Wireless

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A handheld on-board communication station of the maritime mobile service Handheld Maritime VHF.jpg
A handheld on-board communication station of the maritime mobile service

Wireless communication (or just wireless, when the context allows) is the transfer of information ( telecommunication ) between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most common wireless technologies use radio waves. With radio waves, intended distances can be short, such as a few meters for Bluetooth or as far as millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mouse, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones. Somewhat less common methods of achieving wireless communications involve other electromagnetic phenomena, such as light and magnetic or electric fields, or the use of sound.

Contents

The term wireless has been used twice in communications history, with slightly different meanings. It was initially used from about 1890 for the first radio transmitting and receiving technology, as in wireless telegraphy , until the new word radio replaced it around 1920. Radio sets in the UK and the English-speaking world that were not portable continued to be referred to as wireless sets into the 1960s. [1] [2] The term wireless was revived in the 1980s and 1990s mainly to distinguish digital devices that communicate without wires, such as the examples listed in the previous paragraph, from those that require wires or cables. This became its primary usage in the 2000s, due to the advent of technologies such as mobile broadband, Wi-Fi, and Bluetooth.

Wireless operations permit services, such as mobile and interplanetary communications, that are impossible or impractical to implement with the use of wires. The term is commonly used in the telecommunications industry to refer to telecommunications systems (e.g. radio transmitters and receivers, remote controls, etc.) that use some form of energy (e.g. radio waves and acoustic energy) to transfer information without the use of wires. [3] [4] [5] Information is transferred in this manner over both short and long distances.

History

Photophone

Bell and Tainter's photophone, of 1880. Photophony1.jpg
Bell and Tainter's photophone, of 1880.

The first wireless telephone conversation occurred in 1880 when Alexander Graham Bell and Charles Sumner Tainter invented the photophone, the telephone that sent audio over a beam of light. The photophone required sunlight to operate, and a clear line of sight between the transmitter and receiver, which greatly decreased the viability of the photophone in any practical use. [6] It would be several decades before the photophone's principles found their first practical applications in military communications and later in fiber-optic communications.

Electric wireless technology

Early wireless

A number of wireless electrical signaling schemes including sending electric currents through water and the ground using electrostatic and electromagnetic induction were investigated for telegraphy in the late 19th century before practical radio systems became available. These included a patented induction system by Thomas Edison allowing a telegraph on a running train to connect with telegraph wires running parallel to the tracks, a William Preece induction telegraph system for sending messages across bodies of water, and several operational and proposed telegraphy and voice earth conduction systems.

The Edison system was used by stranded trains during the Great Blizzard of 1888 and earth conductive systems found limited use between trenches during World War I but these systems were never successful economically.

Radio waves

Marconi transmitting the first radio signal across the Atlantic. Guglielmo Marconi 1901 wireless signal.jpg
Marconi transmitting the first radio signal across the Atlantic.

In 1894, Guglielmo Marconi began developing a wireless telegraph system using radio waves, which had been known about since proof of their existence in 1888 by Heinrich Hertz, but discounted as a communication format since they seemed, at the time, to be a short-range phenomenon. [7] Marconi soon developed a system that was transmitting signals way beyond distances anyone could have predicted (due in part to the signals bouncing off the then unknown ionosphere). Marconi and Karl Ferdinand Braun were awarded the 1909 Nobel Prize for Physics for their contribution to this form of wireless telegraphy.

Millimetre wave communication was first investigated by Jagadish Chandra Bose during 1894–1896, when he reached an extremely high frequency of up to 60  GHz in his experiments. [8] He also introduced the use of semiconductor junctions to detect radio waves, [9] when he patented the radio crystal detector in 1901. [10] [11]

Wireless revolution

Power MOSFETs, which are used in RF power amplifiers to boost radio frequency (RF) signals in long-distance wireless networks. D2PAK.JPG
Power MOSFETs, which are used in RF power amplifiers to boost radio frequency (RF) signals in long-distance wireless networks.

The wireless revolution began in the 1990s, [12] [13] [14] with the advent of digital wireless networks leading to a social revolution, and a paradigm shift from wired to wireless technology, [15] including the proliferation of commercial wireless technologies such as cell phones, mobile telephony, pagers, wireless computer networks, [12] cellular networks, the wireless Internet, and laptop and handheld computers with wireless connections. [16] The wireless revolution has been driven by advances in radio frequency (RF), microelectronics, and microwave engineering, [12] and the transition from analog to digital RF technology, [15] [16] which enabled a substantial increase in voice traffic along with the delivery of digital data such as text messaging, images and streaming media. [15]

Modes

Wireless communications can be via:

Radio

Radio and microwave communication carry information by modulating properties of electromagnetic waves transmitted through space. Specifically, the transmitter generates artificial electromagnetic waves by applying time-varying electric currents to its antenna. The waves travel away from the antenna until they eventually reach the antenna of a receiver, which induces an electric current in the receiving antenna. This current can be detected and demodulated to recreate the information sent by the transmitter.

Free-space optical

An 8-beam free space optics laser link, rated for 1 Gbit/s at a distance of approximately 2 km. The receptor is the large disc in the middle, and the transmitters are the smaller ones. To the top and right corner is a monocular for assisting the alignment of the two heads. FSO-gigabit-laser-link-0a.jpg
An 8-beam free space optics laser link, rated for 1 Gbit/s at a distance of approximately 2 km. The receptor is the large disc in the middle, and the transmitters are the smaller ones. To the top and right corner is a monocular for assisting the alignment of the two heads.

Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to transmit wireless data for telecommunications or computer networking. "Free space" means the light beams travel through the open air or outer space. This contrasts with other communication technologies that use light beams traveling through transmission lines such as optical fiber or dielectric "light pipes".

The technology is useful where physical connections are impractical due to high costs or other considerations. For example, free space optical links are used in cities between office buildings that are not wired for networking, where the cost of running cable through the building and under the street would be prohibitive. Another widely used example is consumer IR devices such as remote controls and IrDA (Infrared Data Association) networking, which is used as an alternative to WiFi networking to allow laptops, PDAs, printers, and digital cameras to exchange data.

Sonic

Sonic, especially ultrasonic short-range communication involves the transmission and reception of sound.

Electromagnetic induction

Electromagnetic induction only allows short-range communication and power transmission. It has been used in biomedical situations such as pacemakers, as well as for short-range RFID tags.

Services

Common examples of wireless equipment include: [17]

Electromagnetic spectrum

AM and FM radios and other electronic devices make use of the electromagnetic spectrum. The frequencies of the radio spectrum that are available for use for communication are treated as a public resource and are regulated by organizations such as the American Federal Communications Commission, Ofcom in the United Kingdom, the international ITU-R or the European ETSI. Their regulations determine which frequency ranges can be used for what purpose and by whom. In the absence of such control or alternative arrangements such as a privatized electromagnetic spectrum, chaos might result if, for example, airlines did not have specific frequencies to work under and an amateur radio operator was interfering with a pilot's ability to land an aircraft. Wireless communication spans the spectrum from 9 kHz to 300 GHz.[ citation needed ]

Applications

Mobile telephones

One of the best-known examples of wireless technology is the mobile phone, also known as a cellular phone, with more than 6.6 billion mobile cellular subscriptions worldwide as of the end of 2010. [19] These wireless phones use radio waves from signal-transmission towers to enable their users to make phone calls from many locations worldwide. They can be used within the range of the mobile telephone site used to house the equipment required to transmit and receive the radio signals from these instruments. [20]

Data communications

Wireless data communications allow wireless networking between desktop computers, laptops, tablet computers, cell phones, and other related devices. The various available technologies differ in local availability, coverage range, and performance, [21] and in some circumstances, users employ multiple connection types and switch between them using connection manager software [22] [23] or a mobile VPN to handle the multiple connections as a secure, single virtual network. [24] Supporting technologies include:

Wi-Fi is a wireless local area network that enables portable computing devices to connect easily with other devices, peripherals, and the Internet.[ citation needed ] Standardized as IEEE 802.11 a, b, g, n, ac, ax, Wi-Fi has link speeds similar to older standards of wired Ethernet. Wi-Fi has become the de facto standard for access in private homes, within offices, and at public hotspots. [25] Some businesses charge customers a monthly fee for service, while others have begun offering it free in an effort to increase the sales of their goods. [26]
Cellular data service offers coverage within a range of 10-15 miles from the nearest cell site. [21] Speeds have increased as technologies have evolved, from earlier technologies such as GSM, CDMA and GPRS, through 3G, to 4G networks such as W-CDMA, EDGE or CDMA2000. [27] [28] As of 2018, the proposed next generation is 5G.
Low-power wide-area networks (LPWAN) bridge the gap between Wi-Fi and Cellular for low-bitrate Internet of things (IoT) applications.
Mobile-satellite communications may be used where other wireless connections are unavailable, such as in largely rural areas [29] or remote locations. [21] Satellite communications are especially important for transportation, aviation, maritime and military use. [30]
Wireless sensor networks are responsible for sensing noise, interference, and activity in data collection networks. This allows us to detect relevant quantities, monitor and collect data, formulate clear user displays, and to perform decision-making functions [31]

Wireless data communications are used to span a distance beyond the capabilities of typical cabling in point-to-point communication and point-to-multipoint communication, to provide a backup communications link in case of normal network failure, to link portable or temporary workstations, to overcome situations where normal cabling is difficult or financially impractical, or to remotely connect mobile users or networks.

Peripherals

Peripheral devices in computing can also be connected wirelessly, as part of a Wi-Fi network or directly via an optical or radio-frequency (RF) peripheral interface. Originally these units used bulky, highly local transceivers to mediate between a computer and a keyboard and mouse; however, more recent generations have used smaller, higher-performance devices. Radio-frequency interfaces, such as Bluetooth or Wireless USB, provide greater ranges of efficient use, usually up to 10 feet, but distance, physical obstacles, competing signals, and even human bodies can all degrade the signal quality. [32] Concerns about the security of wireless keyboards arose at the end of 2007 when it was revealed that Microsoft's implementation of encryption in some of its 27 MHz models were highly insecure. [33]

Energy transfer

Wireless energy transfer is a process whereby electrical energy is transmitted from a power source to an electrical load that does not have a built-in power source, without the use of interconnecting wires. There are two different fundamental methods for wireless energy transfer. Energy can be transferred using either far-field methods that involve beaming power/lasers, radio or microwave transmissions, or near-field using electromagnetic induction. [34] Wireless energy transfer may be combined with wireless information transmission in what is known as Wireless Powered Communication. [35] In 2015, researchers at the University of Washington demonstrated far-field energy transfer using Wi-Fi signals to power cameras. [36]

Medical technologies

New wireless technologies, such as mobile body area networks (MBAN), have the capability to monitor blood pressure, heart rate, oxygen level, and body temperature. The MBAN works by sending low-powered wireless signals to receivers that feed into nursing stations or monitoring sites. This technology helps with the intentional and unintentional risk of infection or disconnection that arise from wired connections. [37]

Categories of implementations, devices, and standards

See also

Related Research Articles

The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific, and medical (ISM) purposes, excluding applications in telecommunications. Examples of applications for the use of radio frequency (RF) energy in these bands include RF heating, microwave ovens, and medical diathermy machines. The powerful emissions of these devices can create electromagnetic interference and disrupt radio communication using the same frequency, so these devices are limited to certain bands of frequencies. In general, communications equipment operating in ISM bands must tolerate any interference generated by ISM applications, and users have no regulatory protection from ISM device operation in these bands.

<span class="mw-page-title-main">Microwave</span> Electromagnetic radiation with wavelengths from 1 m to 1 mm

Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequencies between 300 MHz and 300 GHz, broadly construed. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz, or between 1 and 3000 GHz . The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range; rather, it indicates that microwaves are small, compared to the radio waves used in prior radio technology.

<span class="mw-page-title-main">Wireless LAN</span> Computer network that links devices using wireless communication within a limited area

A wireless LAN (WLAN) is a wireless computer network that links two or more devices using wireless communication to form a local area network (LAN) within a limited area such as a home, school, computer laboratory, campus, or office building. This gives users the ability to move around within the area and remain connected to the network. Through a gateway, a WLAN can also provide a connection to the wider Internet.

<span class="mw-page-title-main">Wireless network</span> Computer network not fully connected by cables

A wireless network is a computer network that uses wireless data connections between network nodes. Wireless networking allows homes, telecommunications networks and business installations to avoid the costly process of introducing cables into a building, or as a connection between various equipment locations. Admin telecommunications networks are generally implemented and administered using radio communication. This implementation takes place at the physical level (layer) of the OSI model network structure.

In radio communication, a transceiver is an electronic device which is a combination of a radio transmitter and a receiver, hence the name. It can both transmit and receive radio waves using an antenna, for communication purposes. These two related functions are often combined in a single device to reduce manufacturing costs. The term is also used for other devices which can both transmit and receive through a communications channel, such as optical transceivers which transmit and receive light in optical fiber systems, and bus transceivers which transmit and receive digital data in computer data buses.

Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around 20 kHz to around 300 GHz. This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies, and also encompasses the microwave range, though other definitions treat microwaves as a separate band from RF. These are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves, so they are used in radio technology, among other uses. Different sources specify different upper and lower bounds for the frequency range.

<span class="mw-page-title-main">Transmitter</span> Electronic device that emits radio waves

In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna with the purpose of signal transmission up to a radio receiver. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves.

<span class="mw-page-title-main">Wi-Fi</span> Wireless local area network

Wi-Fi is a family of wireless network protocols based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio waves. These are the most widely used computer networks, used globally in home and small office networks to link devices and to provide Internet access with wireless routers and wireless access points in public places such as coffee shops, hotels, libraries, and airports to provide visitors.

<span class="mw-page-title-main">Ultra high frequency</span> Electromagnetic spectrum 300–3000 MHz

Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter. Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, satellite phones, and numerous other applications.

Wireless local loop (WLL) is the use of a wireless communications link as the "last mile / first mile" connection for delivering plain old telephone service (POTS) or Internet access to telecommunications customers. Various types of WLL systems and technologies exist.

<span class="mw-page-title-main">WiMAX</span> Wireless broadband standard

Worldwide Interoperability for Microwave Access (WiMAX) is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide physical layer (PHY) and media access control (MAC) options.

The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the conventional boundary between the UHF and SHF bands at 3.0 GHz. The S band is used by airport surveillance radar for air traffic control, weather radar, surface ship radar, and some communications satellites, especially those satellites used by NASA to communicate with the Space Shuttle and the International Space Station. The 10 cm radar short-band ranges roughly from 1.55 to 5.2 GHz. The S band also contains the 2.4–2.483 GHz ISM band, widely used for low power unlicensed microwave devices such as cordless phones, wireless headphones (Bluetooth), wireless networking (WiFi), garage door openers, keyless vehicle locks, baby monitors as well as for medical diathermy machines and microwave ovens. India's regional satellite navigation network (IRNSS) broadcasts on 2.483778 to 2.500278 GHz.

<span class="mw-page-title-main">Wireless power transfer</span> Transmission of electrical energy without wires as a physical link

Wireless power transfer (WPT), wireless power transmission, wireless energy transmission (WET), or electromagnetic power transfer is the transmission of electrical energy without wires as a physical link. In a wireless power transmission system, an electrically powered transmitter device generates a time-varying electromagnetic field that transmits power across space to a receiver device; the receiver device extracts power from the field and supplies it to an electrical load. The technology of wireless power transmission can eliminate the use of the wires and batteries, thereby increasing the mobility, convenience, and safety of an electronic device for all users. Wireless power transfer is useful to power electrical devices where interconnecting wires are inconvenient, hazardous, or are not possible.

The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU).

<span class="mw-page-title-main">Wireless device radiation and health</span>

The antennas contained in mobile phones, including smartphones, emit radiofrequency (RF) radiation ; the parts of the head or body nearest to the antenna can absorb this energy and convert it to heat. Since at least the 1990s, scientists have researched whether the now-ubiquitous radiation associated with mobile phone antennas or cell phone towers is affecting human health. Mobile phone networks use various bands of RF radiation, some of which overlap with the microwave range. Other digital wireless systems, such as data communication networks, produce similar radiation.

Mobile VoIP or simply mVoIP is an extension of mobility to a voice over IP network. Two types of communication are generally supported: cordless telephones using DECT or PCS protocols for short range or campus communications where all base stations are linked into the same LAN, and wider area communications using 3G or 4G protocols.

<span class="mw-page-title-main">Radio</span> Use of radio waves to carry information

Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.

There are several uses of the 2.4 GHz ISM radio band. Interference may occur between devices operating at 2.4 GHz. This article details the different users of the 2.4 GHz band, how they cause interference to other users and how they are prone to interference from other users.

<span class="mw-page-title-main">Li-Fi</span> Wireless communication technology visible light story

Li-Fi is a wireless communication technology which utilizes light to transmit data and position between devices. The term was first introduced by Harald Haas during a 2011 TEDGlobal talk in Edinburgh.

RF CMOS is a metal–oxide–semiconductor (MOS) integrated circuit (IC) technology that integrates radio-frequency (RF), analog and digital electronics on a mixed-signal CMOS RF circuit chip. It is widely used in modern wireless telecommunications, such as cellular networks, Bluetooth, Wi-Fi, GPS receivers, broadcasting, vehicular communication systems, and the radio transceivers in all modern mobile phones and wireless networking devices. RF CMOS technology was pioneered by Pakistani engineer Asad Ali Abidi at UCLA during the late 1980s to early 1990s, and helped bring about the wireless revolution with the introduction of digital signal processing in wireless communications. The development and design of RF CMOS devices was enabled by van der Ziel's FET RF noise model, which was published in the early 1960s and remained largely forgotten until the 1990s.

References

  1. ↑ U.S. Army (1944). Technical Manual. US War Department. Retrieved 13 August 2022. In definitions given in the index, p. 162, the term "radio set" is listed as synonymous with the term "wireless set"
  2. ↑ Paulu, Burton (1956). British Broadcasting: Radio and Television in the United Kingdom. U of Minnesota Press. ISBN   9781452909547 . Retrieved 13 August 2022. (p.396) In a public opinion poll in Sweden in 1942, 31.4 percent answered 'Yes' to the question "Do you usually listen to the foreign news on the wireless?'
  3. ↑ "ATIS Telecom Glossary 2007". atis.org. Archived from the original on 2 March 2008. Retrieved 16 March 2008.
  4. ↑ Franconi, Nicholas G.; Bunger, Andrew P.; Sejdić, Ervin; Mickle, Marlin H. (24 October 2014). "Wireless Communication in Oil and Gas Wells". Energy Technology. 2 (12): 996–1005. doi:10.1002/ente.201402067. ISSN   2194-4288. S2CID   111149917.
  5. ↑ Biswas, S.; Tatchikou, R.; Dion, F. (January 2006). "Vehicle-to-vehicle wireless communication protocols for enhancing highway traffic safety". IEEE Communications Magazine. 44 (1): 74–82. doi:10.1109/mcom.2006.1580935. ISSN   0163-6804. S2CID   6076106.
  6. ↑ Amédée Guillemin (1891). Electricity and Magnetism. Macmillan and Company. p. 31. Retrieved 17 April 2021.
  7. ↑ Icons of Invention: The Makers of the Modern World from Gutenberg to Gates. ABC-CLIO. 2009. p. 162. ISBN   978-0-313-34743-6.
  8. ↑ "Milestones: First Millimeter-wave Communication Experiments by J.C. Bose, 1894-96". List of IEEE milestones . Institute of Electrical and Electronics Engineers . Retrieved 1 October 2019.
  9. ↑ Emerson, D. T. (1997). "The work of Jagadis Chandra Bose: 100 years of mm-wave research". 1997 IEEE MTT-S International Microwave Symposium Digest, Vol. 3. IEEE Transactions on Microwave Theory and Research. Vol. 45, no. 12. pp. 2267–2273. Bibcode:1997imsd.conf..553E. doi:10.1109/MWSYM.1997.602853. ISBN   9780986488511. S2CID   9039614. reprinted in Igor Grigorov, Ed., Antentop , Vol. 2, No.3, pp. 87–96.
  10. ↑ "Timeline". The Silicon Engine. Computer History Museum . Retrieved 22 August 2019.
  11. ↑ "1901: Semiconductor Rectifiers Patented as "Cat's Whisker" Detectors". The Silicon Engine. Computer History Museum . Retrieved 23 August 2019.
  12. 1 2 3 Golio, Mike; Golio, Janet (2018). RF and Microwave Passive and Active Technologies. CRC Press. pp. ix, I-1, 18–2. ISBN   9781420006728.
  13. ↑ Rappaport, T. S. (November 1991). "The wireless revolution". IEEE Communications Magazine. 29 (11): 52–71. doi:10.1109/35.109666. S2CID   46573735.
  14. ↑ "The wireless revolution". The Economist . 21 January 1999. Retrieved 12 September 2019.
  15. 1 2 3 Baliga, B. Jayant (2005). Silicon RF Power MOSFETS. World Scientific. ISBN   9789812561213.
  16. 1 2 Harvey, Fiona (8 May 2003). "The Wireless Revolution". Encyclopædia Britannica . Retrieved 12 September 2019.
  17. ↑ Tech Target – Definition of Wireless – Posted by Margaret Rouse (2 April control and traffic control systems
  18. ↑ Tsai, Allen. "AT&T Releases Navigator GPS Service with Speech Recognition". Telecom Industry News. Archived from the original on 14 June 2012. Retrieved 2 April 2008.
  19. ↑ "Robust demand for mobile phone service will continue; UN agency predicts". UN News Centre. 15 February 2010. Retrieved 6 September 2011.
  20. ↑ Vilorio, Dennis. "You're a what? Tower Climber" (PDF). Occupational Outlook Quarterly. Archived (PDF) from the original on 3 February 2013. Retrieved 6 December 2013.
  21. 1 2 3 "High Speed Internet on the Road". Archived from the original on 3 September 2011. Retrieved 6 September 2011.
  22. ↑ "What is Connection Manager?". Microsoft Technet. 28 March 2003. Retrieved 6 September 2011.
  23. ↑ "Our Products". Unwired Revolution. Archived from the original on 9 January 2012. Retrieved 6 September 2011.
  24. ↑ "General Dynamics- NetMotion Mobility XE". Archived from the original on 26 September 2011. Retrieved 30 August 2011.
  25. ↑ "Wi-Fi" . Retrieved 6 September 2011.
  26. ↑ O'Brien, J; Marakas, G.M (2008). Management Information Systems. New York, NY: McGraw-Hill Irwin. p. 239.
  27. ↑ Aravamudhan, Lachu; Faccin, Stefano; Mononen, Risto; Patil, Basavaraj; Saifullah, Yousuf; Sharma, Sarvesh; Sreemanthula, Srinivas (4 July 2003). "Getting to Know Wireless Networks and Technology". InformIT. Retrieved 12 July 2011.
  28. ↑ "What really is a Third Generation (3G) Mobile Technology" (PDF). ITU. Archived from the original (PDF) on 7 June 2011. Retrieved 12 July 2011.
  29. ↑ Geier, Jim (2008). "Wireless Network Industry Report 2007" (PDF). Wireless-Nets, Ltd. Archived from the original (PDF) on 12 October 2012. Retrieved 6 September 2011.
  30. ↑ Ilcev, Stojce Dimov (2006). Global Mobile Satellite Communications for Maritime, Land and Aeronautical Applications. Springer. ISBN   9781402027840.
  31. ↑ Lewis, F.L. (2004). "Wireless Sensor Networks" (PDF). Smart Environments: Technologies, Protocols, and Applications. New York: John Wiley: 11–46. doi:10.1002/047168659X.ch2. ISBN   9780471686590.
  32. ↑ Paventi, Jared (26 October 2013). "How does a Wireless Keyboard Work?". Ehow.
  33. ↑ Moser, Max; Schrödel, Philipp (5 December 2007). "27Mhz Wireless Keyboard Analysis Report aka 'We know what you typed last summer'" (PDF). Archived from the original (PDF) on 23 January 2009. Retrieved 6 February 2012.
  34. ↑ Jones, George (14 September 2010). "Future Proof: How Wireless Energy Transfer Will Kill the Power Cable". MaximumPC.
  35. ↑ Dusit Niyato; Lotfollah Shafai (2017). Wireless-Powered Communication Networks. Cambridge University Press. p. 329. ISBN   978-1-107-13569-7 . Retrieved 17 April 2021.
  36. ↑ "First Demonstration of a Surveillance Camera Powered by Ordinary Wi-Fi Broadcasts". MIT Technology Review. Retrieved 20 November 2020.
  37. ↑ Linebaugh, Kate (23 May 2012). "More Hospital Medical Devices to Go Wireless" . The Wall Street Journal . Retrieved 13 May 2022.

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