Unit6RadioFrequencyIdentification[97]

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RFIDBasic[105]

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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字節的數據。

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