Report on Cdma Tech

8/3/2019 Report on Cdma Tech

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RE: CDMA Technology Full Download Seminar Report and Paper Presentation

CDMAThe world is

demanding morefrom wireless

communicationtechnologies than

ever before asmore people

around the worldare subscribing towireless. Add inexciting Third-

Generation (3G)wireless dataservices and

applications -such as wirelessemail, web, digital

picturetaking/sending,assisted-GPS

position locationapplications,

video and audiostreaming and TV

broadcasting -and wireless

networks aredoing much more

than just a fewyears ago.

This is whereCDMA

technology fits in.CDMA

consistentlyprovides better

capacity for voice

and datacommunications

than othercommercial

mobiletechnologies,allowing moresubscribers toconnect at any

given time, and itis the common

platform on which3G technologies


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are built.Code-Division

Multiple Access,a digital Cellulartechnology that

uses spread-spectrum

techniques.Unlike competingsystems such asGSM, that useTDMA. CDMA

does not assign aspecific frequency

to each user.Instead, every

Channel uses thefull availablespectrum.Individual

conversations areencoded with apseudo randomdigital sequence,but give the rightto use both to all

userssimultaneously.

To do this, it usesa technique

known as SpreadSpectrum. In

effect, each useris assigned acode which

spreads its signalbandwidth in such

a way that onlythe same code

can recover it atthe receiver end.This method hasthe property that

the unwantedsignals

with differentcodes get spreadeven more by theprocess, makingthem like noise to

the receiver.Spread Spectrum


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Spread Spectrumis a mean oftransmission

where the dataoccupies a larger

bandwidth thannecessary.Bandwidth

spreading isaccomplished

before thetransmission

through the useof a code, whichis independent ofthe transmitted

data. The samecode is used todemodulate the

data at thereceiving end.The following

figure illustratethe spreading

done on the datasignal x(t) by thespreading signalc(t) resulting inthe messagesignal to be

transmitted, m(t).Originally for

military use toavoid jamming(interferencecreated on

purpose to makea communication

channel

unusable), spreadspectrum

modulation is nowused in personalcommunicationsystems for its

superiorperformance inan interference-

dominatedenvironment.

Processing GainIn spread


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spectrum, thedata is modulated

by a spreadingsignal, whichuses more

bandwidth thanthe data signal.

Sincemultiplication inthe time domaincorresponds to

convolution in thefrequency

domain, a narrowband signal

multiplied by a

wide band signalends up beingwide band. Oneway of doing thisis to use a binarywaveform as a

spreadingfunction, at a

higher rate thanthe data signal.Here the three

signalscorresponds to

x(t), c(t) and m(t)discussed above.

The first twosignals aremultiplied

together to givethe third

waveform.Bits of the

spreading signal

are called chips.On the above

figure, Tbrepresents theperiod of one

data bit and Tcrepresents theperiod of onechip. The chip

rate, 1/Tc, is oftenused to

characterize aspread spectrum


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transmissionsystem.

The ProcessingGain or

sometimes called

the SpreadingFactor is definedas the ratio of the

information bitduration over the

chip duration:PG = SF = Tb /

TcHence, it

represents thenumber of chips

contained in onedata bit. HigherProcessing Gain

(PG) means morespreading. HighPG also meansthat more codescan be allocated

on the samefrequency

channel (more onthat later).

Pseudo-NoiseSequences

So far we haven'tdiscussed whatproperties we

would want thespreading signal

to have. Thisdepends on the

type of system wewant to

implement. Let'sfirst consider a

system where wewant to use

spread spectrumto avoid jammingor narrow band

interference.If we want the

signal toovercome narrow

bandinterference, the


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spreadingfunction needs tobehave like noise.

Random binarysequences are

such functions.They have the

followingimportant

properties:Balanced: theyhave an equal

number of 1's and0's

Single Peak auto correlation

functionIn fact, the auto-correlation

function of arandom binarysequence is a

triangularwaveform as in

the followingfigure, where TCis the period of

one chip:Hence the

spectral densityof such a

waveform is a sinfunction squared,with first zeros at

1/TCPN sequences

are periodicsequences that

have a noise like

behavior. Theyare generated

using shiftregisters, modulo-

2 adders (XORgates) and

feedback loops.The following

diagramillustrates this:

The length of the

register and theconfiguration of


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the feedbacknetwork

determine themaximum length

of a PN

sequence. An Nbits register cantake up to 2N

differentcombinations ofzeros and ones.

Since thefeedback network

performs linearoperations, if all

the inputs (i.e. the

content of the flip-flops) are zero,the output of the

feedback networkwill also be zero.Therefore, the allzero combinationwill always give

zero output for allsubsequent clockcycles, so we donot include it inthe sequence.

Thus, themaximum length

of any PNsequence is 2N-1and sequences of

that length arecalled Maximum-

LengthSequences or m-sequences. They

are usefulbecause longersequences havebetter properties.PN sequencesare therefore

periodic noise likebinary functionsgenerated by a

network offeedback loops,

modulo-2 addersand flip-flops.


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Maximum lengthPN functions

have a period of2N-1.

Advantages of

CDMAThe advantage of

CDMA forpersonal

communicationservices is its

ability toaccommodate

many user on thesame frequency

at the same time.

As we mentionedearlier, a specificcode is assignedto each user and

only that codecan demodulatethe transmitted

signal.There are two

ways ofseparating users

in CDMA:Orthogonal

Multiple AccessNon-orthogonalMultiple Accessor Asynchronous

CDMAOrthogonal

Multiple AccessEach user is

assigned one ormany orthogonal

waveform derivedfrom an

orthogonal code.Since the

waveforms areorthogonal, users

with differentcodes do notinterfere witheach other.Orthogonal-

CDMA or O-CDMA requires


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synchronizationamong the users,

since thewaveforms are

orthogonal only if

they are alignedin time.

OrthogonalCodes

An important setof orthogonal

code is the Walshset. Walsh

functions aregenerated using

an iterative

process ofconstructing aHadamard matrix.starting with H1 =

[0]. TheHadamard matrix

is built by:For example,here are the

Walsh-Hadamardcodes of length 2

and 4respectively:

From thecorresponding

matrix, theWalsh-Hadamardcode words are

given by therows. Note thatwe usually map

the binary data topolar form so we

can use realnumbers

arithmetic whencomputing the

correlations. So0's are mapped to

1's and 1's aremapped to -1.

Walsh-Hadamardcodes areimportant

because theyform the basis for


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orthogonal codeswith different

spreading factors.This property

becomes useful

when we wantsignals with

differentSpreading

Factors to sharethe samefrequency

channel. Thecodes thatposses thisproperty are

called OrthogonalVariableSpreading Factor(OVSF) codes.

To construct suchcodes, it is betterto use a differentapproach than

matrixmanipulation.Using a Tree

Structureallows better

visualization ofthe relation

between differentcode length and

orthogonalitybetween them.

For example, let'ssee if the secondcodeword of W2

which we will

denote W2.2 andthe third

codeword of W4,W4.3, are

orthogonal. Sincethey are of

different length,we repeat W2.2

to match thelength of W4.3.

Hence we get the

following twocode words, in


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polar form:W2.2 => (1 -1 | 1-1) and W4.3 =>

(1 1 -1 -1)Computing the

orthogonality, weget: (multiplying

elements byelements)

(1 x 1) + (-1 x 1) +(1 x -1) + (-1 x -1)= 1 - 1 - 1 + 1 = 0Hence, W2.2 and

W4.3 areorthogonal.

However, the

auto-correlationfunction of Walsh-Hadamard codewords does not

have goodcharacteristics. Itcan have morethan one peak

and therefore, it isnot possible forthe receiver to

detect thebeginning of the

codeword withoutan external

synchronizationscheme. The

cross - correlationcan also be non-zero for a numberof time shifts andun-synchronized

users can

interfere witheach other. Thisis why Walsh-

Hadamard codescan only be usedin synchronous

CDMA.Walsh-Hadamard

codes do nothave the best

spreading

behavior. They donot spread data


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as well as PNsequences doesbecause therepower spectral

density is

concentrated in asmall number of

discretefrequencies.

Non-OrthogonalCDMA

The conceptbehind this is to

give uporthogonality

among users and

reduce theinterference byusing spread

spectrumtechniques. PNsequences areused to spreadthe spectrum.

The family of PNsequences, calledGold sequencesare in particularpopular for non-

orthogonalCDMA. Gold

sequences haveonly three cross-correlation peaks,which tend to getless important asthe length of thecode increases.

They also have a

single auto-correlation peakat zero, just like

ordinary PNsequences.

Gold sequences(codes) are

constructed fromthe modulo-2

addition of twomaximum length

preferred PNsequences. By


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shifting one of thetwo PN

sequence, we geta different Goldsequence. This

property can beuse to generatecodes which willpermit multipleaccess on the

channel.The use of Gold

sequencespermits the

transmission tobe asynchronous.

The receiver cansynchronize usingthe auto-

correlationproperty of the

Gold sequence.THE CONCEPT

OF MULTIMEDIAMurali Krishna

Manikyam1/3 M.C.A IISemester

INTRODUCTIONAs the name

suggests,multimedia is a

set of more thanone media

element used toproduce a

concrete andmore structured

way of

communication.In other wordsmultimedia is

simultaneous useof data from

different sources.These sources inmultimedia are

known as mediaelements. With

growing and very

fast changinginformation


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technology,Multimedia has

become a crucialpart of computer

world. Its

importance hasrealized in almostall walks of life,

may it beeducation,cinema,

advertising,fashion and what

not.Throughout the

1960s, 1970s and

1980s, computershave beenrestricted to

dealing with twomain types of

data - words andnumbers. But thecutting edge of

informationtechnology

introduced fastersystem capable

of handlinggraphics, audio,animation andvideo. And the

entire world wastaken aback by

the power ofmultimedia.

OBJECTIVESexplain what is

multimedia

understand theimportance of

individual mediaelements

identify differenthardware

componentsrequired to run a

multimediaappreciate the

impact of audio in

educationalpresentation


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describe howvisual images,graphics andaudio can beadded to a

presentationenhance thecapability ofmultimedia

throughinteractive video

impactWHAT IS

MULTIMEDIA?Multimedia is

nothing but the

processing andpresentation ofinformation in amore structured

andunderstandablemanner usingmore than onemedia such astext, graphics,

animation, audioand video. Thus

multimediaproducts can be

an academicpresentation,

game orcorporate

presentation,information kiosk,fashion-designingetc. Multimedia

systems are

those computerplatforms andsoftware tools

that support theinteractive usesof text, graphics,animation, audio,or motion video.In other words, acomputer capableof handling text,

graphics, audio,animation and


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video is calledmultimedia

computer. If theuser can control

the sequence and

timing of thesemedia elements,

then one canname it asInteractiveMultimedia.DIFFERENT

MEDIAELEMENTS

(i) TextInclusion of

textualinformation inmultimedia is the

basic steptowards

development ofmultimedia

software. Textcan be of anytype, may be aword, a single

line, or aparagraph. Thetextual data formultimedia canbe developedusing any text

editor. Howeverto give special

effects, oneneeds graphicssoftware which

supports this kind

of job. Even onecan use any of

the most popularword processing

software to createtextual data for

inclusion inmultimedia. The

text can havedifferent type,size, color and

style to suit theprofessional


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requirement ofthe multimedia

software.(ii) Graphics

Another

interestingelement in

multimedia isgraphics. As amatter of fact,

taking intoconsideration thehuman nature, asubject is moreexplained withsome sort of

pictorial/graphicalrepresentation,rather than as alarge chunk oftext. This also

helps to developa clean

multimediascreen, whereas

use of largeamount of text ina screen make it

dull inpresentation.

Unlike text, whichuses a universal

ASCII format,graphics does not

have a singleagreed format.

They havedifferent format to

suit different

requirement.Most commonlyused format for

graphics is .BMPor bitmap

pictures. The sizeof a graphics

depends on theresolution it is

using. Acomputer image

uses pixel or dotson the screen to


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form itself. Andthese dots orpixel, when

combined withnumber of colors

and other aspectsare calledresolution.

Resolution of animage or graphics

is basically thepixel density andnumber of colorsit uses. And the

size of the imagedepends on its

resolution. Astandard VGA(Virtual GraphicsArrays) screencan display a

screen resolutionof 640 480 =307200 pixel. And

a Super VGAscreen can

display up-to1024 768 =786432 pixel on

the screen. Whiledevelopingmultimedia

graphics oneshould always

keep in mind theimage resolutionand number of

colors to be used,as this has a

direct relationwith the image

size. If the imagesize is bigger, ittakes more timeto load and alsorequires higher

memory forprocessing and

larger disk-spacefor storage.

However,different graphics


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formats areavailable whichtake less spaceand are faster to

load into the

memory.There are several

graphicspackages

available todevelop excellentimages and also

to compress themso that they takelesser disk-space

but use higher

resolution andmore colours.Packages likeAdobe PhotoShop, Adobe

Illustrator,PaintShop Pro

etc. are excellentgraphics

packages. Thereare Graphics

gallery available

in CDs(Compact Disk)with readymadeimages to suitalmost everyrequirement.

These imagescan directly be

incorporated intomultimedia

development.

(iii) AnimationMoving images

have anoverpoweringeffect on the

human peripheralvision. Followingsare few points for

its popularity.Showing

continuity in

transitions:Animation is a set


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of static state,related to each

other withtransition. Whensomething has

two or morestates, then

changes betweenstates will be

much easier forusers to

understand if thetransitions are

animated insteadof being

instantaneous. An

animatedtransition allowsthe user to track

the mappingbetween differentsubparts through

the perceptualsystem instead ofhaving to involve

the cognitivesystem to deduce

the mappings.Indicating

dimensionality intransitions:Sometimes

oppositeanimated

transitions can beused to indicatemovement backand forth along

some

navigationaldimension. Oneexample used in

several userinterfaces is the

use of zooming toindicate that anew object isgrown from aprevious one

(e.g., a detailed

view or propertylist opened by


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clicking on anicon) or that an

object is closed orminimized to a

smaller

representation.Zooming out fromthe small object

to theenlargement is a

navigationaldimension and

zooming in againas the

enlargement isclosed down is

the oppositedirection alongthat dimension.

Illustratingchange over timeSince animationis a time-varying

display, itprovides a one-to-one mappingto phenomena

that change overtime. Forexample,

deforestation ofthe rain forest canbe illustrated byshowing a map

with an animationof the coveredarea changing

over time.Multiplexing the

displayAnimation can be

used to showmultiple

informationobjects in the

same space. Atypical example isclient-side image

maps withexplanations that

pop up as theuser moves the


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cursor over thevarious hypertext

anchors.Enrichinggraphical

representationsSome types ofinformation are

easier to visualizewith movementthan with still

pictures.Consider, for

example, how tovisualize the toolused to remove

pixels in agraphicsapplication.

Visualizing three-dimensionalstructures

As you know thecomputer screen

is two-dimensional.

Hence users cannever get a full

understanding ofa three-

dimensionalstructure by a

single illustration,no matter howwell designed.

Animation can beused to

emphasize thethree-dimensional

nature of objectsand make it

easier for users tovisualize their

spatial structure.The animation

need notnecessarily spin

the object in a fullcircle - just slowly

turning it back

and forth a littlewill often be


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sufficient. Themovement shouldbe slow to allowthe user to focuson the structure

of the object.You can alsomove three-dimensional

objects, but oftenit is better if you

determine inadvance how

best to animate amovement that

provides optimal

understanding ofthe object. Thispre-determinedanimation can

then be activatedby simply placingthe cursor over

the object. On theother hand, user-

controlledmovements

require the userto understand

how tomanipulate theobject (which is

inherently difficultwith a two-dimensional

control device likethe mouse used

with mostcomputers - to be

honest, 3D isnever going to

make it big timein user interfacesuntil we get a true

3D controldevice).

Attractingattention

Finally, there area few cases

where the abilityof animation to


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dominate theusers visualawareness canbe turned to an

advantage in the

interface. If thegoal is to drawthe usersattention to a

single elementout of several orto alert the user

to updatedinformation then

an animatedheadline will do

the trick.Animated textshould be drawn

by a one-timeanimation (e.g.,

text sliding infrom the right,

growing from thefirst character, or

smoothlybecoming larger)and never by a

continuousanimation sincemoving text is

more difficult toread than statictext. The user

should be drawnto the new text by

the initialanimation and

then left in peace

to read the textwithout further

distraction.One of the

excellent softwareavailable to

create animationis Animator Pro.

This providestools to create

impressive

animation formultimedia


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development.Video

Beside animationthere is one moremedia element,

which is knownas video. With

latest technologyit is possible toinclude video

impact on clips ofany type into any

multimediacreation, be it

corporatepresentation,

fashion design,entertainmentgames, etc.

The video clipsmay contain

some dialoguesor sound effects

and movingpictures. These

video clips can becombined withthe audio, text

and graphics formultimedia

presentation.Incorporation of

video in amultimedia

package is moreimportant and

complicated thanother media

elements. One

can procure videoclips from varioussources such as

existing videofilms or even cango for an outdoorvideo shooting.

All the videoavailable are in

analog format. Tomake it usable by

computer, thevideo clips are


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needed to beconverted into

computerunderstandable

format, i.e., digital

format. Bothcombinations of

software andhardware make it

possible toconvert the

analog video clipsinto digital format.This alone doesnot help, as thedigitized video

clips take lots ofhard disk spaceto store,

depending on theframe rate usedfor digitization.The computer

reads a particularvideo clip as aseries of still

pictures calledframes. Thus

video clip is madeof a series of

separate frameswhere each frameis slightly differentfrom the previous

one. Thecomputer readseach frame as abitmap image.Generally there

are 15 to 25frames per

second so thatthe movement is

smooth. If wetake less frames

than this, themovement of theimages will not be

smooth.To cut down the

space there areseveral modern


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technologies inwindows

environment.Essentially these

technologies

compress thevideo image so

that lesser spaceis required.

However, latestvideo

compressionsoftware makes it

possible tocompress thedigitised video

clips to itsmaximum. In theprocess, it takeslesser storage

space. One moreadvantage of

using digital videois, the quality of

video will notdeteriorate fromcopy to copy asthe digital video

signal is made upof digital code

and not electricalsignal. Cautionshould be takenwhile digitizingthe video from

analog source toavoid frame

droppings anddistortion. A good

quality videosource should be

used fordigitization.

Currently, video isgood for:

Promotingtelevision shows,

films, or othernon-computer

media that

traditionally haveused trailers in


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their advertising.Giving users animpression of a

speakerspersonality.

Showing thingsthat move. Forexample a clipfrom a motion

picture. Productdemos of physicalproducts are also

well suited forvideo.Audio:

Audio has a

greater role toplay in multimediadevelopment. Itgives life to thestatic state ofmultimedia.

Incorporation ofaudio is one of

the mostimportant

features ofmultimedia, which

enhance themultimedia

usability to its fullpotential. There

are several typesof sound, whichcan be used in

multimedia. Theyare human

voices,instrumental

notes, naturalsound and manymore. All thesecan be used in

any combinationas long as they

give somemeaning to their

inclusion inmultimedia.

There are many

ways in whichthese sounds can


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be incorporatedinto the computer.

For example;1. Using

microphone,

human voice candirectly be

recorded in acomputer.

2. Pre-recordedcassettes can be

used to recordthe sound into

computer.3. Instrumentalsound can also

be played directlyfrom a musicalinstrument for

recording into thecomputer.The sound

transmitted fromthese sources isof analog nature.

To enable thecomputer toprocess this

sound, they needto be digitized.

As all of us knowthat sound is a

repeated patternof pressure in the

air and amicrophone

converts a soundwave into an

electrical wave.

The clarity ofsound, the finaloutput dependsentirely on the

shape andfrequency of the

sound wave.When digitized(recording intocomputer), theerror in sound

can be drasticallyreduced. Audio


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need to beconverted into

digital format toproduce digitizedaudio in order to

use them inmultimedia. Andthese digitized

sounds again canbe re-convertedinto analog formso that the usercan hear them

though thespeakers.Musical

InstrumentDigitizationInterface or MIDI

provides aprotocol or a setof rules, using

which the detailsof a musical note

from aninstrument is

communicated tothe computer. ButMIDI data is not

digitized sound. Itis directly

recorded into thecomputer from

musicalinstruments,

whereas digitizedaudio is createdfrom the analog

sound. The

quality of MIDIdata depends

upon the qualityof musical

instrument andthe sound

system. A MIDIfile is basically alist command to

produce thesound. For

example,pressing of a


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guitar key can berepresented as a

computercommand. Whenthe MIDI device

processes thiscommand, the

result will be thesound from the

guitar. MIDI filesoccupy lesser

space ascompared to thedigitized audioand they areeditable also.

The main benefitof audio is that itprovides an

exclusive channelthat is separatefrom that of thedisplay. Speechcan be used to

offer commentaryor help without

obscuringinformation on thescreen. Audio can

also be used toprovide a sense

of place or mood.Mood-settingaudio should

employ very quietbackground

sounds in ordernot to competewith the main

information forthe users

attention. Music isprobably the most

obvious use ofsound. Whenever

you need toinform the userabout a certainwork of music, it

makes much

more sense tosimply play it than


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to show the notesor to try to

describe it inwords.

MULTIMEDIA

HARDWAREREQUIREMENTS

For producingmultimedia youneed hardware,

software andcreativity. In thissection we will

discuss themultimediaequipment

required in apersonalcomputer (PC) sothat multimedia

can be produced.(a) Central

Processing UnitAs you know,

CentralProcessing Unit

(CPU) is anessential part inany computer. Itis considered as

the brain ofcomputer, whereprocessing andsynchronizationof all activities

takes place. Theefficiency of acomputer is

judged by the

speed of the CPUin processing of

data. For amultimediacomputer a

Pentiumprocessor is

preferredbecause of higher

efficiency.However, the

CPU ofmultimedia


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computer shouldbe at least 486

with mathcoprocessor. The

Pentium

processor is onestep up theevolutionary

chain from the486 series

processor andPentium Pro isone step above

the Pentium. Andthe speed of the

processor is

measured inmegahertz. Itdefines thenumber of

commands thecomputer canperform in asecond. The

faster the speed,the faster theCPU and the

faster thecomputer will beable to perform.

As the multimediainvolves more

than one medialelement,

including high-resolution

graphics, highquality motionvideo, and one

need a fasterprocessor for

betterperformance.In todaysscenario, a

Pentiumprocessor with

MMX technologyand a speed of166 to 200 MHz

(Megahertz) is anideal processor


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for multimedia. Inaddition to the

processor one willneed a minimum16 MB RAM to

run WINDOWS toedit large imagesor video clips. But

a 32 or 64 MBRAM enhancesthe capacity of

multimediacomputer.(b) Monitor

As you know thatmonitor is used to

see the computeroutput. Generally,it displays 25rows and 80

columns of text.The text or

graphics in amonitor is createdas a result of anarrangement oftiny dots, called

pixels. Resolutionis the amount of

details themonitor can

render.Resolution is

defined in termsof horizontal and

vertical pixel(picture elements)displayed on the

screen. The

greater thenumber of pixels,

bettervisualization of

the image.Like any other

computer device,monitor requiresa source of input.The signals that

monitor gets from

the processor arerouted through a


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graphics card.But there arecomputers

available wherethis card is in-built

into themotherboard.

This card is alsocalled the

graphics adapteror display

adapter. Thiscard controls theindividual pixels

or tiny points on ascreen that make

up image. Thereare several typesof display adapteravailable. But themost popular oneis Super VirtualGraphics Arrays(SVGA) card and

it suits themultimedia

requirement. Theadvantage of

having a SVGAcard is that the

quality ofgraphics and

pictures is better.Now the PCs,

which are comingto the market, arefitted with SVGAgraphics card.

That allows

images of up to1024 768

pixels to bedisplayed in up to

16 millions ofcolours. Whatdetermines the

maximumresolution and

color depth is theamount of

memory on thedisplay adapters.


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Often you canselect the amount

of memoryrequired such as

512KB, 1MB,

2MB, 4MB, etc.However,standard

multimediarequirement is a2MB of display

memory (or VideoRAM). But onemust keep inmind that thisincreases the

speed of thecomputer, also itallows displayingmore colours andmore resolutions.One can easilycalculate the

minimum amountof memoryrequired for

display adapteras

(Max. HorizontalResolution x Max.

VerticalResolution

Colour Depths. inBits )/8192 = Theminimum video

(or display)memory required

in KB.For example, if

SVGA resolution(800600) with

65,536 colours(with colour depth

of 16) you willneed 937.5 KB,

i.e.,approximately 1MB of display

memory.Another

considerationshould be the


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refresh rate, i.e.,the number of

times the imagesis painted on the

screen per

second. More therefresh rate,

better the imageformation. Often a

minimum of 70-72Mhz is used to

reduce eyefatigue. As amatter of fact

higher resolutionrequires higher

refresh rates toprevent screenflickers.

Video GrabbingCard

As we havealready

discussed, weneed to convertthe analog videosignal to digital

signal forprocessing in a

computer. Normalcomputer will notbe able to do it

alone. It requiresspecial

equipment calledvideo grabbing

card and softwareto this conversion

process. This

card translatesthe analog signalit receives from

conventionalsources such asa VCR or a video

camera, andconverts them

into digital format.The software

available with it

will capture thisdigital signal and


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store them intocomputer file. It

also helps tocompress the

digitized video so

that it takeslesser disk spaceas compared to anon-compresseddigitized video.

This card is fittedinto a free slot onthe motherboard

inside thecomputer and

gets connected to

an outside sourcesuch as TV, VCRor a video camerawith the help of acable. This cardreceives both

video and audiosignal from theoutside sourceand conversionfrom analog todigital signal

takes place. Thisprocess of

conversion isknown as

sampling. Thisprocess convertsthe analog signal

to digital datastreams so that

this signal can bestored in binary

data format of0s and 1s.This digital datastream is thencompressed

using the videocapturing

software andstores them in the

hard disk as afile. This file is

then used forincorporation into


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multimedia. Thisdigitized file canalso be edited

according to therequirements

using variousediting softwaresuch as Adobe

Premiere.A number of

digitizer or videograbbing cardsare available in

the market.However, one

from Intel called

Intel Smart VideoRecorder III doesa very good job of

capturing andcompressing

video.(d) Sound Card

Todayscomputers are

capable ofcreating theprofessionalmultimedia

needs. Not onlyyou can usecomputer to

compose yourown music, but itcan also be usedfor recognition of

speech andsynthesis. It caneven read back

the entiredocument for you.But before all this

happens, weneed to convertthe conventionalsound signal to

computerunderstandabledigital signals.This is done

using a specialcomponent added


40/47

to the systemcalled soundcard. This is

installed into afree slot on the

computermotherboard. As

in the case ofvideo grabber

card, sound cardwill take the

sound input fromoutside source

(such as humanvoice, pre-

recorded sounds,

natural soundsetc.) and convertthem into digitalsound signal of

0s and 1s.The recordingsoftware usedalong with thesound card will

store this digitizedsound stream in afile. This file can

latter be usedwith multimediasoftware. One

can even edit thedigitized sound

file and addspecial soundeffects into it.Most popularsound card isfrom Creative

Systems such asSound Blaster-16,

AWE32, etc.AWE32 sound

card supports 16channel, 32 voice

and 128instruments and10 drums soundreproduction. Italso has CD-

ROM interface.(e) CD-ROM


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DriveCD-ROM is a

magnetic disk of4.7 inches

diameter and it

can contain dataup to 680

Megabytes. It hasbecome a

standard by itselfbasically for its

massive storagecapacity, faster

data transfer rate.To access CD-

ROM a very

special drive isrequired and it isknown as CD-ROM drive. Letus look into theterm ROM that

stands forRead OnlyMemory. It

means thematerial

contained in itcan be read (asmany times, asyou like) but the

content cannot bechanged.

As multimediainvolves highresolution of

graphics, highquality video andsound, it requires

large amount ofstorage space

and at the sametime require a

media, which cansupport faster

data transfer. CD-ROM solves this

problem bysatisfying bothrequirements.

Similar to thehard disk drive,


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the CD-ROMdrive has certain

specification,which will help to

decide which

drive suit best toyour multimedia

requirement.(i) Transfer RateTransfer rate is

basically theamount of data

the drive iscapable of

transferring at asustained rate

from the CD tothe CPU. This ismeasured in KBper second. For

example, 1x driveis capable oftransferring

150KB of datafrom the CD to

the CPU. In otherterms 1x CD drive

will sustain atransfer rate of

150KB/sec,where x standsfor 150 KB. This

is the basemeasurementand all higher

rates are multipleof this number, x.Latest CD-ROMdrive available is

of 64x, thatmeans it iscapable of

sustaining a datatransfer rate of

64x150=9600 KB=9.38MB per

second from theCD to the CPU.

(ii) Average Seektime

The amount oftime lapses


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between requestand its delivery is

known asaverage seekstime. The lower

the value bettersthe result and

time is measuredin milliseconds. Agood access time

is 150ms.Recentlycomputer

technology hasmade

tremendous

progress. Youcan now haveCDs which canwrite many,read many

times. Thismeans you can

write your files into a blank CD

through a laserbeam. The written

material can beread many times

and they caneven be erasedand re-written

again. Basicallythis re-writableCDs can beused a simple

floppy disk.

(f) Scanner

Multimediarequires high

quality of images,graphics to be

used. And it takeslot of time

creating them.However there

are ready-madesources such as

real life

photographs,books, arts, etc.


44/47

available fromwhere one easily

digitized therequired pictures.To convert these

photographs todigital format, one

need a smallpiece of

equipment calledscanner attachedto the computer.A scanner is a

piece of computerhardware that

sends a beam of

light across apicture ordocument andrecords it. It

captures imagesfrom various

sources such asphotograph,

poster, magazine,book, and similarsources. These

pictures then canbe displayed and

edited on acomputer. The

captured orscanned picturescan be stored invarious formats

like;File FormatExplanation

PICT

A widely usedformat compatible

with mostMacintosh.

JPEGJoint

PhotographicExperts Group - a

format thatcompresses files

and lets you

choosecompression


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versus qualityTIFF

Tagged ImageFile Format - a

widely used

format compatiblewith both

Macintosh andWindows systems

Windows BMPA format

commonly usedon MS-DOS and

MS-Windowscomputers

GIF

GraphicsInterchangeFormat - a format

used on theInternet, GIF

supports only 256colors or grays.Scanners areavailable in

various shapesand sizes like

hand-held, feed-in, and flatbed

types. They arealso for scanningblack-and-white

only or color.Some of the

reputed vendorsof scanner are

Epson, Hewlett-Packard, Microtek

and Relisys.

(g) Touch screenAs the name

suggests, touchscreen is used

where the user isrequired to touchthe surface of the

screen ormonitor. It isbasically a

monitor that

allows user tointeract with


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computer bytouching the

display screen.This uses beamsof infrared light

that are projectedacross the screen

surface.Interrupting the

beams generatesan electronic

signal identifyingthe location of thescreen. And the

associatedsoftware

interprets thesignal andperforms the

required action.For example,touching the

screen twice inquick successionworks as double

clicking of themouse. Imaginehow useful this

will be for visuallyhandicapped

people who canidentify things by

touching asurface. Touch

screen isnormally not usedfor development

of multimedia, it israther used for

multimediapresentation

arena like tradeshow, information

kiosk, etc.Uses of

MultimediaPlacing the mediain a perspective

within theinstructional

process is animportant role of


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the teacher andlibrary

professional.Following are thepossible areas of

application ofmultimedia:

l Can be used asreinforcement

l Can be used toclarify or

symbolize aconcept

l Creates thepositive attitude

of individuals

toward what theyare learning andthe learning

process itself canbe enhanced.

l The content of atopic can be morecarefully selected

and organizedl The teaching

and learning canbe more

interesting andinteractive

l The delivery ofinstruction can be

morestandardized.l The length of

time needed forinstruction can be

reduce

Reference:http://www.seminarprojects.com/Thread-cdma-technology-full-download-seminar-report-and-paper-presentation#ixzz1f4wE5klQ
http://www.seminarprojects.com/Thread-cdma-technology-full-download-seminar-report-and-paper-presentation#ixzz1f4wE5klQhttp://www.seminarprojects.com/Thread-cdma-technology-full-download-seminar-report-and-paper-presentation#ixzz1f4wE5klQhttp://www.seminarprojects.com/Thread-cdma-technology-full-download-seminar-report-and-paper-presentation#ixzz1f4wE5klQhttp://www.seminarprojects.com/Thread-cdma-technology-full-download-seminar-report-and-paper-presentation#ixzz1f4wE5klQhttp://www.seminarprojects.com/Thread-cdma-technology-full-download-seminar-report-and-paper-presentation#ixzz1f4wE5klQhttp://www.seminarprojects.com/Thread-cdma-technology-full-download-seminar-report-and-paper-presentation#ixzz1f4wE5klQ

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