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COMPUTER &COMMUNICATION
1 . INTRODUCTION
2 . DATA TRANSMISSION
3 . DATA TRANSMISSION TECHNIQUE
4 . METHODS OF TRANSMISSION
5 . COMMUNICATION CHANNEL
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G ROUP MEMBERS
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NAME ROLL NOHARSH PATEL 26HITESH PATEL 27JITENDRA PATEL 28NAITIK PATEL 29PRATIK PATEL 30
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INTRODUCTION
OLD COMMUNICATION EQUIPMENTDutch people Old telephoneuse canal forsend messages
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BASIC COMMUNICATIONSYSTEM
SOURCE OFINFORMATION
TRANSMITTER CHANNEL RECEIVER
USER
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NOW A DAYS COMMUNICATION
EQUIPMENT USE IN COMMUNICATION
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DATA TRANSMISSION
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Introduction of data transmissionDataTransmission
Form of data when being transmittedAnalog data signalDigital data signal
ADC and DACAnalog to Digital convertersDigital to Analog converters
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INTRODUCTION OF DATA TRANSMISSION
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Data:-A collection of facts from which conclusions may be drawn;
"statistical data" .
Transmission :-Transfer of this type of data from one particular point to
another point.
Data transmission:-Data transmission is the transfer of data from point to point
often represented as an over electro-magnetic signal over a physicalpoint to point or point to multipoint communication channel.
The term refers in two way one is digital and second is analogform.
Data transmission is a subset of data communication,computer networking.
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FORM OF DATA WHEN BEIN G TRANSMITTED
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Analog data signalMeaningCharacteristics of an analog data signal
Digital data signalMeaning
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FORM OF DATA WHEN BEIN G TRANSMITTED cont«.
Analog data signal
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y Meaning :-Analog data signals are in the form of continuous wave forms which
may be ,periodic or non periodic.e.g., human voice, sound, light, temperature
Analog signals can have an infinite number of values in a range.
It differs from a digital signal, in that small fluctuations in thesignal are meaningful
Analog is usually through of in an electrical context. However,mechanical, hydraulic and other system may also convey analog signals.
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FORM OF DATA WHEN BEIN G TRANSMITTED cont«.
Analog data signal
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y Figure of Analog Data Signal
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FORM OF DATA WHEN BEIN G TRANSMITTED cont«.
Analog data signal
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Figure of amplitude, frequency and phase.
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FORM OF DATA WHEN BEIN G TRANSMITTED cont«.
Digital data signal
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Meaning :-Data that consists, at its most basic level, of just 0s and 1s.
Digital data signal can exist only in two states µON¶ and
µOFF¶. The ON state represent a µ1¶ and the µOFF¶ state represent a µ0¶.
Digital data have discrete states and take discrete valuese.g., bit string in RAM
Digital signals can have only a limited number of values.
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FORM OF DATA WHEN BEIN G TRANSMITTED cont«.
Digital data signal
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Figure of digital data signal
0 1 0 1 0 1
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ADC and DAC
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y Analog to digital convertersRamp conversionSuccessive approximation
y Digital to analog converters
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ADC and DAC cont«.Analog to digital converters
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Analog to digital converters:-Requires a codec (encoder/decoder)Allows use of digital telephony, voice mail
only transmits analog signals, without regard for data contentattenuation overcome with amplifierssignal is not evaluated or regenerated
Already in placeSignificantly less expensiveFully sufficient for transmission of voice signals
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ADC and DAC cont«.Analog to digital converters
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There are many methods by which analog to digitalconversion is possible but we shall discuss only of them in this book.They are
Ramp conversion
successive approximationRamp conversion :-
Ramp conversion although the cheapest of all is theslowest method of converting analog information to digital. It is used indigital voltmeters.
Successive approximation :-the successive approximation method is costlier then the
ramp method but it is very fast.
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ADC and DAC cont«.Digital to analog converters
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Digital to analog convertersIn electronics, a digital-to-analog converter
(DAC ) is a device for converting a digital (usually binary)
code to an analog signal(current, voltage or charges).
DACs are the interface between the abstractdigital world and the analog real life.
Simple switches, a network of resistors, currentsources or capacitors may implement this conversion.
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DATA TRANSMISSION TECHNIQUE
y Data transmission means two or more computerexchanging information over telephone line.
y Each computer must be connected with modem,which should be connected with telephone line.
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THE MODEM
y MODEM = MOdulation + DEM odulation.y Modulation: Convert digital signals to analog signals.y
Demodulation: Convert analog signal to digital signals
Analog signals Digital signals
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TYPES OF MODEM
y Acoustic Coupler Modem:
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a) External direct connect modems- Externally connected to the computer
and telephone line.
- Separate power supply.
- ³ Intelligent modem ´
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External direct connect modem
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b) Internal direct connect modem :-- Printed circuit board
- Plugged into slots of motherboard
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THE MODEM LI G HTS
y High Speed (HS)- Operating at its highest availabletransmission.
y Auto Answer (AA)- Modem will automatically answer any incoming calls.
y
Carrier Detect (CD)- It detect the signal of twocomputers and connect them successfully.
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THE MODEM LI G HTS cont«
y OFF HOOK (OH)-Light goes on whenever modemtakes control of the phone line.
y Receive Data (RD)-This light flickers, whenmodem gets data from other computer.
y Send Data (SD)- This light flashes, when computersend data to other computer.
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THE MODEM LI G HTS cont«y Terminal Ready (TR)- it inform communication
program is loaded and is ready to run.
y Modem ready (MR)- show modem is turned onand ready to operate.
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METHODS OF TRANSMISSION
y Data can be transmitted in either of thefollowing two ways :
1. Asynchronous transmission
2. Synchronous transmission
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1.ASYNCHRONOUS TRANSMISSION
y The transmission of data in which each character is aself contained unit with its own start and stop bits.Intervals between characters may be uneven. It is thecommon method of transmission between acomputer and a modem, although the modem may be switch to synchronous transmission tocommunicate with the other modem. Also called³Start / Stop ´ transmission.
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1.ASYNCHRONOUS TRANSMISSION cont«.
y Simple interface (limited data rate, typically < 64 kbps)y Used for connecting: Printer, Terminal, Modem, home
connections to the Internety No clock sent (Tx & Rx have own clocks)y Requires start and stop bits which provides byte timing
and increases overheady Parity often used to validate correct reception
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START CHARACTER PARITY STOP
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2. SYNCHRONOUS TRANSMISSION
y The transmission of data in which both stations aresynchronized codes are sent from the transmittingstation to the receiving station to establish the
synchronization, and the data are then transmittedin continuous streams.
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SYNCHRONOUS TRANSMISSION cont«
y More complex interface (high data rates supportedup to ~ 10 Gbps)
y Used for: Connections between computer and
telephony networksy Clock sent with data (more configuration options)
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The synchronous character not only indicates the startbit but also informs about the number of character
SynchronousCharacteristics Characteristics Characteristics Characteristics Parity Stop
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ERROR DETECTION
y Many methods for error detection are available butthe simplest technique of them all is that of addingan extra bit, known as a parity bit to each
character or block of characters when beingtransmitted.
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COMMUNICATION PARAMETERS
y The basic communication parameters are :-
1. Word length2. Baud rate3. Parity 4. Start and stop bits
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MODES OF TRANSMISSION
y Data can be transmitted in one of thefollowing three modes :-
1. Simplex mode
2. Half-duplex mode
3. Full-duplex mode
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1. SIMPLEX METHOD
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2. HALF -DUPLEX MODE
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3. FULL- DUPLEX MODE
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COMMUNICATION CHANNEL
B A N D W I D T H S
T R A N S M I S S I O N M E D I A
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COMMUNICATION CHANNELBANDWIDTH
y What is bandwidth?
The bandwidth of a communication
channel decides the data volume aswell as the data transmission rate.
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TYPES OF BANDWIDTH CHANNEL cont«
Narrow bandHandle low volume of data.Transmission rate is low.Approximately 40 to 300 baud.Telegraph lines works.
V oice bandHandle moderate volumes of data.Transmission rates vary from 300 to 9600 baud.Telephone lines works
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TYPES OF BANDWIDTH CHANNEL cont«
Broad band
Handle large volumes of data and very high
rate of transmission rate.
Satellite communication is good example
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TRANSMISSION MEDIA
What is transmission media?
Transmission media refers to the medium
through which data transmission from thetransmitter to the receiver takes place.
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TYPES OF TRANSMISSION MEDIA
1) Fiber optics
2) Microwave
3) Satellite links
4) Wire cables
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1) FIBER OPTICS
y Very thin tube made of glass orplastic.
y Transmit light pulses from the lightsource to the detector.
y Presence of light indicate 1 bit andabsence of light indicate 0 bit.
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FIBER OPTICS cont«
y Transmission of data through it is very fast ascompare to copper telephone line by 75,600.
y More expensive than copper wires but provide high
bandwidths.
Transmitter Fiber optic cable Receiver
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2) MICROWA V E
Microwaves have wave length thatcan be measured in centimeters.The longer microwaves those closer
to a foot in length, are the waves
which heat our food in a microwaveoven.
This microwave tower can transmitinformation like telephone calls andcomputer data from one city toanother.
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3) SATELLITE
y One form of communicationthrough satellite is by usingmicrowave signals.
y Another form of communicationthrough satellite is by using radioand TV waves
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4) WIRE CABLES
Types
A. Twisted pair
B. Coaxial cables
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A) Twisted pair
y It is consist of two insulated copper wires twistedtogether in a helical form.
y It¶s speed is low than the optic cables.
y Cost is low so easily available.
y Twisted pair cable may either be SHIELDED orUNSHIELDED
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Shielded cable (cont.)
y Shielded cables surround thecentre conductors with a jacketof fine, braided wires.
y It transfer data at a higher ratethan the unshielded cable.
y It is costlier than the unshieldedcable.
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Unshielded cable (cont)
y Unshielded cables are lessexpensive than the shieldedcables.
y It is commonly used but they aremore prone to electromagneticinterference.
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B) Coaxial cable
y It transmit the data atvery high frequenciesand transmission rateis also higher than thetwisted pair cable.
y You see the use of itin your TV cablenetwork.
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TYPES OF COAXIAL CABLES
Base band coaxial cable
Base band coaxial cable are used for digital datatransmission, therefore base band cables are usually employed for LAN ( local area network)
Broadband coaxial cable
Broadband coaxial cable can work at frequencies as high as 450megahertz. they can transit many simultaneous signals usingdifferent frequencies. the data carried by this cable are usually analog in nature.
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