Telecommunications And Computer Networks

Telecommunications and Computer networks

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Telecommunication Communication of information by electronic means over some distance

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Telecommunication Components  Computers

 to process information

 Input output devices

 to send or receive data

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Telecommunication Components  Communications channels

 links

between sending and receiving devices to transmit data

 use various transmission media  telephone lines, coaxial cables, twisted wire cables, fiber optic cables, and wireless media 4

Telecommunication Components  communications processes

modems, multiplexes, NICs  provide support functions 

 communications software

 control communication

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Twisted wire cables 

consisted of pairs of twisted copper wire



used for both analogue and digital transmission



low in cost



low in transmission speed 6

Twisted wire cables Useful for local and wide are networks

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Coaxial Cable  A thick insulated copper wire  Can transmit large volumes of data quickly  Faster and more interference free medium  Speed up to 200MB per second  Cannot support analogue phone

conversations 8

Coaxial Cable

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Fiber optic cable  Consists of strands of clear glass fiber  Has the thickness of a human hair  Data are transformed into pulses of light  Rate 500kb – several trillion bit per second

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Fiber optic cable  Faster lighter and more durable than wire

media  Suitable to transfer large volumes of data  More expensive

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Fiber optic cable  Difficult to work with  Harder to install  Used for backbone cabling 

that handle the major traffic 

a primary path

 No delays and no degradation in quality

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Fiber optic cable

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Wireless transmission  Sends signals through air or space  Technologies include 

microwave transmission communication satellites



pagers



cellular phones



smart phones



PDAs



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Microwave Wireless transmission  High frequency radio signals are transmitted trough the

atmosphere from one terrestrial transmission station to another

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Microwave  A high volume  long distance  point – to – point transmission method

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Smart phone  Wireless phone with

voice  text and  internet capabilities 

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Personal Digital Assistant (PDA)  Small  pen –based  handheld computer with  built in wireless telecommunications

Wireless networks and devices can be more expensive, slower and more error prone 19

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Bandwidth  The capacity of a communications channel 

Number of bits transmitted per second

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Communications Networks  Different ways to organize communications

Networks and components  Can be classified as their

components are arranged (topologies)  geographical scope 

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Network Topologies  Star  Bus  Ring

A topology is a method of arranging networks

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Star Network  Number of computers are connected to a central

computer 

A hub



Switch

Special purpose computers

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Star Network  All communications must pass through the

central computer, the traffic controller

 central computer stop functioning 

network down

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Star Network

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Bus Network  All the computers are connected to a single

circuit - a line  Signals are broadcasted in both directions to

the entire Network  If one computer fails no other computer fails

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Bus Network  can handle only one message at a time 

degrade performance at high traffic volum

 Collisions may occur 

messages has to be re – sent

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Bus Network

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Ring Network  All computers are linked by a close loop  Computer to computer message transmitting 

following a single direction

 Each computer operate independently 

If one fails no interruption to the others

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Ring Network

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Geographic scope classification

LAN

WAN

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Local Area Networks (LANs)  Link local resources 

computers and terminals



Printers and Scanners, etc



Files and programs

in the same department or building of a firm Sharing local resources 33

Local Area Networks (LANs)  Encompasses a limited distance 

usually one building or several buildings in close proximity

 Mostly within 2000 foot radius

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Local Area Networks (LANs)  Link computers and computer controlled

machines in a factory

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Local Area Networks (LANs)  Often controlled and operated by 

end user groups or



departments in a firm

 Require own communications channels

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Network Operating System (NOS)  Software that

manages communications  coordinate Network resources 

on the network

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WAN  Span over broad geographical distance 

Ranging from 

several miles to



entire continents

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Wide Area Network (WAN)  May consists of  a combination of  switched and dedicated lines  variety of  cable  satellite and  microwave technologies 39

WAN

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Other Network Services Circuit switching  A direct connection  between two nodes in a Network  For the duration of the transmission must be maintained

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Packet switching  Breaks up a lengthy block of data into small

fixed bundles called packets

Data bits Error checking bits

Address and packet number bits 43

Packet switching  A packet may contain   

data bits error checking bits and destination address specifying bits

Divided into separate sections

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Packet switching  Packets can be routed 

in different paths



in different communication channels

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Packet switching

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Types of signals Analogue signal  A continuous waveform that passes through a

communications medium  Used for voice communication

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Analogue signal

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Types of signals A digital signal  A discreet waveform

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Modem  Convert analogue signals into digital signals

and vice versa

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