LEO Mesh Routing

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1、LEOMeshRoutingPeterT.S.Tam20April1999AbstractThisarticlediscusstheLEOmeshroutingalgorithm.1IntroductionAtypicalLowEarthOrbitSatellitesystem,orLEOsystemforshort,canbemodeledasameshstructure,withanorth-southwrap-aroundproperty.WeassumethattheLEOsystemisaregulartopol

2、ogysuchthateachsatellitehasfoursinter-satellitelinks(ISLs)wheretwoISLsareconnectedtotheintra-orbitneighborsandtheothertwoISLsareconnectedtotheeastandwestinter-orbitneighbors.ThisregulartopologyisresembletotheIRIDIUMsystem[4].AnillustrativeexampleisshowninFigure1wi

3、th6orbitsand11satellitesperorbitwhichisthesettingoftheIRIDIDUMsystem.ThecircularnodesarethesatellitesandtheedgesaretheISLs.Thenodeslieonthesameverticallineisthesatellitesinthesameorbits,andtheconnectionofnodesarewrappedaroundsuchthattherstsatelliteconnectstothela

4、stoneinthesameorbit.Noticethatthesatellitesinorbit1donotconnecttothesatellitesinthelastorbit,duetothecounter-rotatingpropertyoftherstandthelastorbitswhichisalsoacommonpropertyforcommonLEOsystems.Ingeneral,ameshisformedwithnorth-southwraparoundbutnoteast-westwrapa

5、round.Wechooseourmodelofregulartopologywithxedlinkassignmentasopposedtothedynamiclinkassignmentscheme[5]becauseofthefollowingreasons:First,theradiopropagationmayhaveasevereinterferenceiftwoormoredynamicassignedlinksareoverlappingwitheachother,whichhindersthefrequ

6、encyreusestrategyandfadeoutthenicepropertyofhighlyreliablechannelinaLEOsystem.Thedynamicassignmentschemerequiresacom-plicatedon-boardprocessortochangethedirectionoftransceiversonthesatellitetoadopttothechangeofISLsconnectionwithdierentneighbors.1Figure1:Anexample

7、meshrepresentationofaLEOsystemBesides,anyminorerrorontheprocessormaycausethetransceiverstosendandreceiveerrorpronesignalanditisdiculttodiagnosethefaultonanon-boardprocessoroncethesatelliteislaunched.Moreover,accordingtotheexperimentdonein[5],theongoingcallblockin

8、grateishigherforthedynamicassignmentschemewhencomparetotheoneforregulartopology.Itmayduetothefrequentchangeoflinkassignmentwhichislikelytobreakthelinkof