Is telecommunication a word

Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems.^[1][2] It has its origin in the desire of humans for communication over a distance greater than that feasible with the human voice, but with a similar scale of expediency; thus, slow systems (such as postal mail) are excluded from the field.

The transmission media in telecommunication have evolved through numerous stages of technology, from beacons and other visual signals (such as smoke signals, semaphore telegraphs, signal flags, and optical heliographs), to electrical cable and electromagnetic radiation, including light. Such transmission paths are often divided into communication channels, which afford the advantages of multiplexing multiple concurrent communication sessions. Telecommunication is often used in its plural form.

Other examples of pre-modern long-distance communication included audio messages, such as coded drumbeats, lung-blown horns, and loud whistles. 20th- and 21st-century technologies for long-distance communication usually involve electrical and electromagnetic technologies, such as telegraph, telephone, television and teleprinter, networks, radio, microwave transmission, optical fiber, and communications satellites.

A revolution in wireless communication began in the first decade of the 20th century with the pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize in Physics in 1909, and other notable pioneering inventors and developers in the field of electrical and electronic telecommunications. These included Charles Wheatstone and Samuel Morse (inventors of the telegraph), Antonio Meucci and Alexander Graham Bell (some of the inventors and developers of the telephone, see Invention of the telephone), Edwin Armstrong and Lee de Forest (inventors of radio), as well as Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth (some of the inventors of television).

The early telecommunication networks were created with copper wires as the physical medium for signal transmission. For many years, these networks were used for basic phone services, namely voice and telegrams. Since the mid-1990s, as the internet has grown in popularity, voice has been gradually supplanted by data. This soon demonstrated the limitations of copper in data transmission, prompting the development of optics.^[3][4][5]

Etymology[edit]

Telecommunication is a compound noun of the Greek prefix tele- (τῆλε), meaning distant, far off, or afar,^[6] and the Latin verb communicare, meaning to share. Its modern use is adapted from the French,^[7] because its written use was recorded in 1904 by the French engineer and novelist Édouard Estaunié.^[8][9] Communication was first used as an English word in the late 14th century. It comes from Old French comunicacion (14c., Modern French communication), from Latin communicationem (nominative communicatio), noun of action from past participle stem of communicare, «to share, divide out; communicate, impart, inform; join, unite, participate in,» literally, «to make common,» from communis.»^[10]

History[edit]

At the 1932 Plenipotentiary Telegraph Conference and the International Radiotelegraph Conference in Madrid, the two organizations decided to merge to form the International Telecommunication Union (ITU).^[11] They defined telecommunication as «any telegraphic or telephonic communication of signs, signals, writing, facsimiles and sounds of any kind, by wire, wireless or other systems or processes of electric signaling or visual signaling (semaphores).»

The definition was later reconfirmed, according to Article 1.3 of the Radio Regulations (RR), telecommunication, which defined it as «Any transmission, emission or reception of signs, signals, writings, images and sounds or intelligence of any nature by wire, radio, optical, or other electromagnetic systems».

Beacons and pigeons[edit]

Homing pigeons have been used throughout history by different cultures. Pigeon post had Persian roots and was later used by the Romans to aid their military. Frontinus claimed Julius Caesar used pigeons as messengers in his conquest of Gaul.^[12]
The Greeks also conveyed the names of the victors at the Olympic Games to various cities using homing pigeons.^[13] In the early 19th century, the Dutch government used the system in Java and Sumatra. And in 1849, Paul Julius Reuter started a pigeon service to fly stock prices between Aachen and Brussels, a service that operated for a year until the gap in the telegraph link was closed.^[14]

In the Middle Ages, chains of beacons 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, when a beacon chain relayed a signal from Plymouth to London.^[15]

In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system (or semaphore line) between Lille and Paris.^[16] 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.^[17]

Telegraph and telephone[edit]

On July 25, 1837, the first commercial electrical telegraph was demonstrated by English inventor Sir William Fothergill Cooke and English scientist Sir Charles Wheatstone.^[18][19] Both inventors viewed their device as «an improvement to the [existing] electromagnetic telegraph» and not as a new device.^[20]

Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on September 2, 1837. His code was an important advance over Wheatstone’s signaling method. The first transatlantic telegraph cable was successfully completed on July 27, 1866, allowing transatlantic telecommunication for the first time.^[21]

The conventional telephone was patented by Alexander Bell in 1876. Elisha Gray also filed a caveat for it in 1876. Gray abandoned his caveat and because he did not contest Bell’s priority, the examiner approved Bell’s patent on March 3, 1876. Gray had filed his caveat for the variable resistance telephone, but Bell was the first to document the idea and test it in a telephone.[88]^[22] Antonio Meucci invented a device that allowed the electrical transmission of voice over a line nearly 30 years before in 1849, but his device was of little practical value because it relied on the electrophonic effect requiring users to place the receiver in their mouths to «hear.»^[23] The first commercial telephone services were set up by the Bell Telephone Company in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London.^[24][25]

Radio and television[edit]

In 1894, Italian inventor Guglielmo Marconi began developing a wireless communication using the then-newly discovered phenomenon of radio waves, showing by 1901 that they could be transmitted across the Atlantic Ocean.^[26] This was the start of wireless telegraphy by radio. On 17 December 1902, a transmission from the Marconi station in Glace Bay, Nova Scotia, Canada, became the world’s first radio message to cross the Atlantic from North America. In 1904, a commercial service was established to transmit nightly news summaries to subscribing ships, which incorporated them into their onboard newspapers.^[27]

World War I accelerated the development of radio for military communications. After the war, commercial radio AM broadcasting began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated the development of radio for the wartime purposes of aircraft and land communication, radio navigation, and radar.^[28] Development of stereo FM broadcasting of radio began in the 1930s in the United States and the 1970s in the United Kingdom, displacing AM as the dominant commercial standard.^[29]

On March 25, 1925, John Logie Baird demonstrated the transmission of moving pictures at the London department store Selfridges. Baird’s device relied upon the Nipkow disk and thus became known as the mechanical television. It formed the basis of experimental broadcasts done by the British Broadcasting Corporation beginning on 30 September 1929.^[30] However, for most of the 20th century, televisions depended on 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.^[31] After World War II, interrupted experiments resumed and television became an important home entertainment broadcast medium.

Thermionic valves[edit]

The type of device known as a thermionic tube or thermionic valve uses thermionic emission of electrons from a heated cathode for a number of fundamental electronic functions such as signal amplification and current rectification.

The simplest vacuum tube, the diode invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—from the cathode to the anode. Adding one or more control grids within the tube enables the current between the cathode and anode to be controlled by the voltage on the grid or grids.^[32] These devices became a key component of electronic circuits for the first half of the 20th century and were crucial to the development of radio, television, radar, sound recording and reproduction, long-distance telephone networks, and analogue and early digital computers. While some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, leading to the creation of electronics.^[33]

In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, cheaper, and more efficient, reliable, and durable than thermionic tubes. Starting in the mid-1960s, thermionic tubes were replaced with the transistor. Thermionic tubes still have some applications for certain high-frequency amplifiers.

Computer networks and the Internet[edit]

On 11 September 1940, George Stibitz transmitted problems for his Complex Number Calculator in New York using a teletype and received the computed results back at Dartmouth College in New Hampshire.^[34] This configuration of a centralized computer (mainframe) with remote dumb terminals remained popular well into the 1970s. In the 1960s, researchers started to investigate packet switching, a technology that sends a message in portions to its destination asynchronously without passing it through a centralized mainframe. A four-node network emerged on 5 December 1969, constituting the beginnings of the ARPANET, which by 1981 had grown to 213 nodes.^[35] ARPANET eventually merged with other networks to form the Internet. While Internet development was a focus of the Internet Engineering Task Force (IETF) who published a series of Request for Comments documents, other networking advancements occurred in industrial laboratories, such as the local area network (LAN) developments of Ethernet (1983) and Token Ring (1984)^{[citation needed]}.

Growth of transmission capacity[edit]

The effective capacity to exchange information worldwide through two-way telecommunication networks grew from 281 petabytes (pB) of optimally compressed information in 1986 to 471 pB in 1993 to 2.2 exabytes (eB) in 2000 to 65 eB in 2007.^[36] This is the informational equivalent of two newspaper pages per person per day in 1986, and six entire newspapers per person per day by 2007.^[37] Given this growth, telecommunications play an increasingly important role in the world economy and the global telecommunications industry was about a $4.7 trillion sector in 2012.^[38][39] The service revenue of the global telecommunications industry was estimated to be $1.5 trillion in 2010, corresponding to 2.4% of the world’s gross domestic product (GDP).^[38]

Technical concepts[edit]

Modern telecommunication is founded on a series of key concepts that experienced progressive development and refinement in a period of well over a century:

Basic elements[edit]

Telecommunication technologies may primarily be divided into wired and wireless methods. Overall, a basic telecommunication system consists of three main parts that are always present in some form or another:

• A transmitter that takes information and converts it to a signal
• A transmission medium, also called the physical channel, that carries the signal (e.g. the «free space channel»)
• A receiver that takes the signal from the channel and converts it back into usable information for the recipient

In a radio broadcasting station, the station’s large power amplifier is the transmitter and the broadcasting antenna is the interface between the power amplifier and the free space channel. The free space channel is the transmission medium and the receiver’s antenna is the interface between the free space channel and the receiver. Next, the radio receiver is the destination of the radio signal, where it is converted from electricity to sound.

Telecommunication systems are occasionally «duplex» (two-way systems) with a single box of electronics working as both the transmitter and a receiver, or a transceiver (e.g., a mobile phone).^[40] The transmission electronics and the receiver electronics within a transceiver are quite independent of one another. This can be explained by the fact that radio transmitters contain power amplifiers that operate with electrical powers measured in watts or kilowatts, but radio receivers deal with radio powers measured in microwatts or nanowatts. Hence, transceivers have to be carefully designed and built to isolate their high-power circuitry and their low-power circuitry from each other to avoid interference.

Telecommunication over fixed lines is called point-to-point communication because it occurs between a transmitter and a receiver. Telecommunication through radio broadcasts is called broadcast communication because it occurs between a powerful transmitter and numerous low-power but sensitive radio receivers.^[40]

Telecommunications in which multiple transmitters and multiple receivers have been designed to cooperate and share the same physical channel are called multiplex systems. The sharing of physical channels using multiplexing often results in significant cost reduction. Multiplexed systems are laid out in telecommunication networks and multiplexed signals are switched at nodes through to the correct destination terminal receiver.

Analog versus digital communications[edit]

Communications signals can be sent by analog signals or digital signals via analog communication systems or digital communication systems. Analog signals vary continuously with respect to the information, while digital signals encode information as a set of discrete values (e.g., a set of ones and zeroes).^[41] During propagation and reception, information contained in analog signals is degraded by undesirable physical noise. Commonly, the noise in a communication system can be expressed as adding or subtracting from the desirable signal in a random way. This form of noise is called additive noise, with the understanding that the noise can be negative or positive at different instances.

Unless the additive noise disturbance exceeds a certain threshold, the information contained in digital signals will remain intact. Their resistance to noise represents a key advantage of digital signals over analog signals. However, digital systems fail catastrophically when noise exceeds the system’s ability to autocorrect. On the other hand, analog systems fail gracefully: as noise increases, the signal becomes progressively more degraded but still usable. Also, digital transmission of continuous data unavoidably adds quantization noise to the output. This can be reduced, but not eliminated, only at the expense of increasing the channel bandwidth requirement.

Communication channels[edit]

The term «channel» has two different meanings. In one meaning, a channel is the physical medium that carries a signal between the transmitter and the receiver. Examples of this include the atmosphere for sound communications, glass optical fibers for some kinds of optical communications, coaxial cables for communications by way of the voltages and electric currents in them, and free space for communications using visible light, infrared waves, ultraviolet light, and radio waves. Coaxial cable types are classified by RG type or «radio guide», terminology derived from World War II. The various RG designations are used to classify the specific signal transmission applications.^[42] This last channel is called the «free space channel». The sending of radio waves from one place to another has nothing to do with the presence or absence of an atmosphere between the two. Radio waves travel through a perfect vacuum just as easily as they travel through air, fog, clouds, or any other kind of gas.

The other meaning of the term «channel» in telecommunications is seen in the phrase communications channel, which is a subdivision of a transmission medium so that it can be used to send multiple streams of information simultaneously. For example, one radio station can broadcast radio waves into free space at frequencies in the neighborhood of 94.5 MHz (megahertz) while another radio station can simultaneously broadcast radio waves at frequencies in the neighborhood of 96.1 MHz. Each radio station would transmit radio waves over a frequency bandwidth of about 180 kHz (kilohertz), centered at frequencies such as the above, which are called the «carrier frequencies». Each station in this example is separated from its adjacent stations by 200 kHz, and the difference between 200 kHz and 180 kHz (20 kHz) is an engineering allowance for the imperfections in the communication system.

In the example above, the «free space channel» has been divided into communications channels according to frequencies, and each channel is assigned a separate frequency bandwidth in which to broadcast radio waves. This system of dividing the medium into channels according to frequency is called «frequency-division multiplexing». Another term for the same concept is «wavelength-division multiplexing», which is more commonly used in optical communications when multiple transmitters share the same physical medium.

Another way of dividing a communications medium into channels is to allocate each sender a recurring segment of time (a «time slot», for example, 20 milliseconds out of each second), and to allow each sender to send messages only within its own time slot. This method of dividing the medium into communication channels is called «time-division multiplexing» (TDM), and is used in optical fibre communication. Some radio communication systems use TDM within an allocated FDM channel. Hence, these systems use a hybrid of TDM and FDM.

Modulation[edit]

The shaping of a signal to convey information is known as modulation. Modulation can be used to represent a digital message as an analog waveform. This is commonly called «keying»—a term derived from the older use of Morse Code in telecommunications—and several keying techniques exist (these include phase-shift keying, frequency-shift keying, and amplitude-shift keying). The «Bluetooth» system, for example, uses phase-shift keying to exchange information between various devices.^[43][44] In addition, there are combinations of phase-shift keying and amplitude-shift keying which is called (in the jargon of the field) «quadrature amplitude modulation» (QAM) that are used in high-capacity digital radio communication systems.

Modulation can also be used to transmit the information of low-frequency analog signals at higher frequencies. This is helpful because low-frequency analog signals cannot be effectively transmitted over free space. Hence the information from a low-frequency analog signal must be impressed into 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 (AM) and frequency modulation (FM)]. An example of this process is a disc jockey’s voice being impressed into a 96 MHz carrier wave using frequency modulation (the voice would then be received on a radio as the channel «96 FM»).^[45] In addition, modulation has the advantage that it may use frequency division multiplexing (FDM).

Telecommunication networks[edit]

A telecommunications network is a collection of transmitters, receivers, and communications channels that send messages to one another. Some digital communications networks contain one or more routers that work together to transmit information to the correct user. An analog communications network consists of one or more switches that establish a connection between two or more users. For both types of networks, 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 the noise.^[46]
Another advantage of digital systems over analog is that their output is easier to store in memory, i.e. two voltage states (high and low) are easier to store than a continuous range of states.

Societal impact[edit]

Telecommunication has a significant social, cultural and economic impact on modern society. In 2008, estimates placed the telecommunication industry’s revenue at US$4.7 trillion or just under three percent of the gross world product (official exchange rate).^[38] Several following sections discuss the impact of telecommunication on society.

Microeconomics[edit]

On the microeconomic scale, companies have used telecommunications to help build global business empires. This is self-evident in the case of online retailer Amazon.com but, according to academic Edward Lenert, even the conventional retailer Walmart has benefited from better telecommunication infrastructure compared to its competitors.^[47] In cities throughout the world, home owners use their telephones to order and arrange a variety of home services ranging from pizza deliveries to electricians. Even relatively poor communities have been noted to use telecommunication to their advantage. In Bangladesh’s Narsingdi District, isolated villagers use cellular phones to speak directly to wholesalers and arrange a better price for their goods. In Côte d’Ivoire, coffee growers share mobile phones to follow hourly variations in coffee prices and sell at the best price.^[48]

Macroeconomics[edit]

On the macroeconomic scale, Lars-Hendrik Röller and Leonard Waverman suggested a causal link between good telecommunication infrastructure and economic growth.^[49][50] Few dispute the existence of a correlation although some argue it is wrong to view the relationship as causal.^[51]

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 a third of countries have fewer than one mobile subscription for every 20 people and one-third of countries have fewer than one land-line telephone subscription for every 20 people. In terms of Internet access, roughly half of all countries have fewer than one out of 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.^[52] Using this measure, Sweden, Denmark and Iceland received the highest ranking while the African countries Nigeria, Burkina Faso and Mali received the lowest.^[53]

[edit]

Telecommunication has played a significant role in social relationships. Nevertheless, devices like the telephone system were originally advertised with an emphasis on the practical dimensions of the device (such as the ability to conduct business or order home services) as opposed to the social dimensions. It was not until the late 1920s and 1930s that the social dimensions of the device became a prominent theme in telephone advertisements. New promotions started appealing to consumers’ emotions, stressing the importance of social conversations and staying connected to family and friends.^[54]

Since then the role that telecommunications has played in social relations has become increasingly important. 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, sexual preference and relationship status. In this way, these sites can play important role in everything from organising social engagements to courtship.^[55]

Prior to social networking sites, technologies like short message service (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.^[56]

Entertainment, news, and advertising[edit]

News source preference of Americans in 2006.^[57]

Local TV	59%
National TV	47%
Radio	44%
Local paper	38%
Internet	23%
National paper	12%
Survey permitted multiple answers

In cultural terms, telecommunication has increased the public’s ability to access 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 2006 survey (right table) of slightly more than 3,000 Americans by the non-profit Pew Internet and American Life Project in the United States the majority specified television or radio over newspapers.

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 media that depend upon telecommunication.^[58]

Advertising expenditures in US in 2007

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

Regulation[edit]

Many countries have enacted legislation which conforms to the International Telecommunication Regulations established by the International Telecommunication Union (ITU), which is the «leading UN agency for information and communication technology issues».^[59] In 1947, at the Atlantic City Conference, the ITU decided to «afford international protection to all frequencies registered in a new international frequency list and used in conformity with the Radio Regulation». According to the ITU’s Radio Regulations adopted in Atlantic City, all frequencies referenced in the International Frequency Registration Board, examined by the board and registered on the International Frequency List «shall have the right to international protection from harmful interference».^[60]

From a global perspective, there have been political debates and legislation regarding the management of telecommunication and broadcasting. The history of broadcasting discusses some debates in relation to balancing conventional communication such as printing and telecommunication such as radio broadcasting.^[61] The onset of World War II brought on the first explosion of international broadcasting propaganda.^[61] Countries, their governments, insurgents, terrorists, and militiamen have all used telecommunication and broadcasting techniques to promote propaganda.^[61][62] Patriotic propaganda for political movements and colonization started the mid-1930s. In 1936, the BBC broadcast propaganda to the Arab World to partly counter similar broadcasts from Italy, which also had colonial interests in North Africa.^[61] Modern political debates in telecommunication include the reclassification of broadband Internet service as a telecommunications service (also called net neutrality),^[63][64] regulation of phone spam,^[65][66] and expanding affordable broadband access.^[67]

Modern media[edit]

Worldwide equipment sales[edit]

According to data collected by Gartner^[68][69] and Ars Technica^[70] sales of main consumer’s telecommunication equipment worldwide in millions of units was:

Equipment / year	1975	1980	1985	1990	1994	1996	1998	2000	2002	2004	2006	2008
Computers	0	1	8	20	40	75	100	135	130	175	230	280
Cell phones	N/A	N/A	N/A	N/A	N/A	N/A	180	400	420	660	830	1000

Telephone[edit]

In a telephone network, the caller is connected to the person to whom they wish to talk 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.

As of 2015, the landline telephones in most residential homes are analog—that is, the speaker’s voice directly determines the signal’s voltage.^[71] Although short-distance calls may be handled from end-to-end as analog signals, increasingly telephone service providers are transparently converting the signals to digital signals for transmission. 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 analog 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).^[72] In terms of new subscriptions over the five years from 1999, Africa has outpaced other markets with 58.2% growth.^[73] 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 deprecate analog systems such as AMPS.^[74]

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 optical fibers. The benefit of communicating with optical fibers 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 optical fibre cables are able to carry 25 times as many telephone calls as TAT-8.^[75] This increase in data capacity is due to several factors: First, optical 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.^[76] Lastly, improvements in multiplexing have led to an exponential growth in the data capacity of a single fibre.^[77][78]

Assisting communication across many modern optical 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.^[79] 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.^[80][81]

Radio and television[edit]

In a broadcast system, the 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 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 analog (signal is varied continuously with respect to the information) or digital (information is encoded as a set of discrete values).^[40][82]

The broadcast media industry is at a critical turning point in its development, with many countries moving from analog 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 common to traditional analog broadcasts. For television, this includes the elimination of problems such as snowy pictures, ghosting and other distortion. These occur because of the nature of analog 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.^[83][84]

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.^[85][86] 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 is 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 analog transmissions.^[87]

However, despite the pending switch to digital, analog television remains being transmitted in most countries. An exception is the United States that ended analog television transmission (by all but the very low-power TV stations) on 12 June 2009^[88] after twice delaying the switchover deadline. Kenya also ended analog television transmission in December 2014 after multiple delays. For analog television, there were three standards in use for broadcasting color TV (see a map on adoption here). These are known as PAL (German designed), NTSC (American designed), and SECAM (French-designed). For analog radio, the switch to digital radio is made more difficult by the higher cost of digital receivers.^[89] The choice of modulation for analog radio is typically between amplitude (AM) or frequency modulation (FM). To achieve stereo playback, an amplitude modulated subcarrier is used for stereo FM, and quadrature amplitude modulation is used for stereo AM or C-QUAM.

Internet[edit]

The Internet is a worldwide network of computers and computer networks that communicate with each other using the Internet Protocol (IP).^[90] 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. The Internet is thus an exchange of messages between computers.^[91]

It is estimated that 51% of the information flowing through two-way telecommunications networks in the year 2000 were flowing through the Internet (most of the rest (42%) through the landline telephone). By 2007 the Internet clearly dominated and captured 97% of all the information in telecommunication networks (most of the rest (2%) through mobile phones).^[36] As of 2008, 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%).^[92] In terms of broadband access, Iceland (26.7%), South Korea (25.4%) and the Netherlands (25.3%) led the world.^[93]

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.^[94]

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 fiber. 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.^[95]

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 whereas 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 nor 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.^[96] Because certain application-level protocols use certain ports, network administrators can manipulate traffic to suit particular requirements. Examples are to restrict Internet access by blocking the traffic destined for a particular port or to affect the performance of certain applications by assigning priority.

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 data transferred between two parties remains completely confidential.^[97] 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 XMPP (instant messaging).

Voice over Internet Protocol (VoIP) allows data packets to be used for synchronous voice communications. The data packets are marked as voice type packets and can be prioritized by the network administrators so that the real-time, synchronous conversation is less subject to contention with other types of data traffic which can be delayed (i.e. file transfer or email) or buffered in advance (i.e. audio and video) without detriment. That prioritization is fine when the network has sufficient capacity for all the VoIP calls taking place at the same time and the network is enabled for prioritization i.e. a private corporate-style network, but the Internet is not generally managed in this way and so there can be a big difference in the quality of VoIP calls over a private network and over the public Internet.^[98]

Local area networks and wide area networks[edit]

Despite the growth of the Internet, the characteristics of local area networks (LANs)—computer networks that do not extend beyond 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. When they are not connected with the Internet, they also have the advantages of privacy and security. However, purposefully lacking a direct connection to the Internet does not provide assured protection from hackers, military forces, or economic powers. These threats exist if there are any methods for connecting remotely to the LAN.

Wide area networks (WANs) are private computer networks that may extend for thousands of kilometres. Once again, some of their advantages include privacy and security. Prime users of private LANs and WANs include armed forces and intelligence agencies that must keep their information secure and secret.

In the mid-1980s, several sets of communication protocols emerged to fill the gaps between the data-link layer and the application layer of the OSI reference model. These included AppleTalk, IPX, and NetBIOS with the dominant protocol set during the early 1990s being IPX due to its popularity with MS-DOS users. TCP/IP existed at this point, but it was typically only used by large government and research facilities.^[99]

As the Internet grew in popularity and its traffic was required to be routed into private networks, the TCP/IP protocols replaced existing local area network technologies. Additional technologies, such as DHCP, allowed TCP/IP-based computers to self-configure in the network. Such functions also existed in the AppleTalk/ IPX/ NetBIOS protocol sets.^[100]

Whereas Asynchronous Transfer Mode (ATM) or Multiprotocol Label Switching (MPLS) are typical data-link protocols for larger networks such as WANs; Ethernet and Token Ring are typical data-link protocols for LANs. 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 medium access control. Both of these differences allow for more economical systems.^[101]

Despite the modest popularity of Token Ring in the 1980s and 1990s, virtually all LANs now use either wired or wireless Ethernet facilities. At the physical layer, most wired Ethernet implementations use copper twisted-pair cables (including the common 10BASE-T networks). However, some early implementations used heavier coaxial cables and some recent implementations (especially high-speed ones) use optical fibers.^[102] When optic fibers are used, the distinction must be made between multimode fibers and single-mode fibers. Multimode fibers can be thought of as thicker optical fibers that are cheaper to manufacture devices for, but that suffer from less usable bandwidth and worse attenuation—implying poorer long-distance performance.^[103]

See also[edit]

References[edit]

Citations[edit]

Bibliography[edit]

• Goggin, Gerard, Global Mobile Media (New York: Routledge, 2011), p. 176. ISBN 978-0-415-46918-0.
• OECD, Universal Service and Rate Restructuring in Telecommunications, Organisation for Economic Co-operation and Development (OECD) Publishing, 1991. ISBN 92-64-13497-2.
• Wheen, Andrew. Dot-Dash to Dot.Com: How Modern Telecommunications Evolved from the Telegraph to the Internet (Springer, 2011).

External links[edit]

• International Teletraffic Congress
• International Telecommunication Union (ITU)
• ATIS Telecom Glossary
• Federal Communications Commission
• IEEE Communications Society
• International Telecommunication Union
• Ericsson’s Understanding Telecommunications at the Wayback Machine (archived 13 April 2004) (Ericsson removed the book from their site in September 2005)

Telecommunication is the transmission of signals over a distance for the purpose of communication. In modern times, this process typically involves the sending of electromagnetic waves by electronic transmitters, but in earlier years it may have involved the use of smoke signals, drums or semaphore. Today, telecommunication is widespread and devices that assist the process, such as the television, radio and telephone, are common in many parts of the world. There are also many networks that connect these devices, including computer networks, public telephone networks, radio networks and television networks. Computer communication across the Internet is one of many examples of telecommunication.

Telecommunication systems are generally designed by telecommunication engineers. Early inventors in the field include Alexander Graham Bell, Guglielmo Marconi, and John Logie Baird. Telecommunication is an important part of the world economy; this industry’s revenue has been placed at just under 3 percent of the gross world product.

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.’[1]

Basic elements

Each telecommunication system consists of three basic elements:

• a transmitter that takes information and converts it to a signal
• a transmission medium over which the signal is transmitted
• a receiver that receives the signal and converts it back into usable information

For example, consider a radio broadcast: In this case the broadcast tower is the transmitter, the radio is the receiver and the transmission medium is free space.

Each of the elements of the telecommunications system processes or carries an information-bearing signal. Each of the elements contributes undesired noise, so one of the figures of merit of a telecommunications system is its signal-to-noise ratio.

Often telecommunication systems are two-way and a single device acts as both a transmitter and receiver or transceiver. For example, a mobile phone is a transceiver. Telecommunication over a phone 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.^[2]

Analog or digital

Signals can either be analog 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, 1s and 0s). During transmission, the information contained in analog signals will be degraded by noise. Conversely, unless the noise exceeds a certain threshold, the information contained in digital signals will remain intact. This represents a key advantage of digital signals over analog signals.^[3]

Networks

A collection of transmitters, receivers or transceivers that communicate with each other is known as a network. Digital networks may consist of one or more routers that route data to the correct user. An analogue network may consist of one or more switches that establish a connection between two or more users. For both types of network, a repeater 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.^[4]

Channels

A channel is a division in a transmission medium so that it can be used to send multiple independent streams of data. For example, a radio station may broadcast at 96 MHz while another radio station may broadcast at 94.5 MHz. In this case the medium has been divided by frequency and each channel received a separate frequency to broadcast on. Alternatively one could allocate each channel a recurring segment of time over which to broadcast.^[4]

The above usage of channel refers to analog communications. In digital communications, a time slot in a sequence of bits is a traditional time-division multiplexing channel. More complex digital telecommunications systems called statistical multiplexing precedes the information with a channel identifier, so bandwidth need not be allocated to silent channels. Modern packet-switching, as in X.25 or the Internet Protocol (IP) is a more generalized version of statistical digital multiplexing.

Modulation

The shaping of a signal to convey information is known as modulation. Modulation is a key concept in telecommunications and is frequently used to impose the information of one signal on another. Modulation is 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, amplitude-shift keying and minimum-shift keying. Bluetooth, for example, uses phase-shift keying for exchanges between devices.^[5]

However, more relevant to earlier discussion, modulation is also used to boost the frequency of analogue signals. This is because a raw signal is often not suitable for transmission over long distances of free space due to its low frequencies. Hence its information must be superimposed on a higher frequency signal (known as a carrier wave) before transmission. There are several different modulation schemes available to achieve this—some 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”).^[6]

Society and telecommunication

Telecommunication is an important part of many modern societies. In 2006, estimates place the telecommunication industry’s revenue at $1.2 trillion or just under three percent of the gross world product.^[7] Good telecommunication infrastructure is widely acknowledged as important for economic success in the modern world on both the micro- and macroeconomic scale.

On the microeconomic scale, companies have used telecommunication to help build global empires, this is self-evident in the business of online retailer Amazon.com but even the conventional retailer Wal-Mart has benefited from superior telecommunication infrastructure compared to its competitors.^[8] In modern Western society, home owners often use their telephone 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.^[9] With respect to the macroeconomic scale, Lars-Hendrik Röller and Leonard Waverman suggested a causal link between good telecommunication infrastructure and economic growth in 2001.^[10] Few dispute the existence of a correlation although some argue it is wrong to view the relationship as causal.^[11]

Due to the economic benefits of good telecommunication infrastructure there is increasing worry about the digital divide. This stems from the fact that the world’s population does not have equal access to telecommunication systems. A 2003 survey by the International Telecommunication Union revealed that roughly one-third of countries have less than one mobile subscription for every 20 people and one-third of countries have less than one fixed line subscription for every 20 people. In terms of internet access, roughly half of countries have less than one in 20 people with internet access. From this information, as well as educational data, the ITU was able to compile a Digital Access Index^[12] that measures the overall ability of citizens to access and use information and communication technologies. Using this measure, countries such as Sweden, Denmark and Iceland receive the highest ranking while African countries such as Niger, Burkina Faso and Mali receive the lowest.^[13]

History

Early telecommunications

Early forms of telecommunication include smoke signals and drums. Drums were used by natives in Africa, New Guinea and South America whereas smoke signals were used by natives in North America and China. Contrary to what one might think, these systems were often used to do more than merely announce the presence of a camp.^[14][15]

In 1792, a French engineer, Claude Chappe, built the first fixed visual telegraphy (or semaphore) system between Lille and Paris.^[16] However semaphore as a communication system suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometers (six to nineteen miles). As a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880.^[17]

Telegraph and telephone

The first commercial electrical telegraph was constructed by Sir Charles Wheatstone and Sir William Fothergill Cooke and opened on April 9, 1839. Both Wheatstone and Cooke viewed their device as «an improvement to the [existing] electromagnetic telegraph» not as a new device.^[18]

Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on September 2, 1837. His code was an important advance over Wheatstone’s signaling method. The first transatlantic telegraph cable was successfully completed on July 27, 1866, allowing transatlantic telecommunication for the first time.^[19]

The conventional telephone was independently invented by Alexander Graham Bell and by Elisha Gray in 1876.^[20] Antonio Meucci in 1849 invented a device that allowed the electrical transmission of voice over a line. But Meucci’s device was of little practical value because it relied upon the electrophonic effect and thus required users to place the receiver in their mouth to “hear” what was being said. The first commercial telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven, Connecticut and London.^[21][22]

Radio and television

In 1832 James Lindsay gave a classroom demonstration of wireless telegraphy to his students. By 1854 he was able to demonstrate a transmission across the Firth of Tay from Dundee, Scotland to Woodhaven, a distance of two miles, using water as the transmission medium.^[23] In December 1901, Guglielmo Marconi established wireless communication between St. John’s, Newfoundland (Canada) and Poldhu, Cornwall (England), earning him the Nobel Prize in physics in 1909 (which he shared with Karl Braun).^[24] However, small-scale radio communication had already been demonstrated in 1893 by Nikola Tesla in a presentation to the National Electric Light Association.^[25]

On March 25, 1925, John Logie Baird was able to demonstrate the transmission of moving pictures at the London department store Selfridges. Baird’s device relied upon the Nipkow disk and thus became known as the mechanical television. It formed the basis of experimental broadcasts done by the British Broadcasting Corporation beginning September 30, 1929.^[26] 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 September 7, 1927. ^[27]

Computer networks and the Internet

On September 11, 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.^[28] 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 December 5, 1969; this network would become ARPANET, which by 1981 would consist of 213 nodes.^[29]

ARPANET’s development centered on the Request for Comment process and on April 7, 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 this 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 October 29, 1974.^[30] 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.^[31] These protocols are discussed in more detail in the next section.

Modern operation

Telephone

In a conventional wire telephone system, the caller is connected to the person he wants to talk to by the switches at various 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 transformed back into sound by a small speaker in that person’s handset. This electrical connection works both ways, allowing the users to converse.^[32]
The fixed-line telephones in most residential homes are analog—that is, the speaker’s voice wave directly determines the signal’s voltage. Although short-distance calls may be handled from end-to-end as analog signals, usually telephone service providers transparently convert the signals to digital for switching and transmission before converting them back to analogue for reception. The advantage of this is that digitized voice data can travel more cheaply, side-by-side with data from the internet and can be perfectly reproduced in long distance communication as opposed to analogue signals which 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 totaled 816.6 million with that figure being almost equally shared amongst the markets of Asia/Pacific (204 million), Western Europe (164 million), CEMEA (Central Europe, the Middle East and Africa) (153.5 million), North America (148 million) and Latin America (102 million).^[33] In terms of new subscriptions over the five years from 1999, Africa has outpaced other markets with 58.2 percent growth.^[34] 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 analog systems such as AMPS.^[35]

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 upon optic fibers. The benefit of communicating with optic fibers is that they offer a drastic increase in data capacity. TAT-8 itself was able to carry ten times as many telephone calls as the last copper cable laid at that time and today’s optic fiber cables are able to carry 25 times as many telephone calls as TAT-8.^[22] This drastic increase in data capacity is due to several factors. First, optic fibers 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.^[36] Lastly, improvements in multiplexing have lead to an exponential growth in the data capacity of a single fiber.^[37][38]

Assisting communication across these networks is a protocol known as Asynchronous Transfer Mode (ATM) that allows the side-by-side data transmission mentioned in the first paragraph. The importance of the ATM protocol is chiefly in its notion of establishing pathways for data through the network and associating a traffic contract with these pathways. 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 can not 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.^[39] 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.^[40]

Radio and television

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).^[41][42]

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 binary data 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.^[43]

In digital television broadcasting, there are three competing standards that are likely to be adopted worldwide. These are the ATSC, DVB and ISDB standards and 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.^[44] 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—this allows digital information to «piggyback» on normal AM or FM analog transmissions, avoiding the bandwidth allocation issues of Eureka 147 and therefore being strongly advocated National Association of Broadcasters, who felt there was a lack of new spectrum to allocate for the Eureka 147 standard. In terms of audio compression, DAB like DVB can use a variety of codecs but typically uses MPEG-1 Part 3 Layer 2 and HD Radio uses High-Definition Coding.

However, despite the pending switch to digital, analog receivers still remain widespread. Analog television is still transmitted in practically all countries. The United States had hoped to end analog broadcasts by December 31, 2006, however this was pushed back to February 17, 2009.^[45] For analog, there are three standards in use. These are known as PAL, NTSC and SECAM.

For analog radio, the switch to digital is made more difficult by the fact that analogue receivers cost a fraction of the cost of digital receivers. For example while you can get a good analog receiver for under US$20; a digital receiver will set you back at least US$75. 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 and quadrature amplitude modulation is used for stereo AM or C-QUAM.

The Internet

The Internet is a worldwide network of computers that mostly operates over the public switched telephone network. 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 communicate with any other computer and the Internet can therefore be viewed as an exchange of messages between computers.^[46] An estimated 16.9 percent of the world population has access to the Internet with the highest participation (measured as percent of population) in North America (69.7 percent), Oceania/Australia (53.5 percent) and Europe (38.9 percent).^[47] In terms of broadband access, countries such as Iceland (26.7 percent), South Korea (25.4 percent) and the Netherlands (25.3 percent) lead the world.^[48]

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 largely 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—a model that emerged in 1983 as the first step in a doomed attempt to build a universally adopted networking protocol suite.^[49] The model itself is outlined in the picture to the right. It is important to note that the Internet’s protocol suite, like many modern protocol suites, does not rigidly follow this model but can still be talked about in the context of this model.

For the Internet, the physical medium and data link protocol can vary several times as packets travel between client nodes. Though it is likely that the majority of the distance traveled will be using the Asynchronous Transfer Mode (ATM) data link protocol (or a modern equivalent) across optical fiber this is in no way guaranteed. A connection may also encounter data link protocols such as Ethernet, Wi-Fi and the Point-to-Point Protocol (PPP) and physical media such as twisted-pair cables and free space.

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 (for example, 72.14.207.99 is derived from www.google.com) using the Domain Name System. At the moment the most widely used version of the Internet Protocol is version four but a move to version six is imminent. At the transport layer most communication adopts either the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). Broadly speaking, 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 (this ordering also allows duplicate packets to be eliminated). 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 handed to on the client’s computer.^[50] Because certain application-level protocols use certain ports, network administrators can restrict Internet access by blocking or throttling traffic destined for a particular port.

Above the transport layer there are certain protocols that loosely fit in the session and presentation layers and are sometimes adopted, 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 at the bottom of your web browser. Another protocol that loosely fits in the session and presentation layers is the Real-time Transport Protocol (RTP) most notably used to stream QuickTime video.^[51] 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) and IRC (Internet chat) but also less common protocols such as BitTorrent (file sharing) and ICQ (instant messaging).

Local area networks

Despite the growth of the Internet, the characteristics of local area networks (computer networks that run over at most a few kilometers) remain distinct. This is because networks on this scale do not require all the features associated with larger-scale systems and are often more cost-effective and speedier 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.^[52] However as the Internet grew in popularity and a larger percentage of local area network traffic became Internet-related, LANs 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 introduced in RFC 2131 that allowed TCP/IP clients to discover their own network address—a functionality that came standard with the AppleTalk/IPX/NetBIOS protocol suites.

However it is at the data link layer that modern local area networks diverge from the Internet. Where as 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. The latter LAN protocols differ from the former protocols in that they are simpler (for example, they omit features such as quality of service guarantees) and offer collision prevention. Both of these differences allow for more economic setups. For example, omitting quality of service guarantees simplifies routers and the guarantees are not really necessary for local area networks because they tend not to carry real time communication (such as voice communication). Including collision prevention allows multiple clients (as opposed to just two) to share the same cable again reducing costs.^[53]

Despite Token Ring’s modest popularity in the 1980s and 1990s, with the advent of the twenty-first century, the majority of local area networks have now settled on Ethernet. At the physical layer most Ethernet implementations use copper twisted-pair cables (including the common 10BASE-T networks). Some early implementations used coaxial cables. And some implementations (especially high speed ones) use optical fibers. Optical fibers are also likely to feature prominently in the forthcoming 10-gigabit Ethernet implementations.^[54] Where optical fiber is used, the distinction must be made between multi-mode fiber and single-mode fiber. Multi-mode fiber can be thought of as thicker optical fiber that is cheaper to manufacture but that suffers from less usable bandwidth and greater attenuation (that is poorer performance).

See also

• Information technology
• Radio
• Telephone
• Television
• Internet

Notes

References

ISBN links support NWE through referral fees

• Coleniewski, Lillian, and Kitty Wilson Jarrett. 2006. Telecommunications Essentials: The Complete Global Source, 2nd ed. Boston, MA: Addison-Wesley Professional. ISBN 0321427610
• Dodd, Annabel Z. 2005. Essential Guide to Telecommunications, 4th ed. Upper Saddle River, NJ: Prentice Hall. ISBN 0131487256
• Hill Associates, Inc. 2001. Telecommunications: A Beginner’s Guide. Columbus, OH: McGraw-Hill Osborne Media. ISBN 0072193565

External links

All links retrieved February 26, 2023.

• International Telecommunication Union
• Federal Communications Commission.
• IEEE Communications Society
• ATIS Telecom Glossary

What is telecommunications (telecom)?

Telecommunications, also known as telecom, is the exchange of information over significant distances by electronic means and refers to all types of voice, data and video transmission. This is a broad term that includes a wide range of information-transmitting technologies and communications infrastructures, such as wired phones; mobile devices, such as cellphones; microwave communications; fiber optics; satellites; radio and television broadcasting; the internet; and telegraphs.

A complete, single telecommunications circuit consists of two stations, each equipped with a transmitter and a receiver. The transmitter and receiver at any station may be combined into a single device called a transceiver. The medium of signal transmission can be via electrical wire or cable — also known as copper — optical fiber, electromagnetic fields or light. The free space transmission and reception of data by means of electromagnetic fields is called wireless communications.

Types of telecommunications networks

The simplest form of telecommunications takes place between two stations, but it is common for multiple transmitting and receiving stations to exchange data among themselves. Such an arrangement is called a telecom network. The internet is the largest example of a telecommunications network. On a smaller scale, examples include the following:

• corporate and academic wide area networks (WANs);
• telephone networks;
• cellular networks;
• police and fire communications systems;
• taxi dispatch networks;
• groups of amateur (ham) radio operators; and
• broadcast networks.

Data is transmitted in a telecommunications circuit by means of an electrical signal called the carrier or the carrier wave. In order for a carrier to convey information, some form of modulation is required. The mode of modulation can be categorized broadly as analog or digital.

In analog modulation, some aspect of the carrier is varied in a continuous fashion. The oldest form of analog modulation is amplitude modulation (AM), which is still used in radio broadcasting at some frequencies. Digital modulation actually predates AM; the earliest form was Morse code. Modern telecommunications use internet protocols to carry data across underlying physical transmissions.

Telecommunications industry and service providers

Telecommunications systems are generally run by telecommunications service providers, also known as communications service providers. These providers historically offered telephone and related services and now offer a variety of internet and WAN services, as well as metropolitan area network (MAN) and global services.

In many countries, telecom service providers were primarily government-owned and -operated. That is no longer the case, and many have been privatized. The International Telecommunication Union (ITU) is the United Nations (UN) agency that administers telecommunications and broadcasting regulations, although most countries also have their own government agencies to set and enforce telecommunications guidelines. In the United States, the Federal Communications Commission (FCC) is the primary regulatory agency.

A large umbrella of companies provide different types of telecommunications services, including internet service providers (ISPs), telecom equipment providers, wireless service providers, radio and television broadcasters, cable companies, satellite television providers and managed service providers (MSPs).

The three main segments within the telecom industry are manufacturers of telecom equipment, telecom services and wireless communications. Within these sectors, telecom equipment — which includes customer equipment, such as routers and modems; transmission equipment, such as transmission lines and wireless semiconductors; and analog or digital public switching equipment — is the largest, and wireless communications is the smallest.

Large global service providers include the following:

• AT&T
• Verizon
• Nippon Telegraph and Telephone (NTT)
• China Mobile Limited
• Deutsche Telekom AG
• SoftBank Group
• China Telecom
• Telefónica SA
• Vodafone
• Qualcomm
• América Móvil

Use of smartphones, such as the iPhone,

was widespread by 2012.

Recently, service providers have been focusing on growing services, such as data and video, as opposed to voice communication services.

History of telecommunications

The word telecommunications comes from the Greek prefix tele-, which means «distant,» combined with the Latin word communicare, which means «to share.»

Important telecommunication technologies include the telegraph, telephone, radio, television, videotelephony, satellites, closed computer networks and the public internet.

• 1876. The first telephone was invented by Alexander Graham Bell. This early model required an interpreter, or telegrapher, at both ends. These first telephones were intercom systems, where two phones were connected directly.
• 1877. The invention of the switchboard exchange telephone system enabled any combination of two phone lines to connect and talk with each other.
• 1891. Dial telephones were invented, which bypassed the need for an operator on each call. This made it much quicker and easier to make calls via telephone.
• 1947. The transistor was invented, which led to the development of modern electronics, such as computers and calculators.
• 1948. Microwaves began to be used to transmit phone signals, in places where phone wires did not exist.
• 1960. Phones began to transition from mechanical switching to electronic switching, which enabled features such as voice messaging, speed dialing and caller ID.
• 1984. The Bell System, which provided AT&T with a near-monopoly over telecommunications services in the U.S., was broken up, opening up space for competition for other providers.
• 1984. Cellular and personal communications service (PCS) phone use, which offered mobile communications beyond two-way radio use, was introduced.
• 1990s. Use of the modern internet became widespread.
• 2000s and beyond. The first decade of the 2000s saw mobile phones grow increasingly sophisticated. By 2012, smartphone usage was widespread.

This was last updated in September 2021

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— Updated example sentences

Telecommunication Definition

The concept of telecommunication encloses all forms of remote communication. The word includes the Greek prefix tele, which means “distance” or “far.”

Therefore, telecom is a technique that involves the transmission of a message from one point to another. Usually this happens with the additional feature of being bidirectional. Telephony, radio, television, and data transmission through computers are part of the telecommunications sector.

Telecommunications includes many technologies such as radio, television, telephone, and mobile telephony. And also data communications, computer networks, the Internet, radio navigation, or GPS or telemetry.

Much of these technologies, which were born to meet military or scientific needs, have converged in others focused on non-specialized consumption called information and communication technologies. Nowadays technology has great importance in the daily lives of people, companies or institutions State and political.

The current trend is the communion of telecommunication with other disciplines such as computer science, electronics, and telematics. Which are, to design and offer these products and services, complex and multidisciplinary enough. It is sure, that the border between the contribution of these disciplines are not perceived by people.

Telecommunication Uses

The term telecommunications is already part of our daily vocabulary. We listen to it on television, read the news on the subject in the newspapers. And also listen to report about the sector almost every day. We have the feeling that it is something new that has come with the Internet and it is, although its origin is a bit older.

The word telecommunications is composed of two words that will help us find its meaning: technology and communications. Therefore, we define telecommunication as all types of transmission, emission, or reception of signals, whether written, images, sounds (conversation) through a wire, radio electricity, optical media, or electromagnetic systems (technology).

Compared to other disciplines, telecommunication has a more or less recent history. Today it is a term that is in full swing, but its history dates back to the 19th century.

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Uses Of Telecommunication In Modern Era

In general, the modern age of communication coincides with the invention of the printing press. This hypothesis is legitimate with two reservations: first of all, we must not forget that the technique of multiple reproductions, of images and writings previously recorded in stone or wood, first arose about 25 centuries ago.

Secondly, this invention served to encourage more, in an initial phase, the multiplication of knowledge and ideas (through books), than the development of information from the masses, which only appeared late.

In civilizations such as those in Egypt, China, India, and the Latin Greco world, the book was an invaluable repository of thought and knowledge.

The printing technique made its appearance in China in the ninth century and then developed in Europe in the fifteenth century. In the seventeenth century, after the books, came the pamphlets and, later, the newspapers.

Some of the first newspapers collected and disseminated information on trade, available raw materials, the movement of banks, and other similar issues, providing a service needed by the nascent capitalist system.

Modern cities are constituted in free spaces to approach the different forms of construction of public opinion. They bring together preachers, writers, and readers of very varied professional socio-condition. And which flood the streets, squares, markets, and theatres of the XVI-XVII centuries with words.

Other mediums such as,  journal, manual, and pamphlets which circulate from hand to hand and also transmitted lively. They become, together with scientific books, sermons or literary works, agents that create states of opinion.

Conclusion

Telecommunications have advanced a lot, by making our lives much simpler every day with their technological advances. These advances are an achievement for all humanity and they perform such as the first satellites in space.

But, in addition to all these benefits and complacency provided by telecommunications we live in a time in which telecommunications are essential for us. Since we have become very dependent on them, and this can become a massive disadvantage. And the day we do not have them we will be very vulnerable.

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