Wireless is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few metres for television remote control, or as far as thousands or even millions of kilometres for deep-space radio communications. It encompasses various types of fixed, mobile, and portable , cellular telephone, (PDAs), and . Other examples of wireless technology include GPS units, or garage doors, wireless computer mice, keyboard and Headset, , , satellite television, broadcast television and cordless .
Introduction
Wireless operations permit services, such as long range 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, computer networks, network terminals, etc.) which use some form of energy (e.g.
radio frequency (RF),acoustic energy, etc.) to transfer information without the use of wires.
Information is transferred in this manner over both short and long distances.
Wireless services
Common examples of wireless equipment include:
Wireless networks
Wireless networking (i.e. the various types of unlicensed 2.4 GHz WiFi devices) is used to meet many needs. Perhaps the most common use is to connect laptop users who travel from location to location. Another common use is for mobile networks that connect via satellite. A wireless transmission method is a logical choice to network a LAN segment that must frequently change locations. The following situations justify the use of wireless technology:
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To span a distance beyond the capabilities of typical cabling,
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To provide a backup communications link in case of normal network failure,
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To link portable or temporary workstations,
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To overcome situations where normal cabling is difficult or financially impractical, or
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To remotely connect mobile users or networks.
Modes
Wireless communications can be via:
Applications may involve
point-to-point communication,
point-to-multipoint communication,
broadcasting,
and other
.
Cordless
The term "wireless" should not be confused with the term "
cordless", which is generally used to refer to powered electrical or electronic devices that are able to operate from a portable power source (e.g. a battery pack) without any cable or cord to limit the mobility of the cordless device through a connection to the mains power supply.
Some cordless devices, such as cordless telephones, are also wireless in the sense that information is transferred from the cordless telephone to the telephone's base unit via some type of wireless communications link. This has caused some disparity in the usage of the term "cordless", for example in Digital Enhanced Cordless Telecommunications.
History
Photophone
The world's first wireless telephone conversation occurred in 1880, when
Alexander Graham Bell and
Charles Sumner Tainter invented and patented the
photophone, a telephone that conducted audio conversations wirelessly over modulated
(which are narrow projections of
electromagnetic waves). In that distant era when utilities did not yet exist to provide
electricity, and
had not even been conceived of in
science fiction, there were no practical applications for their invention, which was highly limited by the availability of both sunlight and good weather. Similar to
free space optical communication, the photophone also required a clear line of sight between its transmitter and its receiver. It would be several decades before the photophone's principles found their first practical applications in
military communications and later in
.
Early wireless work
David E. Hughes transmitted radio signals over a few hundred yards by means of a clockwork keyed transmitter in 1879. As this was before Maxwell's work was understood, Hughes' contemporaries dismissed his achievement as mere "Induction". In 1885,
Thomas Edison used a vibrator magnet for induction transmission. In 1888, Edison deployed a system of signaling on the Lehigh Valley Railroad. In 1891, Edison obtained the wireless patent for this method using inductance ().
In the history of wireless technology, the demonstration of the theory of by Heinrich Hertz in 1888 was important.[J.C. Bose, Collected Physical Papers. New York, N.Y.: Longmans, Green and Co., 1927] Practical applications of wireless radio communication and radio remote control technology were implemented by later inventors, such as Nikola Tesla.
Radio
The term "wireless" came into public use to refer to a radio receiver or
transceiver (a dual purpose receiver and transmitter device), establishing its usage in the field of wireless telegraphy early on; now the term is used to describe modern wireless connections such as in cellular networks and wireless broadband Internet. It is also used in a general sense to refer to any type of operation that is implemented without the use of wires, such as "wireless remote control" or "wireless energy transfer", regardless of the specific technology (e.g.
radio,
infrared,
ultrasonic) used.
Guglielmo Marconi and
Karl Ferdinand Braun were awarded the 1909
Nobel Prize for Physics for their contribution to wireless telegraphy.
Electromagnetic spectrum
Light, colors, AM and FM radio, and 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 national organizations such as the
Federal Communications Commission in the USA, or
Ofcom in the United Kingdom. This determines 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 didn't have specific frequencies to work under and an
amateur radio operator were interfering with the pilot's ability to land an
aircraft. Wireless communication spans the spectrum from 9 kHz to 300 GHz.
Henreich Hertz was the discoverer of the electromagnetic wave, it gave a platform for further inventions in wireless communication.
Applications of wireless technology
Mobile telephones
One of the best-known examples of wireless technology is the
mobile phone, also known as a cellular phone, with more than 4.6 billion mobile cellular subscriptions worldwide as of the end of 2010.
[ Robust demand for mobile phone service will continue, UN agency predicts UN News Centre February 15, 2010] These wireless phones use radio waves to enable their users to make phone calls from many locations worldwide. They can be used within range of the
mobile telephone site used to house the equipment required to transmit and receive the
radio signal from these instruments.
Wireless data communications
Wireless data communications are an essential component of mobile computing.
[ Insights On Rugged Mobile Computers.pdf TCO Insights on Rugged Mobile Computers, VDC Research, 2007.] The various available technologies differ in local availability, coverage range and performance,
[High Speed Internet on the Road, http://www.geeksontour.com/showme/wifi/wifi00_3ways.cfm][Mitchell, Bradley. Wireless Internet Service: An Introduction] and in some circumstances, users must be able to employ multiple connection types and switch between them. To simplify the experience for the user, connection manager software can be used,
[ What is Connection Manager? Microsoft Technet, March 28, 2003][ Unwired Revolution] or a
mobile VPN deployed to handle the multiple connections as a secure, single
virtual network.
[http://www.gd-itronix.com/index.cfm?page=Products:MobilityXE] Supporting technologies include:
- Wi-Fi is a wireless local area network that enables portable computing devices to connect easily to the Internet.
[ About.com] Standardized as IEEE 802.11 a,b,g,n, Wi-Fi approaches speeds of some types of wired Ethernet. Wi-Fi has become the de facto standard for access in private homes, within offices, and at public hotspots.[ "Wi-Fi"] Some businesses charge customers a monthly fee for service, while others have begun offering it for free in an effort to increase the sales of their goods.[O'Brien, J. & Marakas, G.M.(2008) Management Information Systems (pp. 239). New York, NY: McGraw-Hill Irwin]
- Cellular data service offers coverage within a range of 10-15 miles from the nearest cell site.
[Lachu Aravamudhan, Stefano Faccin, Risto Mononen, Basavaraj Patil, Yousuf Saifullah, Sarvesh Sharma, Srinivas Sreemanthula. "Getting to Know Wireless Networks and Technology", InformIT][ "What really is a Third Generation (3G) Mobile Technology", ITU]
- Mobile Satellite Communications may be used where other wireless connections are unavailable, such as in largely rural areas
[Geier, Jim. Wireless Network Industry Report 2007, Wireless-Nets, Ltd., 2008] or remote locations.[Ilcev, Stojce Dimov, Global Mobile Satellite Communications for Maritime, Land and Aeronautical Applications, Springer, 2005]
Wireless 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.
Computer interface devices
Answering the call of customers frustrated with cord clutter, many manufactures of computer peripherals turned to wireless technology to satisfy their consumer base. Originally these units used bulky, highly limited transceivers to mediate between a computer and a keyboard and mouse, however more recent generations have used small, high quality devices, some even incorporating
Bluetooth. These systems have become so ubiquitous that some users have begun complaining about a lack of wired peripherals. Wireless devices tend to have a slightly slower response time than their wired counterparts, however the gap is decreasing. 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 was highly insecure.
Categories of wireless implementations, devices and standards
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Radio communication system
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Broadcasting
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Amateur radio
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Land Mobile Radio or Professional Mobile Radio: TETRA, P25, OpenSky, EDACS, DMR, dPMR
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Cordless telephony:DECT (Digital Enhanced Cordless Telecommunications)
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: 0G, 1G, 2G, 3G, Beyond 3G, Future wireless
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List of emerging technologies
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Short-range point-to-point communication : , , IrDA, RFID, TransferJet, Wireless USB, DSRC, EnOcean, Near Field Communication
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: ZigBee, EnOcean; , Bluetooth, TransferJet, Ultra-wideband (UWB from WiMedia Alliance).
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: Wireless LAN (WLAN), (IEEE 802.11 branded as Wi-Fi and HiperLAN), (WMAN) and (LMDS, WiMAX, and HiperMAN)
See also
Further reading
External links
References
