How RFID Works.docx

How RFID Works.docx

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HowRFIDWorks

HowRFIDWorks?

1.IntroductiontoHowRFIDWorks

Longcheckoutlinesatthegrocerystoreareoneofthebiggestcomplaintsabouttheshoppingexperience.Soon,theselinescoulddisappearwhentheubiquitousUniversalProductCode（UPC）barcodeisreplacedbysmartlabels,alsocalledRadioFrequencyIdentification（RFID）tags.RFIDtagsareintelligentbarcodesthatcantalktoanetworkedsystemtotrackeveryproductthatyouputinyourshoppingcart.

Imaginegoingtothegrocerystore,fillingupyourcartandwalkingrightoutofthedoor.Nolongerwillyouhavetowaitassomeoneringsupeachiteminyourcartoneatatime.Instead,theseRFIDtagswillcommunicatewithanelectronicreaderthatwilldetecteveryiteminthecartandringeachupalmostinstantly.Thereaderwillbeconnecttoalargenetworkthatwillsendinformationonyourproductstotheretailerandproductmanufacturers.Yourbankwillthenbenotifiedandtheamountofthebillbedeductedfromyouraccount.Nolines,nowaiting.

RFIDtags,atechnologyoncelimitedtotrackingcattle,aretrackingconsumerproductsworldwide.Manymanufacturersusethetagstotrackthelocationofeachproducttheymakefromthetimeit'smadeuntilit'spulledofftheshelfandtossedinashoppingcart.

Outsidetherealmofretailmerchandise,RFIDtagsaretrackingvehicles,airlinepassengers,Alzheimer'spatientsand pets.Soon,theymayeventrackyourpreferenceforchunkyorcreamypeanutbutter.SomecriticssayRFIDtechnologyisbecomingtoomuchapartofourlives--thatis,ifwe'reevenawareofallthepartsofourlivesthatitaffects.

2.ReinventingtheBarCode

AlmosteverythingthatyoubuyfromretailershasaUPCbarcode printedonit.Thesebarcodeshelpmanufacturersandretailerskeeptrackofinventory.Theyalsogivevaluableinformationaboutthequantityofproductsbeingboughtand,tosomeextent,theconsumersbuyingthem.Thesecodesserveasproductfingerprints madeofmachine-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,RFIDtagshavealsobeenaddedtotransportationdeviceslikehighway tollpasscards and subway passes.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--itis electromagnetic.Becauseofthis,youcancreateamagneticfieldwith electricity,andyoucancreateelectricalcurrentwithamagneticfield.Thename"inductivelycoupled"comesfromthisprocess--themagneticfield inducts acurrentinthewire. 

Capacitivelycoupledtags werecreatednextinanattempttolowerthetechnology'scost.Theseweremeanttobedisposabletagsthatcouldbeappliedtolessexpensivemerchandiseandmadeasuniversalasbarcodes.Capacitivelycoupledtagsusedconductivecarboninkinsteadofmetalcoilstotransmitdata.Theinkwasprintedonpaperlabelsandscannedbyreaders. Motorola'sBiStatixRFIDtags werethefrontrunnersinthistechnology.Theyusedasiliconchipthatwasonly3millimeterswideandstored96bitsofinformation.Thistechnologydidn'tcatchonwithretailers,andBiStatixwasshutdownin2001.

NewerinnovationsintheRFIDindustryinclude active,semi-activeandpassiveRFIDtags. Thesetagscanstoreupto2kilobytesofdataandarecomposedofamicrochip,antennaand,inthecaseofactiveandsemi-passivetags,a battery.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-passiveRFIDtagsuseinternal batteries topowertheircircuits.Anactivetagalsousesitsbatterytobroadcast radio wavestoareader,whereasasemi-passivetagreliesonthereadertosupplyitspowerforbroadcasting.BecausethesetagscontainmorehardwarethanpassiveRFIDtags,theyaremoreexpensive.Activeandsemi-passivetagsarereservedforcostlyitemsthatarereadovergreaterdistances--theybroadcasthighfrequenciesfrom850to950MHzthatcanberead100feet（30.5meters）ormoreaway.Ifitisnecessarytoreadthetagsfromevenfartheraway,additionalbatteriescanboostatag'srangetoover300feet（100meters）.

Likeotherwirelessdevices,RFIDtagsbroadcastoveraportionoftheelectromagneticspectrum.TheexactfrequencyisvariableandcanbechosentoavoidinterferencewithotherelectronicsoramongRFIDtagsandreadersintheformof taginterference or readerinterference.RFIDsystemscanuseacellularsystemcalledTimeDivisionMultipleAccess（TDMA）tomakesurethewirelesscommunicationishandledproperly.

PassiveRFIDtagsrelyentirelyonthereaderastheirpowersource.Thesetagsarereadupto20feet（sixmeters）away,andtheyhavelowerproductioncosts,meaningthattheycanbeappliedtolessexpensivemerchandise.Thesetagsaremanufacturedtobedisposable,alongwiththedisposableconsumergoodsonwhichtheyareplaced.WhereasarailwaycarwouldhaveanactiveRFIDtag,abottleofshampoowouldhaveapassivetag.

AnotherfactorthatinfluencesthecostofRFIDtagsisdatastorage.Therearethreestoragetypes:

 read-write,read-only and WORM（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.Storeshelveswillbefullofsmart-labeledproductsthatcanbetrackedfrompurchasetotrashcan.Theshelvesthemselveswillcommunicatewirelesslywiththenetwork.Thetagswillbejustonecomponentofthislargeproduct-trackingnetwork.

Theothertwopiecestothisnetworkwillbethe readers thatcommunicatewiththetagsandthe Internet,whichwillprovidecommunicationslinesforthenetwork.

Let'slookatareal-worldscenarioofthissystem:

•Atthegrocerystore,youbuyacartonofmilk.ThemilkcontainerswillhaveanRFIDtagthatstoresthemilk'sexpirationdateandprice.