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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
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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.
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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
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