooth signal, or a button press on one or all the devices.

Wi-Fi Protected Access

Wi-Fi Protected Access (WPA), Wi-Fi Protected Access II (WPA2), and Wi-Fi Protected Access 3 (WPA3) are three security protocols and security certification programs developed by the Wi-Fi Alliance to secure wireless computer networks. The Alliance defined these in response to serious weaknesses researchers had found in the previous system, Wired Equivalent Privacy (WEP).WPA (sometimes referred to as the draft IEEE 802.11i standard) became available in 2003. The Wi-Fi Alliance intended it as an intermediate measure in anticipation of the availability of the more secure and complex WPA2, which became available in 2004 and is a common shorthand for the full IEEE 802.11i (or IEEE 802.11i-2004) standard.

In January 2018, Wi-Fi Alliance announced the release of WPA3 with several security improvements over WPA2.

Wireless access point

In computer networking, a wireless access point (WAP), or more generally just access point (AP), is a networking hardware device that allows other Wi-Fi devices to connect to a wired network. The AP usually connects to a router (via a wired network) as a standalone device, but it can also be an integral component of the router itself. An AP is differentiated from a hotspot, which is the physical location where Wi-Fi access to a WLAN is available.

Wireless router

A wireless router is a device that performs the functions of a router and also includes the functions of a wireless access point. It is used to provide access to the Internet or a private computer network. Depending on the manufacturer and model, it can function in a wired local area network, in a wireless-only LAN, or in a mixed wired and wireless network.

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