18599_Frequency Assignment and Spectrum Conservation

8/9/2019 18599_Frequency Assignment and Spectrum Conservation

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V.impWhy do we need

frequency assignment andspectrum conservation

To establish Harmonic functions among radiodevices

To prevent interference

To make our system compatible so that it can

withstand with the increasing demands

To design ecient spectrum


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. !requency allocation and

frequency assignment"adio waves are not con#ned to national

boundaries $hence to prevent interference the%nternational Telecommunication &nion '%T&(de#nes the use of each frequency band forradio services.


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. !actors a)ecting !*..(!requency planning

..+( Technical characteristics of transmitters

and receivers,ote- These factors are carefully considered in

the %T& and in the periodic meetings of World*dministrative "adio onference 'W*"( in

order to reach international level agreementon the usage of frequency spectrum


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/tandards to be followed

during !*0ntire world has been divided into three regions hence some

standards are to be followed in order to establish world wideinteroperability


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/tandards to be followed by

member countries during!*

*112%*32%2%T4 T5 TH0 "06&2*T%5,/1&32%/H07 %, %T&.

,5 H*"8!&2 %,T0"!0"0,08%,%8&8 0//0,T%*2 ,5 5! !"09&0,4 *,7

/10T"&8 /1*0


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*112%*32%2%T4 T5 TH0 "06&2*T%5,/1&32%/H07 %, %T&.

To note


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,5 H*"8!&2 %,T0"!0"0,0

To note


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8inimum essential no of frequency andspectrum space

To note


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.+ spectrum utili:ation&tili:ation of radio frequency and ecient

planning of radio communication servicesdepends critically on-

.+. radio propagation

.+.+ "adio noise data


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1arameters of spectrum

utili:ation&tili:ation time

3andwidth

0)ective area


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&tili:ation timeTo note


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3andwidth

%n order to avoid any interference amongchannels proper 3W to the channels should be

assigned

2et transmitter has a bandwidth !t

Where $ are the bandwidth occupied bymodulated signal on either side of a carrier center frequency$and frequency instability respectively

)(2 imt ffF +=mf if


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3andwidth 'continued(How can we have proper

use of spectrum withoutinterference

6uard band concept

To note


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V.%mp 0)ective areaTo note


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.; evaluation of spectrum

utili:ation.;.( /pectrum utili:ation eciency

.;.+(5ptimum communication system


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utili:ation.;.( /pectrum utili:ation eciency

To note


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utili:ation.;.+(5ptimum communication system

To note


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ondition for optimaldesign

To note


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2) ModulationtechniquesModulation is the process by which

some characteristics of the carrier wave(usually amplitude , frequency or phase)is varied in accordance with themodulating signal wave


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2.1 Types ofmodulation2.1.1) Analog modulation

2.1.2)Digital modulation


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Types of *nalog8odulation *mplitude 8odulation '*8(

*mplitude modulation is the process of varying theamplitude of a carrier wave in proportion to theamplitude of a baseband signal.The frequency of

the carrier remains constant !requency 8odulation '!8(

!requency modulation is the process of varying thefrequency of a carrier wave in proportion to theamplitude of a baseband signal.The amplitude of

the carrier remains constant


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*mplitude 8odulation

Carrier wave

Baseband signal

Modulated waveAmplitude varying-frequency constant


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The *8 wave is the algebraic sum of thecarrier and upper and lower side

a(%ntelligence ormodulating

signal.b( 2owersideband

c(arrier.d(&ppersideband.e(omposite *8wave


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/ome Types of 7igital 8odulation *mplitude /hift


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*mplitude /hift


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!requency /hift


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1hase shift keying


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Time domain description of

*mplitude 8odulation signalTo note


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,umerical no -A modulating signal 2! cos(2&pi&t) is used to modulate a

carrier signal '! cos (!!&pi&t) find AM wave epression

for '* modulation+


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,umerical +The carrier wave is represented 3y equation

0c't(>?sin'+@pi@f@t($7raw waveform of *8signal for modulation inde= ?.A.


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,umerical no ; -A modulating signal ! sin(2&pi&!,t) is used to

modulate a carrier signal 2! sin(2&pi&(!,.)t)

%ind Modulation inde/

%ind 0ercentage modulation/

%ind Amplitude of eac1 sideband/


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1ower relation in *mplitude

8odulationTo note


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,umerical no B-A ! 3 carrier wave is amplitude modulated at 4!*

dept1 of modulation by a sinusoidal modulating

signal5calculate +

sideband power5

total power

transmission efficiency


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,umerical no A -61e antenna current of an AM transmitter is ! AM0

w1en modulation inde is !* if current increases to

AM0 w1at will be t1e modulation inde due to second

wave/


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,umerical no C*n *8 signal is generated by modulating the

carrier of frequency D?? ??FEm't(Gcos'+@pi@fc@t(

7etermine and 7raw the spectrum of the *8signal

7etermine the average power in the carrier and

in the sideband


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/pectrum conservation/pectrum management is a tool for achieving

optimum use of frequencies

!requency 1lanning and conservation intelecommunication is a comple= mathematicale=ercise.

The obective of frequency planning is to

ensure ma=imum radio communicationcarrying capacity in a given frequency bandalong with 95/ in radio services consideration


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1rimary consideration of

radio servicesTo note


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1arameters to be

considered in frequencyassignmento channel interference

Transmitter intermodulation interference

"eceiver intermodulation interference*dacent channel interference

%nterference from image$ harmonic andspurious frequencies

Threshold level


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1arameters to be

considered in frequencyassignmento channel interference

To note


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1arameters to be

considered in frequencyassignmentTransmitter intermodulation interference

To note


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1arameters to be

considered in frequencyassignment

*dacent channel interference

To note


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1arameters to be

considered in frequencyassignment%nterference from image$ harmonic and

spurious frequencies

To note


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/pectrum conservation

methods8inimi:ation 5f 5bective !unction

6raph oloring

2inear *lgebra 8ethod !or 6rid !requency*ssignment


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2inear *lgebra based

method*%8-Translation of various 08 interferencecriteria into 1hysical distance constraints


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8inimi:ation 5f 5bective

!unctionTo note


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8inimi:ation 5f 5bective

!unction *%8-%nstead of complete elimination ofinterference an acceptable upper bound is

speci#ed for interference


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L


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*,7 !"09&0,4

5,/T"*%,0751T%8%M*T%5,

To note

!@7 constrained channel


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!@7 constrained channelassignment

T5 note


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!requency constrained

channel assignmentTo note


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6raph coloring approachTo note

18599_Frequency Assignment and Spectrum Conservation

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