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Unit6RadioFrequencyIdentification[97]
TextA
RFIDBasic[105]
TextB
HowRFIDWorks?[114]參考譯文RFID基礎
1.WhatisRFID?
RFIDstandsforRadio-FrequencyIDentification.Theacronymreferstosmallelectronicdevicesthatconsistofasmallchipandanantenna.Thechiptypicallyiscapableofcarrying2,000bytesofdataorless.RFIDBasic
TheRFIDdeviceservesthesamepurposeasabarcodeoramagneticstriponthebackofacreditcardorATMcard;itprovidesauniqueidentifierforthatobject.And,justasabarcodeormagneticstripmustbescannedtogettheinformation,theRFIDdevicemustbescannedtoretrievetheidentifyinginformation.
1.1AdvantagesofRFIDoverBarcodes
AsignificantadvantageofRFIDdevicesovertheothersmentionedaboveisthattheRFIDdevicedoesnotneedtobepositionedpreciselyrelativetothescanner.We'reallfamiliarwiththedifficultythatstorecheckoutclerkssometimeshaveinmakingsurethatabarcodecanberead.Andobviously,creditcardsandATMcardsmustbeswipedthroughaspecialreader.
Incontrast,RFIDdeviceswillworkwithinafewfeet(upto20feetforhigh-frequencydevices)ofthescanner.Forexample,youcouldjustputallofyourgroceriesorpurchasesinabag,andsetthebagonthescanner.ItwouldbeabletoqueryalloftheRFIDdevicesandtotalyourpurchaseimmediately.
RFIDtechnologyhasbeenavailableformorethanfiftyyears.IthasonlybeenrecentlythattheabilitytomanufacturetheRFIDdeviceshasfallentothepointwheretheycanbeusedasa"throwaway"inventoryorcontroldevice.AlienTechnologiesrecentlysold500millionRFIDtagstoGilletteatacostofabouttencentspertag.
OnereasonthatithastakensolongforRFIDtocomeintocommonuseisthelackofstandardsintheindustry.MostcompaniesinvestedinRFIDtechnologyonlyusethetagstotrackitemswithintheircontrol;manyofthebenefitsofRFIDcomewhenitemsaretrackedfromcompanytocompanyorfromcountrytocountry.
1.2CommonProblemswithRFID
SomecommonproblemswithRFIDarereadercollisionandtagcollision.Readercollisionoccurswhenthesignalsfromtwoormorereadersoverlap.Thetagisunabletorespondtosimultaneousqueries.Systemsmustbecarefullysetuptoavoidthisproblem.Tagcollisionoccurswhenmanytagsarepresentinasmallarea;butsincethereadtimeisveryfast,itiseasierforvendorstodevelopsystemsthatensurethattagsrespondoneatatime.(SeeFigure6.1)
Figure6.1RFIDcommunication
2.HowRFIDWorks
HowdoesRFIDwork?ARadio-FrequencyIDentificationsystemhasthreeparts:
·Ascanningantenna;
·Atransceiverwithadecodertointerpretthedata;
·Atransponder—theRFIDtag—thathasbeenprogrammedwithinformation.
Thescanningantennaputsoutradio-frequencysignalsinarelativelyshortrange.TheRFradiationdoestwothings:
·Itprovidesameansofcommunicatingwiththetransponder(theRFIDtag).
·ItprovidestheRFIDtagwiththeenergytocommunicate(inthecaseofpassiveRFIDtags).Thisisanabsolutelykeypartofthetechnology.RFIDtagsdonotneedtocontainbatteries,andcanthereforeremainusableforverylongperiodsoftime(maybedecades).
Thescanningantennascanbepermanentlyaffixedtoasurface;handheldantennasarealsoavailable.Theycantakewhatevershapeyouneed.Forexample,youcouldbuildthemintoadoorframetoacceptdatafrompersonsorobjectspassingthrough.
WhenanRFIDtagpassesthroughthefieldofthescanningantenna,itdetectstheactivationsignalfromtheantenna.That"wakesup"theRFIDchip,andittransmitstheinformationonitsmicrochiptobepickedupbythescanningantenna.
Inaddition,theRFIDtagmaybeofoneoftwotypes.ActiveRFIDtagshavetheirownpowersource;theadvantageofthesetagsisthatthereadercanbemuchfartherawayandstillgetthesignal.Eventhoughsomeofthesedevicesarebuilttohaveuptoa10yearlifespan,theyhavelimitedlifespans.PassiveRFIDtags,however,donotrequirebatteries,andcanbemuchsmallerandhaveavirtuallyunlimitedlifespan.
RFIDtagscanbereadinawidevarietyofcircumstances,wherebarcodesorotheropticallyreadtechnologiesareuseless.
·Thetagneednotbeonthesurfaceoftheobject(andisthereforenotsubjecttowear);
·Thereadtimeistypicallylessthan100milliseconds;
·Largenumbersoftagscanbereadatonceratherthanitembyitem.
3.WhatcanRFIDbeusedfor?
RFIDtagscomeinawidevarietyofshapesandsizes;theymaybeencasedinavarietyofmaterials:
·Animaltrackingtags,insertedbeneaththeskin,canberice-sized.
·Tagscanbescrew-shapedtoidentifytreesorwoodenitems.
·Credit-cardshapedforuseinaccessapplications.
·Theanti-thefthardplastictagsattachedtomerchandiseinstoresarealsoRFIDtags.
·Heavy-duty120by100by50millimeterrectangulartranspondersareusedtotrackshippingcontainers,orheavymachinery,trucks,andrailroadcars.
RFIDdeviceshavebeenusedforyearstoidentifydogs,forameansofpermanentidentification.Dogownershadlongusedtattoos,permanentinkmarkings,typicallyontheears.However,thesecanfadewithageanditmaybedifficulttogettheanimaltositstillwhileyouexaminehimformarkings.
Manymusicalinstrumentsarestoleneveryyear.Forexample,custom-builtorvintageguitarsareworthasmuchas$50,000each.Snagg,aCaliforniacompanyspecializinginRFIDmicrochipsforinstruments,hasembeddedtinychipsin30,000Fenderguitarsalready.ThedatabaseofRFIDchipIDsismadeavailabletolawenforcementofficials,dealers,repairshopsandluthiers.
4.IsRFIDTechnologySecureandPrivate?
Unfortunately,notveryofteninthesystemstowhichconsumersarelikelytobeexposed.AnyonewithanappropriatelyequippedscannerandcloseaccesstotheRFIDdevicecanactivateitandreaditscontents.Obviously,someconcernsaregreaterthanothers.Ifsomeonewalksbyyourbagofbooksfromthebookstorewitha13.56MHz"sniffer"withanRFfieldthatwillactivatetheRFIDdevicesinthebooksyoubought,thatpersoncangetacompletelistofwhatyoujustbought.That'scertainlyaninvasionofyourprivacy,butitcouldbeworse.Anotherscenarioinvolvesamilitarysituationinwhichtheothersidescansvehiclesgoingby,lookingfortagsthatareassociatedwithitemsthatonlyhigh-rankingofficerscanhave,andtargetingaccordingly.
CompaniesaremoreconcernedwiththeincreasinguseofRFIDdevicesincompanybadges.AnappropriateRFfieldwillcausetheRFIDchipinthebadgeto"spillthebeans"towhomeveractivatesit.Thisinformationcanthenbestoredandreplayedtocompanyscanners,allowingthethiefaccess—andyourbadgeistheonethatis"credited"withtheaccess.
Thesmallesttagsthatwilllikelybeusedforconsumeritemsdon'thaveenoughcomputingpowertododataencryptiontoprotectyourprivacy.ThemosttheycandoisPIN-styleorpassword-basedprotection.
5.
Next-GenerationUsesofRFID?
SomevendorshavebeencombiningRFIDtagswithsensorsofdifferentkinds.Thiswouldallowthetagtoreportnotsimplythesameinformationoverandover,butidentifyinginformationalongwithcurrentdatapickedupbythesensor.Forexample,anRFIDtagattachedtoalegoflambcouldreportonthetemperaturereadingsofthepast24hours,toensurethatthemeatwasproperlykeptcool.
Overtime,theproportionof"scan-it-yourself"aislesinretailstoreswillincrease.Eventually,wemaywindupwithstoresthathavemostly"scan-it-yourself"aislesandonlyafewcheckoutstationsforpeoplewhoaredisabledorunwilling.
1.IntroductiontoHowRFIDWorks
Longcheckoutlinesatthegrocerystoreareoneofthebiggestcomplaintsabouttheshoppingexperience.Soon,theselinescoulddisappearwhentheubiquitousUniversalProductCode(UPC)barcodeisreplacedbysmartlabels,alsocalledRadioFrequencyIDentification(RFID)tags.RFIDtagsareintelligentbarcodesthatcantalktoanetworkedsystemtotrackeveryproductthatyouputinyourshoppingcart.HowRFIDWorks?
Imaginegoingtothegrocerystore,fillingupyourcartandwalkingrightoutofthedoor.Nolongerwillyouhavetowaitassomeoneringsupeachiteminyourcartoneatatime.Instead,theseRFIDtagswillcommunicatewithanelectronicreaderthatwilldetecteveryiteminthecartandringeachupalmostinstantly.Thereaderwillbeconnectedtoalargenetworkthatwillsendinformationonyourproductstotheretailerandproductmanufacturers.Yourbankwillthenbenotifiedandtheamountofthebillwillbedeductedfromyouraccount.Nolines,nowaiting.
RFIDtags,atechnologyoncelimitedtotrackingcattle,aretrackingconsumerproductsworldwide.Manymanufacturersusethetagstotrackthelocationofeachproducttheymakefromthetimeit'smadeuntilit'spulledofftheshelfandtossedinashoppingcart.
Outsidetherealmofretailmerchandise,RFIDtagsaretrackingvehicles,airlinepassengers,Alzheimer'spatientsandpets.Soon,theymayeventrackyourpreferenceforchunkyorcreamypeanutbutter.SomecriticssayRFIDtechnologyisbecomingtoomuchapartofourlives—thatis,ifwe'reevenawareofallthepartsofourlivesthatitaffects.
2.ReinventingtheBarCode
AlmosteverythingthatyoubuyfromretailershasaUPCbarcodeprintedonit.Thesebarcodeshelpmanufacturersandretailerskeeptrackofinventory.Theyalsogivevaluableinformationaboutthequantityofproductsbeingboughtand,tosomeextent,theconsumersbuyingthem.Thesecodesserveasproductfingerprintsmadeofmachine-readableparallelbarsthatstorebinarycode.
Createdintheearly1970stospeedupthecheckoutprocess,barcodeshaveafewdisadvantages:
·Inordertokeepupwithinventories,companiesmustscaneachbarcodeoneveryboxofaparticularproduct.
·Goingthroughthecheckoutlineinvolvesthesameprocessofscanningeachbarcodeoneachitem.
·Barcodeisaread-onlytechnology,meaningthatitcannotsendoutanyinformation.
RFIDtagsareanimprovementoverbarcodesbecausethetagshavereadandwritecapabilities.DatastoredonRFIDtagscanbechanged,updatedandlocked.SomestoresthathavebegunusingRFIDtagshavefoundthatthetechnologyoffersabetterwaytotrackmerchandiseforstockingandmarketingpurposes.ThroughRFIDtags,storescanseehowquicklytheproductsleavetheshelvesandwhichshoppersarebuyingthem.
RFIDtagswon'tentirelyreplacebarcodesinthenearfuture—fartoomanyretailoutletscurrentlyuseUPCscannersinbillionsoftransactionseveryyear.Butastimegoesonwe'lldefinitelyseemoreproductstaggedwithRFIDsandanincreasedfocusonseamlesswirelesstransactionslikethatrosyinstantcheckoutpicturepaintedintheintroduction.Infact,theworldisalreadymovingtowardusingRFIDtechnologyinpaymentsthroughspecialcreditcardsandsmartphones—we'llgetintothatlater.
Inadditiontoretailmerchandise,RFIDtagshavealsobeenaddedtotransportationdeviceslikehighwaytollpasscardsandsubwaypasses.Becauseoftheirabilitytostoredatasoefficiently,RFIDtagscantabulatethecostoftollsandfaresanddeductthecostelectronicallyfromtheamountofmoneythattheuserplacesonthecard.Ratherthanwaitingtopayatollatatollboothorshellingoutcoinsatatokencounter,passengersuseRFIDchip-embeddedpasseslikedebitcards.
ButwouldyouentrustyourmedicalhistorytoanRFIDtag?Howaboutyourhomeaddressoryourbaby'ssafety?Let'slookattwotypesofRFIDtagsandhowtheystoreandtransmitdatabeforewemovepastgrocerystorepurchasestohumanlives.
3.RFIDTagsPastandPresent
RFIDtechnologyhasbeenaroundsince1970,butuntilrecently,ithasbeentooexpensivetouseonalargescale.Originally,RFIDtagswereusedtotracklargeitems,likecows,railroadcarsandairlineluggage,whichwereshippedoverlongdistances.Theseoriginaltags,calledinductivelycoupledRFIDtags,werecomplexsystemsofmetalcoils,antennaeandglass.
InductivelycoupledRFIDtagswerepoweredbyamagneticfieldgeneratedbytheRFIDreader.Electricalcurrenthasanelectricalcomponentandamagneticcomponent—itiselectromagnetic.Becauseofthis,youcancreateamagneticfieldwithelectricity,andyoucancreateelectricalcurrentwithamagneticfield.Thename"inductivelycoupled"comesfromthisprocess—themagneticfieldinductsacurrentinthewire.(SeeFigure6.2)
RFIDtagsliketheseusedtobemadeonlyfor
trackingluggageandlargeparcels.
Figure6.2RFIDtags
Capacitivelycoupledtagswerecreatednextinanattempttolowerthetechnology'scost.Theseweremeanttobedisposabletagsthatcouldbeappliedtolessexpensivemerchandiseandmadeasuniversalasbarcodes.Capacitivelycoupledtagsusedconductivecarboninkinsteadofmetalcoilstotransmitdata.Theinkwasprintedonpaperlabelsandscannedbyreaders.Motorola'sBiStatixRFIDtagswerethefrontrunnersinthistechnology.Theyusedasiliconchipthatwasonly3millimeterswideandstored96bitsofinformation.Thistechnologydidn'tcatchonwithretailers,andBiStatixwasshutdownin2001.
NewerinnovationsintheRFIDindustryincludeactive,semi-activeandpassiveRFIDtags.Thesetagscanstoreupto2kilobytesofdataandarecomposedofamicrochip,antennaand,inthecaseofactiveandsemi-passivetags,abattery.Thetag'scomponentsareenclosedwithinplastic,siliconorsometimesglass.
Atabasiclevel,eachtagworksinthesameway:
·DatastoredwithinanRFIDtag'smicrochipwaitstoberead.
·Thetag'santennareceiveselectromagneticenergyfromanRFIDreader'santenna.
·Usingpowerfromitsinternalbatteryorpowerharvestedfromthereader'selectromagneticfield,thetagsendsradiowavesbacktothereader.
·Thereaderpicksupthetag'sradiowavesandinterpretsthefrequenciesasmeaningfuldata.
InductivelycoupledandcapacitivelycoupledRFIDtagsaren'tusedascommonlytodaybecausetheyareexpensiveandbulky.Inthenextsection,we'lllearnmoreaboutactive,semi-passiveandpassiveRFIDtags.
4.Active,Semi-passiveandPassiveRFIDTags
Active,semi-passiveandpassiveRFIDtagsaremakingRFIDtechnologymoreaccessibleandprominentinourworld.Thesetagsarelessexpensivetoproduce,andtheycanbemadesmallenoughtofitonalmostanyproduct.
Activeandsemi-passiveRFIDtagsuseinternalbatteriestopowertheircircuits.Anactivetagalsousesitsbatterytobroadcastradiowavestoareader,whereasasemi-passivetagreliesonthereadertosupplyitspowerforbroadcasting.BecausethesetagscontainmorehardwarethanpassiveRFIDtags,theyaremoreexpensive.Activeandsemi-passivetagsarereservedforcostlyitemsthatarereadovergreaterdistances—theybroadcasthighfrequenciesfrom850to950MHzthatcanberead100feet(30.5meters)ormoreaway.Ifitisnecessarytoreadthetagsfromevenfartheraway,additionalbatteriescanboostatag'srangetoover300feet(100meters).
Likeotherwirelessdevices,RFIDtagsbroadcastoveraportionoftheelectromagneticspectrum.TheexactfrequencyisvariableandcanbechosentoavoidinterferencewithotherelectronicsoramongRFIDtagsandreadersintheformoftaginterferenceorreaderinterference.RFIDsystemscanuseacellularsystemcalledTimeDivisionMultipleAccess(TDMA)tomakesurethewirelesscommunicationishandledproperly.
PassiveRFIDtagsrelyentirelyonthereaderastheirpowersource.Thesetagsarereadupto20feet(sixmeters)away,andtheyhavelowerproductioncosts,meaningthattheycanbeappliedtolessexpensivemerchandise.Thesetagsaremanufacturedtobedisposable,alongwiththedisposableconsumergoodsonwhichtheyareplaced.WhereasarailwaycarwouldhaveanactiveRFIDtag,abottleofshampoowouldhaveapassivetag.
AnotherfactorthatinfluencesthecostofRFIDtagsisdatastorage.Therearethreestoragetypes:read-write,read-onlyandWORM(WriteOnce,ReadMany).Aread-writetag'sdatacanbeaddedtooroverwritten.Read-onlytagscannotbeaddedtooroverwritten—theycontainonlythedatathatisstoredinthemwhentheyweremade.WORMtagscanhaveadditionaldata(likeanotherserialnumber)addedonce,buttheycannotbeoverwritten.
MostpassiveRFIDtagscostbetweensevenand20centsU.S.each.Activeandsemi-passivetagsaremoreexpensive,andRFIDmanufacturerstypicallydonotquotepricesforthesetagswithoutfirstdeterminingtheirrange,storagetypeandquantity.TheRFIDindustry'sgoalistogetthecostofapassiveRFIDtagdowntofivecentseachoncemoremerchandisersadoptit.
5.TalkingTags
WhentheRFIDindustryisabletolowerthepriceoftags,itwillleadtoaubiquitousnetworkofsmartpackagesthattrackeveryphaseofthesupplychain.Store-shelveswillbefullofsmart-labeledproductsthatcanbetrackedfrompurchasetotrashcan.Theshelvesthemselveswillcommunicatewirelesslywiththenetwork.Thetagswillbejustonecomponentofthislargeproduct-trackingnetwork.
TheothertwopiecestothisnetworkwillbethereadersthatcommunicatewiththetagsandtheInternet,whichwillprovidecommunicationslinesforthenetwork.
Let'slookatareal-worldscenarioofthissystem:
·Atthegrocerystore,youbuyacartonofmilk.ThemilkcontainerswillhaveanRFIDtagthatstoresthemilk'sexpirationdateandprice.Whenyouliftthemilkfromtheshelf,theshelfmaydisplaythemilk'sspecificexpirationdate,ortheinformationcouldbewirelesslysenttoyourpersonaldigitalassistantorcellphone.
·Asyouexitthestore,youpassthroughdoorswithanembeddedtagreader.Thisreadertabulatesthecostofalltheitemsinyourshoppingcartandsendsthegrocerybilltoyourbank,whichdeductstheamountfromyouraccount.Productmanufacturersknowthatyou'veboughttheirproduct,andthestore'scomputersknowexactlyhowmanyofeachproductneedtobereordered.
·Onceyougethome,youputyourmilkintherefrigerator,whichisalsoequippedwitha
tagreader.Thissmartrefrigeratoriscapableoftrackingallofthegroceriesstoredinit.Itcantrackthefoodsyouuseandhowoftenyourestockyourrefrigerator,andcanletyouknowwhenthatmilkandotherfoodsspoil.
·Productsarealsotrackedwhentheyarethrownintoatrashcanorrecyclebin.Atthis
point,yourrefrigeratorcouldaddmilktoyourgrocerylist,oryoucouldprogramthefridgetoordertheseitemsautomatically.
·Basedontheproductsyoubuy,yourgrocerystoregetstoknowyouruniquepreferences.Insteadofreceivinggenericnewsletterswithweeklygroceryspecials,youmightreceiveonecreatedjustforyou.Ifyouhavetwoschool-agechildrenandapuppy,yourgrocerystorecanusecustomer-specificmarketingbysendingyoucouponsforitemslikejuiceboxesanddogfood.
Inorderforthissystemtowork,eachproductwillbegivenauniqueproductnumber.MIT'sAuto-IDCenterisworkingonanElectronicProductCode(EPC)identifierthatcouldreplacetheUPC.Everysmartlabelcouldcontain96bitsofinformation,includingtheproductmanufacturer,productnameanda40-bitserialnumber.Usingthissystem,asmartlabelwouldcommunicatewithanetworkcalledtheObjectNamingService.Thisdatabasewouldretrieveinformationaboutaproductandthendirectinformationtothemanufacturer'scomputers.
TheinformationstoredonthesmartlabelswouldbewritteninaProductMarkupLanguage(PML),whichisbasedontheeXtensibleMarkupLanguage(XML).PMLwouldallowallcomputerstocommunicatewithanycomputersystemsimilartothewaythatWebserversreadHyperTextMarkupLanguage(HTML),thecommonlanguageusedtocreateWebpages.
We'renotatthispointyet,butRFIDtagsaremoreprominentinyourlifethanyoumayrealize.Wal-MartandBestBuyarejusttwomajormerchandisersthatuseRFIDtagsforstockingandmarketingpurposes.AutomatedsystemscalledintelligentsoftwareagentsmanageallthedatacominginandgoingoutfromRFIDtagsandwillcarryoutaspecificcourseofactionlikesortingitems.
TheUnitedStatesretailmarketisonthecuspofembracingamajorimplementationof
RFIDtechnologythroughpaymentsystemsthatuseNearFieldCommunication.Thesearethecreditcardsofthefuture.
6.NearFieldCommunication,SmartPhonesandRFID
NFCtechnologyispromisingbecauseitpresentsthenextevolutionofconvenientpaymentwithanaddedlayerofsecurity.SomecreditcardshaveNFCchipsembeddedinthemandcanbetappedagainstNFCpaymentterminalsinsteadofswiped,whicheliminatesthepossibilitythatsomeonecouldskimyourdataviathemagneticstrip.Thissamesystemworkswithcellularphones,too:readuponhowcellularelectronicpaymentsworktodigintothetechnology.
GoogleisonecompanypushingNFCpaymentswithGoogleWallet.TheapplicationstorescreditcardinformationundermultiplelayersofsecurityandallowsforquicktappaymentsatNFCterminals.Thatmeansthetechnology'susefulnessislimitedbythenumberofNFCpaymentterminalsavailableinretaillocationsandthenumberofphonesthatsupportthetechnology—atlaunch,GoogleWalletonlyworkswiththeAndroidNexusSsmartphone.
SowhatdoesthishavetodowithRFID?NearFieldCommunicationdevicescanreadpassiveRFIDtagsandextracttheinformationstoredinthem.Thistechnologyisbeingusedinmodernadvertising.Forexample,pictureanormalposteradvertisingapairofjeans,thekindofpaperyou'dseeplasteredonawallinashoppingmall.Advertiserscanmake"smart"posterswithRFIDtagsthataddanewlevelofinteractionwithcustomers.TapanNFCphoneagainsta"smart"posterequippedwithanRFIDtag,andyoumaygeta10percentoffcouponforthosejeansatMacy's.PassiveRFIDtagsarecheapenoughtobeusedinpromotionalmaterialsjusttoengagecustomers.
NFCandRFIDtechnologieshavehugefuturesaheadofthemintheretailworld,butsecurityremainsacommonconcern.Somecriticsfindtheideaofmerchandiserstrackingandrecordingpurchasestobealarming.
1.什么是RFID?
RFID譯為射頻識別,該縮寫對應于包含一個小芯片和一個小天線的小型電子設備。其中的芯片通常能存儲2000字節(jié)的數(shù)據(jù)。
RFID設備的作用與條形碼或銀行卡或ATM卡背面的磁條一樣,它提供物體的唯一性標識。并且,正如條形碼和磁條必須通過掃描來獲得信息一樣,RFID設備也必須通過掃描來檢索
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