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Telecommunications and Computer networks by subasheela

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									Telecommunications and Computer networks

venisha

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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
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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
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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
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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
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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
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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

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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
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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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