Satelliittiviestintä

Määritelmä ja johdanto

Satelliittiviestintä:Käytä keinotekoisia maasatelliitteja välitysasemina radioaaltojen välittämiseen, jolloin saavutetaan tiedonsiirto kahden tai useamman maa-aseman välillä.

Artificialearthsatellitesareclassifiedintoactiveartificialearthsatellitesandpassiveartificialearthsatellitesaccordingtowhethertheyhavethefunctionofamplifyingradiosignalsandtransmittingfunctions.Sincethesignalsreflectedbypassiveartificialearthsatellitesaretooweaktobeofpracticalvalue,peoplearedevotingthemselvestoresearchonactiveartificialearthsatelliteswithfunctionsofamplification,frequencyconversionandforwarding—communicationssatellitestorealizesatellitecommunication.Amongthem,thegeosynchronoussatellitewhoseperiodoforbitingaroundtheearth'sequatorisequaltotheperiodoftheearth'srotationhassuperiorperformance,andcommunicationusingsynchronoussatelliteshasbecomethemainsatellitecommunicationmethod.Low-orbitsatellitesthatdonotoperateingeosynchronousorbitsaremostlyusedinsatellitemobilecommunications.

Synchronoussatellitecommunicationisacommunicationsatellitethatorbitstheearthinacircularorbitabout36000kmabovetheearth’sequator.Theyarerelativelystationary,sotheyarecalledgeostationarysatellites,fixedsatellitesorgeostationarysatellites,andtheirorbitsarecalledgeosynchronousorbits(GEO).

Communicationscarriedoutonthegroundusingthemicrowaverelaycommunicationsystem,duetoline-of-sightpropagation,onaverageevery2500kmassumingthatthereferencecircuitpasses54relaytransfersperspanofapproximately46km.Ifthecommunicationsatelliteisusedforrelay,thecommunicationwithagrounddistanceofmorethan10,000kilometerscanbeconnectedbyonehopthroughthecommunicationsatellite(fromthegroundtothesatellite,andthenfromthesatellitetothegroundisonehop,includingtworelays),andTherelaydistanceofradiowavetransmissionisabout40,000kilometers,asshowninFigure1.

Historialyhennetty

Idea keinotekoisten maasatelliittien käyttämisestä synkronisina orbitteinä välitysasemina viestintää vartenBritishphysicistACClarken perusteella(ArtherC.Se ehdotettiin artikkelissa"Extra-EarthRelay,6,julkaisussa" 0s.

Beforetheadventofsynchronoussatellites,variouslow-orbitsatelliteswereusedforscientificexperimentsandcommunications.Theworld'sfirstartificialsatellite"Satellite1"wassuccessfullylaunchedbytheSovietUniononOctober4,1957andorbitedtheearth.Theearthreceivedradiowavesfromanartificialsatelliteforthefirsttime.

InAugust1960,theUnitedStateslaunchedthealuminum-coatedballoonsatellite"Echo1"withadiameterof30mintoacircularorbitabout1600kminheightforcommunicationexperiments.Thisistheworld'searliestso-calledpassiverelaytestwithoutusinganamplifier.

TheUnitedStateslaunchedthelow-orbitsatellite"Relay1"onFebruary13,1962.OnNovember23,1963,thestarachievedthefirsttelevisionbroadcastacrossthePacificbetweenJapanandtheUnitedStates.Atthistime,itcoincidedwiththeassassinationofUSPresidentJ.F.Kennedy.ThenewswastransmittedtoJapanviasatelliteandbroadcastonTVnews.Thelong-distancereal-timetransmissionofsatellitesleftadeepimpressiononpeopleandgreatlyimprovedthestatusofartificialsatellitesincommunications.

Theworld’sfirstsynchronouscommunicationssatellitewasthe"Synchronous2"satellitelaunchedbyNASAinJuly1963.Ithasaninclinationangleof30°totheequatorialplaneandmovesinafigureofeightrelativetotheground.Therefore,itcannotbecalledageostationarysatellite,anditisusedforcommunicationservicesforthefirsttimeintheAtlanticOcean.The"Synchronous3"satellitelaunchedinAugust1964wasfixedneartheinternationaldatelineoverthePacificequatorandwastheworld'sfirstgeostationarysatellite.InOctober1964,thelivebroadcastofthe(Tokyo)OlympicGameswasbroadcastbythestar.Sofar,satellitecommunicationisstillintheexperimentalstage.OnApril6,1965,thefirstsemi-experimentalandsemi-practicalgeostationarysatellite"MorningBird"waslaunchedforcommercialsatellitecommunicationsbetweenEuropeandtheUnitedStates.Sincethen,satellitecommunicationshaveenteredapracticalstage.

Coverage

GeostationaryEarthOrbit(GEO)Satellite

GlobalcoverageofGeostationaryEarthOrbit(GEO)satelliteforfixedsatellitecommunicationsservices,withanorbitheightofapproximately36000km,inacircularorbit,aslongasthreeuniformlydistributedsatellitesseparatedby120°cancoverthewholeworld.TheIntelsatI-IXgenerationsatelliteoftheInternationalSatelliteCommunicationsOrganization.Itisthebestexampleofglobalcoverage,whichhasbeendevelopedtotheninthgeneration.

Thesatelliteactsasarelaystationintheair,thatis,amplifyingtheelectromagneticwavesentfromtheearthstationandthensendingitbacktoanotherearthstation.Theearthstationisthelinkformedbythesatellitesystem.Sincethegeostationarysatelliteis36,000kilometersabovetheequator,itstimetoorbittheearthexactlycoincideswiththerotationoftheearth(23hours,56minutes,4seconds),anditlooksasifitisstationaryfromtheground.Threesatellitesseparatedby120degreescancovertheentireequatorialcircumference.Therefore,satellitecommunicationiseasytorealizetransoceanicandintercontinentalcommunication.Themostsuitablefrequencyforsatellitecommunicationisthe1-10GHzfrequencyband,thatis,themicrowavefrequencyband.Inordertomeetmoreandmoredemands,newfrequencybandshavebeenstudiedandapplied,suchas12GHz,14GHz,20GHzand30GHz.

Mobilesatellitecommunications

Inmarsat,aglobalmobilesatellitecommunicationssystem,isamobilesatellitecommunicationssystemwithglobalcoverage.Itoperatesthird-generationmaritimecommunicationssatellites,whicharedistributedintheAtlanticOcean.Intheeasternandwesternregions,theIndianOceanandthePacificregions,thefourth-generationInmarsat-4satelliteshavelaunchedtheirfirstsatelliteinMarch2005,andanothersatelliteisalsoreadytobelaunched.Theyarefixedat64respectively.Eand53.W,withaglobalbeam,19widespotbeams,228narrowspotbeams,usingadigitalsignalprocessor.Therearechannelselectionandbeamformingfunctions.

Thelow-orbitmobilecommunicationsatelliteswithglobalcoverageinclude"Iridium"andGlobalstar.The"Iridium"systemhas66stars,dividedinto6orbits,eachofwhichhas11Thesatelliteshaveanorbitalheightof765km.Thelinksbetweenthesatellites,betweenthesatellitesandthegatewayandthesystemcontrolcenterusethekaband,andthelinksbetweenthesatelliteandtheuserusetheL-band.AttheendofJune2005,thenumberofIridiumsatelliteusersreached127,000.DuringthedisasterofHurricaneKatrina,theservicetrafficofIridiumsatelliteincreasedby30times,andthesatellitephonecommunicationvolumeincreasedby5times.

Globalstariscomposedof48satellites,distributedin8circularinclinedorbitplanes,withanorbitheightof1389kmandaninclinationangleof52degrees.Thenumberofusershassteadilyincreasedyearbyyear,andthecosthasdecreased.In2005,thenumberofvoiceusersincreasedcomparedwith2004.

Multipleaccessmethod

Multipleaccessmeansthatthesamesatellitetranspondercanbeconnectedtomultipleearthstations.Multipleaccesstechnologydividesthesignalandrecognizesthesignalaccordingtothecharacteristicsofthesignal.,Thesignalusuallyhasthecharacteristicsoffrequency,time,spaceandsoon.Commonlyusedmultipleaccessmethodsforsatellitecommunicationsincludefrequencydivisionmultipleaccess(FDMA),timedivisionmultipleaccess(TDMA),codedivisionmultipleaccess(CDMA)andspacedivisionmultipleaccess(SDMA).Inaddition,frequencyreusetechnologyisalsoItisamultipleaccessmethod.

Inthemicrowavefrequencyband,theworkingfrequencybandoftheentirecommunicationsatellitehasawidthofabout500MHz.Inordertofacilitateamplificationandtransmissionandreducemodulationinterference,severaltranspondersaregenerallyinstalledonthesatellite.Satellitecommunicationswithaworkingfrequencybandwidthof36MHzor72MHzforeachtranspondermostlyusefrequencydivisionmultipleaccesstechnology.Differentearthstationsoccupydifferentfrequencies,thatis,differentcarriersareused.Itismoresuitableforpoint-to-pointlarge-capacitycommunication.Timedivisionmultipleaccesstechnologyhasbeengraduallyadopted,thatis,eachearthstationoccupiesthesamefrequencybandbutdifferenttimeslots.Comparedwithfrequencydivisionmultipleaccess,ithasaseriesofadvantages.Thestationsignalsareseparated,suitablefordigitalcommunication,andcanbeallocatedondemandaccordingtochangesinbusinessvolume.Newtechnologiessuchasdigitalvoiceplug-incanbeusedtoincreasethecapacityby5times.Anothermultipleaccesstechnologymakescodedivisionmultipleaccess(CDMA),thatis,differentearthstationsoccupythesamefrequencyandthesametime,buthavedifferentrandomcodestodistinguishdifferentaddresses.Itadoptsspreadspectrumcommunicationtechnology,hastheadvantagesofstronganti-interferenceability,betterconfidentialcommunicationability,andflexiblevoicechannelscheduling.Itsshortcomingsmakethespectrumutilizationratelow.Itismoresuitableforsystemswithsmallcapacity,widedistribution,andcertainconfidentialityrequirements.

Thecompositionofthesatellitecommunicationsystem

Thesatellitecommunicationsystemincludesalltheequipmentforcommunicationandguaranteeingcommunication.Generally,itconsistsoffourparts:spacesubsystem,communicationearthstation,trackingtelemetryandcommandsubsystem,andmonitoringmanagementsubsystem,asshowninthefigure.

1.Seurantatelemetria- ja komentoalijärjestelmä

Thetrackingtelemetryandcommandsubsystemisresponsiblefortrackingandmeasuringsatellitesandcontrollingthemtoaccuratelyenterthedesignatedpositiononthegeostationaryorbit.Afterthesatelliteisinnormaloperation,theorbitpositioncorrectionandattitudemaintenanceofthesatelliteshouldbecarriedoutonaregularbasis.

2.Seuranta- ja hallintaalijärjestelmä

Themonitoringandmanagementsub-systemisresponsibleforthedetectionandcontrolofthecommunicationperformanceofthefixed-pointsatellitebeforeandaftertheserviceisopened,suchasthepowerofthesatellitetransponder,thegainofthesatelliteantenna,andthepowertransmittedbyeachearthstationThebasiccommunicationparameterssuchasradiofrequencyandbandwidtharemonitoredtoensurenormalcommunication.

3.Avaruusosajärjestelmä (viestintäsatelliitti)

Communicationsatellitesmainlyincludecommunicationsystems,telemetrycommanddevices,controlsystems,andpowersupplydevices(includingsolarcellsandstoragebatteries).

Thecommunicationsystemisthemainbodyofthecommunicationsatellite.Itmainlyincludesoneormoretransponders.Eachtranspondercanreceiveandforwardsignalsfrommultipleearthstationsatthesametime,thusactingasarelaystation.

4.Communication Earth Station

Thecommunicationearthstationisamicrowaveradioreceivingandtransmittingstationthroughwhichusersaccesssatellitelinesforcommunication.

Introductiontofrequencybandsynchronoussatellitecommunicationservice

Thefrequencybandsynchronoussatellitecommunicationserviceisdividedintofixedsatellitecommunicationservice(FSS)andsatellitemobilecommunicationservice(MSS).Thefrequencybandsallocatedtothemarealsodifferent.FSSusesC-bandandKu-band.MSSusestheLfrequencyband(seesynchronoussatellitemobilecommunications),andmostoftheKutranspondersworkingintheKufrequencybandareoriginallyspotbeams.Sincethe1990s,theKustaroftheInternationalTelecommunicationsSatelliteOrganization(INTELSAT,abbreviatedasIS)iscalledISK,whichprovidesawiderrangeofservices.Regionalbeamstomeetdemand.ThefrequencydivisionsoftheCandKubandsofFSSareasfollows(theupperlineisthefrequencyusedbytheearthstationtothesatellite,andthelowerlineisthefrequencyusedbythesatellitetotheearthstation).

①Cband (MHz)

Ylävirtaan 5925～6425kaistanleveys 500 MHz

Downstream 3700 - 4200kaistanleveys 500 MHz

FortheextensionofFSSThefrequencyspectrumhasbeenadjustedfromJanuary1,1984to:

Ylävirtaan: Alue 15725～7075kaistanleveys 1350 MHz

Ala2 ja 35850～7075Kaistanleveys1225MHz

3400–4200kokonaiskaistanleveys

Alaslinkki:Vyöhyke1,2 ja3

4500-4800l100MHz

②Kutaajuuskaista (GHz)

4500-4800l100MHz

Nouseva linkki: vyöhykkeet 1, 2 ja 3, 14,0 - 14,25 kaistanleveys 250 MHz

14,25–14,5, Kaistanleveys 250 MHz

Downlink: vyöhykkeet 1, 2 ja 310,95 - 11,20 kaistanleveys 250 MHz

11,45–11,7 Kaistanleveys 250 MHz

Osa 211,7 - 11,95 Kaistanleveys 250 MHz

11,95–12,2 Kaistanleveys 250 MHz

No.3 Zone 12,2 - 12,5 Kaistanleveys 300 MHz

Ensimmäiset thirdzonit 12,5 - 12,75 kaistanleveys 250 MHz

Accordingtothefrequencyallocationofthe1992InternationalAdministrativeRadioConference(WARC-92),theInternationalTelecommunicationsSatelliteOrganizationThenewlyallocated13.75～14.0GHz(uplink)withabandwidthof250MHzcanbeusedonJanuary1,2000tomeettheneedsofdevelopment.

ThetransmissionofC-bandisrelativelystable,andtheequipmenttechnologyismature,butitiseasytointerferewiththegroundmicrowavesystemofthesamefrequencyband.Theuplinkofsatellitecommunicationinterfereswiththe6GHzmicrowavesystem,andthedownlinkisinterferedbythe4GHzmicrowavesystem.Thisrequirespre-coordinationandcorrespondingshieldingmeasurestosolveit(seesatellitecommunicationsysteminterferencecoordination).TheKubandtransmissionisattenuatedbyrainandfog.,NotasstableastheC-band,especiallyinareaswithheavyrainfall.Ifsufficientmarginisleftinthecalculationoftheuplinkanddownlink,andtheuplinkpoweradjustmentfunctionisequipped,satisfactoryresultscanalsobeobtained.TheKufrequencybandhasabundantspectrumresourcesandhaslittlemutualinterferencewithterrestrialmicrowavesystems,anditsapplicationisverypromising.

Attheendofthe20thcenturyorthebeginningofthe21stcentury,theCandKufrequencybandswillbecrowded.FSSwilldevelopservicesintheKafrequencybandfrom20GHzto30GHz.Thefrequencyis:

Nouseva linkki (GHz) 29,5–30 kaistanleveys 500 MHz

Downlink (GHz) 19,7 - 20,2 kaistanleveys 500 MHz

Satellitecommunicationmethod

SatellitecommunicationmethodThesatellitecommunicationsystemuseswhentransmittingordistributinginformationTheworkingmethodiscalledsatellitecommunicationmethod.

Internationalsatellitecommunicationshaveshiftedfrombeingbasedonanalogfrequencydivisiontodigitaltimedivision.Digitalsatellitecommunicationmethodsinclude120Mbit/sdigitalvoiceinsertion(DSI)timedivisionmultipleaccess(TDMA/DSI),ortimedivisionmultipleaccesswithoutvoiceinsertion(DNI),andon-boardswitchingtimedivisionmultipleaccess(SS-TDMA);Therearealsoalargenumberofsatellitedigitalchannel(IDR)methodsbasedon2.048Mbit/sand1.544Mbit/s.Addingdigitalcircuitmultiplexingequipment(DCME)cangenerallyexpandthecapacityby3to4times,upto5times.The2Mbit/sIDRbears30circuits,andthesmallercapacityIDRhas1.024Mbit/s(16circuits)and512kbit/s(8circuits).Thedigitalprivatelineservice(IBS)fordedicatedcommunicationshasdevelopedrapidly,andtheKu-bandreachingtheISDNqualityleveliscalledthesuperdigitalprivatelineservice(su-perIBS).Thereisstillamarketforthesparserouting(VISTA)businessmode,amongwhichthereisamodeofon-demandallocationofmultipleaccess(DAMA)functionscalledthesuperthinrouting(su-perVISTA)mode.TheSPADEmethodofnon-centrallycontrolledrareroutinghasbeeneliminatedduetocomplexequipment.Thepolarizationmodeofinternationalsatellitecommunicationsisdoublecircularpolarization.

DomesticsatellitecommunicationmethodsgenerallyimitatetheC-bandandKu-bandusedbyinternationalsatellitecommunications,andKa-bandisalsouseful.ThegeneralTDMAmethodisbelow60Mbit/s,andthereareSS-TDMAandtransponderfrequencyhoppingTDMAmethods,satellitedigitalchannel(IDR/DCME)methodswithdigitalcircuitmultiplexingequipment,andadaptivedifferentialpulsecodingSatellitedigitalchannel(IDR/ADPCM)mode.Becausetheanalogfrequencydivisionmultipleaccess(FDMA)technologyismature,itisstillinuse.Thecall-basedsparserouting(VISTA)methodisusedmoreinthecountry,includingsinglecarriersinglechannel/syllabiccompandingfrequencymodulation/on-demandmultipleaccess(SCPC/CFM/DAMA)methodandsinglecarriersinglechannel/4phaseshiftkeying/on-demandmultipleaccess(SCPC/QPSK/DAMA)modeandlowerrateTDMAmode.Themarketforverysmallantennaearthstationsystemsisverylarge.Itisastarnetworkwithdatatransmissionasthemainpartandvoicetransmission.Therearemanyformatsandspeedsforuserstochoosefrom.Thepolarizationmodeofdomesticsatellitecommunicationisgenerallylinearpolarization,andcircularpolarizationisalsousedinsomecases.

InternationalanddomesticsatelliteTVtransmissionadoptsanalogFMsystem.TheinternationalTVprogramexchangeusestheglobalbeamtransponderandtheAstandardearthstation,anditsreceptionqualityisbetter.Onetranspondercantransmittwochannelsof20MHzbandwidthTVprograms.DomesticandregionalsatelliteTVtransmissionsuseadomesticorregionalbeamtranspondertoturnononlyoneTV,andtakethefullpowerofthetransponder,sothatalargenumberofsmallTVsingle-receivingearthstationsareeasytoreceive.

Thecompositeanalogcomponent(MAC)systemisalsoinuse.Atwo-channelTVsysteminwhichtwochannelsofTVaretransmittedbyonecarrierisusedasafixed-pointTVprogramtransmissionmethod,whichcansavespacesectioncosts,soitisalsoadopted.High-qualitysatellitedigitalTVtransmissionandhigh-resolutionsatelliteTVtransmissionarebeingtested.AtranspondertransmissionmethodofdigitalTVwithmultiplecompressioncodingisabouttoappear.

Thesatellitevideoteleconferencebusinessismainlybasedon2Mbit/1.5Mbit.Then×384kbiversionhasalreadycomeout,anditisexpectedthatthem×64kbitversionwillalsohaveitsadvantages.

ThesmallC/Kuearthstation,joka on asennettu erityisajoneuvoon ja helppo kuljettaa, on laajalti käytössä useissa kotimaisissa ja kansainvälisissä tilanteissa. Sitä voidaan käyttää television, puhelimen, faksin, lennätin ja datan jne. lähettämiseen. Useimmiten käytetään hätätilanteissa.

Ominaisuudet

Muihin viestintämenetelmiin verrattuna satelliittiviestinnällä on seuraavat ominaisuudet:

①Thecommunicationdistanceislong,andthecosthasnothingtodowiththecommunicationdistance..ItcanbeseenfromFigure16.2thatusinggeostationarysatellites,themaximumcommunicationdistanceisabout18100km.Moreover,theconstructioncostandoperatingcostdonotchangeduetothedistancebetweenthecommunicationstationsandtheharshnaturalconditionsonthegroundbetweenthetwocommunicationstations.Thishasobviousadvantagesovermicrowaverelay,cables,opticalcables,andshort-wavecommunicationsinlong-distancecommunications.

②Itworksinbroadcastmodeandcancarryoutmulti-addresscommunication.Generally,othertypesofcommunicationmethodscanonlyachievepoint-to-pointcommunication,whilesatellitesworkinbroadcastmode.Anearthstationcanbesetupatanypointintheentireareacoveredbythesatelliteantennabeam,andtheseearthstationscanshareacommunicationsatellite.Toachievebilateralormultilateralcommunication,thatis,multiple-accesscommunication.Inaddition,anin-orbitsatelliteisequivalenttolayingcountlessinvisiblecircuitsthatcanreachanypointinacertainarea.Itprovideshighefficiencyandflexibilityforthecompositionofthecommunicationnetwork.

③Largecommunicationcapacity,suitableforavarietyofbusinesstransmission.Satellitecommunicationsusemicrowavefrequencybands,andtheusablefrequencybandsareverywide.Generally,thesatellitebandwidthoftheCandKubandscanreach500-800MHz,andtheKabandcanreachseveralGHz.

④Itcanbemonitoredspontaneously.Generally,thesenderearthstationcanalsoreceivethesignalsentbyitself,sothatitcanmonitorwhetherthemessagesentbythestationiscorrectandthequalityofthetransmission.

⑤Seamlesscoveragecapability.Usingsatellitemobilecommunications,itispossibletoestablishaglobalsea,land,andairintegratedcommunicationsystemwithoutbeingrestrictedbygeographicalenvironment,climateconditionsandtime.

⑥Theabilitytoconstructwide-areacomplexnetworktopologies.Thehighpowerdensityandflexiblemulti-pointbeamcapabilityofsatellitecommunicationscombinedwithon-boardswitchingprocessingtechnologycanprovideawiderangeofpoint-to-pointandmulti-point-to-multipointcomplexnetworktopologiesatanexcellentprice-performanceratio.

⑦Safetyandreliability.Factshaveprovedthatinthefaceofearthquakerelieforinternationalsubmarine/opticalcablefailures,satellitecommunicationisanunparalleledimportantmeansofcommunication.Eveniftherearemoreperfectself-healingbackuporcircuitousterrestrialfiberopticcableandsubmarinefiberopticcablenetworksinthefuture,wisenetworkplannersanddesignerscanstillunderstandtheimportanceandimportanceofsatellitecommunicationsasthebasiclinkofthetransmissionmediumemergencybackupandinformationhighwayhybridnetwork.necessity.

Satelliittiviestinnän edut

Satelliittiviestinnän tärkeimmät edut on tiivistetty seuraavasti:

1.Longcommunicationdistance:Thelongestcommunicationdistanceinthesatellitebeamcoveragearea13000kilometers;

2,notrestrictedbyanycomplicatedgeographicalconditionsbetweenthetwopointsofcommunication;

3,joihin ei vaikuta luonnonkatastrofit ja ihmisen aiheuttamat tapahtumat kahden viestintäpisteen välillä;

4.Thecommunicationqualityishighandthesystemreliabilityishigh.Itisoftenusedasasupportsystemduringthesubmarinecablerepairperiod;

5. Mitä pidempi viestintäetäisyys, sitä alhaisemmat suhteelliset kustannukset;

6.ItcanrealizethetransmissionanddatainteractionofTVprograms,radioprogramsandnewsinalargearea;

7.Itishighlymobileandcanrealizesatellitemobilecommunicationandemergencycommunication;

8.Thesignalconfigurationisflexible,whichcanprovidehundreds,thousandsoreventensofthousandsofvoicechannelsandmediumandhigh-speeddatachannelsbetweentwopoints.

9,helpostisaada moniosoitelähetys;

9.p>

10.On helppoa toteuttaa erilaisia liiketoimintatoimintoja.

Satelliittiviestinnän haitat

Puhutaan monista satelliittiviestinnän eduista, satelliittiviestinnässä on myös monia haittoja!

1.Pitkä lähetysviive: 500 millisekuntia - 800 millisekuntia;

2,on vaikea toteuttaa satelliittiviestintää korkeilla leveysasteilla;

3,inordertoavoidmutualinterferencebetweensatellitecommunicationsystems,satellitesinsynchronousorbitsThereisalimittothenumberofsatellites,andthenumberofsatellitescannotbeincreasedwithoutlimit;

4.Thesolartransitandeclipsephenomenainspacewillinterruptandaffectsatellitecommunications;

5,Thesuccessrateofsatellitelaunchis80%,andthelifetimeofthesatelliteisseveraltotenyears;thedevelopmentofsatellitecommunicationsrequireslong-termplanningandtheriskoflaunchfailure.

Thecharacteristicsofsynchronoussatellitecommunication

Themainadvantagesare:①Thecommunicationdistanceislong,andthecommunicationdistanceofonehopinthesatellitebeamcoverageareaisabout13×103km(usingtheglobalbeam,Theelevationangleoftheearthstationtothesatelliteisabove5°);②Itisnotrestrictedbyanycomplicatedgeographicalconditionsbetweenthetwopointsofcommunication;③Itisnotaffectedbyanynaturaldisastersandman-madeeventsbetweenthetwopointsofcommunication;④OnlyonehopthroughthesatelliteItcanreachtheotherparty,sothecommunicationqualityishigh,andthesystemreliabilityishigh.Itisoftenusedasthesupportsystemduringthesubmarinecablerepairperiod;⑤Thelongerthecommunicationdistance,thelowerthecost;⑥ItcanrealizeTVprograms,radioprogramsandnewsinalargearea.Itissuitableforbroadcastanduser-typeservices,aswellasinteractivedatatransmissionandevenvoicetransmissiondirectlytotheuser’sofficebuilding;⑦highflexibility,canrealizesatellitemobilecommunicationandemergencycommunication;⑧flexibility,canbebetweentwopointsProvidehundreds,thousandsoreventensofthousandsofvoicechannels,providetensofmegabits(Mbit/s)oreven120Mbit/smediumandhigh-speeddatachannels,andcanalsoprovideatleastonevoicechannelor1.2kbit/s,2-4kbit/sdatachannel;⑨easytorealizemulti-addresstransmission;⑩hasthefunctionoftransmittingmultipleservices.

Themaindisadvantagesare:①Thetransmissiondelayislarge.Thesatelliteearthstationcommunicatesthroughtheforwardingofacommunicationsatelliteabout36,000kmabovetheequator.Dependingonthelatitudeoftheearthstation,theone-wayspacedistanceofonehopis72,000～80,000km.Theradiowavepropagatingataspeedof300,000km/scanreachtheoppositeearthstationafteraspacetransmissiondelayof240msto260ms.Inaddition,thedelaywillincreaseduetotheprocessingtimeofthedigitalsignalbytheterminalequipment.AccordingtotherecommendationoftheInternationalTelegraphandTelephoneConsultativeCommittee(Rec.114),one-waytransmissionshouldnotexceed400ms.Foracall,ittakes500msto800msforthecallertoheartheotherparty'simmediatereply,whichisacceptableandaccustomedtothecaller.However,theleakagecausedbytheimbalanceofthetwo/four-wirehybridcoilsofthetwopartiesintheconversationwillcauseunbearableechoes.Therefore,echocancellersmustbeinstalledwithoutexception.②Atlatitude75south.Inhighlatitudesaboveandabove75°northlatitude,itisdifficulttorealizesatellitecommunicationbecausetheelevationangleofthesynchronoussatelliteislessthan5°.Generallyspeaking,thegroundatthelatitudebelow70°andtheaircraftbelow80°canbeestablishedviathesynchronoussatellite.Communication.③Thelocationofthesynchronousorbitislimited,andthenumberofsatellitesandthedistancebetweensatellitescannotbeincreasedindefinitely.④Everyyear,thereareunavoidableinterruptionsofsolartransitandstareclipsesthatmustbetakenthrough.⑤Itisnecessarytohavealong-termplanforsatellitedeployment.Theservicelifeofasatelliteisgenerallyseveraltotenyears,andthedesignandproductioncycleofasatelliteislong.Itisnecessarytoarrangeasuccessorsatelliteasearlyaspossible.However,thesatellitelaunchsuccessrateisabout80%onaverage,socertainrisksmustbeassumed.

Relatedcategories

Thedevelopmentofnewsatellitecommunicationtechnologiesisendless.Forexample,theverysmall-apertureantennaearthstation(VSAT)systemandthemobilesatellitecommunicationsysteminlow-mediumorbithavereceivedextensiveattentionandapplications.Satellitecommunicationisalsoanimportantpartofthefutureglobalinformationhighway.Itisknownforitswidecoverageandlargecommunicationcapacity.Theadvantagesoflong-distancecommunication,nogeographicalenvironmentrestriction,excellentquality,andhigheconomicbenefitswerefirstappliedinChinain1972anddevelopedrapidly.Togetherwithopticalfibercommunicationanddigitalmicrowavecommunication,ithasbecomethebackboneofcontemporarylong-distancecommunicationinChina.

Sincesatellitecommunicationisnotrestrictedbygeographicalconditionsandhasflexiblemobility,itstilldevelopsinnovativelybasedonitsadvantages.However,itisalsochallengedbytherapiddevelopmentofopticalfibercommunications.Ithasalargercapacityandhighertransmissionratethansatellitecommunications.Manytransoceaniccommunicationshavebeenreplacedbysubmarineopticalcables,andsimilarsituationsexistonlandtrunklines.Inthemidtolate1990s,satelliteTVlivebroadcasting(DBs-DirectBroadcastSatelliteorDTH-DirectToHome),satellitesoundbroadcasting,satellitemobilecommunications,andsatellitebroadbandmultimediacommunicationsbecamethefournewdevelopmenttrends.

FixedSatelliteCommunications

TheIntelsatseriesoftheInternationalSatelliteCommunicationsOrganizationhasbeendevelopedtotheninthgeneration.Thebusinessvolumehasbasicallygrownsteadilyfrom1996to2004.Thetotalglobalrevenuein2004was94BillionUSdollars,theUnitedStatesisexpectedtoreachonemillionusersin2006,andVSATapplicationswillincreaseby15%-20%annually.Broadbandaccessandmultimediaservicesaregraduallydeveloping.Ka-bandwillbecomethemainstreamofbroadbandservices.LeadingbroadbandservicesareCanada’stelecommunicationssatellites.Company(Telesat),WildBlueCompanyoftheUnitedStatesandShinSatelliteCompanyofThailand.

Intermsofsatelliteperformance,increasethetransmissionpower,increasetheEIRPvalue,increasethenumberofsatellitetransponders,increasebandwidth,reducecosts,andreducethesizeandcostofgroundterminalequipment.TheAniklaunchedbyCanadaonJuly18,2004.TheF2satellitehasatotalof114transponders,50ofwhichareintheKa-band.TheIpstarsatellitelaunchedonAugust11,2005inThailandhas114transpondersandacommunicationcapacityof45Gbit/s.Itiscurrentlytheworld’slargestcommercialcommunicationssatelliteinEurope.Largersatellitesarebeingdevelopedand250transpondersarebeinginstalled,whicharescheduledtobelaunchedin2008.

Thesatelliteusesdigitalsignalprocessorstoimprovesignalexchangecapabilities,reducegroundequipment,establishearthstationswithtelemetry,remotecontrol,trackingandmonitoringfunctions,andnetworkmanagementfunctionstorealizesatellitedynamiccontrolandmanagement.Satellitebroadbandcommunicationisusedtobroadcastlivehigh-definitionTV,andconnecttotheInternettodevelopnetworkTV.

Mobilesatellitecommunications

Mobilesatellitecommunicationscanbeglobalorregional,usingmediumandlow-orbitsatellitesglobally.Geostationaryorbitcommunicationsatellitesareusedregionally.RegionalmobilecommunicationsatellitesincludeIndonesia’sAsianCellularSatellite(Aees),alsoknownasGarula-1,launchedonFebruary12,2000.Itistheworld’sfirstregionalmobilecommunicationsatellite.Itisapersonalgeostationaryorbitpersonalmobilecommunicationsatellitewith140spotbeamsand11,000simultaneousvoicechannels.ThebeamcoverstheAsia-Pacificregion,whichaccountsfor60%oftheworld’spopulation.TheUnitedArabEmirateslaunchedThuraya_1and-2satellitesonOctober20,2000andJune10,2003,respectively.Eachsatellitehasacapacityof13,750simultaneouscalls.ItcoversEuropeandAsia.,Non-106countries.

InternationalMobileSatelliteCorporationlaunchedthefourth-generationInmarsat-4satelliteinMarch2005.Ithasaglobalbeam,19widespotbeamsand228narrowspotbeams,andtwosatellitessupporttheInmarsatsystem.Mostofthebusiness.ItwillintroduceaseriesofnewservicesoftheBroadbandGlobalAreaNetwork(BGAN)withatransmissionrateof432kbit/s.ThesatellitewilluseanL-bandantennaandadigitalsignalprocessor(DSP).TheDSPhaschannelselectionandbeamformingfunctionstogeneratebroadbandChannelmatchingpowerandbandwidthresources,DSPcanalsotailorthesatellitecoverageandadjustthebeamtomeettherequirementsofcapacityandbusinesstypes,andcanalsohandlethefailureofsolid-statepoweramplifiersandlownoiseamplifiers.ThebroadbandglobalareanetworkwilltransmitInternet,intranet,video-on-demand,videoconferencing,fax,e-mail,telephoneandlocalareanetworkaccessservices.

Thebusinessofglobalmobilesatellitecommunicationsinlowandmediumorbitsismainlyvoiceanddata.ItcanalsobeconnectedtotheInternettofurtherdevelopmultimediacommunications.

Thegeneraldevelopmenttrendofsatellitecommunicationislarge-capacity,high-power,high-speed,broadband,low-cost,high-transmittingfrequency,multi-transponder,multi-spotbeamandshapedbeam,whichareappliedonsatelliteProcessingtechnologyswitchingsignals,processingsignals,etc.,inthe21stcentury,directsatellitetelevision(DBS-TV),personalmobilesatellitecommunications,multimediasatellitecommunications,satelliteaudiobroadcasting,satellitenetworktelevision,etc.willbedevelopedinalargeamount.ThebusinessscopeofVSATcontinuestoexpandandpenetratesintovariousfieldsofthenationaleconomy,showingitseconomicandsocialbenefits.TheapplicationofKa-bandmakestheequipmentmorecompact,andofcourseitalsobringsseriousattenuationdefects.Theapplicationofopticalcommunicationinsatellitecommunicationhasgraduallybecomematureanddesirable.Itrequiresprecisesatellitecontroltechnology.Itisstillintheinternationalresearchanddevelopmentstageandisexpectedtoenterthepracticalstagesoon.

Kiinan satelliittiviestintäteollisuus kehittyy myös nopeasti.12. huhtikuuta 2005 Aasia-Tyynenmeren-6(Apstar-6)-satelliitti lanseerattiin. Siinä on 38C-kaistainen ja 14Ku-kaistainen transponderi.Vuonna 2006 se julkaisi2-2-suoraa-telliä. kaistatransponderit (tällä hetkellä tekninen vika).Satelliittiviestinnän sovellusalat laajenevat jatkuvasti. ,arvopaperit,posti-ja televiestintä,meteorologia,maanjäristysja muut osastot,etäopetus,telelääketiede,hätäkatastrofipalvelut,hätäviestintä,hätätelevisiolähetykset,meret,maajailmavigointi,Internet-puhelimet,televisiot, jne. raketit johtavat maailmaa,jaKiina on onnistuneesti testannut suuren työntövoiman, saastuttamattomia, myrkyttömiä ja ympäristöystävällisiä raketimoottoreita. Tämä on luonut etuja Kiinan kehitykselle 'suuren mittakaavan viestintäsatelliitit ja miehitettyjen avaruuslentojen ja kuun tutkimusprojektien kunto.

Chinawillmovealongthelong-termdevelopmentdirectionofintegrationofworldandearth,complementaryadvantages,andmilitary-civilianintegration.

Historicalreview

AsearlyasOctober1945,ArthurC.Clarkeproposedtheideaofgeostationarysatellitecommunication.Inthe10thissueoftheBritish"RadioWorld"magazine,hepublishedanarticleentitled"ExtraterrestrialRelay-CanSatellitesProvideRadioCoverageonaGlobalRange?"Communicationlaidthetheoreticalfoundation.ThedevelopmentofmodernsatellitecommunicationshasconfirmedthescientificnatureofClark'svision.

Thedevelopmentprocessofsatellitecommunicationscanbedividedintothefollowingtwostages.

(1)Satelliittiviestinnän kokeellinen vaihe

Since1954,theUnitedStateshassuccessivelyusedthemoon,passiveballoonsatellites,andcopperneedlepassivedipolebeltsasrelaystations.PassivesatellitecommunicationtestssuchastelephoneandTVtransmissionhaveprovedtobeoflittlepracticalvalue.Itwasnotuntil1957thattheformerSovietUnionlauncheditsfirstartificialsatellite,whichmadesatellitecommunicationsentertheactivesatellitetestphase.

InDecember1958,theUnitedStatesusedanAtlasrockettolauncha150-poundlow-orbitsatelliteintoanellipticalorbit(perigee200km,apogee1700km),andlauncheditonboardTheoutputpowerofthemachineis8W,andthefrequencyis150MHz.Thesatelliteusestapetorecord,andrelaystheinformation(telephone,telegram)sentbystationAtostationBwithadelay.InOctober1960,theUSDepartmentofDefenselaunchedthe"Messenger"satelliteintoanorbitwithanaltitudeof1,000kmandaninclinationof28.3°,usingafrequencyof2GHz,andconductedalow-orbitdelaycommunicationtestsimilartotheabove.

InJune1962,NASAusedaDeltarockettosendthe"ElectricStar"satelliteintoanellipticalorbitof1060-4500km;inDecemberofthesameyear,itlauncheda"relay"satelliteandenteredWithanellipticalorbitof1270～8300km,manytelephone,TV,andfaxdatatransmissiontestshavebeencarriedoutbetweentheUnitedStates,Europe,andSouthAmerica,andtechnicalissuessuchassatellitecommunicationfrequency,attitudecontrol,telemetrytracking,andcommunicationmethodshavebeenconducted.Experimented.

Since1963,synchronoussatellitecommunicationexperimentshavebeencarriedout.InJuly1963andAugust1964,NASAlaunchedthreeSYNCOMsatellites.Thefirstonefailedtoenterthepredeterminedorbit;thesecondoneenteredatiltedorbitwithaperiodof24h;thelastoneenteredacircularshape.ThegeostationarygeostationaryorbitofChinahasbecometheworld’sfirstexperimentalgeostationarycommunicationssatellite.Itwasusedtosuccessfullycarryouttelephone,TVandfaxtransmissiontests,andinthefallof1964,itwasusedtobroadcasttheliveeventsoftheOlympicGamesheldinTokyo,JapantotheUnitedStates.Atthispoint,theexperimentalphaseofsatellitecommunicationsisbasicallyover.

(2)Satelliittiviestinnän käytännön vaihe

Atthesametimeasthedevelopmentofsatellitecommunicationtechnology,theorganizationresponsibleforsatellitecommunicationbusinessandmanagementhasgraduallybeencompleted.OnAugust20,1964,Inordertoestablishasingleglobalcommercialsatellitenetwork,11WesterncountriesincludingtheUnitedStatesandJapanestablishedatemporaryglobalcommercialsatelliteorganizationinWashington,USA,andofficiallynamedittheInternationalTelecommunicationSatelliteOrganization(INTELSAT,InternationalTelecommunicationSatelliteOrganization)inNovember1965.).Theorganizationlaunchedthefirstgenerationof"INTELSAT-I"(IS-I,formerlyknownas"MorningBird")intothegeostationaryorbitinApril1965,andofficiallyassumedtheinternationalcommunicationbusiness.Thismarksthebeginningofanewstageofpracticalityanddevelopmentforsatellitecommunications.

Satelliittiviestinnän nykytila ja näkymät maassani

(1)Kiinteät palvelut

Vuonna 1972 maani alkoi rakentaa ensimmäistä satelliittiviestinnän maa-asemaa,joka onnistui TV-ohjelmat.Sittemmin Pekingissä, Shanghaissa ja Guangzhoussa on rakennettu kansainvälisiä vientiasemia, ja noin 25 000 suoraa kansainvälistä satelliittikanavaa on avattu;Peking onkeskus,jaLhasa,Urumqi,Hohhot,Guangzhou,Chengdu,Qi'aning ,jne.ovat aluekeskuksia.Kiinan useilla maa-asemilla on yli 10 000 kotimaan linjaa.

Thedevelopmentofprivatenetworkconstructionisveryrapid,thePeople’sBankofChina,XinhuaNewsAgency,transportation,oilandgas,economyandtrade,railways,electricpower,waterconservancy,civilaviation,ChinaNationalNuclearCorporation,NationalEarthquakeAdministration,MeteorologicalAdministration,YunnanTobacco,ShenzhenStockcompanies,nationaldefense,publicsecurityandotherdepartmentshaveestablishedmorethan20satellitecommunicationnetworks,andsatellitecommunicationearthstations(especiallyVSAT)havereached10,000.

(2)Satelliitti-TV-lähetystoiminta

Vuonna 1984 "Dongfanghong"-satelliitti käynnistettiin onnistuneesti, luomaani maani uudelle satelliittikäytölle radio- ja televisio-ohjelmien lähettämiseen.Vuodesta 2015 4 sarjaa CCTV, EducationChannel,Hongfanghong,Xinjiang,Tibet,Yunnanan,H,Shan,Zhenanichu,Shan,G Guangdong, Guangxi, Hebei ja yli tusina maakuntatason televisio-ohjelmaa ja yli 40 kielellä lähetysohjelmia on lähetetty satelliiteilla. Satelliitti-TV:n maanpäällisiä asemia on 100 000 ja noin 300 ,000 televisioasemaa (TVRO). Monet järjestelmät käyttävät kehittyneempää digitaalista pakkaustekniikkaa.

(3)Satelliittimatkaviestintäpalvelut

Satellitemobilecommunicationmainlysolvesthecommunicationtasksbetweenvarioustargetsonland,seaandairandwithgroundpublicnetworks.AsamemberofINMARSAT,ChinahasashorestationinBeijing,whichcanprovidecommunicationservicesforthePacific,IndianOceanandAsia-Pacificregions.Inaddition,mycountryisgraduallydevelopingairbornesatellitemobilecommunicationsservices.石油、地质、新闻、水利、外交、海关、体育、抢险救灾、银行、安全、军事和国防等部门均配备了相应业务终端。现我国已进入INMARSAT的M站和C站，有近5000部机载、船载和陆地终端。

（4）未来展望

随着我国现代化建设和以多媒体为代表的信息高速公路的发展，今后10年我国卫星通信将有一个更大的发展，并将以我国自主的大容量通信卫星为主体，建立起完善、长期稳定运行的卫星通信系统。若以每年递增15%～17%计算，到2002年，卫星通信公用网开通的线路将是1996年的2.7～3倍，大、中城市将建立起大、中型卫星通信地球站约50～60座，中、小型地球站约200～300座(不包括VSAT站)。到2005年，卫星通信公用网线路将发展到数十万条。

我国今后卫星通信技术发展趋势为：

①开发新频段，提高现有频段的频谱利用率。从现有单一的C频段发展到Ku、Ka、UHF、L、S、X等频段。

②公用干线通信网向高速、数字、宽带发展，速率将达60Mbit/s、120Mbit/s和1000Mbit/s，并利用SDH和ATM，建立国家信息高速公路——天基宽带综合业务数字通信网。

③进一步发展小型化、智能化VSAT专用卫星通信网。业务也将从单一的数据或话音为主，发展为话音、数据、图文、电视兼容的综合业务。

④卫星移动通信系统将大力发展新技术，如星上大天线技术、多波束技术、星上交换、星上处理和星间链路技术、越区切换技术等。

⑤开展卫星通信网与其他异构网的互通、互联,完成异构网协议变换，网络同步与交换技术及信令呼叫接口技术等。

⑥网络管理和控制及网络动态分配处理的自动化技术。

⑦卫星通信网的网络安全、保密技术。

⑧与我国卫星通信设备产业化发展有关的生产、工艺加工技术等等。

展望21世纪，卫星通信将获得重大发展，尤其是世界上新技术，如光开关、光信息处理、智能化星上网控、超导、新的发射工具和新的轨道技术的实现，将使卫星通信产生革命性的变化，卫星通信将对我国的国民经济发展，对产业信息化产生巨大的促进作用。

Satelliittiviestintä

Määritelmä ja johdanto

Historialyhennetty