外文翻译原文-基于低功耗无线技术的室内定位系统

19thTelecommunicationsforumTELFOR2011Serbia,Belgrade,November22-24,2011.978-1-4577-1500-6/11/$26.002011IEEEAbstractRecently,alotoflocalizationsystemshavebeenstudied.Thesesystemsaresuccessfullyusedinmanyreal-worldapplicationsasinventorymanagement,assettracking,locationdetectionofproductsstoredinawarehouse,locationdetectionofmedicalpersonnel,patientsorequipmentinahospital,andsoon.Forfindinglocationofanobject,asystemusingTag4Mdevicesisproposedinthispaper.Thelocalizationisbasedondistancemeasurementusingreceivedsignalstrengthindicator.ThedistancesbetweentheWi-Fitagandeachaccesspointarerepresentedascircleshavingthecentreintheaccesspointlocationswhichhaveknowncoordinates.Thetargetspositionisgivenbythepointattheintersectionofthecircles.KeywordsIndoorpositioning,RSSI,Tag4M,Wi-Fi.I.INTRODUCTIONNDOORlocalizationsystemshavebeenactivelyresearchedinrecentyears.Thesesystemsmaydetectthelocationofanobjectinanautomaticallymanner.Therearemanyreal-worldapplicationsthatdependonsuchautomation,likesecurityissues,airports,universitiesoreducationcenters,inventorymanagement,assettracking,guidanceoftouristsinlargemuseums,locationdetectionofproductsstoredinawarehouse,locationdetectionofmedicalpersonnel,patientsorequipmentinahospital,trackingthemovementoffirefightersinsideburningbuildings,etc.Localizationisdefinedastheprocessofdeterminingthecurrentpositionofanobjectorapersonwithinaspecificarea.Thesystemwhichconsistsofanetworkofdevices,usedtowirelesslylocaterequiredobjectsorpeopleinsideabuildingarecalledindoorpositioningsystem(IPS).ThemostpopularpositioningsystemforfindingthelocationandtheobjectspositionandfortrackingusersinoutdoorenvironmentsistheGlobalPositioningSystem(GPS).Itsworldwidesatellitenetworkisusedtomeasurethedistancewithahighaccuracy.Duetotheinabilityofthesatellitesignalstopenetratewalls,GPSisnotsuitableAlltheauthorshavethesamescientificcontributionstothispaper.A.DobrcuisPhDstudentattheFacultyofAutomationandComputerScience,TechnicalUniversityofCluj-Napoca,Cluj,Romania(phone:0040745367224;e-mail:ancuta.dobircauaut.utcluj.ro).S.FoleaisAssociateProfessorattheFacultyofAutomationandComputerScience,TechnicalUniversityofCluj-NapocaCluj,Romania(e-mail:silviu.foleaaut.utcluj.ro).D.BordenceaisAssistantProfessorattheFacultyofAutomationandComputerScience,TechnicalUniversityofCluj-Napoca,Cluj,Romania(e-mail:daniela.bordenceaaut.utcluj.ro).H.VleanisProfessorattheFacultyofAutomationandComputerScience,TechnicalUniversityofCluj-Napoca,Cluj,Romania(e-mail:honoriu.valeanaut.utcluj.ro).forindooruse.Bycomparisonwithoutdoor,indoorenvironmentshaveahighercomplexityduetovariousobstacleslikewalls,equipment,propagationofelectromagneticwaves.Withtheprogressofthewirelesstechnologiesandbecausewirelessinformationaccessisnowwidelyavailable,localizationtechniquesbasedonwirelessnetworksareeffectiveforaccuratepositioninginindoorandoutdoorenvironments.In1,theprocessofdeterminingalocationusingwirelesstechnologiesiscalledlocationsensing,geo-location,positionlocationorradiolocation.Themostindoorpositioningsystemsuseradio,ultrasoundorinfraredsignalsforfindingthelocationwithhigherprecisionwhereGPSsignalcannotbeused.Eachofthesesystemsbringsadvantagesanddisadvantages.Someofthemareexpensivetoimplementthetechnologyandhaveahighcostofproduction;othershavealowcostofproductionbuttheyalsohavethedisadvantageofgettinglargeerrorsduringlocalization.Thefollowingparagraphswillgiveabriefoverviewofsomelocalizationtechnologiesandsystems.II.SURVEYOFINDOORPOSITIONINGSYSTEMSAsolutionfordesigningawirelesspositioningsystemistodevelopasignalingsystemandanetworkinfrastructureofdevicesformeasuringthelocation.Thissolutionhastheadvantageofcontrollingthephysicalspecificationandalsothequalityoflocalizationresults.Anothersolutionistouseanexistingnetworkinfrastructuretolocateatarget,throughwhichmaybeavoidedtheinfrastructuretime-consumingdeployment.Apositioningsystembasedoninfrared(IR)isoneofthemostsimpleandcommon,duetotheavailabilityofIRtechnologyonvariousdevices.Theaccuracyofthistypeofsystemwhichusesinfraredisabout5-10m.Infrared-basedsystemsarecomposedofareceiverandatransmitterthatcommunicateusingopticalspectrum.Severaladvantagesofthesesystemsarelowcostimplementationandlowpowerconsumptionandthedisadvantagesaresensitivitytosunlight,highcostsinstallationandmaintenanceonalarge-scale.AmongthefirstindoorpositioningsystemsbasedonIRtechnologyistheActiveBadgesystem2developedbyAT&TCambridgein1990s.AnothersystemdesignedbyCybernetSystemCorporationisFirefly3.ThisisanIR-basedmotiontrackingsystem.OPTOTRAKPROseries4systemisdesignedbyNorthernDigitalInc.forcongestedshopsandworkplaces.InfraredIndoorScourLocalPositioningSystem5isanexampleofanopticalIRlocalIndoorLocalizationSystemBasedonLowPowerWi-FiTechnologyA.Dobrcu,S.Folea,H.Vlean,D.BordenceaI317positioningsystem.Somecommonadvantagesofthesesystemsarepositioningestimationsinaveryaccurateway,simplicityofsystemarchitectureandIRdevicesaresmall,light-weightandsuitabletobecarriedbyaperson.Somedisadvantagesare:expensivesystemhardwarerequirements,securityissues,interferences.TheTopaz6solutionwasdevelopedfortrackinghumansandassetsinindoorenvironments.ThislocationsystemusesBluetoothtechnologyincombinationwithIR-basedpositioningtechniqueinordertoprovideaccuracy.AnothersystemsbasedonBluetoothtechnologyarepresentedin7and8.Bluetoothdevicesareidealforlocalizationbecausetheycontainamechanismtoidentifyneighboringdevices,havingthepossibilitytocommunicatedirectlywiththem.Thistechnologyisabletoreadupto50manditisalow-costandlow-powertechnology.Moreover,theimplementationcostonasmallscaleisrelativelyreduced.However,thistechnologyisexpensiveforlarge-scaledevelopmentandtheRSSI(ReceivedSignalStrengthIndicator)cannotbeusedtodeterminelocationresultswithaprecisemeasurement.Positioningsystemsbasedonultrasoundcanbeusedonlyforindoorpositioningatroom-levelbecauseultrasoundcannotpenetratewalls.Eachobjectorpersonwhichshouldbelocatedhasattachedatagtoit.Thetagstransmittoreceiverstheiruniqueidentificationsignal,usingultrasounds.Thereceivers,placedintheroomswherelocalizationisdesired,getultrasonicsignalsfromtagsandthentransmitdigitalsignalsatatrackingunitusingwiredorwirelessLAN.Inthisway,isdeterminedthepositionoftheobject.Someadvantagesthistechnologyarethelowcostofthedevice,itssimplicityandprecisemeasurementspossibilities.Ifaccuracywithinafewcentimetersisneededthentheimplementationcostsandmaintenancearehigher.Tomeasurethelocationofatagcarriedbyapersonusingultrasounds,theActiveBatpositioningsystemwasdeveloped9,10.Cricket11canrealizereal-timetrackingandSonitor12cantrackandlocatepeopleanddevicesinrealtimewithroomlevelaccuracy.Dolphin13isanotherultrasonicpositioningsystemconsistsofdistributedwirelesssensornodes.RFID(RadioFrequencyIdentification)isanoldandwidelyusedtechnologyincomplexindoorenvironmentssuchashospital,warehouses,etc.Withthistechnology,identificationofapersonordeviceisflexibleandcheap.ThesystemsthatuseRFIDhaveseveraladvantages,includinglightandsmallsizeoftagsattachedtotargetstobetracked,abilitytoworkinsevereenvironmentalconditions,fastresponsetime,lowimplementationcost.SpotON14andLANDMARC15aretwopopularRFID-basedsystemsforfindinglocation.TagsuseRSSIvaluestocalculatedistancebetweenthetags.ZebraTechnologiesCorporationoffersWhereNet16realtimelocatingsystem.Wi-Fiisatechnologyusedworldwideforprovidinglocationinformationwithinthebuilding.ManypositioningsystemsbasedonWi-Fiareavailableonmarketplace.ThisisduetotheavailabilityofWi-Fisignalsinalmostallthebuildings,sonoadditionalhardwareisrequiredtoinstallapositioningsysteminthoseplaces.ThebasicprinciplesusedbymostWi-FibasedpositioningsystemsareRSSIandTDOA(TimeDifferenceofArrival).Forfindingthedistancefromdifferenttags,RSSIvaluebetweenanaccesspointandatagistransformedindistance.Wi-Fisystemshaveanaccuracyofabout3-5m.TheadvantageoflowcostandtheeaseofinstallationmakeindoorlocalizationbasedonWi-Fisignaltobecomeincreasinglypopular.LowcostimplementationisgivenbythepossibilityofusingexistingIEEE802.11infrastructure.RADAR17isapopularWi-Fi-basedsystemsuitableforlocatingandtrackingobjectsorpeopleinindoors.ProposedbyaMicrosoftresearchgroup,RADARusestheexistingWLANinfrastructureandWi-Fisignalstrength.Ekahau18isaWi-FibasedrealtimelocationsystemthatcanoperateoveranyWi-Finetworkinordertomonitorthemotionofdevicesandtagsincontinuallymanner.TargetslocationisdeterminedusingtheRSSIvalues.COMPASSisapositioningsystembasedon802.11networkinfrastructureanddigitalcompasses19.ThepositionofauserthatcarriesaWLAN-enableddeviceisestimatedbasedonthesignalstrengthmeasuredbydifferentaccesspoints.III.SYSTEMARCHITECTUREThegeneralstructureoftheproposedsystemispresentedintheFig.1.Asitcanbeseen,themaincomponentofthesystemistheTag4M20board.DuetotheWi-Ficommunicationcapabilities,thetagisabletocommunicatedirectlywithanaccesspoint.Whenthedeviceispowereditsearchesforandassociateswithanaccesspoint.Thetags,connectedtotheAccessPoints(APs),transfertheinformationreceivedfromsensors,overtheWi-Fitechnology,toaPC.Fig.1.GeneralSystemstructureTheTag4M21device,presentedinFig.2isaWi-FiRFIDactivedevicewithmeasurementcapabilities.DifferentsensorscanbeattachedtoitsI/Oterminalblocksandhavethepossibilitytosenddatatoacomputer.Severaladvantagesofthesystemarereduceddimensionsandweight,thecapabilitytorunonbatterypowerforyearsandportability.Thedeviceincorporatesthefollowingcomponents:32-bitCPU,amemoryunit,aneCosreal-timeoperatingsystem,aUDPorTCP/IPstack,ananalogicalsensorinterface,apowermanagementunit,ahardwarecryptographicacceleratorandarealtimeclock.Asanextensiontothetag,forapplicationswheretheassetsmaybeaffectedbydifferentenvironmentalconditionsashigherorlowertemperature,humidity,presenceofsomegassesintheair,andsooneormaybesensitiveatdifferentsituationsincludingshocksthereexist318thepossibilityfortheusertobenotifiedbyvisibleandaudiblewarningsusingbuzzerandled.Fig.2.Tag4MDataAcquisitionSystemIV.EXPERIMENTSThesystempresentedabovecanbeusedforobjectsorpeoplelocalizationinanindoorenvironment.Letssupposeabuildingwhereseveralobjectsaredistributedallover.Forabetterunderstandingofthesystem,itisshowedanexperimentwheretheobjectsareplacedonlyatonefloor.Eachoftheseobjectshasattachedatag.ThedevicesareusedtodeterminethelocationoftheobjectsinthebuildingandthedistancebetweentagsandAPs.Tomeasurethedistance,theRSSIisprocessed.Thismethodisnotveryaccurateandisstrongdependedtotheenvironment,butisveryeasytoimplementwiththeTag4M.TheFig.3presentstheexperimentenvironmentforonefloorwherethecoloredcirclesrepresentstheAPsandtherectanglesrepresentstheobjectsintendedtobelocated.Thisfloorisdividedinsixroomsseparatedbywalls.Fig.3.TheExperimentEnvironmentFirststepinfindingthelocationisdistancemeasurementusingtheRSSIsignal.TheexperimentforcomputingthedistanceispresentedinFig.4.Theexperimentalprecisionsofmeasurementsarelessthan5meters.Fig.4.DistancemeasurementusingtheRSSIsignal.Thesystemisusedtodeterminethedistancebetweentagsand2,3,4ormoreAPs.ThetagscansaftertheAPsandsendstheRSSIvaluesforeachAPtotheAPwhichisassociated.InordertoreadthecorrespondingRSSIvaluesofallfoundaccesspoints,a“scan”operationisimplementedatTag4Mlevel.Thetimetoscanissmallerthanfewmilliseconds,becausethetagdoesntassociatewiththeallAPs.ThesevaluesaresenttoaPCwherethelocalizationalgorithmisimplementedinLabVIEW2010(seeFig.5).Table1presentsascanoperationresult.InthiscasefourAPs(whichareplacedinthefloorbuilding)namedHawk,Helicopter,Tag4MandWitagServeraredetected.ThecorrespondingRSSIvalues(indBm)measuredbytheTag4MarereportedforeveryAP.TABLE1.ASEQUENCEOFRESULTSFORTHE“SCAN”OPERATIONEXECUTEDONTHETAG4MDEVICEscanRSSIScanResults:4TimeSSIDChAd-HocSecWPSMACAddressERPWMMRSSISupportedRates(Mbit/s,*Mandatory)CryptoSuitesCWMax/MinAP_SCAN,Hawk,-57dBm,AP_SCAN,Helicopter,-50dBm,AP_SCAN,Tag4M,-68dBm,AP_SCAN,WitagServer,-45dBm.TheRSSIvaluesareconvertedtodistancevaluesusingformula(1).Thevalueofthereceivedsignalstrengthisafunctionofthetransmittedpowerandthedistancebetweenthesenderandthereceiver.Thereceivedsignalstrengthwilldecreasewhenthedistanceincreasesasthefollowingequationshows23.RSSI=(10nlog10d+A)(1)Where:-nrepresentsthesignalpropagationconstant,alsonamedpropagationexponent,-drepresentsthedistancefromsender,-Arepresentsthereceivedsignalstrengthatadistanceofonemeter.319Fig.5.BlockDiagramofthelocalizationprogramTheapplicationcomputethedistancesbetweentheWi-FiTagsplacedontargetsandtheAPsplacedinindoorenvironment.Forthiscase,threeAPsareenoughbutthenumberofAPscanbeincreasedforobtainingmoreaccuratepositionestimation.ThedistancesbetweentheWi-FiTagsandeachAParerepresentedascircles,asitcanbeseeninFig.6,havingthecentreintheAPlocationswhichhavepreviouslyknowncoordinates.Thetargetspositionisgivenbythepointattheintersectionofthethreecircles.Fig.6.FrontPanelofthelocalizationprogramThesimplicityandcostefficiencyoftheRSSIbasedlocalizationmaketheproposedsystemadesiredcandidateforspecificapplicationsliketrackingandpositioningsystems.V.CONCLUSIONInthispaper,anindoorlocalizationsystembasedonultra-lowpowerWi-Fitechnologyanddesignedtodeterminelocationofobjectsinaclosedenvironmentisproposed.Inthefirstpartofthispaperasurveyofexistingindoorpositioningsystemswasmade.InthesecondpartwaspresentedthewayinwhichanobjectcanbelocalizedbyusingaccesspointsandTag4MdeviceswhichmayreadtheRSSIvalues.Theimportanceoftheproposedsystemliesinultra-lowpowerandWi-Fitransmissioncapabilitiesthatareembeddedinaverysmallpackage,whytheyaresuitabletobewornevenbypeople.Thesystemrunsonbatterieshavingacharacteristiclifetimeofacoupleofyearsandoffersaplatformforsensormeasurements.Thus,thesystemcanuseanyexistentinfrastructure,withsignificantdecreaseofimplementationcosts.REFERENCES1H.Liu,H.Darabi,P.BanerjeeandJ.Liu,“SurveyofWirelessIndoorPositioningTechniquesandSystems”,IEEETRANSACTIONSONSYSTEMS,MAN,ANDCYBERNETICSPARTC:APPLICATIONSANDREVIEWS,VOL.37,NO.6,NOVEMBER2007,pp.1067-1080.2R.Want,A.Hopper,V.Falcao,J.Gibbons,”TheActiveBadgeLocationSystem”,ACMTransactionsonInformationSystems,vol.10,no.1,January1992,pp.91-102.3”FireflyMotionTrackingSystemUsersguide”,Version2.2,December1999,/firefly/FireflyUserGuide.pdf4NorthenDigitalInc.Website,OptotrakPROseries,2011,/industrial/optotrakproseries-family.php5E.Aitenbichler,M.Mhlhuser,”AnIRLocalPositioningSystemforSmartItemsandDevices”,Proc.23rdIEEEInternationalConferenceonDistributedComputingSystemsWorkshops(IWSAWC03),2003.6Topaz,2004,http:/www.tadlys.co.il/Pages/Product_content.asp?iGlobalId=27A.Kotanen,M.Hannikainen,H.Leppakoski,andT.D.Hamalainen,“ExperimentsonlocalpositioningwithBluetooth”inProc.IEEEInt.Conf.Inf.Technol.:Comput.Commun.,Apr.2003,pp.297303.8J.Hallberg,M.Nilsson,andK.Synnes,“PositioningwithBluetooth”inProc.IEEE10thInt.Conf.Telecommun.,Mar.2003,vol.2,pp.9549589ActiveBatwebsite,2008,http:/www.cl.cam.a