Upload
derick-anthony
View
217
Download
1
Embed Size (px)
Citation preview
Data & Communication Networks•Data:
–Collection of raw facts and figures represented in the form of,
•Text,•Audio,•Video etc.
•Communication:–Giving/Exchanging of Data/Information/News OR–Activity of conveying information by,
•Visuals & Signals,•Writing,•Speech etc.
•Network:–Infrastructure / Setup that allows entities to,
•Communicate / Exchange Data.
Data & Communication Networks
•Data Communication Networks:–So what is Data & Communication Networks?
•Actually it is supposed to be,–Data Communication Networks–Data Communication & Networks
–Networks that allow (facilitate),•The communication of,•Data between various entities.
Data Communication Networks
•Communication & Networks:–At the other end,
•Scientist by the name of ‘Benjamin Franklin’ was busy doing his experiments.•In one of his famous experiment, he found out something revolutionary.
Communication & Networks
Benjamin Franklin’s Kite Experiment
Reference: http://www.codecheck.com/cc/BenAndTheKite.html
Data Communication Networks•Communication & Networks:
–Electrical Energy & Direct Current (DC):•Later on,
–Scientists found out that due to a reaction between various chemicals such as,
»Zinc & Carbon,»Nickel & Cadmium etc,
–Some kind of energy is produced.•This energy is called:
–Electrical Energy•Reaction that happens between chemicals is called:
–Electrochemical Reaction
–Conclusion:•Scientists were successful in converting,
–‘Chemical’ energy into ‘Electrical’ energy.•Current that was generated out of it was called:
–Direct Current (DC)
Data Communication Networks
•Direct Current Behavior:–To operate or function, most devices require,
•High DC voltage.
–However,•It is very difficult to generate high DC voltage.•Moreover during transmission, so much power is lost in the form of heat due to,
–Resistance of the wire (path).
–Conclusion:•It was virtually impossible to transmit DC voltage directly to the homes of the consumers.
Communication & Networks
5V
Michael Faraday
N
S
EW
Magnetic Field
There is some relation between electric and magnetic energies.Conclusion:
MagneticCompass
Communication & NetworksMichael Faraday
Click here Click here
Conclusion:
Nature of current is Alternating.
This is called:Alternating Current(AC)
Data Communication Networks
•Alternating Current Behavior:–If magnet is moved (by reversing the directions),
•Electric current is produced.•Conclusion:
–‘Mechanical’ energy could be converted into ‘Electrical’ energy.
•Led to the invention of a device called:–Electric Generator.
–If electric current is produced and alternated, •Magnet / Iron can be moved.•Conclusion:
–‘Electrical’ energy could be converted into ‘Mechanical’ energy.
•Led to the invention of a device called:–Electric Motor.
Data Communication Networks
•Alternating Current Behavior:–It is easy to generate,
•High AC voltage compared to high DC voltage.
–Need at that time was:•For transmission to consumers’ homes,
–High voltage is required.»Step-Up Transformer
•Once it reaches to/near consumers’ homes, –Voltage should be reduced.
»Step-Down Transformer
•Moreover most of the devices of the consumers work on DC voltage and not AC voltage.
–So facility should be there to convert AC voltage to DC voltage.
»Rectifier
Electric Power Transmission
Step-Up Transformer
Step-Down TransformerRectifier
Transformer (Step-Up / Step-Down)
Power Plant
Data Communication Networks
•Communication v/s Electricity:–Communication:
•It could not go beyond oceans.
–Electricity:•It could travel across oceans now in the form of,
–Alternating Voltage or Alternating Current OR–Electromagnetic Waves
–Important question was:•How can communication travel across oceans?
Data Communication Networks
Carrier
Information
Put (Encode) the information on the carrier so that information can travel across.
MODULATION Kite Example
Data Communication Networks
Encoding /Modulation
Decoding /De-Modulation
Electromagnetic wave carrying information
Medium
Is physical medium really necessary?
Encoding /Modulation
Decoding /De-ModulationAir is the medium
Electromagnetic wave (not Sound wave) carrying information
No physical medium
No. If Sound waves can travel without any physical medium, why not Electromagnetic waves?
Data Communication Networks
•Data Communication Networks:–Based on this principle of electromagnetic waves,
•Several devices were invented such as:–Microphone, Telephone, Radio, Television etc.
–Question is:•How every device/equipment (Microphone, TV, Radio etc.)
–Generates, understands and reproduces the electric signal?
Data Communication Networks
Voltage
Time
Voltage
Time
Continuous Comparison (Analogy)with Input at all Times.
Data Communication Networks
Size of your laptop?
Comparison (Analogy & Not measurement) with the size of laptop.
Continuously with Time.
Data Communication Networks
How many marbles have you collected?
Comparison (Analogy & Not measurement) with the number of marbles.
Continuously with Time.
Data Communication Networks
Tell the time
Comparison (Analogy & Not measurement) with the position of hands of the clock.
Continuously with Time.
Hour hand is on second ‘1’ of ’11’,Minute hand has touched ‘1’,Second hand is on 5, no about to leave 5.
Data Communication Networks
•Data Communication Networks:–Scientists found out that to generate or reproduce something,
•It is not necessary to continuously monitor it with respect to time.
–Moreover it could be expressed in some other way,
•Rather than ‘Comparison’ or ‘Analogy’.
Data Communication Networks
Measure my laptop
It’s 25 inches.
Not an Analogy (Comparison).
It is measurement in Digits.
Analog Digital
Comparison (Analogy & Not measurement) with the size of laptop.
Continuously with Time. Discontinuous / Discrete with Time.
Data Communication Networks
How many marbles have you collected?
It’s 25 marbles.
Not an Analogy.
It is measurement in Digits.
DigitalAnalog
Comparison (Analogy & Not measurement) with the number of marbles.
Continuously with Time.Discontinuous / Discrete with Time.
Data Communication Networks
Tell the time
- Hour hand is on second ‘1’ of ’11’,- Minute hand has touched ‘1’,- Second hand is one 5, no about to leave 5.
It’s 5 past 11.
DigitalAnalog
Comparison (Analogy & Not measurement) with the position of hands of the clock.
Continuously with Time.
Data Communication Networks
Voltage
Time
Voltage
Time
After every 5/10 sec, just measure the voltage.
1
2
Everything is stored inthe form of digits at
discontinuous (discrete) portion of time.
Data Communication Networks•Analog v/s Digital Communication:
–Analog:•Works on the basis of comparison or analogy.•It is continuous with time.•Problems:
–Continuously monitor with respect to time.»Wastage of bandwidth.
–Prone to noise.
–Digital:•Works on the basis of digits or measurement.•It is discontinuous (discrete) with time.•Most popular digital device today is:
–Computer.»Which in fact uses only 2 unique digits/states to represent everything.»0 or 1.
Data Communication Networks
•Digital (Computer) Communication:–Computer represents everything in the form of:
•Digits (Digital)
–Number of unique digits/states used by a computer to represent everything is:
•2, ie.–0 and 1
»True/False, On/Off etc.
–It definitely gives rise to some questions.
Data Communication Networks
•Digital (Computer) Communication:–1st Question is:
•If computer wanted to be digital,–Why did it select only 2 unique states (Binary Digits 0/1)?
–It could have selected 10 unique states (Decimal Digits 0 to 9)?
–Answer is:•Just like a human being,
–It is also very easy for a circuit to make a decision based on,
»Either/Or, True/False, Yes/No, On/Off, Presence/Absence etc.
•So the size and complexity of the circuit is reduced to a greater extent.
Data Communication Networks
•Digital (Computer) Communication:–2nd Question is:
•Using just or only 2 unique digits/states, –How is it possible to represent so many alphabets, numbers, states etc.?–On top of that, how can the computer distinguish alphabets from all languages also such as English, Hindi, Gujarati etc?
–This Question is similar to:•If there is a bulb recognizing only 2 states, ‘On’ and ‘Off’,
–Can it be used on different occasions to convey different meaning?
•If there is a whistle having only 2 states, ‘Presence’ and ‘Absence’ of sound,
–How can it be used to convey different meanings to players on the field regarding?
»Start the game, Foul, Stop the game etc?
Digital Communication
1 Bulb Off
On
2 Bulbs
Number of Bulbs Possible Combinations
Off Off
Off OnOn Off
On On
Data Communication Networks
•Digital (Computer) Communication:–Answer is:
•1 bulb can convey only 2 messages,–On or Off.–However,
»A series (collection) of such bulbs can be used to create so many effects and combinations.
•1 whistle can convey only 2 messages,–Presence of sound / Absence of sound.–However,
»Collection (Repetition) of same sound from whistle can convey different meaning to the players on the field.