Telecommunication is the assisted transmission In telecommunications, transmission is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired or wireless. Transmission technologies and schemes typically refer to physical layer protocol duties such as modulation, over a distance for the purpose of communication Communication is a process of transferring information from one source to another. Communication processes are sign-mediated interactions between at least two agents which share a repertoire of signs and semiotic rules. Communication is commonly defined as "the imparting or interchange of thoughts, opinions, or information by speech, writing,. In earlier times, this may have involved the use of smoke signals In Ancient China, soldiers stationed along the Great Wall would alert each other of impending enemy attack by signaling from tower to tower. In this way, they were able to transmit a message as far away as 480 km in just a few hours, drums Developed and used by cultures living in forested areas, drums served as an early form of long distance communication, and were used during ceremonial and religious functions, semaphore A semaphore telegraph, optical telegraph, shutter telegraph chain, Chappe telegraph, or Napoleonic semaphore is a system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a, flags Flag signals can mean any of various methods of using flags or pennants to send signals: Flaghoist signalling or the flaghoist signalling system uses sets of flags and pennants to convey messages. The U.S. Navy uses a set of 68 flags, including flags for each letter of the alphabet and each numeral to convey messages of tactical or administrative or heliograph A Heliograph (from the Greek helios , meaning "sun", and graphein (γραφειν) = write) is a wireless solar telegraph that signals using Morse code flashes of sunlight reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter. The heliograph was a simple but highly. In modern times, telecommunication typically involves the use of electronic devices such as the telephone A traditional landline telephone system, also known as "plain old telephone service" , commonly handles both signaling and audio information on the same twisted pair of insulated wires: the telephone line. Although originally designed for voice communication, the system has been adapted for data communication such as Telex, Fax and, television Commercially available since the late 1930s, the television set has become a common communications receiver in homes, businesses and institutions, particularly as a source of entertainment and news. Since the 1970s the availability of video cassettes, laserdiscs, DVDs and now Blu-ray discs, have resulted in the television set frequently being used, radio Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing some property of the radiated waves, such as or computer A computer is a machine that manipulates data according to a set of instructions. Early inventors in the field of telecommunication include Alexander Graham Bell Alexander Graham Bell was an eminent scientist, inventor, engineer and innovator who is credited with inventing the first practical telephone, Guglielmo Marconi Marchese Guglielmo Marconi was an Italian inventor, best known for his development of a radiotelegraph system, which served as the foundation for the establishment of numerous affiliated companies worldwide. He shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun, "in recognition of their contributions to the development of and John Logie Baird John Logie Baird was a Scottish engineer and inventor of the world's first working television system, also the world's first ever colour broadcast. Although Baird's electromechanical system was eventually displaced by purely electronic systems (such as those of Vladimir Zworykin and Philo Farnsworth), his early successes demonstrating working. Telecommunication is an important part of the world economy and the telecommunication industry's revenue was estimated to be $1.2 trillion in 2006.

Contents 1 History 1.1 Early telecommunications 1.2 Telegraph and telephone 1.3 Radio and television 1.4 Computer networks and the Internet 2 Key concepts 2.1 Basic elements 2.2 Analogue or digital 2.3 Networks 2.4 Channels 2.5 Modulation 3 Society and telecommunication 3.1 Economic impact 3.1.1 Microeconomics 3.1.2 Macroeconomics 3.2 Social impact 3.3 Other impacts 4 Modern operation 4.1 Telephone 4.2 Radio and television 4.3 The Internet 4.4 Local area networks 5 Telecommunication by region 6 See also 7 References 8 Further reading 9 External links

History

For more details on this topic, see History of telecommunication The history of telecommunication began with the use of smoke signals and drums in Africa, the Americas and parts of Asia. In the 1790s the first fixed semaphore systems emerged in Europe however it was not until the 1830s that electrical telecommunication systems started to appear. This article details the history of telecommunication and the.

Early telecommunications

A replica of one of Chappe's Claude Chappe was a French inventor who in 1792 demonstrated a practical semaphore system that eventually spanned all of France. This was the first practical telecommunications system of the industrial age, making Chappe the first telecom mogul.[citation needed] semaphore towers A semaphore telegraph, optical telegraph, shutter telegraph chain, Chappe telegraph, or Napoleonic semaphore is a system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a

In the Middle Ages, chains of beacons Beacons help guide navigators to their destinations. Types of navigation beacon include radar reflectors, radio beacons, and sonic or visual signals. Visual beacons range from small, single-pile structures to large lighthouses or light stations and are located on land or in water. Lighted beacons are called lights; unlighted beacons are called were commonly used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "the enemy has been sighted" had to be agreed upon in advance. One notable instance of their use was during the Spanish Armada The Spanish Armada was the Spanish fleet that sailed against England under the command of the Duke of Medina Sidonia in 1588, leading to the Drake–Norris Expedition of 1589, also known as the English Armada against Spanish possessions in the New World and against the Atlantic treasure fleets, when a beacon chain relayed a signal from Plymouth Plymouth ( ˈplɪməθ ) is a city and unitary authority area on the coast of Devon, England, about 190 miles (310 km) south west of London. It is built between the mouths of the rivers Plym to the east and Tamar to the west, where they join Plymouth Sound. Since 1967 the unitary authority of Plymouth has included the suburbs of Plympton and to London signalling the arrival of Spanish ships.^[1]

In 1792, Claude Chappe Claude Chappe was a French inventor who in 1792 demonstrated a practical semaphore system that eventually spanned all of France. This was the first practical telecommunications system of the industrial age, making Chappe the first telecom mogul.[citation needed], a French engineer, built the first fixed visual telegraphy system (or semaphore line A semaphore telegraph, optical telegraph, shutter telegraph chain, Chappe telegraph, or Napoleonic semaphore is a system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a) between Lille Lille is a city in northern France. It is the principal city of the Lille Métropole, the fourth-largest metropolitan area in the country behind those of Paris, Lyon and Marseille. Lille is situated on the Deûle River, near France's border with Belgium. It is the capital of the Nord-Pas de Calais region and the prefecture of the Nord department and Paris.^[2] However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres (six to nineteen miles). As a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880.^[3]

Telegraph and telephone

The first commercial electrical telegraph The electrical telegraph is a telegraph that uses electric signals. The electromagnetic telegraph is a device for human-to-human transmission of coded text messages over wire was constructed by Sir Charles Wheatstone Sir Charles Wheatstone FRS , was a British scientist and inventor of many scientific breakthroughs of the Victorian era, including the English concertina, the stereoscope (a device for displaying three-dimensional images), and the Playfair cipher (an encryption technique). However, Wheatstone is best known for his contributions in the development and Sir William Fothergill Cooke Sir William Fothergill Cooke was, with Charles Wheatstone, the co-inventor of the Cooke-Wheatstone electrical telegraph, which was patented in May 1837. Together with John Lewis Ricardo he founded the Electric Telegraph Company, the world's first public telegraph company, in 1846 and opened on 9 April April 9 is the 99th day of the year in the Gregorian calendar. There are 266 days remaining until the end of the year 1839 Year 1839 was a common year starting on Tuesday (link will display the full calendar) of the Gregorian Calendar (or a common year starting on Sunday of the 12-day slower Julian calendar). Both Wheatstone and Cooke viewed their device as "an improvement to the [existing] electromagnetic telegraph" not as a new device.^[4]

Samuel Morse Samuel Finley Breese Morse was the American creator of a single-wire telegraph system and Morse code and (less notably) a painter of historic scenes independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on 2 September 1837. His code Morse code is a type of character encoding that transmits telegraphic information using rhythm. Morse code uses a standardized sequence of short and long elements to represent the letters, numerals, punctuation and special characters of a given message. The short and long elements can be formed by sounds, marks, or pulses, in on off keying and are was an important advance over Wheatstone's signaling method. The first transatlantic telegraph cable The transatlantic telegraph cable was the first cable used for telegraph communications laid across the floor of the Atlantic Ocean. It crossed from Foilhommerum, Valentia Island, in western Ireland to Heart's Content in eastern Newfoundland. The transatlantic cable bridged North America and Europe, and expedited communication between the two was successfully completed on 27 July 1866, allowing transatlantic telecommunication for the first time.^[5]

The conventional telephone was invented independently by Alexander Bell Alexander Graham Bell was an eminent scientist, inventor, engineer and innovator who is credited with inventing the first practical telephone and Elisha Gray Elisha Gray was an American electrical engineer who cofounded the Western Electric Manufacturing Company. Gray is best known for his development of a telephone prototype in 1876 in Highland Park, Illinois and is considered by many to be the true inventor of the variable resistance telephone. Despite losing out to Alexander Graham Bell for the in 1876.^[6] Antonio Meucci Antonio Meucci was an Italian inventor, who developed a form of voice communication apparatus in 1857. Many credit him with the invention of the telephone; for example, the Enciclopedia Italiana di Scienze, Lettere ed Arti (Italian Encyclopedia of Science, Literature and Art) calls him the "inventore del telefono" (inventor of the invented the first device that allowed the electrical transmission of voice over a line in 1849. However Meucci's device was of little practical value because it relied upon the electrophonic effect The microwave auditory effect, also known as the microwave hearing effect or the Frey effect, consists of audible clicks induced by pulsed/modulated microwave frequencies. The clicks are generated directly inside the human head without the need of any receiving electronic device. The effect was first reported by persons working in the vicinity of and thus required users to place the receiver in their mouth to “hear” what was being said.^[7] The first commercial telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven New Haven is the third largest municipality in Connecticut, after Bridgeport and Hartford, with a core population of about 124,000 people. "New Haven" may also refer to the wider Greater New Haven area, which has nearly 600,000 inhabitants in the immediate area. It is located in New Haven County, on New Haven Harbor, on the northern and London.^[8][9]

Radio and television

In 1832, James Lindsay James Bowman Lindsay was a Scottish inventor and author. He is credited with early developments in several fields, such as incandescent lighting and telegraphy gave a classroom demonstration of wireless telegraphy The term wireless telegraphy is a historic term used today as applied to early radio telegraph communications techniques and practices. Wireless telegraphy originated as a term to describe electrical signaling without the electric wires to connect the end points. The intent was to distinguish it from the conventional electric telegraph signaling to his students. By 1854, he was able to demonstrate a transmission across the Firth of Tay The Firth of Tay is a firth in Scotland between the council areas of Fife, Perth and Kinross, the City of Dundee and Angus, into which Scotland's largest river in terms of flow, the River Tay, empties from Dundee, Scotland Dundee (Scottish Gaelic: Dùn Dèagh) is the fourth-largest city in Scotland and, fully named as Dundee City, one of Scotland's 32 local government council areas. It lies on the north bank of the Firth of Tay, which feeds into the North Sea to Woodhaven Woodhaven used to be a small village between Newport-on-Tay and Wormit in Fife, Scotland but over the years due to expansion of both these villages it is now just the name for a harbour. During World War II the RAF had a flying boat station at Woodhaven, a distance of two miles (3 km), using water as the transmission medium.^[10] In December 1901, Guglielmo Marconi Marchese Guglielmo Marconi was an Italian inventor, best known for his development of a radiotelegraph system, which served as the foundation for the establishment of numerous affiliated companies worldwide. He shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun, "in recognition of their contributions to the development of established wireless communication between St. John's, Newfoundland St. John's is the provincial capital of Newfoundland and Labrador, Canada and located on the eastern tip of the Avalon Peninsula on the island of Newfoundland. St. John's is the most populous Census Metropolitan Area (CMA) in the province, it is the second largest CMA in the Atlantic Provinces after Halifax, and 20th Largest metropolitan area in (Canada) and Poldhu, Cornwall Poldhu is a small area in south Cornwall, England, UK, situated on the Lizard Peninsula it comprises Poldhu Point and Poldhu Cove. It lies on the coast west of Goonhilly Downs, with Mullion 2 km to the south and Porthleven 7 km to the north. Poldhu means "black pool" in Cornish (England), earning him the 1909 Nobel Prize in physics The Nobel Prize in Physics is awarded once a year by the Royal Swedish Academy of Sciences. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the others are the Nobel Prize in chemistry, Nobel Prize in literature, Nobel Peace Prize, and Nobel Prize in physiology or medicine. The first Nobel (which he shared with Karl Braun Karl Ferdinand Braun was a German inventor, physicist and Nobel laureate in physics (1909). Braun contributed significantly to the development of the radio and TV technology).^[11] However small-scale radio communication had already been demonstrated in 1893 by Nikola Tesla Nikola Tesla was an inventor and a mechanical and electrical engineer. Tesla was an ethnic Serb born in the village of Smiljan, Vojna Krajina, in the territory of today's Croatia. He was a subject of the Austrian Empire by birth and later became an American citizen. Tesla is often described as an important scientist and inventor of the modern age, in a presentation to the National Electric Light Association.^[12]

On 25 March 1925, John Logie Baird John Logie Baird was a Scottish engineer and inventor of the world's first working television system, also the world's first ever colour broadcast. Although Baird's electromechanical system was eventually displaced by purely electronic systems (such as those of Vladimir Zworykin and Philo Farnsworth), his early successes demonstrating working was able to demonstrate the transmission of moving pictures at the London department store Selfridges Selfridges is a chain of high end department stores in the United Kingdom. It was founded by Harry Gordon Selfridge. The flagship store in London's Oxford Street is the second largest shop in the UK and was opened on 15 March 1909. More recently, three other stores have been opened; in Trafford, Greater Manchester (1998), in Manchester City Centre'. Baird's device relied upon the Nipkow disk A Nipkow disk , also known as scanning disk, is a mechanical, geometrically operating image scanning device, invented by Paul Gottlieb Nipkow. This scanning disk was a fundamental component in mechanical television through the 1920s and thus became known as the mechanical television. It formed the basis of experimental broadcasts done by the British Broadcasting Corporation beginning 30 September 1929.^[13] However, for most of the twentieth century televisions depended upon the cathode ray tube invented by Karl Braun. The first version of such a television to show promise was produced by Philo Farnsworth and demonstrated to his family on 7 September 1927.^[14]

Computer networks and the Internet

On 11 September 1940, George Stibitz was able to transmit problems using teletype to his Complex Number Calculator in New York and receive the computed results back at Dartmouth College in New Hampshire.^[15] This configuration of a centralized computer or mainframe with remote dumb terminals remained popular throughout the 1950s. However, it was not until the 1960s that researchers started to investigate packet switching — a technology that would allow chunks of data to be sent to different computers without first passing through a centralized mainframe. A four-node network emerged on 5 December 1969; this network would become ARPANET, which by 1981 would consist of 213 nodes.^[16]

ARPANET's development centred around the Request for Comment process and on 7 April 1969, RFC 1 was published. This process is important because ARPANET would eventually merge with other networks to form the Internet and many of the protocols the Internet relies upon today were specified through the Request for Comment process. In September 1981, RFC 791 introduced the Internet Protocol v4 (IPv4) and RFC 793 introduced the Transmission Control Protocol (TCP) — thus creating the TCP/IP protocol that much of the Internet relies upon today.

However, not all important developments were made through the Request for Comment process. Two popular link protocols for local area networks (LANs) also appeared in the 1970s. A patent for the token ring protocol was filed by Olof Soderblom on 29 October 1974 and a paper on the Ethernet protocol was published by Robert Metcalfe and David Boggs in the July 1976 issue of Communications of the ACM.^[17][18]

Key concepts

Etymology

The word telecommunication was adapted from the French word télécommunication. It is a compound of the Greek prefix tele- (τηλε-), meaning 'far off', and the Latin communicare, meaning 'to share'.[19] The French word télécommunication was coined in 1904 by French engineer and novelist Édouard Estaunié.[20]

A number of key concepts reoccur throughout the literature on modern telecommunication systems. Some of these concepts are discussed below.

Basic elements

A basic telecommunication system consists of three elements:

• a transmitter that takes information and converts it to a signal;
• a transmission medium that carries the signal; and,
• a receiver that receives the signal and converts it back into usable information.

For example, in a radio broadcast the broadcast tower is the transmitter, free space is the transmission medium and the radio is the receiver. Often telecommunication systems are two-way with a single device acting as both a transmitter and receiver or transceiver. For example, a mobile phone is a transceiver.^[21]

Telecommunication over a telephone line is called point-to-point communication because it is between one transmitter and one receiver. Telecommunication through radio broadcasts is called broadcast communication because it is between one powerful transmitter and numerous receivers.^[21]

Analogue or digital

Signals can be either analogue or digital. In an analogue signal, the signal is varied continuously with respect to the information. In a digital signal, the information is encoded as a set of discrete values (for example ones and zeros). During transmission the information contained in analogue signals will be degraded by noise. Conversely, unless the noise exceeds a certain threshold, the information contained in digital signals will remain intact. Noise resistance represents a key advantage of digital signals over analogue signals.^[22]

Networks

A network is a collection of transmitters, receivers and transceivers that communicate with each other. Digital networks consist of one or more routers that work together to transmit information to the correct user. An analogue network consists of one or more switches that establish a connection between two or more users. For both types of network, repeaters may be necessary to amplify or recreate the signal when it is being transmitted over long distances. This is to combat attenuation that can render the signal indistinguishable from noise.^[23]

Channels

A channel is a division in a transmission medium so that it can be used to send multiple streams of information. For example, a radio station may broadcast at 96.1 MHz while another radio station may broadcast at 94.5 MHz. In this case, the medium has been divided by frequency and each channel has received a separate frequency to broadcast on. Alternatively, one could allocate each channel a recurring segment of time over which to broadcast—this is known as time-division multiplexing and is sometimes used in digital communication.^[23]

Modulation

The shaping of a signal to convey information is known as modulation. Modulation can be used to represent a digital message as an analogue waveform. This is known as keying and several keying techniques exist (these include phase-shift keying, frequency-shift keying and amplitude-shift keying). Bluetooth, for example, uses phase-shift keying to exchange information between devices.^[24][25]

Modulation can also be used to transmit the information of analogue signals at higher frequencies. This is helpful because low-frequency analogue signals cannot be effectively transmitted over free space. Hence the information from a low-frequency analogue signal must be superimposed on a higher-frequency signal (known as the carrier wave) before transmission. There are several different modulation schemes available to achieve this (two of the most basic being amplitude modulation and frequency modulation). An example of this process is a DJ's voice being superimposed on a 96 MHz carrier wave using frequency modulation (the voice would then be received on a radio as the channel “96 FM”).^[26]

Society and telecommunication

Telecommunication has a significant social, cultural and economic impact on modern society. In 2006, estimates placed the telecommunication industry's revenue at $1.2 trillion (USD) or just under 3% of the gross world product (official exchange rate).^[27]

Economic impact

Microeconomics

On the microeconomic scale, companies have used telecommunication to help build global empires. This is self-evident in the case of online retailer Amazon.com but, according to academic Edward Lenert, even the conventional retailer Wal-Mart has benefited from better telecommunication infrastructure compared to its competitors.^[28] In cities throughout the world, home owners use their telephones to organize many home services ranging from pizza deliveries to electricians. Even relatively poor communities have been noted to use telecommunication to their advantage. In Bangladesh's Narshingdi district, isolated villagers use cell phones to speak directly to wholesalers and arrange a better price for their goods. In Cote d'Ivoire, coffee growers share mobile phones to follow hourly variations in coffee prices and sell at the best price.^[29]

Macroeconomics

On the macroeconomic scale, Lars-Hendrik Röller and Leonard Waverman suggested a causal link between good telecommunication infrastructure and economic growth.^[30] Few dispute the existence of a correlation although some argue it is wrong to view the relationship as causal.^[31]

Because of the economic benefits of good telecommunication infrastructure, there is increasing worry about the inequitable access to telecommunication services amongst various countries of the world—this is known as the digital divide. A 2003 survey by the International Telecommunication Union (ITU) revealed that roughly one-third of countries have less than 1 mobile subscription for every 20 people and one-third of countries have less than 1 fixed line subscription for every 20 people. In terms of Internet access, roughly half of all countries have less than 1 in 20 people with Internet access. From this information, as well as educational data, the ITU was able to compile an index that measures the overall ability of citizens to access and use information and communication technologies.^[32] Using this measure, Sweden, Denmark and Iceland received the highest ranking while the African countries Niger, Burkina Faso and Mali received the lowest.^[33]

Social impact

Telecommunication is playing an increasingly important role in social relationships. In recent years, the popularity of social networking sites has increased dramatically. These sites allow users to communicate with each other as well as post photographs, events and profiles for others to see. The profiles can list a person's age, interests, sexuality and relationship status. In this way, these sites can play important role in everything from organising social engagements to courtship.^[34]

Prior to social networking sites, technologies like SMS and the telephone also had a significant impact on social interactions. In 2000, market research group Ipsos MORI reported that 81% of 15 to 24 year-old SMS users in the United Kingdom had used the service to coordinate social arrangements and 42% to flirt.^[35]

Other impacts

In cultural terms, telecommunication has increased the public's ability to access to music and film. With television, people can watch films they have not seen before in their own home without having to travel to the video store or cinema. With radio and the internet, people can listen to music they have not heard before without having to travel to the music store.

Telecommunication has also transformed the way people receive their news. A survey by the non-profit Pew Internet and American Life Project found that when just over 3,000 people living in the United States were asked where they got their news "yesterday", more people said television or radio than newspapers. The results are summarised in the following table (the percentages add up to more than 100% because people were able to specify more than one source).^[36]

Local TV	National TV	Radio	Local paper	Internet	National paper
59%	47%	44%	38%	23%	12%

Telecommunication has had an equally significant impact on advertising. TNS Media Intelligence reported that in 2007, 58% of advertising expenditure in the United States was spent on mediums that depend upon telecommunication.^[37] The results are summarised in the following table.

	Internet	Radio	Cable TV	Syndicated TV	Spot TV	Network TV	Newspaper	Magazine	Outdoor	Total
Percent	7.6%	7.2%	12.1%	2.8%	11.3%	17.1%	18.9%	20.4%	2.7%	100%
Dollars	$11.31 billion	$10.69 billion	$18.02 billion	$4.17 billion	$16.82 billion	$25.42 billion	$28.22 billion	$30.33 billion	$4.02 billion	$149 billion

Modern operation

Telephone

Optical fiber provides cheaper bandwidth for long distance communication

In an analogue telephone network, the caller is connected to the person he wants to talk to by switches at various telephone exchanges. The switches form an electrical connection between the two users and the setting of these switches is determined electronically when the caller dials the number. Once the connection is made, the caller's voice is transformed to an electrical signal using a small microphone in the caller's handset. This electrical signal is then sent through the network to the user at the other end where it is transformed back into sound by a small speaker in that person's handset. There is a separate electrical connection that works in reverse, allowing the users to converse.^[38][39]

The fixed-line telephones in most residential homes are analogue — that is, the speaker's voice directly determines the signal's voltage. Although short-distance calls may be handled from end-to-end as analogue signals, increasingly telephone service providers are transparently converting the signals to digital for transmission before converting them back to analogue for reception. The advantage of this is that digitized voice data can travel side-by-side with data from the Internet and can be perfectly reproduced in long distance communication (as opposed to analogue signals that are inevitably impacted by noise).

Mobile phones have had a significant impact on telephone networks. Mobile phone subscriptions now outnumber fixed-line subscriptions in many markets. Sales of mobile phones in 2005 totalled 816.6 million with that figure being almost equally shared amongst the markets of Asia/Pacific (204 m), Western Europe (164 m), CEMEA (Central Europe, the Middle East and Africa) (153.5 m), North America (148 m) and Latin America (102 m).^[40] In terms of new subscriptions over the five years from 1999, Africa has outpaced other markets with 58.2% growth.^[41] Increasingly these phones are being serviced by systems where the voice content is transmitted digitally such as GSM or W-CDMA with many markets choosing to depreciate analogue systems such as AMPS.^[42]

There have also been dramatic changes in telephone communication behind the scenes. Starting with the operation of TAT-8 in 1988, the 1990s saw the widespread adoption of systems based on optic fibres. The benefit of communicating with optic fibres is that they offer a drastic increase in data capacity. TAT-8 itself was able to carry 10 times as many telephone calls as the last copper cable laid at that time and today's optic fibre cables are able to carry 25 times as many telephone calls as TAT-8.^[43] This increase in data capacity is due to several factors: First, optic fibres are physically much smaller than competing technologies. Second, they do not suffer from crosstalk which means several hundred of them can be easily bundled together in a single cable.^[44] Lastly, improvements in multiplexing have led to an exponential growth in the data capacity of a single fibre.^[45][46]

Assisting communication across many modern optic fibre networks is a protocol known as Asynchronous Transfer Mode (ATM). The ATM protocol allows for the side-by-side data transmission mentioned in the second paragraph. It is suitable for public telephone networks because it establishes a pathway for data through the network and associates a traffic contract with that pathway. The traffic contract is essentially an agreement between the client and the network about how the network is to handle the data; if the network cannot meet the conditions of the traffic contract it does not accept the connection. This is important because telephone calls can negotiate a contract so as to guarantee themselves a constant bit rate, something that will ensure a caller's voice is not delayed in parts or cut-off completely.^[47] There are competitors to ATM, such as Multiprotocol Label Switching (MPLS), that perform a similar task and are expected to supplant ATM in the future.^[48]

Radio and television

Digital television standards and their adoption worldwide.

In a broadcast system, a central high-powered broadcast tower transmits a high-frequency electromagnetic wave to numerous low-powered receivers. The high-frequency wave sent by the tower is modulated with a signal containing visual or audio information. The antenna of the receiver is then tuned so as to pick up the high-frequency wave and a demodulator is used to retrieve the signal containing the visual or audio information. The broadcast signal can be either analogue (signal is varied continuously with respect to the information) or digital (information is encoded as a set of discrete values).^[21][49]

The broadcast media industry is at a critical turning point in its development, with many countries moving from analogue to digital broadcasts. This move is made possible by the production of cheaper, faster and more capable integrated circuits. The chief advantage of digital broadcasts is that they prevent a number of complaints with traditional analogue broadcasts. For television, this includes the elimination of problems such as snowy pictures, ghosting and other distortion. These occur because of the nature of analogue transmission, which means that perturbations due to noise will be evident in the final output. Digital transmission overcomes this problem because digital signals are reduced to discrete values upon reception and hence small perturbations do not affect the final output. In a simplified example, if a binary message 1011 was transmitted with signal amplitudes [1.0 0.0 1.0 1.0] and received with signal amplitudes [0.9 0.2 1.1 0.9] it would still decode to the binary message 1011 — a perfect reproduction of what was sent. From this example, a problem with digital transmissions can also be seen in that if the noise is great enough it can significantly alter the decoded message. Using forward error correction a receiver can correct a handful of bit errors in the resulting message but too much noise will lead to incomprehensible output and hence a breakdown of the transmission.^[50][51]

In digital television broadcasting, there are three competing standards that are likely to be adopted worldwide. These are the ATSC, DVB and ISDB standards; the adoption of these standards thus far is presented in the captioned map. All three standards use MPEG-2 for video compression. ATSC uses Dolby Digital AC-3 for audio compression, ISDB uses Advanced Audio Coding (MPEG-2 Part 7) and DVB has no standard for audio compression but typically uses MPEG-1 Part 3 Layer 2.^[52][53] The choice of modulation also varies between the schemes. In digital audio broadcasting, standards are much more unified with practically all countries choosing to adopt the Digital Audio Broadcasting standard (also known as the Eureka 147 standard). The exception being the United States which has chosen to adopt HD Radio. HD Radio, unlike Eureka 147, is based upon a transmission method known as in-band on-channel transmission that allows digital information to "piggyback" on normal AM or FM analogue transmissions.^[54]

However, despite the pending switch to digital, analogue television remains transmitted in most countries. An exception is the United States that ended analogue television transmission on the 12th of June 2009^[55] after twice delaying the switch over deadline. For analogue television, there are three standards in use (see a map on adoption here). These are known as PAL, NTSC and SECAM. For analogue radio, the switch to digital is made more difficult by the fact that analogue receivers are a fraction of the cost of digital receivers.^[56][57] The choice of modulation for analogue radio is typically between amplitude modulation (AM) or frequency modulation (FM). To achieve stereo playback, an amplitude modulated subcarrier is used for stereo FM.

The Internet

The OSI reference model

The Internet is a worldwide network of computers and computer networks that can communicate with each other using the Internet Protocol.^[58] Any computer on the Internet has a unique IP address that can be used by other computers to route information to it. Hence, any computer on the Internet can send a message to any other computer using its IP address. These messages carry with them the originating computer's IP address allowing for two-way communication. In this way, the Internet can be seen as an exchange of messages between computers.^[59]

As of 2008^[update], an estimated 21.9% of the world population has access to the Internet with the highest access rates (measured as a percentage of the population) in North America (73.6%), Oceania/Australia (59.5%) and Europe (48.1%).^[60] In terms of broadband access, Iceland (26.7%), South Korea (25.4%) and the Netherlands (25.3%) led the world.^[61]

The Internet works in part because of protocols that govern how the computers and routers communicate with each other. The nature of computer network communication lends itself to a layered approach where individual protocols in the protocol stack run more-or-less independently of other protocols. This allows lower-level protocols to be customized for the network situation while not changing the way higher-level protocols operate. A practical example of why this is important is because it allows an Internet browser to run the same code regardless of whether the computer it is running on is connected to the Internet through an Ethernet or Wi-Fi connection. Protocols are often talked about in terms of their place in the OSI reference model (pictured on the right), which emerged in 1983 as the first step in an unsuccessful attempt to build a universally adopted networking protocol suite.^[62]

For the Internet, the physical medium and data link protocol can vary several times as packets traverse the globe. This is because the Internet places no constraints on what physical medium or data link protocol is used. This leads to the adoption of media and protocols that best suit the local network situation. In practice, most intercontinental communication will use the Asynchronous Transfer Mode (ATM) protocol (or a modern equivalent) on top of optic fibre. This is because for most intercontinental communication the Internet shares the same infrastructure as the public switched telephone network.

At the network layer, things become standardized with the Internet Protocol (IP) being adopted for logical addressing. For the World Wide Web, these “IP addresses” are derived from the human readable form using the Domain Name System (e.g. 72.14.207.99 is derived from www.google.com). At the moment, the most widely used version of the Internet Protocol is version four but a move to version six is imminent.^[63]

At the transport layer, most communication adopts either the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). TCP is used when it is essential every message sent is received by the other computer where as UDP is used when it is merely desirable. With TCP, packets are retransmitted if they are lost and placed in order before they are presented to higher layers. With UDP, packets are not ordered or retransmitted if lost. Both TCP and UDP packets carry port numbers with them to specify what application or process the packet should be handled by.^[64] Because certain application-level protocols use certain ports, network administrators can restrict Internet access by blocking the traffic destined for a particular port.

Above the transport layer, there are certain protocols that are sometimes used and loosely fit in the session and presentation layers, most notably the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols. These protocols ensure that the data transferred between two parties remains completely confidential and one or the other is in use when a padlock appears in the address bar of your web browser.^[65] Finally, at the application layer, are many of the protocols Internet users would be familiar with such as HTTP (web browsing), POP3 (e-mail), FTP (file transfer), IRC (Internet chat), BitTorrent (file sharing) and OSCAR (instant messaging).

Local area networks

Despite the growth of the Internet, the characteristics of local area networks (computer networks that run at most a few kilometres) remain distinct. This is because networks on this scale do not require all the features associated with larger networks and are often more cost-effective and efficient without them.

In the mid-1980s, several protocol suites emerged to fill the gap between the data link and applications layer of the OSI reference model. These were Appletalk, IPX and NetBIOS with the dominant protocol suite during the early 1990s being IPX due to its popularity with MS-DOS users. TCP/IP existed at this point but was typically only used by large government and research facilities.^[66] As the Internet grew in popularity and a larger percentage of traffic became Internet-related, local area networks gradually moved towards TCP/IP and today networks mostly dedicated to TCP/IP traffic are common. The move to TCP/IP was helped by technologies such as DHCP that allowed TCP/IP clients to discover their own network address — a functionality that came standard with the AppleTalk/IPX/NetBIOS protocol suites.^[67]

It is at the data link layer though that most modern local area networks diverge from the Internet. Whereas Asynchronous Transfer Mode (ATM) or Multiprotocol Label Switching (MPLS) are typical data link protocols for larger networks, Ethernet and Token Ring are typical data link protocols for local area networks. These protocols differ from the former protocols in that they are simpler (e.g. they omit features such as Quality of Service guarantees) and offer collision prevention. Both of these differences allow for more economic set-ups.^[68]

Despite the modest popularity of Token Ring in the 80's and 90's, virtually all local area networks now use wired or wireless Ethernet. At the physical layer, most wired Ethernet implementations use copper twisted-pair cables (including the common 10BASE-T networks). However, some early implementations used coaxial cables and some recent implementations (especially high-speed ones) use optic fibres.^[69] Where optic fibre is used, the distinction must be made between multi-mode fibre and single-mode fibre. Multi-mode fibre can be thought of as thicker optical fibre that is cheaper to manufacture but that suffers from less usable bandwidth and greater attenuation (i.e. poor long-distance performance).^[70]

Telecommunication by region

Telecommunications in Europe Sovereign states Albania · Andorra · Armenia1 · Austria · Azerbaijan2 · Belarus · Belgium · Bosnia and Herzegovina · Bulgaria · Croatia · Cyprus1 · Czech Republic · Denmark · Estonia · Finland · France · Georgia2 · Germany · Greece · Hungary · Iceland · Ireland · Italy · Kazakhstan3 · Latvia · Liechtenstein · Lithuania · Luxembourg · Republic of Macedonia · Malta · Moldova · Monaco · Montenegro · Netherlands · Norway · Poland · Portugal · Romania · Russia3 · San Marino · Serbia · Slovakia · Slovenia · Spain · Sweden · Switzerland · Turkey3 · Ukraine · United Kingdom (England • Northern Ireland • Scotland • Wales) Other entities European Union · Sovereign Military Order of Malta Dependencies, autonomies, other territories Abkhazia 2 · Adjara1 · Adygea · Akrotiri and Dhekelia · Åland · Azores · Bashkortostan · Catalonia · Chechnya · Chuvashia · Crimea · Dagestan · Faroe Islands · Gagauzia · Gibraltar · Guernsey · Ingushetia · Jan Mayen · Jersey · Kabardino-Balkaria · Kalmykia · Karachay-Cherkessia · Republic of Karelia · Komi Republic · Kosovo · Madeira · Isle of Man · Mari El · Mordovia · Nagorno-Karabakh1 · Nakhchivan1 · North Ossetia-Alania · Northern Cyprus1 · South Ossetia 2 · Svalbard · Tatarstan · Transnistria · Udmurtia · Vojvodina Italics indicates an unrecognised or partially recognised country. 1 Entirely in Asia, but historically considered European. 2 Partially or entirely in Asia, depending on the border definitions. 3 Transcontinental country.

Telecommunications in North America Sovereign states Antigua and Barbuda · Bahamas · Barbados · Belize · Canada · Costa Rica · Cuba · Dominica · Dominican Republic · El Salvador · Grenada · Guatemala · Haiti · Honduras · Jamaica · Mexico · Nicaragua · Panama1 · Saint Kitts and Nevis · Saint Lucia · Saint Vincent and the Grenadines · Trinidad and Tobago1 · United States Dependencies and other territories Anguilla · Aruba1 · Bermuda · British Virgin Islands · Cayman Islands · Greenland · Guadeloupe · Martinique · Montserrat · Navassa Island · Netherlands Antilles1 · Puerto Rico · Saint Barthélemy · Saint Martin · Saint Pierre and Miquelon · Turks and Caicos Islands · United States Virgin Islands 1 Territories also in or commonly considered to be part of South America.

Telecommunications in South America Sovereign states Argentina · Bolivia · Brazil · Chile · Colombia · Ecuador · Guyana · Panama1 · Paraguay · Peru · Suriname · Trinidad and Tobago1 · Uruguay · Venezuela Dependencies Aruba1 / Netherlands Antilles1 (Netherlands) · Falkland Islands / South Georgia and the South Sandwich Islands (UK) 2 / French Guiana (France) 1 Territories also in or commonly considered to be part of North America and/or Central America. 2 Territories also in or commonly considered to be part of Antarctica.

Telecommunications in Oceania Sovereign states Australia · East Timor1 · Fiji · Indonesia1 · Kiribati · Papua New Guinea · Marshall Islands · Federated States of Micronesia · Nauru · New Zealand · Palau · Samoa · Solomon Islands · Tonga · Tuvalu · Vanuatu Dependencies and other territories American Samoa · Christmas Island · Cocos (Keeling) Islands · Cook Islands · French Polynesia · Guam · Hawaii · New Caledonia · Niue · Norfolk Island · Northern Mariana Islands · Pitcairn Islands · Tokelau · Wallis and Futuna 1 Transcontinental country.

Telecommunications in Africa Sovereign states Algeria · Angola · Benin · Botswana · Burkina Faso · Burundi · Cameroon · Cape Verde · Central African Republic · Chad · Comoros · Democratic Republic of the Congo · Republic of the Congo · Côte d'Ivoire (Ivory Coast) · Djibouti · Egypt1 · Equatorial Guinea · Eritrea · Ethiopia · Gabon · The Gambia · Ghana · Guinea · Guinea-Bissau · Kenya · Lesotho · Liberia · Libya · Madagascar · Malawi · Mali · Mauritania · Mauritius · Morocco · Mozambique · Namibia · Niger · Nigeria · Rwanda · São Tomé and Príncipe · Senegal · Seychelles · Sierra Leone · Somalia · South Africa · Sudan · Swaziland · Tanzania · Togo · Tunisia · Uganda · Zambia · Zimbabwe Dependencies, autonomies, other territories Canary Islands / Ceuta / Melilla (Spain) · Madeira (Portugal) · Mayotte / Réunion (France) · Puntland · St. Helena (UK) · Socotra (Yemen) · Somaliland · Southern Sudan · Western Sahara · Zanzibar (Tanzania) Italics indicate an unrecognised or partially recognised country. 1 Transcontinental country.

Telecommunications in Asia Sovereign states Afghanistan · Armenia1 · Azerbaijan1 · Bahrain · Bangladesh · Bhutan · Brunei · Burma2 · Cambodia · People's Republic of China · Cyprus1 · East Timor3 · Egypt4 · Georgia4 · India · Indonesia · Iran · Iraq · Israel · Japan · Jordan · Kazakhstan4 · North Korea · South Korea · Kuwait · Kyrgyzstan · Laos · Lebanon · Malaysia · Maldives · Mongolia · Nepal · Oman · Pakistan · Philippines · Qatar · Russia4 · Saudi Arabia · Singapore · Sri Lanka · Syria · Tajikistan · Republic of China5 · Thailand · Turkey4 · Turkmenistan · United Arab Emirates · Uzbekistan · Vietnam · Yemen Dependencies, autonomies, other territories Aceh · Adjara1 · Abkhazia1 · Akrotiri and Dhekelia · Altai · British Indian Ocean Territory · Buryatia · Christmas Island · Cocos (Keeling) Islands · Guangxi · Hong Kong · Inner Mongolia · Iraqi Kurdistan · Jakarta · Khakassia · Macau · Nagorno-Karabakh · Nakhchivan · Ningxia · Northern Cyprus · Palestine (Gaza Strip · West Bank) · Papua · Sakha · South Ossetia1 · Tibet · Tuva · West Papua · Xinjiang · Yogyakarta Italics indicates an unrecognised or partially recognised country. 1 Sometimes included in Europe, depending on the border definitions. 2 Officially known as Myanmar. 3 Sometimes included in Oceania, and also known as Timor-Leste. 4 Transcontinental country. 5 Commonly known as Taiwan.

Telecommunications in the Caribbean Anguilla · Antigua and Barbuda · Aruba · Bahamas · Barbados · British Virgin Islands · Cayman Islands · Cuba · Dominica · Dominican Republic · Grenada · Guadeloupe · Haiti · Jamaica · Martinique · Montserrat · Netherlands Antilles · Puerto Rico · St. Barthélemy · St. Kitts and Nevis · St. Lucia · St. Martin · St. Vincent and the Grenadines · Trinidad and Tobago · Turks and Caicos Islands · U.S. Virgin Islands Belize • Bermuda · Colombia · Costa Rica • French Guiana • Guatemala • Guyana • Honduras • Mexico • Nicaragua • Panama • Suriname · Venezuela ·

See also

Telecommunication portal

• Outline of telecommunication

References

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Further reading

• OECD, Universal Service and Rate Restructuring in Telecommunications, Organisation for Economic Co-operation and Development (OECD) Publishing, 1991. ISBN 92-64-13497-2

External links

Find more about Telecommunication on Wikipedia's sister projects: Definitions from Wiktionary

Textbooks from Wikibooks Quotations from Wikiquote Source texts from Wikisource Images and media from Commons News stories from Wikinews

Learning resources from Wikiversity

• ATIS Telecom Glossary
• Communications Engineering Tutorials
• Federal Communications Commission
• IEEE Communications Society
• International Telecommunication Union
• Ericsson's Understanding Telecommunications at archive.org (Ericsson removed the book from their site in Sep 2005)

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