TELECOMMUNICATIONS: EXTENSION OF HANDS
DR. S.M. ALAM
Nov 22 - 28, 2010
Telecommunications is a general term for a vast array of technologies that send information over distances. Mobile phones, landlines, satellite phones, and voice over internet protocol are all telephony technologies - just one field of telecommunications. Radio, television, and networks are a few more examples of other telecommunications.
Telecommunication is the transmission of messages, over significant distances, for the purpose of communication. In earlier times, telecommunications involved the use of visual signals such as beacons, smoke, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded drumbeats, lung-blown horns, or sent by loud whistles, for example. In the modern age of electricity and electronics, telecommunications now also includes the use of electrical devices such as telegraphs, telephones, and teletypes, the use of radio and microwave communications, as well as fiber optics and their associated electronics, plus the use of the orbiting satellites and the internet.
The first breakthrough into modern electrical telecommunications came with the push to fully develop the telegraph starting in the 1830s. The use of these electrical means of communications exploded into use on all of the continents of the world during the 19th century, and these connected the continents via cables on the floors of the ocean. The use of the first three popular systems of electrical telecommunications, the telegraph, telephone and teletype, all required the use of conducting metal wires.
A revolution in wireless telecommunications began in the first decade of the 20th century, with Guglielmo Marconi winning the Nobel Prize in Physics in 1909 for his pioneering developments in wireless radio communications. Other highly notable pioneering inventors and developers in the field of electrical and electronic telecommunications include Charles Wheatstone and Samuel Morse (telegraph), Alexander Graham Bell (telephone), Nikola Tesla, Edwin Armstrong, and Lee de Forest (radio), as well as John Logie Baird and Philo Farnsworth (television). Telecommunications play an important role in the world economy and the worldwide telecommunication industry's revenue was estimated to be $3.85 trillion in 2008. The service revenue of the global telecommunications industry was estimated to be $1.7 trillion in 2008, and is expected to touch $2.7 trillion by 2013.
During 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 that signaled the arrival of the Spanish warships. In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system (or semaphore line) between Lille and Paris. However, semaphore systems suffered from the need for skilled operators and the expensive towers at intervals of ten to thirty kilometers (six to twenty miles). As a result of competition from the electrical telegraph, the last commercial semaphore line was abandoned in 1880.
Sir Charles Wheatstone and Sir William Fothergill Cooke constructed the first commercial electrical telegraph, and its use began on April 9, 1839. Both Wheatstone and Cooke viewed their device as "an improvement to the [already-existing, so-called] electromagnetic telegraph" not as a new device—businessman Samuel F.B. Morse and the physicist Joseph Henry of the United States developed their own, simpler version of the electrical telegraph, independently. Morse successfully demonstrated this system on September 2, 1837. Morse's most important technical contribution to this telegraph was the rather simple and highly efficient Morse Code, which was an important advance over complicated Wheatstone's telegraph system. The communications efficiency of the Morse Code anticipated that of the Huffman code in digital communications by over 100 years, but Morse had developed his code purely empirically, unlike Huffman, who gave a detailed theoretical explanation of how his method worked.
The first permanent transatlantic telegraph cable was successfully completed on 27 July 1866, allowing transatlantic electrical communication for the first time.
An earlier transatlantic cable had operated for a few months in 1859, and among other things, it carried messages of greeting back and forth between President James Buchanan of the United States and Queen Victoria of the United Kingdom. However, that transatlantic cable failed soon, and the project to lay a replacement line was delayed for five years by the American Civil War. Also, these transatlantic cables would have been completely incapable of carrying telephone calls. The first transatlantic telephone cable (which incorporated hundreds of electronic amplifiers) was not operational until 1956.
The conventional telephone now in use worldwide was first patented by Alexander Graham Bell in March 1876. That first patent by Bell was the master patent of the telephone, from which all other patents for electric telephone devices and features flowed. Credit for the invention of the electric telephone has been frequently disputed, and new controversies over the issue have arisen from time-to-time. As with other great inventions such as radio, television, the light bulb, and the digital computer, there were several inventors who did pioneering experimental work on voice transmission over a wire, and then they improved on each other's ideas. However, the key innovators were Alexander Graham Bell and Gardiner Greene Hubbard, who created the first telephone company, the Bell Telephone Company of the United States, which later evolved into American Telephone & Telegraph. 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, England.
In 1832, James Lindsay gave a classroom demonstration of wireless telegraphy via conductive water 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 about two miles (3km), again using water as the transmission medium.
In December 1901, Guglielmo Marconi established wireless communication between St. John's, Newfoundland and Poldhu, Cornwall (England), earning him the Nobel Prize in Physics for 1909, one which he shared with Karl Braun. However, small-scale radio communicatioz had already been demonstrated in 1893 by Nikola Tesla in a presentation before the National Electric Light Association. On March 25, 1925, John Logie Baird of England was able to demonstrate the transmission of moving pictures at the Selfridge's department store in London, England. Baird's system relied upon the fast-rotating Nipkow disk, and thus it became known as the mechanical television. It formed the basis of experimental broadcasts done by the British Broadcasting Corporation. However, for most of the 20th century, television systems were designed around the cathode ray tube, invented by Karl Braun. The first version of such an electronic television to show promise was produced by Philo Farnsworth of the United States, and it was demonstrated to his family in Idaho on September 7, 1927.
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. This configuration of a centralised computer or mainframe computer with remote "dumb terminals" remained popular throughout the 1950s and into the 60's. However, it was not until the 1960s that researchers started to investigate packet switching - a technology that allows chunks of data to be sent between different computers without first passing through a centralised mainframe. A four-node network emerged on December 5, 1969. This network soon became the Arpanet, which by 1981 would consist of 213 nodes.
On the macroeconomic scale, Lars-Hendrik Rˆller and Leonard Waverman suggested a causal link between good telecommunication infrastructure and economic growth. Few dispute the existence of a correlation although some argue it is wrong to view the relationship as causal. 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 fewer than one mobile subscription for every 20 people and one-third of countries have fewer than one landline 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. Using this measure, Sweden, Denmark and Iceland received the highest ranking while the African countries Nigeria, Burkina Faso, and Mali received the lowest.
Social impact: Telecommunications has played a significant role in social relationships. 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.
Optical fiber provides cheaper bandwidth for long distance communication. In an analog 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. The fixed-line telephones in most residential homes are analog ó that is, the speaker's voice directly determines the signal's voltage. 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 for transmission before converting them back to analog for reception.
The advantage of this is that digitised 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).
In terms of new subscriptions over the five years from 1999, Africa has outpaced other markets with 58.2 percent growth. Increasingly, these phones are being serviced by systems where the voice content is transmitted digitally such as GSM with many markets choosing to depreciate analog systems.
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. However, despite the pending switch to digital, analog television remains being transmitted in most countries. An exception is the United States.
For analog television, there are three standards in use for broadcasting color TV. These are known as PAL (British designed), NTSC (North American designed), and SECAM (French designed). (It is important to understand that these are the ways from sending color TV, and they do not have anything to do with the standards for black & white TV, which also vary from country to country.) For analog radio, the switch to digital radio is made more difficult by the fact that analog receivers are sold at a small fraction of the price of digital receivers. The choice of modulation for analog 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 is a worldwide network of computers and computer networks that can communicate with each other using the internet protocol. 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. As of 2008[update], an estimated 21.9 percent 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 percent), Oceania/Australia (59.5 percent) and Europe (48.1 percent). In terms of broadband access, Iceland (26.7 percent), South Korea (25.4 percent) and the Netherlands (25.3 percent) led the world. 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 layer.
Local Area Networks and Wide Area Networks: Despite the growth of the internet, the characteristics of local area networks ("LANs" - computer networks that do not extend beyond a few kilometers in size) 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 will not provide 100 percent protection of the LAN from hackers, military forces, or economic powers. These threats exist if there are any methods for connecting remotely to the LAN. There are also independent wide area networks ("WANs" - private computer networks that can and do extend for thousands of kilometers.) Once again, some of their advantages include their privacy, security, and complete ignoring of any potential hackers - who cannot "touch" them. Of course, prime users of private LANs and WANs include armed forces and intelligence agencies that must keep their information completely secure and secret.
Telecom sector is seeing exorbitant growth in Pakistan. The sector is said to be growing at a fast pace yearly. Mobile subscribers are 95.54 million as of July 2009. In fact, Pakistan has the highest mobile penetration rate in the South Asian region.
The telecom infrastructure is improving dramatically with foreign and domestic investments into fixed-line and mobile networks; fiber systems are being constructed throughout the country to aid in network growth. Major businesses have established their own private systems; since 1988, the government has promoted investment in the national telecommunications system on a priority basis, significantly increasing network capacity. There are currently seven million landline subscribers in the country.
Internet access has been available in Pakistan since the early 1990s. PTCL started offering access via the nationwide local call network in 1995. By early 2006, internet penetration remained low. But, the numbers are growing. The country has been pursuing an aggressive IT policy, aimed at boosting Pakistan's drive for economic modernisation and creating an exportable software industry. Recently, PTCL has started offering free dial-up internet service to all its landline subscribers. Broadband access is now available in the major cities. Also, wireless broadband internet has been introduced by the WLL Networks in many major cities. Most Pakistani companies, educational institutes and government departments maintain web sites.