Satelitní komunikace

Definiceaúvod

Satelitní komunikace:Použijte družice umělé země jako přenosovou stanici pro ukládání rádiových vln, čímž dosáhnete komunikace mezi dvěma nebo více pozemskými stanicemi.

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.

Abriefhistory

TheideaofusingartificialearthsatellitesingeosynchronousorbitsasrelaystationsforcommunicationontheearthisbasedontheBritishphysicistACClarke(ArtherC.Itwasproposedinthearticle"Extra-EarthRelay"publishedintheWorldMagazine,anditbecamearealityinthe1960s.

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.Sledování subsystému telemetrie a příkazů

Thetrackingtelemetryandcommandsubsystemisresponsiblefortrackingandmeasuringsatellitesandcontrollingthemtoaccuratelyenterthedesignatedpositiononthegeostationaryorbit.Afterthesatelliteisinnormaloperation,theorbitpositioncorrectionandattitudemaintenanceofthesatelliteshouldbecarriedoutonaregularbasis.

2. Podsystém monitorování a řízení

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

3.Vesmírný podsystém (komunikační satelit)

Communicationsatellitesmainlyincludecommunicationsystems,telemetrycommanddevices,controlsystems,andpowersupplydevices(includingsolarcellsandstoragebatteries).

Thecommunicationsystemisthemainbodyofthecommunicationsatellite.Itmainlyincludesoneormoretransponders.Eachtranspondercanreceiveandforwardsignalsfrommultipleearthstationsatthesametime,thusactingasarelaystation.

4. Komunikační zemská stanice

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)

Upstream5925–6425Šířka pásma 500MHz

Šířka pásma 3700–4200 po proudu 500 MHz

FortheextensionofFSSThefrequencyspectrumhasbeenadjustedfromJanuary1,1984to:

Odchozí: Oblast 15725–7075 Šířka pásma 1350 MHz

Oblast 2 a 35 850 až 7 075 Šířka pásma 1 225 MHz

3400–4200 celková šířka pásma

Downlink:Zone1,2,and3

4500–4800l100MHz

②Kmifrekvenční pásmo (GHz)

4500–4800l100MHz

Uplink:Zóna 1, 2 a 3, 14,0 až 14,25 šířka pásma 250 MHz

14,25–14,5, šířka pásma 250 MHz

Downlink:Zóna 1, 2 a 310,95 až 11,20 šířka pásma 250 MHz

11,45–11,7 pásma 250 MHz

Sekce 211,7–11,95 Šířka pásma 250 MHz

11,95 až 12,2 pásma 250 MHz

Č. 3Zóna 12,2–12,5 Šířka pásma 300 MHz

První třetí zóny 12,5–12,75 Šířka pásma 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:

Uplink (GHz) 29,5–30 Šířka pásma 500 MHz

Downlink (GHz) 19,7–20,2 šířka pásma 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.

Malá C/Kuearthstation, která je instalována na speciálním vozidle a snadno se přenáší, je široce používána v různých domácích a mezinárodních příležitostech. Lze ji použít k přenosu TV, telefonu, faxu, telegrafu a dat atd., Používá se většinou v nouzových situacích.

Funkce

Ve srovnání s jinými komunikačními metodami má satelitní komunikace následující vlastnosti:

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.

Výhody satelitní komunikace

Hlavní výhody satelitní komunikace jsou shrnuty následovně:

1.Longcommunicationdistance:Thelongestcommunicationdistanceinthesatellitebeamcoveragearea13000kilometers;

2,notrestrictedbyanycomplicatedgeographicalconditionsbetweenthetwopointsofcommunication;

3, není ovlivněn žádnými přírodními katastrofami ani událostmi způsobenými člověkem mezi dvěma body komunikace;

4.Thecommunicationqualityishighandthesystemreliabilityishigh.Itisoftenusedasasupportsystemduringthesubmarinecablerepairperiod;

5. Čím delší komunikační vzdálenost, tím nižší relativní náklady;

6.ItcanrealizethetransmissionanddatainteractionofTVprograms,radioprogramsandnewsinalargearea;

7.Itishighlymobileandcanrealizesatellitemobilecommunicationandemergencycommunication;

8.Thesignalconfigurationisflexible,whichcanprovidehundreds,thousandsoreventensofthousandsofvoicechannelsandmediumandhigh-speeddatachannelsbetweentwopoints.

9,snadno dosažitelný přenos více adres;

9.p>

10.Snadno si uvědomte různé obchodní funkce.

Nevýhody satelitní komunikace

Mluvit o mnoha výhodách satelitní komunikace, satelitní komunikace má také mnoho nevýhod!

1.Dlouhé zpoždění přenosu:500Časové zpoždění milisekund do 800 milisekund;

2,je obtížné realizovat satelitní komunikaci v oblastech s vysokou zeměpisnou šířkou;

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.

Čínský družicový komunikační průmysl se také rychle rozvíjí. 12. dubna 2005 byl spuštěn satelit Asie-Pacifik-6 (Apstar-6). Má 38C pásmo a 2 transpondéry v pásmu 14 Ku. V roce 2006 byl spuštěn 2 satelit pásmové transpondéry (v současné době dochází k technické závadě).Aplikační oblasti satelitní komunikace se neustále rozšiřují. ,zabezpečení,poštovní telekomunikace,meteorologie,zemětřeseníadalší oddělení,dálkové vzdělávání,telemedicína,reakce na mimořádné události,nouzová komunikace,nouzové televizní vysílání,mořská,pozemní a letecká navigace,internetové telefony,televizory,atd.budou široce používané technologie,elektroelektrických elektráren. adsvět a Čína úspěšně otestovaly raketové motory s velkým tahem, neznečišťujícími, netoxickými a šetrnými k životnímu prostředí. To vytvořilo výhody pro rozvoj Číny „velkoplošné komunikační družice a projekty vesmírných letů a průzkumu Měsíce.

Chinawillmovealongthelong-termdevelopmentdirectionofintegrationofworldandearth,complementaryadvantages,andmilitary-civilianintegration.

Historicalreview

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

Thedevelopmentprocessofsatellitecommunicationscanbedividedintothefollowingtwostages.

(1)Experimentální fáze satelitní komunikace

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)Praktická fáze satelitní komunikace

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

Aktuální stav a vyhlídky satelitní komunikace v mé zemi

(1)Pevné služby

V roce 1972 začala moje země budovat první satelitní komunikační pozemskou stanici, která byla úspěšná v roce 1984. První experimentální komunikační družice byla spuštěna v roce 1985. V roce 1985 bylo pět veřejných síťových stanic, včetně Pekingu, ve Lhasu, ve městě Giuqi mitCCTV programy. Od té doby byly vybudovány mezinárodní vývozní stanice v Pekingu, Šanghaji a Guangzhou a bylo otevřeno asi 25 000 přímých mezinárodních satelitních linek; Centrem je Peking a Lhasa, Urumqi, Hohhot, Guangzhou, Chengda, Xi' ,atd.jsou regionálními centry. Na několika čínských pozemských stanicích je více než 10 000 domácích linek.

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

(2)Obchod se satelitním televizním vysíláním

V roce 1984 byl satelit „Dongfanghong“ úspěšně spuštěn, čímž se v mé zemi vytvářely nové způsoby použití satelitních testů pro přenosové a televizní programy. angdong, Guangxi, Hebei a další více než tucet televizních programů na provinční úrovni a více než 40 jazyků Vysílací programy byly přenášeny na satelitech. Existuje 100 000 satelitních televizních pozemních stanic a přibližně 300 ,000 TV stanic (TVRO). Mnoho systémů používá pokročilé technologie digitální komprese.

(3)Satelitní telekomunikační služby

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。

Satelitní komunikace

Definiceaúvod

Abriefhistory

Coverage

GeostationaryEarthOrbit(GEO)Satellite

Mobilesatellitecommunications

Multipleaccessmethod

Thecompositionofthesatellitecommunicationsystem

Introductiontofrequencybandsynchronoussatellitecommunicationservice

Satellitecommunicationmethod

Funkce

Výhody satelitní komunikace

Nevýhody satelitní komunikace

Thecharacteristicsofsynchronoussatellitecommunication

Relatedcategories

FixedSatelliteCommunications

Mobilesatellitecommunications

Historicalreview

Aktuální stav a vyhlídky satelitní komunikace v mé zemi

相关图书

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