computer & communication-prince dudhatra-9724949948

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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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NAME ROLL NOHARSH PATEL 26HITESH PATEL 27JITENDRA PATEL 28NAITIK PATEL 29PRATIK PATEL 30



INTRODUCTION

OLD COMMUNICATION EQUIPMENTDutch people Old telephoneuse canal forsend messages




BASIC COMMUNICATIONSYSTEM

SOURCE OFINFORMATION

TRANSMITTER CHANNEL RECEIVER

USER




NOW A DAYS COMMUNICATION

EQUIPMENT USE IN COMMUNICATION




DATA TRANSMISSION


Introduction of data transmissionDataTransmission

Form of data when being transmittedAnalog data signalDigital data signal

ADC and DACAnalog to Digital convertersDigital to Analog converters



INTRODUCTION OF DATA TRANSMISSION


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.



FORM OF DATA WHEN BEIN G TRANSMITTED


Analog data signalMeaningCharacteristics of an analog data signal

Digital data signalMeaning



FORM OF DATA WHEN BEIN G TRANSMITTED cont«.

Analog data signal


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.




Analog data signal


y Figure of Analog Data Signal




Analog data signal


Figure of amplitude, frequency and phase.




Digital data signal


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.




Digital data signal


Figure of digital data signal

0 1 0 1 0 1



ADC and DAC


y Analog to digital convertersRamp conversionSuccessive approximation

y Digital to analog converters



ADC and DAC cont«.Analog to digital converters


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



ADC and DAC cont«.Analog to digital converters


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.



ADC and DAC cont«.Digital to analog converters


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.



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.




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




TYPES OF MODEM

y Acoustic Coupler Modem:




a) External direct connect modems- Externally connected to the computer

and telephone line.

- Separate power supply.

- ³ Intelligent modem ´




External direct connect modem




b) Internal direct connect modem :-- Printed circuit board

- Plugged into slots of motherboard




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.




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.




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.




METHODS OF TRANSMISSION

y Data can be transmitted in either of thefollowing two ways :

1. Asynchronous transmission

2. Synchronous transmission




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.




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




START CHARACTER PARITY STOP




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.




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)




The synchronous character not only indicates the startbit but also informs about the number of character

SynchronousCharacteristics Characteristics Characteristics Characteristics Parity Stop




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.




COMMUNICATION PARAMETERS

y The basic communication parameters are :-

1. Word length2. Baud rate3. Parity 4. Start and stop bits




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




1. SIMPLEX METHOD




2. HALF -DUPLEX MODE




3. FULL- DUPLEX MODE




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




COMMUNICATION CHANNELBANDWIDTH

y What is bandwidth?

The bandwidth of a communication

channel decides the data volume aswell as the data transmission rate.




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




TYPES OF BANDWIDTH CHANNEL cont«

Broad band

Handle large volumes of data and very high

rate of transmission rate.

Satellite communication is good example




TRANSMISSION MEDIA

What is transmission media?

Transmission media refers to the medium

through which data transmission from thetransmitter to the receiver takes place.




TYPES OF TRANSMISSION MEDIA

1) Fiber optics

2) Microwave

3) Satellite links

4) Wire cables




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.




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

outputInputprince dudhatra-9724949948



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.




3) SATELLITE

y One form of communicationthrough satellite is by usingmicrowave signals.

y Another form of communicationthrough satellite is by using radioand TV waves




4) WIRE CABLES

Types

A. Twisted pair

B. Coaxial cables




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




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.




Unshielded cable (cont)

y Unshielded cables are lessexpensive than the shieldedcables.

y It is commonly used but they aremore prone to electromagneticinterference.




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.




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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