wk1 intro to datacomm

8/10/2019 Wk1 INTRO to DataComm

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Introduction to Data

Communications


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Why Have Data

Communcation Networks? Data Communication networks were

developed to allow users to share

information and resources.

They allow information to be sent more

quickly, more accurately and at less costthan was possible before their existence.


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The Data Communication

Explosion In the last two decades, the growth of

digital data communication networks has

been phenomenal - and not just in thedevelopment of the Internet!

Many traditional telephone systems have

converted to using digital datacommunication networks behind the scenes.

Cellular (portable) telephones use digital

data communication networks


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How is Data Communication

Used? There are so many uses for data

communication that it is impossible to list

them all in a single lecture. Here are just afew examples:

Communicating with friends, relatives and

associates using telephones, email.Accessing information for research, news,

entertainment or simply curiosity.

Controlling remote devices such as robots.


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Where is Data

Communication Used? Data communications is becoming all

pervading. Like computers, we are

increasingly seeing data communications allaround us. Here a some examples:

In education it is used to disseminate teaching

material. In medicine it is used to allow specialists to

diagnose the ailments of distant patients.

In science it is used to share ideas and insights.


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Data Communication in

Business Data communication is becoming

increasingly important in business.

It is used to communicate with associates andkeep them informed of situations and events.

It is used to keep customers informed of

products, services and promotions.

It is used to improve customer service.

It is used to maintain control over finances,

stock and manufacturing systems.


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History of Data

Communication - Semaphore

Communication has always been vital to the

growth and development of human society.

One major problem confronted earlysocieties - how to communicate over large

distances.

One solution was to use either hand signalsor mechanically operated signals known as

semaphore. This, however, required each

station to be in sight of the next.


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History of Data

Communication - Electrical

In the 19th century, a system using

electricity was devised. The first telegraph

lines were opened in 1843 betweenPaddington and Slough by the Great

Western Railway.

In 1872-6, Alexander Graham Bell invented

the telephone. The first commercial

telephone lines were installed in 1877.


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History of Data

Communication - Radio

Guglielmo Marconi constructed the first

practical radio telegraph and, in 1901, he

succeeded in transmitting a radio signalacross the Atlantic.

In the first part of the 20th century, radioevolved and became increasingly important

for long distance communication.


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History of Data

Communication - T.V.

In 1926, John Logi Baird gave the first

demonstration of the television.

The BBC made its first experimental TV

broadcast in 1929 (it had 30 scan lines).

In the near future, analogue TV signals will

be replaced by digital signals.


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History of Data

Communication - Computer

In 1940, Bell laboratories began

experimenting with a communications

system using the COMPLEX computer.This was the forerunner of the

teletypewriter.

In 1954, IBM introduced a system calledRemote Job Entry (RJE) that allowed a

terminal to forward records to a host

computer and receive reports back.


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History of Data

Communication - Satellite

In 1958, the US launched its first

communications satellite. It formed part of

an early warning radar system.

1963 saw the launch of the first

geosynchronous satellite, SYNCOMII. At adistance of 35,880 km (22,300 miles), such

a satellite appears stationary in the sky.


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History of Data

Communication - Microwave

In 1968, the first microwave radio system

was used.

Microwaves can be sent from one station toanother as long as they are in line of sight

(microwave can penetrate walls and fog).

The advantage of using microwave links isthat they are cheaper than installing a land

line.

Low power microwaves are used.


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History of Data

Communication Networks

In the late 1960s and early 1970s, networks

were not designed to allow users on

different networks to share information andresources (such as printers).

In the early 1970s, several groups began

developing the concept of internetworking.Internetworking allowed computers on

different networks to connect and exchange

information.


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History of Data


Internetworking was pioneered by the ITU-

T (International Telecommunication

Union), the ISO (International StandardsOrganization) and the developers of

ARPANET (Advance Research Projects

Agency Network). ARPANET was developed for the U.S.

Department of Defense as an attack resilient

communication system.


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History of Data


ARPANET was used primarily for Research

and Development purposes.

By the mid-1980s, ARPANET becamemore commonly known as the Internet.


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History of Data


Throughout the 1970s and 1980s, telephone

companies have been replacing their

analogue equipment with digital equipment.

This change has come about because digital

equipment has become cheaper, morereliable and more flexible than their

analogue counterparts.

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