Communications: Satellite

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SATELLITE

COMMUNICATIONS

Satel

Satellitelite ParParameameterter andand ConConfigfiguraturationion Sat

Satellelliteite OrbitsOrbits Fre

Frequequencyncy BandsBands Tran

Transmissmissionsion ImpairmentsImpairments Sat

Satellelliteite NetworkNetwork ConfConfiguriguratioationsns 9 2

9 2 CaCapapacicityty Allocation Allocation FrequencyFrequency DivDivisisionion Frequ

Frequencyency DivDivisiisionon MulMultiptiplexlexinging Frequ

Frequencyency DivDivisiisionon MultMultipleiple AcAccecessss 9

9 llocation llocation TImeTImeDivisionDivision

Rec

Recommommendendeded ReReadiadingsngs anan ebeb SiSitete 9 5

9 5 KeKe TeTermrms s ReviewReview QuestiQuestions ons andand ProblProblemsems Ke

Ke TeTermsrms Re

Revievie QueQuestiostionsns Problems

Problems

23 23

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238

238 H PTER H PTER OMMUNI OMMUNI TIONSTIONS Sate

Satellillitete commcommunicaunicationtion cocompmpararabablele impoimportrtanancece toto opoptiticaca fifibebe thethe tion

tion ofof teltelecoecommummunicnicatiationsons andanddatadata cocommmmuniunicacatitionons.s. TheThe fifirsrs sesectctionion ofof ththisis chchapap te

te ntnt ododucuc anan papararamemetetersrs elelatateded toto hehe

nt

nt nnnnasas ThTh reremamainindede ofof thth chchapaptete devo

devotedted toto ststudud ofof cacapapacicityty alallolocacatitionon

Th

Th heartheart ofof sasatetellllitit comcommumuninicatcatioionsns sysyststemem sasatetellllitite-e-basbaseded antennantenn inin ststabablele or

orbibi ababovov thth eaeartrth.h.InIn satsatellelliteite commcommuniunicaticationsons sysyststemem twtw oror mormor ststatatioionsns onon

or

or nearnear thth earearthth cocommmmununicicatat oneone oror momorere atat esesthatthat serveserve s s relrelayay ststatiationsons

in

in acace.e. ThTh anteantennanna ysys emem onon oror nearnear earteart efeferer eded toto s s earearthth stastatiotionsns

tr

tranan mimissssioio frfromom anan earearthth ststatatioio th atth atelel itit refreferrerreded toto s s uplinkuplink whereaswhereas

tr

tranansmsmisissisionon frfromom thethe sasatetellllitit toto thth earteart ststatatioio arar downlinkdownlink ThTh cocompmpononenen th

th atatelel itit ththatat tatakeke anan upup inin anan coconvnverertsts itit toto dodownwnlilinknk cacalllleded

transponder transponder

Ther

Ther arar numbernumber ofof difdifferferentent ofof cacatetegogoririzizingng comcommumunicnicatatioionsns sasatetellllititeses

Coverag

Coverag arareaea GloGlobal,bal, regregionional,al, oror nanatitiononalal ThTh lalargrgerer thethe areaarea ofof covcovererageage

th

th moremore satsatellelliteite mustmust bebe ininvovolvlveded inin sisingnglele netwnetworkorkeded sysy tetem.m. Ser

Servicvic tytypepe FiFixexe seservrvicic sasatetellllitite e FSFSS)S) broadbroadcastcast seservrvicic sasatetellllitite e BSBSS)S) anan mobi

mobilele seservrvicic satsatellellite ite MSMSS)S) ThThisis chapterchapter concconcerneerne witwit FSFS andand eses

Genera

Genera ususagage:e: CommCommerciercial,al, mimililitataryry amateur,amateur, experexperimentimental.al.

number

number ofof didiffffererenencece bebetwtweeee sasatetellllitite-e-babasese anan teterrrresestrtriaia

wir

wireleelessss communicationscommunications thatthat affeaffectct desdesigign:n:

... ThTh areaarea ofof covcoveraeragege ofof sasatetellllitit sysyststemem fafa exexceceeded thatthat ofof teterrrresestrtriaia

tem.

tem. InIn thethe cacasese ofof gegeosostatatitiononarar sasatetellllitite,e, ngng antennaantenna toto aboaboutut

one

one-fo-fourturt ofof thethe eartearth sh s ururfafacece Sp

Spacacececraraftft powpowerer anan alallolocacatete babandndwiwidtdt arar lilimimitete reresosoururcece ththatat oror car

carefuefu tratradeofdeoffsfs inin earthearth station/station/satesatellillitete desdesignign parameteparameters.rs.

Co

Condndititioionsns betbetweewee cocommmmununicicatatinin sasatetellllititeses arar moremore imim ininvavaririanan ththanan

th

thosos betbetweweenen sasatetellllitit anan earthearth stationstation oror betwbetweeneen twtw teterrrresestrtriaia elel

ant

antenennasnas ThThusus satsatelellilitete-t-to-o-sasateltellilitete commcommuniunicatcationion lilinknk cancan bebe desdesigignedned wiwithth great

great prepreciscision.ion.

... TrTranansmsmisissisionon coscos inindedepependndenen ofof thth e se s arareaea

coverage. coverage.

.... BroBroadcadcastast mumultlticicasast,t, andand poinpoint-tt-to-po-poinoin appapplilicatcatioionsns areare reareadildil accaccommommodaodatedted

hi

highgh babandndwiwidtdthshs oror datdat raratete arar avavaiai abab toto thethe erer Al

Alththououghgh sasatetellllitit arar susubjbjecec toto shshorort-t-tetermrm ououtatagege oror degradatdegradationsions thethe

qual

qualityity ofof trantransmissmissiosio normnormallyally extrextremelemel hihighgh For

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LI

LITETEPARAMETERSPARAMETERSA NA N C OC ON FN FI GI GU RU RATIONSATIONS Satellite

Satellite OrbitsOrbits

Sa

Satetellllitit ororbibitsts maymay bebe clclasassisififieded inin nunumbmberer ofofways:ways: be

be circirculcular,ar, witwit thth centercenter ofof hehe atat thth centercenter ofof thth

earth,

earth,oror ellelliptipticaical,l, withwith thth earearth th centcenterer atat onon ofof thth ofofthth ellipse.ellipse.

ar

arououndnd thth eaeartrt differedifferentnt plaplanesnes equatorequatorialial orborbititisis

di

di ecec ababovov thethe earearth th eqequauatotor.r. popolala ororbibi papasssseses overoverbothboth popolele OtherOther

or

orbibitsts arar rerefeferrrreded toto asas inclined orbinclinedorbitsits

Th

Th ofof commucommunicatnicationsions satsatellelliteite isis clclasas ifif eded geogeoststatiationaonaryry ororbibi

GEO ,

GEO , mediummedium earthearth orbitorbit MEa , MEa , anan earearthth ororbibi LEO , LEO , expexplailainedned subsequently.

subsequently.

Distance

Distance FigureFigure illustratesillustrates thth geometrygeometry thatthat didictctatateses sasatetellllitit cocoveveraragege keke

factor

factor isis thth eleelevatvationion anganglele hehe earthearth station whistation whichch isis thth ananglgl frofro thth hori-

hori-zo

zontntal al inin tatangngenen toto thth susu fafaceceofof thth earthearth atat thethe antantennenna a lolocacatitionon toto thth

point

point o no n cecentnterer ofof thth mainmain antantennenn whwhenen thth antantennenn isis pointedpointed

directly

directly atat thth e.e. obobtatainin mamaxiximumu atatelel tete cocoveve agage,e, wowoulul toto

an

an eleelevatvationion ananglgl ofof whwhicic wouwouldld enabenablelethth sasatetellllitite e cocoveveraragege toto extextendend toto thethe

op

optiticaca hohoririzozo frfromom thethe sasatetellllitit inin didi ecec ioionsns HoHowewevever,r, thrthreeee prproboblelemsms didictctatat

Satellite Satellite

arth arth

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4

4 CHAPTERCHAPTER SATELLITESATELLITE COMMUNICATIONSCOMMUNICATIONS

th

thatat thth minminimuimu eleelevatvationion angangleleofof thth earearthth ststatatioion sn s antantennenn bebe somewsomewhathat greagreaterter

than

than [INGL97]:[INGL97]: Bu

Builildidingngs,s, trtreeees,s, andandotherotherterreterrestrialstrial objobjectect thatthatwouwouldld blblockockthth linlin ofof sisighght.t.

he

hesese ayay esesulul atattetenunuatatioio ofof thth ababsosorprp ioio oror inin disdistortortiotionsns due

due toto mulmultipatipathth rereflflecectitionon Atm

Atmosphospherieri attattenuaenuatiotio isis greatergreater atat elelevevatatioio bebecacausus thth tr

travaverersese thethe atmatmosphosphereere fofo lolongenge didiststanancece thethe smsmalallele thethe elelevevatatioio anan El

Elecectrtricicalal nonoisis gengeneraeratedted byby thethe earearth sth sheatheat nearnearitit surfsurfaceace advadvererselsel afaffefectct reception.

reception. For

For dodownwnlilinknks,s, currcurrentent dedesisigngn prpractacticeiceisis toto mimi imim elelevevatat onon

from

from 5°5° toto dedepependndinin onon frfreqequeuencncy.y. ForFor upuplilinknks,s, thetheFCFC rereququirireses mimininimumu

eleva

elevationtion ananglgl 5°5°

Th

Th covcoveraeragege ananglgl isis memeasasurur ofof thth poportrtioio ofof thth eaeartrth h susu acac

to

to thethe sasatetellllitit taktakinging inintoto accaccouountnt thethe mimininimumu eleelevavatitionon ananglgle;e; dedefifinene cici clcl onon th

th eaeartrth h susu acac cecentnterereded onon thth popoinin elelowow thth ThTh equation equation hoholdlds:s: where where sine sine - - ---sin o sin o sin sin sin o sin o cos f3 cos f3 cos cos earth s

earth s raradidiusus 7070kmkm

or

orbitbit heheigight ht alaltititutudede frfromom poipointntonon eaeartrt didirerectctlyly belowbelow satsatellelliteite cove

coveragerage ananglgl min

minimuimu eleelevatvationion ananglgl

Th

Th distancedistance h eh e sasatetellllitit toto thth fufurtrthehe popoinin ofof cocoveveraragege alal

lated

lated follfollowow

sin

sin sinsin

sin

sin cos Ocos O R

R sinsin sinsin cos

cos sinsin The

The rouround-nd-tritri trtransansmimississionon dedelala isis ththereereforfor inin thethe rarangnge:e:

2h 2h R R sinsin -c -cos c cos wh

wherer isis the spethespeeded ofof apprapproxoximimatatelel 1010 m/s.m/s.

9.1) 9.1)

ITh

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PARAMETERS

PARAMETERS ANAN CONFIGUR..ATIONSCONFIGUR..ATIONS 4 4

Geostatio

Geostationarynary altitudealtitude

25 25 15 15 ti ti <:> <:> 15 15 5 5 15 15 :; ::; : 5 5 <l l <l l OIl OIl ·C ·C >< >< <l.l<l.l Orbital

Orbitalheigheightht inin kilkilomeometerter

Figure

Figure 9.29.2 SatelliteSatellite ParametersParameters FuFuncnctitiononofofOrbitOrbitalal HeighHeigh

The

The cocoververagag ofof sasateltellilitete isis tytypipicacallll expexpresressedsed thth diameterdiameter ofof thth areaarea

covered,

covered, whiwhichch isis justjust f3R f3R withwith exprexpressedessed inin raradidianans.s.

Fi

Figugurere shshowow thth satesatellitllit periodperiod ofof rotarotatitionon cocoveverarage ge inin tetermrm ofof terresterres

tri

trialal radradiusius ofof coverage),coverage), anan thth maximaximummum roundround-trip-trip propagationpropagation dedelalay.y. Geostationary

Geostationary SatellitesSatellites TaTableble basedbasedonon oneone inin [I[ITUTU0202],], clclasassisififieses satsatellelliteite

bases

bases ofof heheirir ThTh omom ofof communicationscommunications sate

satellillitete todaytodayisis thethe geostageostationationaryry GEO) GEO)sasatetellllitite,e, fifirsrs propoproposedsed bybythth sciencscienc fificc tion

tion author ArthurauthorArthur lalarkrke,e, inin arartiti lele inin ire ireleless ss orlorl thth satellitesatellite isis inin

ci

circrculularar ororbibi kmkm eartearth h tata eses thth equatorialequatorial plane

plane ofof thth eaeartrth,h, itit rorotatatete atat lyly thth sasameme anangugulala spspeeee asas thth eaeartrt anan re

remamainin ababovov thth sasameme spspotot onon thth equatorequator asas thth eaeartrt rotates.rotates. FigureFigure 9 39 3

de

depipictct thethe EOEO ororbibi thth thth eartearth;h; thethe sasatetellllitit ymymbobolsls arar int

intendendeded toto susuggggeses thatthat therethere areare mamanyny sasatetellllititeses inin GEGE orborbit,it, somsom ofof whwhicic areare quit

(10)

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H PTER

H PTER SASATETELLLLITIT COCOiVLiVL\tl\tlUNUNICAICATITIONSONS

Tklhle

Tklhle OrOrbitbitalal ComComparparisoiso fofo SaSatetellllitit CoCommmmununicicatatioionsns ApAppliplicacatiotionsns Orbits

Orbits

Orbi

Orbitaltal perioperio Alti

Altitudetude ranrangege Visi

Visibilibilityty durationduration Elevation

Elevation

Round-trip Round-trip propagation propagation deldelayay Instantan

Instantaneouseous groundground cove

coverage rage diameterdiameteratat 10

10 elevationelevation Exampl

Exampleses ofof syssystemtem

::::::6 km ::::::6 km Iridium Iridium Globalstar Globalstar Teledesic Teledesic Skyb

Skybridgridge,e, OrbcommOrbcomm

Th

Th orbitorbit haha sevseveraera advadvantantageage toto recomrecommendmend

Because

Becausethth satellitesatellite isis ststatatioionanaryry rerelalatitiveve toto thethe earearthth thetherere isis nono problproblemem wiwithth

fr

freqequeuencnc chchanangege dudu toto thth rere atat veve momotitionon ofof thth sasa elel tete anan anantetennnnasas onon

earth

earth Doppler Doppler effeffecect t

Tracking

Tracking ofof thth satsatelellilitete byby itit earthearth stastatiotionsns simsimplplifiified.ed. 35,863

35,863 abovabov thth earthearth thth sasatetellllitit caca cocommmmununicicatat roro ghgh of

of thth threethree

co

coveve momostst ofof thth inhainhabitebite portportionion of thof th entireentire earthearth exexclclududinin nlnl thth

areas

areas nearnear thth nonortrt anan southsouth popoleles.s. On

On thth otherother hand,hand, thetherere areare prproboblelemsms

Th

Th caca gege ququitit weweakak afaftete trtravavelelinin ovoverer

an

an thth fafa northernnorthern anan sosoututhehernrn hehemimispspheherere arar popoororlyly served

served byby geostageostationtionaryary satsatellelliteite

th

th speedspeed ofof igightht aboutabout kmkm s,s, thth dede enen on

on thth equequatoato benbeneateat thth sasatetellllitit toto thth sasatetellllitit anan babackck isis

substantial. substantial. Th

Th dedelala ofof communicationcommunication betweenbetween twtw lolocatcatioionsns onon earthearth directlydirectly underunder th

th satellitesatellite isis t t 35,863 /300,00035,863 /300,000 0.240.24 FoFo otherother locationslocations nono

directly

directly underunder thth sasatetellllitite,e, thethe deldelayay isis even loeven longngerer thth satesatellitllit lilinknk isis ususeded fofo

telephone

telephone communication,communication, thth addedadded delaydelay betweenbetween whenwhen oneone perpersonsonspeaksspeaks anan th

th otothehe respondsresponds isis incincreasreaseded twtwofofolold,d, toto almalmostost ThisThis isis definidefinitelytely noticenoticeable.able.

nother

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9

9 SATELLITESATELLITEPARAMETERSPARAMETERSANAN C O N F I G U l C O N F I G U l ~ ~ T I O N ST I O N S 4 4

Orbit

Orbit 3535 8686 kmkm at

at thth equaequatortor

satellite satellite ig

igurur GeGeosostatatitiononarar EarthEarth OrbitOrbit GEO GEO

ve

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24

24 H PTER H PTER O M M U N I O M M U N I T I O N ST I O N S

a

a LowLowearthearth orbit:orbit:

often

oftenininpolarpolarorbitorbit at

at toto 15150000kmkm

altitude altitude

b

b MediumMedium earthearthorbit:orbit:

in

incliclinedned toto thethe equequatoator,r,

at

at50500000 toto 1818,0,00000 kmkm

altitude altitude

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SA

SATETE LILITETEP R P R MEMETERTERS S NDND ONFIGUR TIONS ONFIGUR TIONS

Pra

Practicticalcal usus ofof ththisis sysyststemem rerequiquiresres thth mumultltipiplele ororbibitata plplananesesbebe ususeded eaceac

wi

withth mumultltipiplele sasa elellili eses ororbibit.t. CoCommmmununicicatatioio bebetwtweeee earthearth stastatiotionsns tytypipi ca

callll ininvovolvlv hanhandingding offoffthth sisigngnalal frfromom oneone sasatetellllitit toto ananototheher.r.

LE

LE sasatetellllititeses hahaveve numbernumber ofof advadvantantageage overover EOEO satellites.satellites.InIn additionaddition to

to thth rereduducece proppropagatagationion dedelala mentionedmentioned prprevevioioususlyly recereceiveive LELE signalsignal isis

mu

muchch ststrorongngerer thanthan sisigngnalal fofo thth samsam trtranansmsmisissisionon popowewer.r. LELE

co

coveveragrag caca bebe betterbetter loclocalializedzed soso thatthat spespectrctrumum caca bebe betterbetter conserved.conserved.FoFo thisthis reas

reason,on, ththisis tectechnohnologlog isis currcurrentlyently beinbein proposedproposedfofo comcommunmunicaicatintin wiwithth mobmobileile

terminals

terminals anan wiwithth pepersrsononalal tetermrmininalal thatthat neneeded strongestronge sisigngnalal toto function.function. OnOn

hand,

hand, provideprovide broadbroad

needed. needed.

m b

m b cocommmmerercicialal prpropopososalal hahaveve sese clclusustetersrs ofof

LEOs

LEOs to prto provovidid communicommunicationscations seservrviciceses TheseThese proproposposalsals cancan bebe didivividede inintoto two

two catcategoegorieries:s:

nt

nt ndnd GHGH

Th

Theses stst msms arar aiaimeme atat rarackckining,g, anan lolow-w-raratete Orbcomm

Orbcommisis anan exexamamplepleofofsusuchch sasateltellitlit sysyststemem ItIt thethe fifirsrst t lilittttlele EOEO inin

op

operaeratition;itson;its fifirsrs twtw sasatetellllititeses wewerere laulauncnchedhed inin AprAprilil ofof ItIt isis desigdesignedned forfor

pa

pagigingng anan bubursrs cocommmmununicicatatioio andandisis opoptitimimizeze oror hahandndlilingng smsm llll bubursrststs ofof

da

datata ItItisis useuse bubusisinenesssseses toto trtrackack trtraiailelersrs aiaill

he

heavav eqequiuipmpmenent,t, andand othotherer reremotmot andand momobibilele ItIt caca bebe ususeded toto mon

monitoito remoremotete ututililitit metmetersers andand andand storstorageage tatanknks,s, andand pipipepelilinenes.s.

It

It momotete thth

well.

well. ItIt ususeses thethe frefrequequencincieses toto MHzMHz toto thethe sasatetellllititeses andand 3737 toto

MHz

MHz frfromom thethe sasatetellllititeses ItIt haha ovoverer sasatetellllititeses inin lolo earthearth ororbibit.t.ItIt

su

supppporortsts susubsbscrcribiberer datadata raratestesofof toto thth sasa llll tete anan 4 84 8 kbpkbp dodownwn

Wo

Workrk atat frfreqequeuencncieie ababovov GHGH anan susupppporor dadatata toto megabits

megabits pepe sesecoco d.d. ThTheses tete tenten toto ofoffefe thth sasameme asas ofof

sm

smalal LELEOsOs wiwithth thethe adaddidititiononofofvovoicic andand pospositiitioninonin seservrviciceses GlobalGlobalstarstarisis oneone

ex

examamplpl ofof LELE sysyststemem ItIt sasatetellllititeses areare fafairirlyly rurudidimementntarary.y. UnlUnlikeike sosomeme ofof

the

the lilittttleleLELE sysyststemems,s, itit haha nono onboardonboard prprococesessisingngoror commcommunicunicatioationsns betweenbetween

sat

satellelliteites.s. MostMost proceprocessingssingisis dondon byby thethe sysyststem em earteart ststatatioionsns ItIt ususeses DM DM asas

th

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CHAPTER

CHAPTER COMMUNICATIONSCOMMUNICATIONS

Ta

Tablbl FrFreqequeuencnc BaBandnd fofo SaSatetellllitit CoCommmmununicicatatioionsns

Frequency

Frequency BandsBands Ta

Tablbl lilistst thth frefreququenencycy banbandsds avavaiailalablbl fofo sasatetellllitit cocommmmununicicatatioionsns NoteNote thatthat

in

increcreasiasingng bandwibandwidthdth isis avavaiailalablbl inin thethe hihighgherer-f-frereququenencycy babandnds.s. HoHowewevever,r, inin

ra

ra thth hihighgherer thth thth grgreaeatete thth ffff ofof transmitransmissionssion impimpairmairmentsents Th

Th momobibilele sasatetellllitit seservrv ce ce MSMS alallolocacatete frfreqequeuencncieie inin thethe LandLand InIn th

theses babandnds,s, comcomparpareded toto hihighgherer frfreqequeuencnc eses thetherereisis grgreaeatete dedegrgreeee ofof rerefrfracactitionon

and

and greatgreaterer penetrpenetrationation ofof phphysysicicalal obobststacacleles,s, susuchchasas fofoliliagag andand nonnon-me-metaltalliclic ststrucruc

ur

ureses ThTheses chchararacacteteririststicic areare dedesisirarablbl fofo momobibilele seservrv cece HoHowewevever,r, thetheLandLand

ban

bandsds areare alalsoso heheavavilil ususeded fofo terterrestrestriaria apapplplicicatatioionsns ThThusus therethereisis inteintensense comcompepe

ti

titiotio amamongong thethe varvarioiousus mimicrcrowowavav seservrviciceses fofo LandLand bandband capacity.capacity. Fo

Fo rere enen ththerer anan

uplink

uplink bandband anan dodo lilinknk babandnd thth upuplilinknkbandband alalwawaysys ofof highigherher frfreqequeuencncy.y.

Th

Th hihighgherer frfreqequeuencnc ffff grgreaeatete spsprereadadining,g, oror frfreeee spspacac thanthan fr

freqequeuencnc councounterterpartpart ThTh earthearth stastatitionon isis capacapablbl ofof hihighgherer popowewer,r, hihichch hehe psps toto

co

compmpenensasatete fofo thethepoorerpoorerperformanceperformance atat highhigherer frfreqequeuencncy.y.

TranSlnission

TranSlnission ImpairmentsImpairments The

The perperforformamancence ofof sasatetellllitit lilinknk dedepependnd onon threethree fafactctorors:s:

st

stanancece bebetwtweeee earthearth ststatatioio antantennenn andand sasatetellllitit antantennenn In

In thth ofofthth dowdownlnlinkink terreterrestriastria disdistantancece betweenbetween earthearth stastatiotio anteantennanna and

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SA

SATETELLLLITIT PAPARARAM.M.ETETERER ANAN CONFIGUR..ATIONSCONFIGUR..ATIONS

carrie

carrie wavwaveleelengtngt prop

propagaagationtion didiststanancece betwbetweeneen antantennennasas

an

an anan AarAar inin thth sasameme ninits ts memeteters rs Th

Th hihighgherer thth frfr ququ ncncy y shshorortete thth wawavevelelengngth ,th , thth grgreaeatete thth FoFo

GE

GE satesatellllitite,e, thethe frefre spspacac lolossss atat thth equatorequator isis -20log A

-20log A 20log 35.86320log 35.863 1010 2121.9.9 dBdB

-20log A

-20log A 173.07173.07 Losses

Losses atat pointspoints onon earthearth thth equatorequator butbut is

isibiblele frfromom thethe sasatetellllitit bebe sosomemewhwhatat igigheher.r. TheThe mamaxiximumu didiststanance ce frfromom thth at

at llllitit toto thth ororiziz n n fofo GEGE satellitesatellite 4242,7,71111 kmkm ththisis isistatancnce,e, thth frfreeee spa

spacece lolo isis

-20log A

-20log A 174.59174.59

Figure

Figure plplotot thth atattetenunuatatioio fufuncnctitionon ofof frfr ququ anan orbitorbitalal heheighight.t. Satellite

Satellite FootprintFootprint mimicrcrowowavav frfreqequeuencncieies,s, whwhicic arar inin tetellll tete com

communmunicaicatiotions,ns, hihighghlyly direcdirectionationa antennasantennas arar thth

sate

satellitellite nono isotropicallyisotropically broadcastbroadcast utut aiaimeme atat spspececifiifi pointpoint onon thth earth,earth, depending

depending onon whichwhich areaarea ofof covcoveragerag desdesireired.d.TheThe cencenterter popoinin ofof thatthat areaarea willwill receive

receive thth highesthighest power,power, anan powerpower yoyo momoveve awaw

from

from t ht h c ec e t et e pointpoint pattern

pattern knknowow tetellll tete fofo riri anan ThTh

sa

sateltellitlit foofootpritprintnt didispsplalaysys thth effectiveeffective radiatedradiated powerpower ofof thth antennaantenna atat eacheach po

poinint,t, tatakikingng inintoto acaccocounun thth signalsignal powerpower inintoto n an a thth direcdirec

tionality

tionality ofof thth anantetennnna.a. InIn thth exexamampleple fifigugurere fofo ArkansasArkansas isis 36

36 fofo MasMassacsachushusettett isis +3+3 dBdBW.W. ThTh actualactual powerpower receivedreceived atat anyany

point

point footprintfootprint isis fofounun byby susubtbtraractctinin thth frfr papacece frfromom thth effeceffec

tive

tive powerpower figure.figure. A t m o s

A t m o sp h e rp h e ri ci c A t tA t te n u ae n u at it io no n ThTh primaryprimary cacaususeses ofof atmosphericatmospheric attenuationattenuation ar

ar oxoxygygenen whwhicic isis ofof cocourursese prpresesenent,t, anan water.water. AttenuationAttenuation water

water isis presentpresent inin humidhumid aiai anan isis moremore pronouncedpronounced wiwithth fofo anan rain.rain. AnotherAnother

factor

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48

48 H PTER H PTER SATELLITESATELLITE OMMUNI OMMUNI TIONSTIONS

22 22

t:l t:l

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3 3 d d

9.1

9.1 SATELLITESATELLITE PARAMETERSPARAMETERS ANAN CONFIGURATIONSCONFIGURATIONS 2424

Fi

Figugurere ypyp caca SaSatetellllitit FoFootpotprinrin

2 5

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25

25 H PT E R H PT E R SASATETELLLLITIT COCOM1 \M1 \rlrlUNUNICICATATIOIONSNS

Satellite Satellite antenna antenna Earth Earth station station a)

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5 m o t ~

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site site Point-or-sale Point-or-sale Terminals Terminals Fi

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Ti

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Co

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In sesectctioio anan thth nene t,t, exex miminene FDMAFDMA andandTDMA.TDMA. CDMACDMA wawa isis

cu

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252

252 CHAPTERCHAPTER COMMUNICXnONSCOMMUNICXnONS

MH

MH bandwbandwidthidth

M M 36 36 guardbandguardband MHz MHz C3 C3 CSCS C13C13 CISCIS CICI C C C23C23 I I I I I I I I II II II II 372 372 376376 38 38 384384 388 388 392 392 396396 4 4 4 4 4 4 4 4 8 8 412412 41604160 4242 C6 C6 CICI CICI CICI CICI I I I I I I I I 374 378 382 374 378 382 386 386 3939 394394 398398 4 4 4 4 41 41 414 414 418418 37 37 37 37 a)

a)HorizontalHorizontal polarizationpolarization

b

b VerVerticticalal polarizapolarizationtion 4242

f MHz f MHz

Fi

Figugurere SaSatetellllitit TrTrananspsponondede FrFreqequeuencnc PlPlanan fofo thethe DoDownwnlilinknk ChChanannenels ls oror th

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ac ac

of

of kbkbpsps eaeachch On

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minene neneeded totousus CaCarsrson on rurulele [ Equa[ Equatition on didiscscusussese ChapChapterter ThTh bandwidth

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9 :2 CACA.P.PACACITIT ALLOCATION FREQUENCYALLOCATION FREQUENCY DIVISIONDIVISION 5 5

to

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nal

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re

refeferrrreded toto FDMA.FDMA.

Th

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lim

limiteite byby threethree fafactctorors:s: he

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ta Th

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cor

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the sasatetellllitite e amamplplififieiersrs reresusultlt inin hihighgh intintermermoduodulatlationion nonoisise.e. CrCrososstastalklk ststemem frfromom de

desisirere toto inincrcreaeasese cacapapacicityty byby rereususinin frfreqequeuencncieie anan itit bubu doesdoes nono eliminateeliminate that

that prpracactiticece frefreququenencycy bandband cancan bebe reusreuseded ifif anantetennnnasas thatha caca raradidiateate twtw popolalarr ized

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25

CHAPTERCHAPTER COMMUNICATIONSCOMMUNICATIONS 36

36 MHzMHz bandwbandwidthidth

6260 6260 f MHzf MHz 6258 6258 4 4 Station

Station stationstation StationStation StationStation

a

a TransponTransponderder upliuplinknk frefrequequencyncy allallocaocatitionon 132VF 132VF Station Station To To satellitesatellite IMb f 1 IMb f 1 FD

FD sigsignalnal 60

60 VFVF chchanannenelsls mb t mb t FMFM transmittertransmitter s ts t FDMJFMFDMJFM Supergroup Supergroup I I ~ _ ~ _ ; ~; ~ type type fefe 6.6.2424 GHzGHz frequency frequency To To sta:on sta:on s t ~ ~ o s t ~ ~ o

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9

9 CAPACITYCAPACITY ALLOCATION FREQUENCYALLOCATION FREQUENCY DIVISIONDIVISION

SCPC

SCPC isis cucurrerrentntlyly proprovidvideded ininthth babandnd -M-M chchanannene di

divividede inin -k-k ananalal eaeachch dededidicacatete toto sisi plplexex VFVF link,link,

us

usinin FMFM ThereThere isis alalsoso didigigitata SCSCPCPC ususinin QPSQPSK,K, whwhichich provprovideide 6464-k-kbpbp serservivicece

in

in thth sasameme 4545-k-k babandndwiwidtdth,h, enenououghgh fofo didigigi izizeded WiWithth FAMAFAMA pairspairs ofof

ch

chanannenels ls fofo duduplplex ex arar asassisigngneded toto pairspairs ofof earthearth statstations.ions. TyTypipicacalllly,y, eacheach earth

earth stationstation isis mulmultiptiplexlexed,ed, suppsupportiortingng smsmalal numnumberber ofofuseruser ststatatioions.Withns.With mumull

ti

tiplpl ususerer ststatatioionsnspepe eaeartrt ststatatioion,n, hihighgh degdegreeree ofof coconnnnecectitivivityty isis achiachieveeve eveneven wi

withth FAMFAMA.A. AsAs wiwithth conconvenventitionaona FDMAFDMA thth satsatellellitit accaccepeptsts freqfrequenuenciecie acacrorossss th

th ententireire 3636-M-MHzHz chchanannenel,l, tratranslnslateate 4 4 band,band, anan broadcastsbroadcasts

th

th channelchannel toto alal statstations.ions. SCPC

SCPC isis atattrtracactitiveve fofo remoteremote rere erer sese nearnear

eac

eac WheWhereasreasFDMAFDMA isis usus truntrun thth long-halong-haulul telectelecommunommunii

cat

cationion sysyststemem SCPSCP proprovividesdes didirerectct endend-us-userer seservrv cece AltAlthoughoug SCPCSCPC isis moremore effieffi

than

than FDMAFDMA

assignme

assignment.nt. ThiThi isis esespepecicialallyly unsunsuituitablabl inin veveryry remoremotete arareaeas,s, whewherere itit isis typicaltypical thatthat

each

each earthearth ststatatioio seservrv onon oror erer ususerer chch evev grgreaeatete ciency,

ciency,DAMADAMA isis useused.d. WiWithth DAMADAMA hehe sese ofof susubcbchahannnnelel inin chchanannene isis treatedtreated

po

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CHAPTER

36

36 MHzMHz banbandwidwidthdth Commo

Commo signsignalingaling cha

channnnel el CSCCSC

QPSK QPSK signals

signals ₉₉400400-40-403 3 unuunused)sed)

800 800

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To Tosatellitesatellite QPSK QPSK QPSK QPSK signalsignal transmitter transmitter PC PC PC PC PC PC 64kbps64kbps encoder encoder 0

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encoder

encoder transmittertransmitter

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0

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fromom stastationtion

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guardtimetime ,,,,

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9

9 C,J\PACITYC,J\PACITYALLOCATlON TIlVIEDIVISIONALLOCATlON TIlVIEDIVISION 2525

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ReCOlTInlended

ReCOlTInlended SitesSites

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