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Wireless

Wireless telecommunications 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 two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of wireless technology include GPS units, Garage door openers or garage doors, wireless computer mice, keyboards and Headset (audio), headphones, radio receivers, satellite television, broadcast television and cordless telephones.

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:

  • Telemetry control and traffic control systems
  • Infrared and ultrasonic remote control devices
  • Modulated laser light systems for point to point communications
  • Professional LMR (Land Mobile Radio) and SMR (Specialized Mobile Radio) typically used by business, industrial and Public Safety entities.
  • Consumer Two way radio including FRS Family Radio Service, GMRS (General Mobile Radio Service) and Citizens band ("CB") radios.
  • The Amateur Radio Service (Ham radio).
  • Consumer and professional Marine VHF radios.
  • Airband and radio navigation equipment used by aviators and air traffic control
  • Cellular telephones 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 using technology such as Wireless USB or Bluetooth
  • Cordless telephone sets: these are limited-range devices, not to be confused with cell phones.
  • Satellite television: Is broadcast from satellites in geostationary orbit. Typical services use direct broadcast satellite to provide multiple television channels to viewers.

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:

  • To span a distance beyond the capabilities of typical cabling,
  • 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.

Modes

Wireless communications can be via:

  • radio frequency communication,
  • microwave communication, for example long-range line-of-sight via highly directional antennas, or short-range communication,
  • infrared (IR) short-range communication, for example from consumer IR devices such as remote controls or via Infrared Data Association (IrDA).

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

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.

Today the average inhabitant of the western hemisphere knows a little of everything. He has the newspaper on his breakfast table and wireless within reach. For the evening there is the film, cards, or a meeting to complete a day spent in the office or factory where nothing that is essential has been learnt. With slight variation this picture of a low cultural average holds good over the entire range from factory-hand of clerk to manager or director. Only the personal will to culture, in whatever field and however pursued raises modern man above this level.
— Johan Huizinga (1872–1945)

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 light beams (which are narrow projections of electromagnetic waves). In that distant era when utilities did not yet exist to provide electricity, and lasers 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 fiber-optic communications.

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, T. A. 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 (U. S. Patent 465,971).

In the history of wireless technology, the demonstration of the theory of electromagnetic waves by Heinrich Hertz in 1888 was important. The theory of electromagnetic waves was 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. Jagadish Chandra Bose around this time developed an early wireless detection device and helped increase the knowledge of millimeter length electromagnetic waves. Practical applications of wireless radio communication and radio remote control technology were implemented by later inventors, such as Nikola Tesla.

Further information: Invention of radio

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

See also: Spectrum management

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. 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 signals from these instruments.

Wireless data communications

Wireless data communications are an essential component of mobile computing. The various available technologies differ in local availability, coverage range and performance, 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, or a mobile VPN deployed to handle the multiple connections as a secure, single virtual network. Supporting technologies include:

Wi-Fi is a wireless local area network that enables portable computing devices to connect easily to the Internet. 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. 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.
Cellular data service offers coverage within a range of 10-15 miles from the nearest cell site. Speeds have increased as technologies have evolved, from earlier technologies such as GSM, CDMA and GPRS, to 3G networks such as W-CDMA, EDGE or CDMA2000.
Mobile Satellite Communications may be used where other wireless connections are unavailable, such as in largely rural areas or remote locations. Satellite communications are especially important for transportation, aviation, maritime and military use.

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

  • Radio communication system
  • Broadcasting
  • Amateur radio
  • Land Mobile Radio or Professional Mobile Radio: TETRA, P25, OpenSky, EDACS, DMR, dPMR
  • Cordless telephony: DECT (Digital Enhanced Cordless Telecommunications)
  • Cellular networks: 0G, 1G, 2G, 3G, Beyond 3G (4G), Future wireless
  • List of emerging technologies
  • Short-range point-to-point communication : Wireless microphones, Remote controls, IrDA, RFID (Radio Frequency Identification), TransferJet, Wireless USB, DSRC (Dedicated Short Range Communications), EnOcean, Near Field Communication
  • Wireless sensor networks: ZigBee, EnOcean; Personal area networks, Bluetooth, TransferJet, Ultra-wideband (UWB from WiMedia Alliance).
  • Wireless networks: Wireless LAN (WLAN), (IEEE 802.11 branded as Wi-Fi and HiperLAN), Wireless Metropolitan Area Networks (WMAN) and (LMDS, WiMAX, and HiperMAN)



Categories

Further Reading: Wireless

Wireless Electronic Devices And Health ... International guidelines on exposure levels to microwave frequency EMFs such as ICNIRP limit the power levels of wireless devices and it is uncommon for wireless devices to exceed the guidelines... Exposure difference to mobile phones Users of wireless devices are typically exposed for much longer periods than for mobile phones and the strength of wireless devices is not significantly less... Whereas a mobile phone can range from 21 dBm (125 mW) for Power Class 4 to 33 dBm (2W) for Power class 1, a wireless router can range from a typical 15 dBm (30 mW) strength to 27 dBm (500 mW) on the high end...

Computer Network ... Networks may be classified according to a wide variety of characteristics such as the medium used to transport the data, communications protocol used, scale, topology, and organizational scope. Communications protocols define the rules and data formats for exchanging information in a computer network, and provide the basis for network programming...

Google ... Google was first incorporated as a privately held company on September 4, 1998, and its initial public offering followed on August 19, 2004. At that time Larry Page, Sergey Brin, and Eric Schmidt agreed to work together at Google for 20 years, until the year 2024...

Network Performance ... The following list gives examples of Network Performance measures for a circuit-switched network and one type of packet-switched network, viz. ATM: Circuit-switched networks: In circuit switched networks, network performance is synonymous with the grade of service...

Encryption ... In many contexts, the word encryption may also implicitly refer to the reverse process, decryption e.g. “software for encryption” can typically also perform decryption ...

History Of Mobile Phones ... Mobile phone history is often divided into generations (first, second, third and so on) to mark significant step changes in capabilities as the technology improved. Pioneers of radio telephony By 1930, telephone customers in the United States could place a call to a passenger on a liner in the Atlantic Ocean...

Mobile Phone Features ... The common components found on all phones are: A battery, providing the power source for the phone functions. An input mechanism to allow the user to interact with the phone...

Mobile Banking ... Mobile banking has until recently (2010) most often been performed via SMS or the Mobile Web. Apple's initial success with iPhone and the rapid growth of phones based on Google's Android (operating system) have led to increasing use of special client programs, called apps, downloaded to the mobile device...

Wireless Telegraphy ... Wireless telegraphy originated as a term to describe electrical signaling without the electric wires to connect the end points... Wireless telegraphy rapidly came to mean Morse code transmitted with Hertzian waves (electromagnetic waves) decades before it came to be associated with the term radio... Wireless telegraphy is still used widely today by amateur radio hobbyists where it is commonly referred to as radiotelegraphy, continuous wave, or just CW...

Mobile Robot ... The device may be plugged directly into the robot, may be a wireless joystick, or may be an accessory to a wireless computer or other controller... Such robots are often part of the wireless enterprise network, interfaced with other sensing and control systems in the building...

History Of Radio ... In 1895, Marconi built a wireless system capable of transmitting signals at long distances (1.5 mi./ 2.4 km)... Early radio telegraphy and telephony The term wireless telegraphy is a historical term used today to apply to early radio telegraph communications techniques and practices, particularly those used during the first three decades of radio (1887 to 1920) before the term radio came into use... Turn of the 19th to 20th century Around the turn of the 19th to 20th century, the Slaby-Arco wireless system was developed by Adolf Slaby and Georg von Arco...

Cryptanalysis ... Cryptanalysis is also used to refer to any attempt to circumvent the security of other types of cryptographic algorithms and protocols in general, and not just encryption. However, cryptanalysis usually excludes methods of attack that do not primarily target weaknesses in the actual cryptography, such as bribery, physical coercion, burglary, keystroke logging, and social engineering, although these types of attack are an important concern and are often more effective than traditional cryptanalysis...

Photophone ... On April 1, 1880, and also described by plaque as occurring on June 3, Bell's assistant transmitted the world's first wireless telephone message to him on their newly invented form of telecommunication, the far advanced precursor to fiber-optic communications that came into widespread use during the 1980s... The wireless call was sent from the roof of the Franklin School to the window of Bell's laboratory, some 213 metres (700 ft) away...

International Space Station ... The ISS serves as a microgravity and space environment research laboratory in which crew members conduct experiments in biology, human biology, physics, astronomy, meteorology and other fields. The station is suited for the testing of spacecraft systems and equipment required for missions to the Moon and Mars...

Wireless Energy Transfer ... The most common form of wireless power transmission is carried out using direct induction followed by resonant magnetic induction...

Radio-frequency Identification ... RFID tags are used in many industries. An RFID attached to an automobile during production can be used to track its progress through the assembly line...

Voice Over IP ... Internet telephony refers to communications services —voice, fax, SMS, and/or voice-messaging applications— that are transported via the Internet, rather than the public switched telephone network (PSTN). The steps involved in originating a VoIP telephone call are signaling and media channel setup, digitization of the analog voice signal, encoding, packetization, and transmission as Internet Protocol (IP) packets over a packet-switched network...

History Of The Telephone ... A different device, the tin can telephone, or 'lover's phone', has also been known for centuries. It connected two diaphragms with a taut string or wire, which transmitted sound by mechanical vibrations from one to the other along the wire, and not by a modulated electrical current...

Network Security ... Once authenticated, a firewall enforces access policies such as what services are allowed to be accessed by the network users. Though effective to prevent unauthorized access, this component may fail to check potentially harmful content such as computer worms or Trojans being transmitted over the network...

Mobile Phone ... In addition to telephony, modern mobile phones also support a wide variety of other services such as text messaging, MMS, email, Internet access, short-range wireless communications (infrared, Bluetooth), business applications, gaming and photography...

Internet Access ... Broadband Internet access may give access to Internet services such as: Much faster world wide web browsing Telephony, radio, television and videoconferencing Virtual private networks and remote systems administration Online gaming especially massively multiplayer online role-playing games which are interaction-intensive "Broadband penetration" is now treated as a key economic indicator. Even though information signals generally travel nearly the speed of light in the medium no matter what the bit rate, higher rate services are often marketed as "faster" or "higher speeds"...

Intel ... Intel was an early developer of SRAM and DRAM memory chips, and this represented the majority of its business until 1981. Although Intel created the world's first commercial microprocessor chip in 1971, it was not until the success of the personal computer (PC) that this became its primary business...



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