The term wireless is normally used to refer to any type of electrical or electronic operation which is accomplished without the use of a "hard wired" connection. Wireless communication is the transfer of information over a distance without the use of electrical conductors or "wires". The SINTEF Group, The Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology The distances involved may be short (a few meters as in television remote control) or very long (thousands or even millions of kilometers for radio communications). When the context is clear the term is often simply shortened to "wireless". Wireless communications is generally considered to be a branch of telecommunications.

It encompasses cellular telephone, personal digital assistant (PDAs), and wireless networking. Other examples of wireless technology include GPS units, garage door openers and or garage doors, wireless computer mice and keyboard, satellite television and cordless telephones.

Introduction

Wireless operations permits 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), infrared light, laser light, visible light, acoustic energy, etc.) to transfer information without the use of wires.ATIS Committee T1A1 Performance and Signal Processing. ANS T1.523-2001, Telecom Glossary 2000 http://www.atis.org/tg2k/ Information is transferred in this manner over both short and long distances.

Wireless communication may be via:

• radio frequency communication,
• microwave communication, for example long-range line-of-sight via highly directional antennas, or short-range communication, or
• infrared (IR) short-range communication, for example from remote controls or via IRDA,

Applications may involve point-to-point communication, point-to-multipoint communication, broadcasting , cellular networks and other wireless networks.

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.

In the last 50 years, wireless communications industry experienced drastic changes driven by many technology innovations.

History

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", "wireless energy transfer", etc. regardless of the specific technology (e.g., radio, infrared, ultrasonic, etc.) that is used to accomplish the operation.

Early wireless work

David E. Hughes, eight years before Hertz's experiments, induced electromagnetic waves in a signalling system. Hughes transmitted Morse code by an induction apparatus. In 1878, Hughes's induction transmission method utilized a "clockwork transmitter" to transmit signals. In 1885, T. A. Edison uses a vibrator magnet for induction transmission. In 1888, Edison deploys a system of signalling on the Lehigh Valley Railroad. In 1891, Edison attains the wireless patent for this method using inductance ().

In the history of wireless technology, the demonstration of the theory of electromagnetic waves by Heinrich Rudolf Hertz in 1888 was important. Saeed, " Heinrich Rudolf Hertz". The theory of electromagnetic waves were predicted from the research of James Clerk Maxwell and Michael Faraday. Hertz demonstrated that electromagnetic waves could be transmitted and caused to travel through space at straight lines and that they were able to be received by an experimental apparatus. The experiments were not followed up by Hertz and the practical applications of the wireless communication and remote control technology would be implemented by Nikola Tesla.

The electromagnetic spectrum

Light, colours, AM and FM radio, and electronic devices make use of the electromagnetic spectrum. In the US the frequencies that are available for use for communication are treated as a public resource and are regulated by the Federal Communications Commission. 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 a ham radio operator was interfering with the pilot's ability to land an airplane. Wireless communication spans the spectrum from 9 kHz to 300 GHz.

Applications of wireless technology

Security systems

Wireless technology may supplement or replace hard wired implementations in security systems for homes or office buildings. The operations that are required (e.g., detecting whether a door or window is open or closed) may be implemented with the use of hard wired sensors or they may be implemented with the use of wireless sensors which are also equipped with a wireless transmitter (e.g., infrared, radio frequency, etc.) to transmit the information concerning the current state of the door or window.

Television remote control

Some televisions were previously manufactured with hard wired remote controls which plugged in to a receptacle or jack in the television whereas more modern televisions use wireless (generally infrared) remote control units.

Cellular telephones

Perhaps the best known example of wireless technology is the cellular telephone. These instruments use radio waves to enable the operator to make phone calls from many locations world-wide. They can be used anywhere that there is a cellular telephone site to house the equipment that is required to transmit and receive the signal that is used to transfer both voice and data to and from these instruments. (For more information see mobile phones).

Wireless communication

Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or the entire communication path. Common examples of wireless equipment in use today include:

• Cellular phones and pagers: provide connectivity for portable and mobile applications, both personal and business.
• Global Positioning System (GPS): allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth.
• Cordless computer peripherals: the cordless mouse is a common example; keyboards and printers can also be linked to a computer via wireless.
• Cordless telephone sets: these are limited-range devices, not to be confused with cell phones.
• Satellite television: allows viewers in almost any location to select from hundreds of channels.

Wireless networking is used to meet a variety of 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:

• To span a distance beyond the capabilities of typical cabling,
• To avoid obstacles such as physical structures, EMI, or RFI,
• 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.

Environmental concerns and health hazards

Recently there have been concerns risen and research conducted concerning usage of wireless communications and its possible relation to poor concentration, memory loss, nausea, premature senility and even cancer. "Electromagnetic fields". World Health Organization. Last retrieved September 24, 2007. "Consensus Statement on Electromagnetic Radiation (Draft)". Collaborative on Health and the Environment. October 10, 2006. United Kingdom National Physics Laboratory report.

On the PBS show Nature there was a show dedicated to Colony Collapse Disorder where there was mention of some blame on the phenomenon of missing bees particularly due to the wide use of cellphones as the cause of the collapse. However, one interviewed person asserted that the cellphones were not the cause due to misinterpreted report.

Categories of wireless implementations, devices and standards

• ;Broadcasting

• ;Amateur radio

• ;Communication radio

• ;Cordless telephony:DECT (Digital Enhanced Cordless Telecommunications)

• ;Cellular systems:0G, 1G, 2G, 3G, Beyond 3G , Future wireless

• ;Short-range point-to-point communication : Wireless microphones, Remote controls, IrDA, RFID , Wireless USB, DSRC , EnOcean, Near Field Communication

• ;Wireless sensor networks : ZigBee, EnOcean; Personal area networks, Bluetooth, Ultra-wideband (UWB from WiMedia Alliance).

• ;Wireless computer networks: Wireless Local Area Networks (WLAN), (IEEE 802.11 branded as WiFi and HIPERLAN), Wireless Metropolitan Area Networks (WMAN) and Broadband Fixed Access (BWA) (LMDS, WiMAX, and HIPERMAN)