物联网翻译.docx
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物联网翻译.docx
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物联网翻译
第一题:
TheproposedIoTarchitecturefromatechnicalperspectiveisshowninFig.1.Itisdividedintothreelayers.Thebasiclayerandtheirfunctionalitiesaresummarizedasfollows:
Perceptionlayer:
itsmainfunctionistoidentifyobjectsandgatherinformation.Itisformedmainlybysensorsandactuators,monitoringstations(suchascellphone,tabletPC,smartphone,PDA,etc.),nano-nodes,RFIDtagsandreaders/writers.Networklayer:
itconsistsofaconvergednetworkmadeupofwired/wirelessprivatelyownednetworks,Internet,networkadministrationsystems,etc.Itsmainfunctionistotransmitinformationobtainedfromtheperceptionlayer.
Applicationlayer:
itisasetofintelligentsolutionsthatapplytheIoTtechnologytosatisfytheneedsoftheusers.
2.1.Perceptionlayer
Thislayerprovidescontext-awareinformationconcerningtheenvironmentofdisabledpeople.Thecomponentsofthislayeraccordingtothedisabilityoftheperson(visuallyimpaired,hearingimpairedorphysicallyimpaired)aredescribednext.
2.1.1.Visuallyimpaired
Thecomponentsdesignedforthevisuallyimpairedare:
(1)bodymicro-andnano-sensorsand
(2)RFID-basedassistivedevices.Next,thosecomponentsareintroduced.
2.1.1.1.Bodymicro-andnano-sensors.InSchwiebertetal.(2001),aretinalprosthesisisdevelopedtorestoresomevisiontopatientsaffectedbyretinitispigmentosaandage-relatedmaculardegeneration,twodiseasesthatcausedegenerativeblindness.Althoughthesedisordersarecharacterizedbytheprogressivelossofphotoreceptor(rodandcone)cellsoftheouterretina,theydonotaffecttheinnerretinalganglionnervecellswhichformtheopticnerve(Yeetal.,2010).Consequently,acameramountedonapairofglassescanbeusedtotransmitimagedatatoanimplantattachedtotheretina,whichisformedbyanarrayofbodymicro-sensors.Thisartificialretina(Schwiebertetal.,2001)useselectricalimpulsestostimulatetheappropriateganglioncells,whichconverttheseelectricalimpulsesintoneurologicalsignals.Thegeneratedresponseiscarriedviatheopticalnervetothebrain.
Currently,researchersareworkingtodevelopanartificialretinaatthenanoscale.TheventureNanoRetinaisdevelopingBio-Retina,abionicretinathatincorporatesseveralnano-sizedcomponentsinatinyretinalimplant(seeFig.2).Bio-Retinaisdesignedtoreplacethedamagedphotoreceptorintheeyewiththeequivalentofa5000pixel(secondgeneration)retinalimplant.Ittransformsnaturallyreceivedlightintoanelectricalsignalthatstimulatestheneurons,whichsendtheimagesreceivedbyBio-Retinatothebrain.Theimplant’snano-sizedcomponentsarepoweredbyaspecialpairofactivationeyeglasses.Inthenextyears,astechnologyevolves,itwillbepossibletosendinformationconcerningtheimagescapturedbytheartificialretinatowardsthemonitoringstation(smartphone)(seeFig.1),sothatnewIoTapplicationstohelppeoplewithvisualimpairmentsintheirorientation,identificationoffaces,etc.willbedeveloped.
2.1.1.2.RFID-basedassistivedevices.AnessentialRFID-basedapplicationisthenavigationsystem.Ithelpsblindpeoplefindtheirwayinanunfamiliararea.RFIDtagsaredistributedthroughthearea.Theycanforexamplebeplacedinthecenterofthesidewalkstoorienttheblindpersonandpreventpossiblefallsneartheborderofthesidewalk(Saaidetal.,2009).
TheRFIDcane(seeFig.1)hasatagreaderwithanantennathatemitsradiowaves;thetagsrespondbysendingbacktheirstoreddata,henceidentifyingthelocationoftheblindperson.Thetagreader(RFIDcane)transmitsviaBluetoothorZigBeethedatareadfromtheRFIDtag,whichincludesthetagIDstring(D’Atrietal.,2007).ThisdataissentfromthemonitoringstationthroughthenetworklayertotheRFIDserveroftheapplicationlayer.Theblindpersoncanrecordthedestination’snameasavoicemessageusingthemonitoringstation.Directionsarereceivedbythemonitoringstationandplayedasvoicemessages(Shiizuetal.,2007).
Anobstacledetectionsystembasedonanultrasonicsensorcanalsobeadded(Martinetal.,2009).ThesensorismountedontheRFIDcanetoextenditseffectiverangeandperceiveobstaclesthecanealonewouldnotbeabletodetect(suchasagarbagecaninFig.1).Avoicemessageplayedatthemonitoringstationalertsthevisuallyimpairedwhenanobstacleisdetected.Amultiplesensor-basedshoe-mountedsensorinterfaceisalsodevelopedinZhangetal.(2010)asasupplementarydevicetothecanetodetectobstacleswithin61cmaheadofthevisuallyimpaired.
AwidespreadapproachforoutdoornavigationreliesonGlobalPositioningSystem(GPS).Itdoesnotrequiretagstowork.However,itsresolutionislimited(fewmeters)anditcannotworkproperlyindoors.Therefore,somenavigationsystemsforthevisuallyimpairedintegratebothtechnologies(RFIDandGPS)(Yelamarthietal.,2010).
Thislayer(seeFig.1)enablestheaccessofthemonitoringstationstotheradiochanneltotransmittheinformationobtainedfromtheperceptionlayer.AlthoughtheInternetprotocolswereoriginallydesignedforfixednetworks,thereisagrowingneedfortheseprotocolstoaccommodatemobilenetworks,asdemonstratedbytheuseofmanydifferentwirelessaccesstechnologiesinIoT(EUFP7ProjectCASAGRAS,2009).ThedifferenttransmissionmediaincludeWirelessLocalAreaNetworks(WLANs)(IEEE802.11variants),WorldwideInteroperabilityforMicrowaveAccess(WiMAX)(IEEE802.16),Bluetooth(IEEE802.15.1),Ultra-wideband(UWB)(IEEE802.15.4aandECMA-368),ZigBee(IEEE802.15.4),GeneralPacketRadioService(GPRS)andWidebandCodeDivisionMultipleAccess(WCDMA).WirelessadhocnetworksareagoodoptiontoestablishwirelessandmobilecommunicationswithintheIoT,sincetheydonotrelyonapreexistinginfrastructure,theyrequireminimalconfig-urationandaredeployedquicklywithlowcost.Networkscomposedofdifferentaccesstechnologiesareknownasheterogeneousnetworksandtheyshouldmaintainconnectivityandservicefordifferentapplicationsevenwithusermobility.
TheconvergenceofheterogeneousnetworksandapplicationsispossibleduetotheexistenceofasingleInternetProtocol(IP)-basednetwork.TheIPforSmartObject(IPSO)Allianceisanon-profitassociationofmorethan50membersfromleadingtechnology,communicationsandenergycompanies.TheyadvocatetheuseofIPnetworkeddevicestobuildtheIoT(DunkelsandVasseur,2010).TheystressthatIPisalong-livedandstablecommunicationtechnologythatsupportsawiderangeofapplications,devicesandunderlyingcommunicationtechnologies.Inaddition,theend-to-endIParchitectureislightweight,highlyscalableandefficient.Furthermore,theauthorsofInternetØalsorecommendtheuseoftheIPprotocoltooffertheInternet’sinteroperabilityandscalabilitydirectlytoembeddeddevicesratherthanneedinggatewaysforprotocolconversion(GershenfeldandCohen,2006).
Itisnecessarytoensuretheconnectivity,interoperabilityandcompatibilityofheterogeneousnetworks.Thelow-powernet-workingindustry,fromZigBeeadhoccontroltoindustrialautomationstandards(e.g.ISA100),isquicklyconvergingtotheuseofIPtechnology(ShelbyandBormann,2009).Inthissense,6LoWPANisthenameofaworkinggroupoftheInternetEngineeringTaskForce(IETF)thathasdevelopedasetofInternetstandards,whichenabletheefficientuseofIPv6overLow-powerWirelessPersonalAreaNetworks(6LoWPANs).6LoWPANenablesresource-limitedembeddeddevices(oftenbattery-powered)inlow-powerwirelessnetworkstobeInternet-connectedbysimplifyingIPv6(headercompressionofIPv6headerfields)andtakingthenatureofwirelessnetworksintoaccount.
TheIPv6protocolstackwith6LoWPANisshowninFig.4.Asmalladaptationlayer(namedtheLoWPANadaptationlayer)hasbeendefinedinthe6LoWPANprotocolstack(seeFig.4)tooptimizethetransmissionofIPv6packetsoverIEEE802.15.4andsimilarlinklayers(ShelbyandBormann,2009).IEEE802.15.4isastandardthatdefinesthephysicalandMAClayersforlow-power,low-ratewirelessembeddedradiocommunicationsat2.4GHz,915MHzand868MHz.
TheadoptionofInternetprotocolsbywirelessembeddeddevicesischallengingduetoseveralreasons(ShelbyandBormann,2009):
Battery-poweredwirelessdevicesrequirelowdutycycles,whereasIPisbasedonalwaysconnecteddevices.
MulticastisnotsupportednativelyinIEEE802.15.4butitisessentialinmanyIPv6operations.
Sometimesitisdifficulttoroutetrafficinmulti-hopwirelessmeshnetworkstoachievetherequiredcoverageandcostefficiency.
Lowpowerwirelessnetworkshavelowbandwidth(20–250kbit/s)andframesize(IEEE802.15.4packetsarerathersmall,127bytesmaximumatthephysicallayer,minusMAC/securityandadaptationlayeroverhead).Ontheotherhand,theminimumdatagramsizethatallhostsmustbepreparedtoaccept,forIPv6is1280bytes.IPv6requiresthateverylinkintheInternethasaMaximumTransmissionUnit(MTU)of1280bytesorgreater.Onanylinkthatcannotconveya1280-bytepacketinonepiece,link-specificfragmentationandreassemblymustbeprovidedatalayerbelowIPv6.
Standardprotocolsdonotperformwellinlow-powerwirelessnetworks.Forexample,TCPperformsverypoorlyinwirelessnetworksduetoitsinabilitytodistinguishbetweenpacketlossesduetocongestionandthoseduetochannelerror.
2.3.Applicationlayer
Thislayer(seeFig.1)providesanoperationsupportplatform,whichcanbeaccessedbymonitoringstationsandapplications.Itprovidesimportantfunctionalitiessuchasauthentication,billing,servicemanagement,serviceacceptanc
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