Table1 Majorspecificationofaeronauticalearthstation AntennaUnit Frequency: Tx: MHz,Rx: MHz Gain: Tx:12.3dBi,Rx:14.5dBi Radiati

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1 AeronauticalMobileSateliteData CommunicationExperiments ShinichiTAIRA,MasakiSATOH,andShin-ichiYAMAMOTO The Engineering TestSatelite V I has onboard equipments for the mobile satelite communicationssystem usings-bandfrequency.thedatatransmissiontestfortheaeronautical mobilesatelitecommunicationwascarriedoutusingtheengineeringtestsatelitev I.Thetest resultsshowedthatthethroughputperformanceinthecaseofthelevelflightwasalmostassame asthatinthecaseofthestaticcondition,andthatinthecaseofthe20degreesturningflightwas about2dblessthanthatinthecaseofthestaticcondition. 1 Introduction EngineeringTestSateliteV I(ETS-V I,KikuNo.8)is alargegeostationarysatelite(weight:3tons)launchedby anh-iarocketindecember,2006 [1].S-band(2.6/2.5GHz) communicationdevicesaremountedinthesatelite.the performanceofcomponentsmountedonthesatelitewas evaluated and land mobile satelite communication experimentswereperformed bythesedevices [2]-[4].This time,theauthorshadachancetoperform anaeronautical satelitecommunication experiment.in thisexperiment, theearth ssurfacewasimagedwithasyntheticaperture radarfrom anaircraft,dataweretransmitedtotheearth station via satelite,the image data were succesfuly transmitedtotheearthstationatapproximately100kbps, atransmisiontestbypacketsignalwasexecutedinorder toobtainbasicperformanceinformationintransmision during flightand data such asthroughputrate and receivingpowerwereobtained.thispapergivesanoutline oftheaeronauticalsatelitecommunicationsystem usedin the experiment, and describes the results of the transmisionexperimentperformed. 2 Theaeronauticalsatelite communicationsystem TheaircraftusedinthisexperimentwasaGulfstream I. Aflattypeactivephasedarayantenna(APAA)developed forvehiclewasused [6] fortheantennaoftheaeronautical earthstation.theantennawasmountedonthetopofthe aircraft.theantennaradomeusedintheka-bandmobile satelitecommunicationexperiment [7] performedinthepast wasused forthistest.a syntheticapertureradarfor imagingismountedbelowtheaircraft.figure1showsthe configurationoftheexperimentsystem.thebasestation wasbuiltatthekashimaspacetechnologycenter.an S-bandbasestationhavingaparabolicantennaof3.6m in diameterwasused.table1showsthespecificationsofthe aeronauticalearthstation.themodem isacommercial item andhasbpsk,qpskandofsetqpskasmodulation methods.thetransmisionspeedcanbeadjustedfrom 5kbpsto3Mbps. A faultwasfound in thelargedeployableantenna receiving system [8] of the ETS-V I in the initial performancetestperformedafterlaunching.a parabolic antennawithanapertureof1m indiameterforpositioning experimentwasusedforreceivingthes-banduplinkinthe communication test.thefigureofmerit(g/t)ofthe receiving system is approximately -6dBK. That is approximately20db lowerthantheg/t thatthelarge deployableantennaissupposedtohave(approximately 14dBK).TheS-bandwasusedforup-linkanddown-link. Abent-pipemodewassettothesatelite.Table2showsan exampleoflinkbudgetinthecaseoflevelflight.asshown intable2,thecommunicationqualityofthedown-linkis highenough.communicationqualityisdecidedbytheuplinksignalwhichistransmitedfrom theaeronauticalearth stationtothesatelite.thestandardsignalpowervs.noise powerdensityratio(c/no)thatcanbesettothesatelite linkisapproximately56dbhz. 101

Table1 Majorspecificationofaeronauticalearthstation AntennaUnit Frequency: Tx:2655.5-2658.0MHz,Rx:2500.5-2503.0MHz Gain: Tx:12.3dBi,Rx:14.

2 Table1 Majorspecificationofaeronauticalearthstation AntennaUnit Frequency: Tx: MHz,Rx: MHz Gain: Tx:12.3dBi,Rx:14.5dBi Radiatingelement:Two-layerself-diplexingantenna Upperlayer:Circularpatch(Tx) Lowerlayer:Ringpatch(Rx) Numberofelements:18 Phaseshifter:Endlesanalogphaseshifter EIRP:26.3dBW G/T:-12.3dBK Polarization:Lefthandsidecircularpolarization Size:440mm (Diameter) 117mm (Height) Weight:18.7kg Powerconsumption:354W Trackingmethod:Closedloop,Openloop Trackingspeed:30degree/sec(max) Fig.1 System diagram foraeronauticalsatelitecommunication experiment Modem Unit Modulation:BPSK,QPSK,OfsetQPSK TransmisionRate:5kbps-3Mbps Erorcorection:Convolutionalcode,Reed-Solomoncode, Turbocode Table2 Anexampleoflinkbudgetofreturnlink 3 Flightexperiment 3.1 Experimentparameters TheC/Novalueonthesatelitelinkexpectedinlevel flightisnotsolarge:approximately56dbhz.measurement timeinflightislimited.therefore,qpskwasselectedas themodulation method.theinformation transmision amountforcolectingstatisticaldatawassecuredwhilethe packetsignaltransmisionspeedwassetto10kbps.the non-modulationwavesignalformeasuringpowerwasnot transmited simultaneously by anotherfrequency.the receivingpacketsignalpowermodulationwasmeasuredby seting thespectrum analyzerresolution bandwidth to 30kHz.Erorcorectingcodewasnotused.Thesignal length ofthepacketsignalused fortransmision was 100 bytes.thesatelitetracking methodsused in the aeronauticalearthstationincludedthesteptrackclosed loopmethod,andanopenloopmethodusinginformation aboutthepositionanddirectionoftheaircraftasacontrol. Intheflightexperiment,receivedpowerwasmeasuredby both methods for comparison.with regard to the evaluationofsatelitelink,datareceptioncharacteristics were obtained during levelflight,and data reception characteristicsduringturningflightatan angleoftilt 20degrees.Intheimagetransmisionexperimentduring thesameflight,thesignaltransmisionratewassetto 128kbpsandaturbocodewithacoderate3/4wasusedas aneror-corectingcode.therefore,theinformationrate 102 JournaloftheNationalInstituteofInformationandCommunicationsTechnology Vol.61No.1(2014)

3 4-2AeronauticalMobileSateliteDataCommunicationExperiments intheimagetransmisionexperimentwas96kbps.with regardtotheimagesignal,animagefilewithasizeof 654KbytewastransferedbyFileTransferProtocol(FTP) andthetransfertimewasmeasured. 3.2 Experimentalresult (1)Receivedsignalcharacteristics A signalwastransmitedfrom theaeronauticalearth station to the S-band base station atkashima Space TechnologyCenterviathesateliteandthereceivedpower wasmeasuredinordertofindthepropagationcondition duringsignaltransmision.figure2showsthefluctuation ofreceivedpowerduringlevelflight.theantennawas controledbyan open loopcontrolmethodwherethe satelitewastrackedaccordingtoinformationsuchasits atitude.figure2showsthereceivedsignallevelisstable andthefluctuationwidthiswithin1db. Received Power Level (dbm) Time (sec) Fig.2 Received poweron levelflightwith open loop satelite tracking InFigure3,solidlinesshowthefluctuationofreceived powervaluemeasuredbytheaircraftduringturningata tiltangleof20degrees.theaircraftcircled clockwise 360degreesoverItako city,ibarakiprefecture,starting towardtheeast.dotedlinesshowthevaluesofcalculated receivedpoweratthes-bandbasestation. ThevalueinFig.3wascalculatedbythefolowing procedure.therelativeelevationangleofthesateliteseen from theaircraftchangesnearlyin asinusoidalwave againstthetravelingdirectionoftheairplane(yaw axis) betweenapproximately30to70degrees.figure4shows thecalculatedrelativeelevation angleofets-v Iseen from theaircraftcirclingaboveitakocity.theantennawas aflat,phasedarayantenna.iftheantennaisonaflat plane,thesmalerthesateliteelevationangleis,thesmaler theantennagaingets.infigure.5,circlesshowtheactual measured value ofantenna transmision gain against sateliteelevationanglewhentheantennaishorizontal. ThedotedlineinFig.5isafunctioncurveestimatedfrom actualmeasuredvalues.basedondatainfigs.4and5,itis posibleto find theantennatransmision gain against Fig.4 ElevationangleinturningflightoverItakocity(20degrees bankangle) Gain (dbi) Elevation (deg) Fig.3 Receivedpowerinturningflightwithopenloopsatelite tracking(20degreesbankangle) Fig.5 Elevationangleversustransmitingantennagain 103

4 traveling direction ofacircling aircraft.byusing the obtainedgain,thelinkbudgetintable2,andthelevel diagram ofthes-bandbasestation,thereceivedsignal powervalueduringflightcanbecalculated. Intheantennapart,18antennaelementsarearanged incircularsymmetry.iftheantennagainintheazimuth angleisstable,thepowervaluewilchangeinasinusoidal wavecurvelikethecalculateddotedlinecurve.asshown bythesolidlineinfig.3,thereceivedlevelchangeis slightlydiferentform asinusoidalwavecurve.thecauses oferorincludegapsinflightatitudeinrolandpitchaxis, andvariationsinthereceivingantennagaininazimuth angledirection.thetransmisiongainoftheaeronautical earthstationantennaisnotmeasuredona3dbasis.however, atanelevationangleof45degrees,eachtransmisiongain atazimuth angleof0,90,180,and 270degreeswas measured.themeasuredvalueswere12.3dbi,13.9dbi, 13.1dBi and 13.5dBi. There is a diference of approximately1.5dbonlywithinmeasuredpoints. The method ofsatelite tracking by antenna also includedclosedloopcontrolbythestep-trackmethod.in thismethod,measurementwasperformedatatiltangleof 20degrees:Figure6showstheresult.Thefluctuationofthe receivedlevelislargerthantheopenloopsincethesatelite istrackedbythesteptrackmethodandthebeam direction ismovingcontinuously.however,levelfluctuationshowsa similartrait. In Figure 6,receiving leveldata islacking from approximately160to170seconds,itshowsthattrouble occuredinthedatacolectionsystem attheearthstation. During thisperiod,theaircraftreceivedsignalsfrom the satelite.inthecaseofclosedloopcontrol,landmobile satelitecommunicationexperimentsshowedthatasatelite couldstilbetrackedeveniftherewasananglechangeof approximately30degreespersecond.inthisexperiment,it isestimatedthattheantennadidnotlosethesatelite,but actualytrackeditsincetheangleoftheaircraftchanged 5degreesorlespersecondintheclosedloopmethod.The receptionlevelcharacteristicsoftheopenloopmethodand theclosedloopmethodshow almostthesameresults. Thus,it sconsideredthatthesatelitewasalsotrackedby openloopmethod. (2)Packetsignaltransmisioncharacteristics [9] As basic performance of data transmision, the throughputofpacketsignaltowardthereceivedc/nowas measuredduringtheflightbyopenloopcontroltotrack thesatelite.figure7showstheresult.circlesshow the datainastaticcondition.themeasurementtimeofeach circleisfrom 3to5minutes.Invertedtrianglesshowthe dataoflevelflight.themeasurementtimeofeachinverted triangleis10seconds.thereceptionlevelisalmoststable. There isa litle variation in throughputbecause the measured packetnumberissmal.however,ifitis averaged,thethroughputvaluetowardsthec/novaluein thecaseoflevelflightisalmostthesameasthatinthecase ofastaticcondition. -indicationisthedata,shownin Fig.7,whentheaircraftisturningatatiltof20degrees. Themeasurementtimeof -indicationisalso10seconds. Therearesignificantvariationsin reception leveland throughput since the aircraft changes its atitude significantly.figure 7 shows that C/No value with degradedthroughputperformanceislowerthanthatof staticconditionandlevelflightby2db.weexploitedthe Fig.6 Receivedpowerinturningflightwithclosedloopsatelite tracking(20degreesbankangle) Fig.7 Throughputperformance 104 JournaloftheNationalInstituteofInformationandCommunicationsTechnology Vol.61No.1(2014)

5 4-2AeronauticalMobileSateliteDataCommunicationExperiments Table3 Imagedatafiletransmissiontest Modulation:QPSK Transmisionrate:128kbps Erorcorection:Turbocode(codingrate=3/4) Informationrate:96kbps Imagedatasize:654Kbyte Protocol:FileTransferProtocol Transmisionperiod:62seconds Actualinformationrate:86.4kbps Eficiency:90% posibility thatthe S-band frequency was usable for aeronauticalsatelitecommunicationonatechnicalbasis. areslightlydegradedifanaircraftsignificantlychangesits atitude.intheimagetransmisionexperiment,thesatelite linkqualitywaslow andtherealizeddatatransmision speedwasaslowasapproximately100kbps.howeverwe areplanningin thefutureto constructasystem that realizesaeronauticalmobilesatelitecommunicationwitha high transmision rate of over 10Mbps using the Wideband InterNetworking engineering test and DemonstrationSatelite(WINDS)curentlybeingoperated. Acknowledgments (3)Imagesignaltransmisioncharacteristics The purpose of the image signal transmision experimentwastotransmitimagedatafrom thesynthetic aperture radar that could be useful to understand conditionsindistresedareasoftheworldusingasatelite communication system thatwasnotafected by their disasters.table3showstheexperimentalconditionsand results.thetransmisionintable3wasperformedinlevel flightwheretheatitudeoftheaircraftwasstable.line qualitywaslow andtherealizeddatatransmisionspeed wasaslowasapproximately100kbps.untilthispoint,an aircraftwouldhavetolandonthegroundtocolectdata. Thelength oftimecan besignificantly shortened by transmiting data from an aircraftto theground via satelitelink.informationcanbecolectedatanearlystage. Whenanaircraftturns,thefluctuationwidthofthesignal levelislargeand filetransmision isincompleteand terminated.in the future,we should make a data transmision protocol that can corespond to level fluctuation.that is a chalenge for mobile satelite communications. 4 Summary We performed an aeronautical mobile satelite communication experiment in the S-band using the EngineeringTestSateliteV I.Itwasconfirmedthatdata transmisioncharacteristicsduringlevelflightwherethe signallevelisstablewerealmostthesameasthoseofthe staticcondition.thethroughputperformanceinturning with a tilt angle of 20 degrees was degraded by approximately 2dB on the basisofthe C/No value compared to levelflightor a static condition.this experimentshowedthatthes-bandfrequencycouldbe usedinaeronauticalmobilesatelitecommunicationfrom a technicalpointofview,thoughtransmisioncharacteristics Weexpresourthanksto KazuyoshiKAWASAKI, SeniorResearcher,who worked cooperatively on this experiment,andsetsukokobayashiwhocooperatedto procesdata. References 1 N.Hamamoto,S.Yoshimoto,andM.Imae, Overview oftheengineering TestSateliteV I(ETS-V I)Project,JournaloftheCommunications ResearchLaboratory,Vol.50,Nos.3/4,pp.3-11,Sept./Dec Y.Fujino,H.Watanabe,K.Kawasaki,S.Yamamoto,TOrikasa,T.Ojima,and M.Matsuura, ReceivingTestofETS-V Ibyan ActivePhased Aray AntennaMounted formobilevehicle, IEICE GeneralConference2009, B-3-18,March2009.(inJapanese) 3 M.Satoh,T.Orikasa,andY.Fujino, ReceivingTestofETS-V IbyanActive PhasedArayAntennaMountedforMobileVehicle, IEICETransactionson Communications,Vol.J94-B,No.3,pp ,March2011.(inJapanese) 4 S.Taira,S.Yamamoto,andM.Yoneda, RegenerativeRepeatingPerformance ofan OnboardPacketSwitch forthefadingchannelin Geostationary SateliteOrbit, 62ndInternationalAstronauticalCongres,IAC11-B.2.4.8, Oct J.Uemoto,S.Uratsuka,T.Umehara,S.Yamamoto,S.Taira,M.Satake, S.Kojima,T.Kobayashi,M.Satoh,K.Kawasaki,T.Matsuoka,A.Nadai,and R.Suzuki, DevelopmentoftheonboardprocesorforPI-SAR2, 2011IEEE InternationalGeoscienceandRemoteSensingSymposium,PaperNo.2656, July A.Miura,Y.Fujino,S.Taira,N.Obata,M.Tanaka,T.Ojima,andK.Sakauchi, S-bandActiveArayAntennawithAnalogPhasedShiftersusingDouble BalancedMixersforMobileSATCOM Vehicles, IEEETrans.Antennaand Propagation,Vol.53,No.8,Aug Huan-BangLi,A.Miura,M.Satoh,andH.Wakana, DisasterInformation Colection and Transmision Experiments using Ka-band Aeronautical SateliteCommunications, ProceedingsofThe14thIEEE2003International Symposium onpersonal,indoorandmobileradiocommunication,pp ,sept M.Tanaka,N.Hamamoto,S.Taira,Y.Suzuki,andS.Ohmori, Failureofthe receivingfeedsystem forthelargedeployableantennaoftheets-v I, 51st SpaceSciencesandTechnologyConference,IJ13,Oct.2007.(inJapanese) 9 H.Noda,K.Sano,andS.Hama, HighAccuracyClock, pp ,vol. 50,Nos.3/4,Sept./Dec S.Taira,S.Yamamoto,and M. Satoh, Aeronauticalmobile satelite communicationsexperimentsusingtheengineeringtestsateliteeight, 29thInternationalSymposium onspacetechnologyandscience,2013-j-17, June

SpaceCommunication,Antenna Shin-ichiYAM AM OTO SeniorResearcher,SpaceCommunication

6 ShinichiTAIRA AssociateDirector,SpaceCommunication SystemsLaboratory,WirelessNetwork ResearchInstitute MobileSateliteCommnication,Switching System MasakiSATOH Manager,ColaborativeResearchDepertment SpaceCommunication,Antenna Shin-ichiYAM AM OTO SeniorResearcher,SpaceCommunication SystemsLaboratory,WirelessNetwork ResearchInstitute MobileSateliteCommnication 106 JournaloftheNationalInstituteofInformationandCommunicationsTechnology Vol.61No.1(2014)

HC50246_2009

HC50246_2009 Page: 1 of 7 Date: June 2, 2009 WINMATE COMMUNICATION INC. 9 F, NO. 111-6, SHING-DE RD., SAN-CHUNG CITY, TAIPEI, TAIWAN, R.O.C. The following merchandise was submitted and identified by the vendor as: