2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 1 Development of Complex Curricula for Molecular Bionics and Infobionics Programs within a consortial* framework** Consortium leader PETER PAZMANY CATHOLIC UNIVERSITY Consortium members SEMMELWEIS UNIVERSITY, DIALOG CAMPUS PUBLISHER The Project has been realised with the support of the European Union and has been co-financed by the European Social Fund *** **Molekuláris bionika és Infobionika Szakok tananyagának komplex fejlesztése konzorciumi keretben ***A projekt az Európai Unió támogatásával, az Európai Szociális Alap társfinanszírozásával valósul meg. PETER PAZMANY CATHOLIC UNIVERSITY SEMMELWEIS UNIVERSITY sote_logo.jpg dk_fejlec.gif INFOBLOKK 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 2 Peter Pazmany Catholic University Faculty of Information Technology ELECTRICAL MEASUREMENTS Positioning systems www.itk.ppke.hu (Elektronikai alapmérések) Helymeghatározó rendszerek Dr. Oláh András 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 3 Electrical measurements: Positioning systems Lecture 4 review • About the decibel • Description signal in transform domain (Fourier andLaplace transformation) • The bandwidth of signal • Analog-to-Digital Conversation • Thanoise 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 4 Outline • Principleofpositioning • Satellitebasedpositioningsystem(GPS) • Othersatellitebasedpositioningsystems • FeatureofGPS • Thecoordinatesystems • Thetimesystems • ApplciationsofGPS • TheNMEAProtocol • RealTimePositioningSystems Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 5 Abbreviations • GNSS–GlobalNavigationSatelliteSystems • GPS–GlobalPositioningSystem(USA) • NAVSTAR-GPS–NAVigationSystemwithTimingAndRangingGPS • SPS–StandardPositioningSystem(incommercialuse) • PPS–PrecisePositioningSystem(inmilitaryuse) • A-GPS–AssistedGPS–GPSsuppertedbyterestrialmobilecellularwirelesscommunicationsystems. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 6 Basic concepts of positioning • Passiveone-waymeasurement:pointsAandBhaveindependentbutshyncronizedclock.Weknowthetimewhenwesendamessage.Thereceiverusesthismessageitreceivestodeterminethetransittimeofmessageandcomputesthedistancetotransmitter. Electrical measurements: Positioning systems A B B’ c.t c.t Where:.t –transit time (from A to B) c –speed of light .t –clock error AB= c.t AB’= c.t+c.t (transmitter) (receiver) (real distance) (pseudorange with clock error) 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 7 Positioning based on time measurements • Activemeasurements: Electrical measurements: Positioning systems A B .t’=2 .t AB= 1c.t (transmitter) (receiver) There is not clock failure effect! Why not use? The number of users is limited! 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 8 Principle of positioning Electrical measurements: Positioning systems p1 p2 p3 xAyA x1y1 x2y2 x3y3 3 equations, 2 variables, 1 redundant meaurement? pseudo distant AB= c.t 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 9 Principle of positioning taking into account clock failure Electrical measurements: Positioning systems p1 p2 p3 xAyA x1y1 x2y2 x3y3 3 equations, 3 unknown variables! 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 10 Satellite based positioning system: GPS • TheGPSisaspace-basedGNSSthatprovideslocationandtimeinformationinallweather,anywhereonorneartheEarth,wherethereisanunobstructedlineofsighttofourormoreGPSsatellites(asreferencepoints). • Detailsofcoordinatesystems:cartesian,geographic,topocentric,inertial. • Detailsoftimesystems:universaltime,coordinateduniversaltime,GPStime. • Signalsareencodedusingcodedivisionmultipleaccess(CDMA)allowingmessagesfromindividualsatellitestobedistinguishedfromeachotherbasedonuniqueencodingsforeachsatellite(thatthereceivermustbeawareof). • CommonusesofGPS(eg.military,automobile,marine,lansseaandairnavigationandtracking). Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 11 Satellite based positioning system: GPS (cont’) • GPSusessatellitesasreferencepointstocalculateaccuratepositions. • Consistsof24GPSsatellitesinmediumEarthorbit(Theregionofspacebetween2000kmand35,786km) • Eachsatelliteorbitstheearthevery12hours(2completerotationseveryday). • Constellationdesign:atleast4satellitesinviewfromanylocationatanytimetoallownavigation(solutionfor3position+1stationclockunknowns) Electrical measurements: Positioning systems p1 p2 p3 p4 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 12 Trilateration Electrical measurements: Positioning systems Pseudoranges Clock errors Remark:Trilaterationisusedtodeterminethepositionbasedonthreesatellite'spseudoranges.Usingmorethanfourisanover-determinedsystemofequationswithnouniquesolution,whichmustbesolvedbyleast-squaresorasimilartechnique: is the coveriance matrix of the measured codedistance. where 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 13 Available satellite based positioning systems • PSwascreatedandrealizedbytheU.S.DepartmentofDefense(USDOD)andwasoriginallyrunwith24satellites.Itbecamefullyoperationalin1994. • Whileoriginallyamilitaryproject,GPSisconsideredadual-usetechnology,meaningithassignificantmilitaryandcivilianapplications. • Characterizedbycontinuousdevelopmentandmodernization. • TherearealternativeandcomplementGNSSsystems: Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 14 GPS system • ThenavigationalsignalstransmittedbyGPSsatellitesencodeavarietyofinformationincludingsatellitepositions,thestateoftheinternalclocks,andthehealthofthenetwork. • Thelocationisexpressedinaspecificcoordinatesystem(WorldGeodeticSystem,WGS84) • TheGPSconsistsof3mainsegments:– SpaceSegment:theconstellationofsatellites – ControlSegment:operationandmonitoringoftheGPSSystem – UserSegment:allGPSreceiversandprocessingsoftware's – Wemightadda4thsegment.GroundSegment:permanentciviliannetworksofreferencesites,associatedanalysesandarchives(e.g.IGS) Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 15 • 24+satellites • Satellitesequallydistributedin6orbitingplanesaroundtheEarth • 55degreeinclination • 20200kmaboveEarth • GPSsatellitesrepeattheirgroundtracksafter:1siderealday=23h56min=2orbitalperiods.Thesamegeometryisreached4minutesearliereveryday. • 5hoursviewinhorizon • Constellationdesign:atleast4satellitesinviewfromanylocationatanytimetoallownavigation(solutionfor3position+1stationclockunknowns) • EachGPSsatellitesthentransmitsignalstotheGPSreceivers.Thesesignalsindicatessatellite’slocationandthecurrenttime. • EachGPSsatellitehasspecialclockstoprovideveryaccuratetimereference(atomicclocks). Electrical measurements: Positioning systems gps GPS space segment 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 16 GPS satellites Electrical measurements: Positioning systems navstar1 navstar3 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 17 GPS dedicated monitor stations Electrical measurements: Positioning systems kovetoallomasok Hawaii Ascension Diego Garcia Kwajalein Colorado Springs 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 18 • AllGPSreceiversonland,onsea,intheairandinspace. • GPSreceiversaregenerallycomposedofanantenna,tunedtothefrequenciestransmittedbytheGPSsatellites. • Knowingthedistancefromatleast4GPSsatellites,theGPSreceivercancalculatetheirpositioningroundorinair(foraircraft). • GPSalsocantellyou– Whatdirectionyouareheading – Howfastyouaregoing – Youraltitude – Amaptohelpyouarriveatadestination – Howfaryouhavetraveled – Howlongyouhavebeentraveling – Estimatedtimeofarrival Electrical measurements: Positioning systems GPS user segment GPS_trendyimports_1689_1347201 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 19 GPS history • 1978-1992– thefirstexperimentalBlock-IGPSsatellitewaslaunched(1978). – thefirstmodernBlock-IIsatellitewaslaunched(1989). • 1993– GPSachievedinitialoperationalcapability(IOC),indicatingafullconstellation(24satellites)wasavailableandprovidingtheSPS. – 3channelreceivers,10min.setuptime,andthereceiverswere5timesexpensivethantoday. • 2000– 12channelreceivers,15-20sec.setuptime – improvingtheprecisionofcivilianGPSfrom300metersto20meters • 2005– firstmodernizedGPSsatellitewaslaunchedandbegantransmittingasecondciviliansignal(L2C)forenhanceduserperformance. • 2010– GPSNextGenerationOperationalControlSystem(OCX)toimproveaccuracyandavailabilityofGPSnavigationsignals,andserveasacriticalpartofGPSmodernization. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 20 The european brother • Galileoisaglobalnavigationsatellitesystem(GNSS)currentlybeingbuiltbytheEuropeanUnion(EU)andEuropeanSpaceAgency(ESA).The€3.4billionprojectisanalternativeandacomplementtotheU.S.NAVSTARGlobalPositioningSystem(GPS)andtheRussianGLONASS.On30November2007the27EUtransportationministersinvolvedreachedanagreementthatitshouldbeoperationalby2013,butlaterpressreleasessuggestitwasdelayedto2014. • ThepoliticalaimistoprovideanindependentpositioningsystemuponwhichEuropeannationscanrelyevenintimesofwarorpoliticaldisagreement,sincetheUSAcoulddisableuseoftheirnationalsystembyothers(throughencryption). Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 21 Galileo and GPS • OneofthereasonsgivenfordevelopingGalileoasanindependentsystemwasthatGPSiswidelyusedworldwideforcivilianapplications,whichuntil2000haduniversalSelectiveAvailability(SA)enabled(andstillbearsthepossibilityofbeingreenabled).ThiscouldintentionallyrenderthelocationsgivenviaGPSinaccurate.Galileo'sproponentsarguedthatcivilinfrastructure,includingaeroplanenavigationandlanding,shouldnotrelysolelyuponGPS. • AsoldsatellitesarereplacedintheGPSmodernizationprogram,SAwillceasetoexist.ThemodernizationprogrammealsocontainsstandardizedfeaturesthatallowGPSIIIandGalileosystemstointer-operate,allowinganewreceivertoutilisebothsystemstoimproveprecision.BycombiningGPSandGalileo,itcancreateanevenmorepreciseGNSSsystem. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 22 GPS signals Electrical measurements: Positioning systems The frequency of atomic clockson satellite: 10,23 MHz Carrier frequency: The modulation: Amplitude P-code W-code Data code, 50 bit/s C/A-code 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 23 GPS signals Electrical measurements: Positioning systems •Bitsencodedoncarrierbyphasemodulation:– C/A-code(ClearAccess/CoarseAcquisition):1.023MHz(.=300m),10.23/10 – P-code(Protected/Precise):10.23MHz(.=30m)atfundamentalfrequency – NavigationMessage:(systemtime,“Broadcast”orbits,satelliteclockcorrections,almanacs,ionosphericinformation,etc.),50bpsonbothL1andL2 • TheC/Acodeisa1,023bitdeterministicsequencecalledpseudorandomnoise(PRN).EachsatellitetransmitsauniquePRNcode,whichdoesnotcorrelatewellwithanyothersatellite'sPRNcode. • TheP-codeisalsoaPRNbutlongerthanC/A.TheextremelengthoftheP-codeincreasesitscorrelationgain. 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 24 GPS codes Electrical measurements: Positioning systems P-code (Protected): code length: 2,36*1014bit accuracy: 0,3m C/A-code (Clear Acquisition): Code length: 1023 bit accuracy: 3m 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 25 BPSK modulation technique Electrical measurements: Positioning systems jel 1 -1 1 1 -1 Carrier wave PRN code (modulation) Modulated wave cycle 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 26 Electrical measurements: Positioning systems Error sources in GPS Sources Type C/A-code P-code Satellite Clock error 3.0 3.0 Orbit error 1.0 1.0 other 0.5 0.5 Control stations Satellite track error 4.2 4.2 other 0.9 0.9 Propagation Ionosphere 5.0 –10.0 2.3 Troposphere 2.0 2.0 Multipath 1.2 1.2 Receiver Mérési zaj 7.5 1.5 Other 0.5 0.5 Total effect (.) 10.8 –13.8 6.5 Remark: this applies the pseudorange. 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 27 Receiver clock errors Electrical measurements: Positioning systems •Receiversuseinexpensivequartzcrystalsource.Thereasonistokeepthereceivercoststoanaffordablelevel. • Thereceiverclockerrorislargerthanthesatelliteclockerrors.Anerrorof1microsecond(0.000001seconds)causesarangeerrorofabout300metres. • Ifthereceiverclockisinerror,theerrorwillaffectallthemeasurementstoallsatellites.Thereceiverclockerrorisidenticalforallsatellitesobservedsimultaneously. • Todeterminethe3Dposition,threeunbiasedsatellitesmeasurementsarerequired.Toaccountforthereceiverclockerror,anadditionalsatelliteisobserved. 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 28 Coordinate systems • Cartesiancoordinatesystem:– ItrotatestogetherwiththeEarth–geocentric – ThecoordinateoriginistheEarth'scenterofmass – thex-,y-,andz-axesinaright-handedsystem. – TheSIunitismeter. – Z-axispointingtothereferencepole – X-axisisonthemeridianplane Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 29 Coordinate systems (cont’) • Sphericalcoordinatesystem:– ThesphericalcoordinatesofapointAarethendefinedasfollows:• theradiusorradialdistanceistheEuclideandistancefromtheoriginOtoA. • theinclination(orpolarangle)istheanglebetweenthezenithdirectionandthelinesegmentOA. • theazimuth(orazimuthalangle)isthesignedanglemeasuredfromtheazimuthreferencedirectiontotheorthogonalprojectionofthelinesegmentOAonthereferenceplane. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 30 Coordinate systems (cont’) • LatitudeandLongitudearesphericalcoordinatesonthesurfaceoftheearth. • LatitudeismeasuredNorthorSouthoftheEquator. • LongitudeismeasuredEastorWestofGreenwich. • GPSusesLatitudesandLongitudestoreferencelocations. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 31 Coordinate transformation Electrical measurements: Positioning systems It is a conversion from one system to another: whereN, R, echaracterizes the elipsoid 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 32 Coordinate systems: WGS84 • WorldGeodeticSystem(WGS)1984:– ThecoordinateoriginismeanttobelocatedattheEarth'scenterofmass. – themeridianofzerolongitudeistheIERSReferenceMeridian. – ZtengelyeegybeesikaFöldforgástengelyének1900-1905.éviközéphelyzetével – XYsíkjaaforgástengelyremerõlegesenatömegközéppontonátmenõsík – theX-,Y-,andZ-axesinaright-handedsystem. • CurrentgeodeticrealizationsofthegeocentricreferencesystemfamilyInternationalTerrestrialReferenceSystem(ITRS)maintainedbytheIERSaregeocentric,andinternallyconsistent,atthefew-cmlevel,whilestillbeingmetre-levelconsistentwithWGS84. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 33 Universal Time(s) • GreenwichApparentSiderealTime:isthehourangleofthevernalequinoxattheprimemeridianatGreenwich,England. • UniversalTime(UT1):conceptuallyitismeansolartimeat0°longitude(precisemeasurementsoftheSunaredifficult). • GreenwichMeanTime(GMT):atermoriginallyreferringtomeansolartimeattheRoyalObservatoryinGreenwich,London. • GreenwichMeanSiderealTime:atime-keepingsystemastronomersusetokeeptrackofthedirectiontopointtheirtelescopestoviewagivenstarinthenightsky • UniversalTimeCoordinated(UTC):anatomictimescalethatapproximatesUT1.Itistheinternationalstandardonwhichciviltimeisbased. • InternationalAtomicTime(TAI):sahigh-precisionatomiccoordinatetimestandardbasedonthenotionalpassageofpropertimeonEarth'sgeoid. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 34 Universal Time(s) Electrical measurements: Positioning systems Due to avarage Right ascension and precession 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 35 Universal Time(s) • 1980.január6:GPStimewassettomatchCoordinatedUniversalTime(UTC)in1980,buthassincediverged • GPST=604800WN+TOW– WN(WeekNumber):istransmittedasaten-bitfieldintheC/AandP(Y)navigationmessages – TOW(TimeOfWeek)orseconds-into-weeknumber • ThedifferenceisthatGPStimeisnotcorrectedtomatchtherotationoftheEarth,soitdoesnotcontainleapsecondsorothercorrectionsthatareperiodicallyaddedtoUTC. • ThedifferencebetweenGPStimeandUTC,whichasof2011is15secondsbecauseoftheleapsecondaddedtoUTCDecember31,2008. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 36 Applications • Military. • Searchandrescue. • Disasterrelief. • Surveying. • Marine,aeronauticalandterrestrialnavigation. • Remotecontrolledvehicleandrobotguidance. • Satellitepositioningandtracking. • Shipping. • GeographicInformationSystems(GIS). • Recreation. • Locationofinventoryorpermanentplots. • Mappingroads,trails,streams. • Mappingwildlifenestorobservationlocations • … Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 37 NMEA protocol • NationalMarineEducationAssociation • Itisacombinedelectricalanddataspecificationforcommunicationbetweenmarineelectronicdevicessuchasechosounder,sonars,anemometer,gyrocompass,autopilot,GPSreceiversandmanyothertypesofinstruments.Ithasbeendefinedby,andiscontrolledby,theU.S.-basedNationalMarineElectronicsAssociation. • TheNMEAstandardusesasimpleASCII,serialcommunicationsprotocolthatdefineshowdataistransmittedina"sentence"fromone"talker"tomultiple"listeners"atatime.Throughtheuseofintermediateexpanders,atalkercanhaveaunidirectionalconversationwithanearlyunlimitednumberoflisteners,andusingmultiplexers,multiplesensorscantalktoasinglecomputerport. • MostGPSmanufacturersincludespecialmessagesinadditiontothestandardNMEAsetintheirproductsformaintenanceanddiagnosticspurposes.Theseextendedmessagesarenotstandardizedatallandarenormallydifferentfromvendortovendor. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 38 NMEA grammer • Eachmessage'sstartingcharacterisadollarsign. • Thenextfivecharactersidentifythetalker(twocharacters)andthetypeofmessage(threecharacters). • Alldatafieldsthatfollowarecomma-delimited. • Thefirstcharacterthatimmediatelyfollowsthelastdatafieldcharacterisanasterisk,butitisonlyincludedifachecksumissupplied. • Theasteriskisimmediatelyfollowedbyatwo-digitchecksumrepresentingahexadecimalnumber.ThechecksumistheexclusiveORofallcharactersbetweenthe$and*.Accordingtotheofficialspecification,thechecksumisoptionalformostdatasentences,butiscompulsoryforRMA,RMB,andRMC(amongothers). • endsthemessage. Electrical measurements: Positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 39 NMEA example Electrical measurements: Positioning systems Sentence Description $GPGGA Global positioning system fixed data $GPGLL Geographic position -latitude / longitude $GPGSA GNSS DOP and active satellites $GPGSV GNSS satellites in view $GPRMC Recommended minimum specific GNSS data $GPVTG Courseover groundand groundspeed 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 40 $GPGGA Sentence (Fix data) Electrical measurements: Positioning systems Field Example Comments Sentence ID $GPGGA UTC Time 092204.999 hhmmss.sss Latitude 4250.5589 ddmm.mmmm N/S Indicator S N = North, S = South Longitude 14718.5084 dddmm.mmmm E/W Indicator E E = East, W = West Position Fix 1 0 = Invalid, 1 = Valid SPS, 2 = Valid DGPS, 3 = Valid PPS Satellites Used 04 Satellites being used (0-12) HDOP 24.4 Horizontal dilution of precision Altitude 19.7 Altitude in meters according to WGS-84 ellipsoid Altitude Units M M = Meters Geoid Seperation Geoid seperation in meters according to WGS-84 ellipsoid Seperation Units M = Meters DGPS Age Age of DGPS data in seconds DGPS Station ID 0000 Checksum *1F 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 41 VisualGPS Electrical measurements: Positioning systems It is a NMEA 0183 GPS compliant software 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 42 VisualGPS plots Electrical measurements: Positioning systems Electrical measurements: Positioning systems Real Time Location Systems • Thewirelessdevicesarebecomingmoreandmoreintegratedintoourdailylives. • Wirelessdevicesarebecomingmorecontextaware:asystemiscontextawareifitusescontextstoproviderelevantinformationandservices(time,location,temperature,speed,orientation,biometrics,audio/videorecordings,etc.)totheuser,whererelevancydependsontheuser’stasks. • Betweenthesevariablesthatdefineacontext,locationisprobablythemostimportantinputsthatdefineaspecificsituation. • Localizationservesasanenablingtechnology(RealTimeLocationSystems)thatmakesnumerouscontext-awareservicesandapplicationspossible(LocationBasedServices). Electrical measurements: Positioning systems Taxonomy of location systems • Signalingscheme– Infraredsignal(inexpensive,lowpower;itissusceptibleagainstsunlight;itcannotpenetratethroughobstructions) – Opticalsignal(LoS,lowpower,itisaffectedbysunlight,itprovideshighaccuraciesintheshortranges(10m)) – Ultrahangjelek(highaccuraciesintheshortrange,inexpensiveinLoSconditions,powerhungry) – Radiofrequency(mostcommonlyused,itcanpenetratethroughobstaclesandcanpropagatetolongdistances.)• UWB,CDMA,OFDM,etc. • Cellularsystems,WLAN,WPAN,RFID,WSN • Location estimation unit– handset-based(self-positioning,eg.:GPS) – network-based(remote-positioning,eg.:WSN) • Indoorversusoutdoorlocalization Electrical measurements: Positioning systems Why is localization important? • Veryfundamentalcomponentformanyotherservices– GPSdoesnotworkeverywhere – SmartSystems–devicesneedtoknowwheretheyare – Geographicrouting&coverageproblems – Peopleandassettracking – Needspatialreferencewhenmonitoringspatialphenomena • Inmanyapplicationsweareinterestedinidentifyingtheexactlocation:– Wheresomethinghashappened? – WhereisanObject? Electrical measurements: Positioning systems Taxonomy of location systems (cont’) • Localizationtype:– ActiveLocalization:systemsendssignalstolocalizetarget. – CooperativeLocalization:thetargetcooperateswiththesystem. – PassiveLocalization:systemdeduceslocationfromobservationofsignalsthatare“alreadypresent”. – BlindLocalization:systemdeduceslocationoftargetwithoutaprioriknowledgeofitscharacteristics. • Centralizedversusdistributed • Software-based versus hardware-based • Relative coordinate versus absolute coordinate • Basedonperformance– accuracyvs.precision,calibration,cost,energyconsumption,sensitivity,selforganizationcapability,delay,datarate,etc. Electrical measurements: Positioning systems •Position-relatedparameters:– received signal strength (RSS) P(d)=P0-10nlog10(d/d0) – angle of arrival (AOA) ri(t)=.s(t - .i)+ ni(t) .i. d/c +(lisin .)/c, ahol li= l(Na + 1)/2 - i) – time-of-arrival (TOA) correlation based, synchronization is needed – time difference of arrival (TDOA) Taxonomy of location systems (cont’) Electrical measurements: Positioning systems Localization algorithm • CellIDlocalization(thenearestreferencenode) • Geometricalmethods– Triangulation(atleastthreenodes) – Trilateration(in2Datleastthreenode,in3Datleastfournodes) – Multilateration • Statisticalmethods • Fingerprintbasedorpattern-matching Electrical measurements: Positioning systems Computation models • Eachapproachmaybeappropriateforadifferentapplication • Centralizedapproachesrequireroutingandleaderelection • Fullydistributedapproachdoesnothavethisrequirement Electrical measurements: Positioning systems Accuracy requirements Applications Range Accuracy Core apps. Sports tracking (NASCAR, horse races, soccer) 150m 10-30cm Cargo tracking at large depots 300m 300cm Children in large amusement parks 300m 300cm Animal tracking 300m 150cm Military Military training facilities 300m 30cm Military search and rescue: lost pilot, man overboard, coastguard rescue operations 300m 300cm Civil Tracking guards and prisoners 300m 30cm Aircraft landing systems 300m 30cm Tracking firefighters and emergency responders 300m 30cm Supermarket carts 150m 30cm Electrical measurements: Positioning systems Measurements technologies • AvailableTechnologies:Bluetooth,Cellular,Satellite,Television,Wi-Fi,ZigBee,UltraWideBand,RFID,Infrared,Ultrasound,Laser • UltrasonicToA– Commonfrequencies25–40KHz,rangefewmeters(ortensofmeters),avg.caseaccuracy~2-5cm,lobe-shapedbeamangleinmostofthecasesWide-bandultrasonictransducersalsoavailable,mostlyinprototypephases • AcousticToA– Range–tensofmeters,accuracy=10cm • RFToA– UbinetUWBclaims=~6inches • AcousticAoA– Averageaccuracy=~5degrees(e.gacousticbeamformer,MITCricket) • RSSIbasedlocalization– WSN:Accuracy=2-3m,Range=~10m – 802.11:Accuracy=~3m Electrical measurements: Positioning systems Challenges in WSN • Physicallayerimposesmeasurementchallenges– Multipath,shadowing,sensorimperfections,changesinpropagationproperties(RSSIbasedlocalization) • Extensivecomputationaspects– Manyformulationsoflocalizationproblems,howdowesolvethisoptimizationproblem?Wehavetosolvetheproblemonamemoryconstrainedprocessor. – Howdowesolvetheprobleminadistributedmanner? • Networkingandcoordinationissues– Weareusingitforrouting[›seeChapter9],itmeanswehaveroutingsupporttosolvetheproblem! • SystemIntegrationissues– Howdoyoubuildawholesystemforlocalization? – Howdoyouintegratelocationserviceswithotherapplications? Electrical measurements: Positioning systems Available localization systems Technology Location method Accuracy Remarks GPS ToA satellite based 1-5m Expensive, Not works indoors Ekahau (WLAN) RSS-based pattern matching 1m No extra cost over existing wireless LAN structure,extensive utilities Microsoft RADAR RSS-based pattern matching 3-4m Scalability problems, no extra cost over existingwireless LAN structure LOKI (WLAN) Closest AP cell size Installed as a free software. Used for locating theclosest restaurant Ubisense TDOA and AOA 30cm Maximum tag-sensor distances greater than 50m Indoor GPS AOA 1mm Laser positioning system for indoors.Transmission range expandable from 2 to300 m. Electrical measurements: Positioning systems Available localization systems: WSN Technology Location method Accuracy Remarks Active Badges Infra-red-basedproximity of wearablebadges to predeployed sensors Room-size Installation costs, cheap tags and sensors,sunlight and fluorescent interference, Active Bats Ultrasound ToA 9cm Ceiling sensor installation costs Cricket RSS and ultrasound-based localization 1m $10 beacons and receivers, installation costs SpotON RSS-based ad-hoc localization Depends on cluster size $30 per tag, inaccuracy of RSS metric Electrical measurements: Positioning systems Tracking in WSN • Trackingmobiletargetsinvolvesfindingoutthelocationofmobiletargetsbasedonwirelesssensornodeswithknownpositions(tracingthepath). • Giventhelocationsofthenodesandaccuraterangeinformationtothetarget,itisstraightforwardtodeterminethetarget'sposition. • Traditionaltrackingapplicationstendtobesplitintotwoseparatephases:– Localizationphase:thenetworkislocalizedusingaspecializedalgorithm. – Trackingphase:afterlocalizationcompletes,targetpositionsareestimatedbasedonthediscoveredsensorpositions. 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 56 Electrical measurements: Positioning systems GSM based positioning systems 2011.10.24.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 57 Electrical measurements: Positioning systems Summary • Locationisprobablythemostimportantinputsofcontextawaresystems. • Commoncharacteristicofnumerouslocationsystem:eachofthemiswirelesssystem. • Network-basedservicesthatintegrateaderivedestimateofamobiledevice’slocationorpositionwithotherinformationsoastoprovideaddedvaluetotheuser. • Mostlocation-basedserviceswillincludetwomajoractions:(1)Obtainingthelocationofauser,and(2)Utilizingthisinformationtoprovideaservice. • Theaccuracyandprecisionrequirementsoflocation-basedapplicationsarehighlydependentontheapplicationcharacteristics. • Therearenumerouslocalizationtechnologiescurrentlyavailablewhichhavedifferentranges,accuracylevels,costs,andcomplexities. • Next lecture:Theoretical approach to networks and systems