Module5-WWAN

ELEC6099WirelessCommunicationandNetworkingModule5:WirelessWide-AreaNetworksOutline GSMEvolution GSMDataRateEnhancement GSMto3G UMTS HSDPA cdmaOneEvolution cdma2000overview Transmitdiversity Powercontrol cdma2000architecture cdma20001xEV-DO MobileIP MobileIPScenarios Co-LocatedAddresses,Registration,Tunneling EncapsulationOptions Micro-Mobility 4GandLTE Introduction GSMwasdesignedandimplementedwithonlyvoiceservicesinmind Datarateislow Withmobiledataingreatdemand(Internet!),highspeedtransmissionsareneeded Packetswitchedtransmissions,basedonIP Approaches: Evolutionary:HSCSD,EDGE,GPRS Revolutionary:3G,UMTSGSMDataEnhancement:HSCSD Asseenearlier,GSMcansupportdataservicedirectlybyusingtheTDMAslottocarrydatabitsinsteadofvoiceinformation acircuitswitcheddataconnection,withtheTCH/Fchannel withbitrate9.6kbpsonly HSCSD(HighSpeedCircuitSwitchedData)isasimpleextensionoftheabovebasicdataservice Byreducingtheerror-correctionoverhead,thebaserateisincreasedto14.4kbps upto4slotscanbeallocatedtooneuser,resultinginadatarateof57.6kbps Circuitswitchedconnectionisnotefficientforcomputerapplications(e.g.,Webbrowsing)GSMDataEnhancement:GPRS GPRS(GeneralPacketRadioService)isdesignedtoovercometheefficiencyproblemincircuitswitcheddataconnection packetswitched,i.e.,timeslotsarenotallocatedstaticallyforeveryframebutarecompetedbyuserson-demand(contentionbased) needamultipleaccesscontrolprotocol differentchannelcoding/compressionschemesallowforawiderangeofdatarates,upto171.2kbpsfor8slotstransmissionGSMDataEnhancement:GPRS However,GPRSrequiressoftware/firmwareupgradingtoexistingdevices/systems Twonewelements: GatewayGPRSSupportNode(GGSN):agatewayconnectingtheGPRScellularnetworkwiththeexternalpacketdatanetwork(e.g.,theInternet) containsroutinginformationforGPRSusers,performsaddressconversion,andtunnelsdatatoauserviaencapsulation ServingGPRSSupportNode(SGSN):arouterconnectingtheGGSNandtheBSS requestsuseraddressesfromtheGPRSregister keepstrackofindividualdevices’locations responsibleforcollectingbillinginformation(e.g.,countingvolumeoftrafficinbytes) performsseveralsecurityfunctionssuchasaccesscontrolGSMDataEnhancement:GPRSGSMDataEnhancement:GPRS Asitispacketswitched,multipleaccesscontrolisneeded AR-TDMAmultipleaccessschemeisused Reservationcontentionprecedingdatatransmissionframes First-come-first-servedscheduling Theassigneddatarateforauserdependson: Numberoftime-slotsallocated Channeladaptation(affectingtheerror-protection)GSMDataEnhancement:GPRSGSMDataEnhancement:ChannelAdaptation Observation:Channelqualityfluctuates,sometimesgood,sometimesbad(why?) Whenchannelqualityisgood,biterrorrateislower,and, Doesnotneedmucherrorprotection Thatmeansmoreaggressivechannelcodingandmodulation Ultimately,highereffectivedatarate Whenchannelqualityisbad,biterrorrateishigher,and, Needsmoreerrorprotection Thatmeansmoreconservativechannelcodingandmodulation Ultimately,lowereffectivedatarate Key:Beingabletoquicklyrespondtothefluctuatingchannelquality ThatisamajorfactorinenablingGPRS,EDGE,etc.improvethedatarateGSMDataEnhancement:EDGE EnhancedDataratesforGSMEnhancementGSMto3G TheInternationalTelecommunicationUnion(ITU)’sviewon3Gservices: Voicequalitycomparabletothepublicswitchedtelephonenetwork 144kbpsdatarateavailabletousersinhigh-speedmotorvehiclesoverlargeareas 384kbpsavailabletopedestriansstandingormovingslowlyoversmallareas Supportfor2.048Mbpsforstationary(e.g.,office)use Symmetrical/asymmetricaldatatransmissionrates Supportforbothpacketswitchedandcircuitswitcheddataservices AnadaptiveinterfacetotheInternettoreflectefficientlythecommonasymmetrybetweeninboundandoutboundtraffic Moreefficientuseoftheavailablespectrumingeneral Supportforawidevarietyofmobileequipment FlexibilitytoallowtheintroductionofnewservicesandtechnologiesGSMto3G IncrementalenhancementstoGSMcannotsupporthigherdatarates(e.g.,2Mbps) Asystemre-designisneeded Asearlyas1992,theITUidentified230MHzofspectruminthe2GHzbandtoimplementtheso-calledIMT-2000system DifferentCDMAbasedsolutionsareconsideredandembraced Toprovidereasonableevolutionarypathstodifferentexisting2GstandardsGSMto3GGSMto3GGSMto3G IMT-DS:ForsomeEuropeanandJapanesesystems IMT-TC:ForGSMandtheChineseTD-synchronousCDMA IMT-MC:FortheU.S.’scdmaOne,cdma2000 IMT-SC:FortheU.S.’sTDMAsystems IMT-FT:ForsomeDigitalEuropeanCordlessTechnology(DECT)systems Notreallycompatible…GSMto3GGSMto3G:UMTS UniversalMobileTelecommunicationSystemGSMto3G:UMTSGSMto3G:UMTSGSMto3G:UMTS Significantchanges: Frequencyband Airinterface(channelcoding,modulation,etc.) Powercontrol SignificantinvestmentisneededtorevamptheexistingGSMsystem: NodeBservingasthenewBS RNCservingasthenewBScontrollerUMTS:ChannelStructureUMTS:ChannelStructure PhysicalLayer: Forwarderrorcorrection(FEC),bit-interleaving,etc. Signalmeasurements Softhandoffexecution Modulation/demodulation,spreading/despreading Frequency/timesynchronization PowercontrolUMTS:ChannelStructure MACLayer: Multiplexingtherandomaccesschannel(RACH),forwardaccesschannel(FACH),anddedicatedchannel(DCH) Priorityhandling AccesscontrolonRACHandFACH ContentionresolutionUMTS:ChannelStructure RadioLinkControl(RLC)Layer: Segmentationandassemblyofdatapackets Retransmission Flowcontrol RadioResourceControl(RRC)Layer: Broadcastsysteminformation Paging EstablishingandreleasingofconnectionsUMTS:RNCandNodeB RNCisresponsiblefor: Radioresourcecontrol Radiolinkcontrol Activesetmodification Priorityhandling NodeBisresponsiblefor: Schedulingofbroadcast,pagingandnotificationmessages CollisionresolutiononRACHUMTS:CoreNetworkArchitecture Separatingthecircuitswitched(CS)andpacketswitched(PS)domains CSdomain: MSC GatewayMSC(GMSC) PSdomain: ServingGPRSSupportNode(SGSN) GatewayGPRSSupportNode(GGSN) DNSServer,DHCPServer,etc.UMTS:CoreNetworkArchitectureUMTS:3G-MSC MaincomponenttoprovideCSservices Responsiblefor: Mobilitymanagement Callmanagement CSdataservices(e.g.,fax) SMS VLRfunctionalityUMTS:3G-SGSN MaincomponentforprovidingPSservices Responsiblefor: Sessionmanagement SignalingtoconnecttoanIP-basednetwork Subscriberdatabasefunctionality ChargingforradionetworkusageUMTS:3G-GGSN GGSNprovidesinternetworkingwiththeexternalIPnetwork Responsiblefor: Maintainlocationinformation GatewaybetweenUMTSandanexternalnetwork Userdatascreening/security Userleveladdressallocation ChargingforexternaldatanetworkusageUMTS:BearerServiceHSDPA HighSpeedDownlinkPacketAccess Providedataratesupto8-10Mbps UsingMIMO(Multiple-Input-Multiple-Output),multi-antennasystems Canevengoupto20Mbps Designedbasedon: Channeladaptation(i.e.,highordermodulationandcoding) IntelligentARQretransmission Intelligentscheduling ShorterframesizesIntroduction 3GCDMA:cdma2000 Wideband,spreadspectrumradiointerfacethatusesthe2GCDMA(IS-95)technology Backwardcompatiblewiththe2GCDMA,i.e.,cdmaOne Alsoreferredtoas3G1XEV-DO(evolutionfordata-onlysystems),orhighdatarate(HDR) Supportdatarates(bothcircuitswitchedandpacketswitched)from9.6kbpsto2MbpsIntroduction:cdma2000 Canbeoperatedeconomicallyinawiderangeofenvironments: Outdoormega-cells(>35kmradius) Outdoormacro-cells(1-35kmradius) Indoor/outdoormicro-cells(upto1kmradius) Indoor/outdoorpico-cells(<50mradius)cdma2000LayeredStructure—UpperLayers Voiceservices:telephony End-userdatabearingservices: Circuitswitcheddata Packetdata(TCP/IP,UDP/IP) Signaling:controltrafficcdma2000LayeredStructure—LowerLayers Linklayer: Provideprotocolsupportandcontrolfordatatransport Dividedintotwosub-layers:linkaccesscontrol(LAC)andmediumaccesscontrol(MAC) LAC: Provideend-to-endreliablelinkconnection MAC: Includesanumberofdifferentstates ProvideQoSsupportcdma2000LayeredStructurecdma2000LayeredStructure—MAC MACcontrolstate: Controllingtheaccessofdataservice(packetandcircuit)tothephysicallayer Besteffortdelivery: Reasonablyreliabletransmissionovertheradiolink MultiplexingandQoScontrol: EnforcementofnegotiatedQoSlevelsbycoordinationandschedulingcdma2000LayeredStructure—MACcdma2000LayeredStructure—MAC Nullstate: Defaultstatepriortoactivationofpacketdataservice Afterthepacketserviceisinvoked,atransitiontotheinitializationstateoccurs Activestate: Traffic,powercontrol,andcontrolchannelsareassigned Controlholdstate: Dedicatedcontrolchannelismaintainedbetweenthemobiledeviceandthebasestation,fortransmissionofMACcontrolcommands(e.g.,tobeginahighdatarateburst) Powercontrolisalsomaintainedcdma2000LayeredStructure—MAC Suspendedholdstate: Nodedicatedchannelismaintained Stateinformationismaintained Basestationandmobiledevicebothmaintainsavirtualactivesetsothatitisclearwhichbasestationisthebest,whenthereistraffic Mobiledeviceenterspowerpreservationmode Dormantstate: Shortdataburstmode—shortmessagescanbedeliveredcdma2000ForwardLink SupportschipratesofNx1.2288Mcps(whereN=1,3,6,9,12) ForN=1,thespreadingissimilartoIS-95 However,QPSKmodulationandfastclosedlooppowercontrolareused ForN>1,themulti-carrieroptionisused De-multiplexontoNseparate1.25MHzcarrierscdma2000ForwardLinkTransmitDiversity TransmitdiversitycanreducetherequiredEb/N0,i.e.,therequiredtransmitpowerperchannel Thus,enhancingsystemcapacity Transmitdiversitycanbeimplementedby: Multi-carriertransmitdiversity Direct-spreadtransmitdiversitycdma2000Multi-CarrierTransmitDiversity Antennadiversitycanbeimplementedinamulti-carrierforwardlinkwithnoimpactonthesubscriberterminal Asubsetofcarriersistransmittedoneachantenna Frequencydiversity=spreadingofdatasignaloverentirebandwidth Bothtimeandfrequencydiversityareused Fastpowercontrolisusedcdma2000Multi-CarrierTransmitDiversity 3X1.25MHzscenario Samecodeisusedineachcarriercdma2000Direct-SpreadTransmitDiversity Orthogonaltransmitdiversity(OTD)maybeusedtoprovidetransmitdiversityfordirectspread(i.e.,N=1) Codedbitsaresplitintotwodatastreamsandaretransmittedviaseparateantennas Adifferentcodeisusedforeachantenna Self-interferenceiseliminatedPowerControl:Basics Thereceivedpowermustbesufficientlyabovethebackgroundnoiseforeffectivecommunication,whichdictatestherequiredtransmittedpower Asthemobileunitmovesawayfromthetransmitter,thereceivedpowerdeclinesduetonormalattenuation(pathloss) Inaddition,theeffectsofreflection,diffraction,andscatteringcancauserapidchangesinreceivedpowerlevelsoversmalldistances Thisisbecausethepowerlevelisthesumofsignalpowerlevelscomingfromanumberofdifferentpathsandthephasesofthosepathsarerandom,sometimesaddingandsometimessubtracting Asthemobileunitmoves,thecontributionsalongvariouspathschange Atthesametime,itisdesirabletominimizethepowerinthetransmittedsignalfromthemobile,toreduceco-channelinterference,alleviatehealthconcerns,andsavebatterypower Inspreadspectrum(SS)systemsusingcodedivisionmultipleaccess(CDMA),itisdesirabletoequalizethereceivedpowerlevelfromallmobileunitsattheBS.ThisiscrucialinCDMAasallusersareassignedthesamefrequencyPowerControl:Basics Openlooppowercontrol: dependssolelyonthemobileunit,withnofeedbackfromtheBS isusedinsomeSSsystems,inwhichtheBScontinuouslytransmitsanun-modulatedsignal,knownasthepilot thepilotsignalallowsamobiledevicetoacquirethetimingoftheforwardlinkandprovidesaphasereferencefordemodulation itcanalsobeusedforpowercontrol themobiledevicemonitorsthereceivedpowerofthepilotandsetsthetransmittedpowerinthereverselinkinverselyproportionaltoit thisapproachassumesthattheforwardandreverselinksignalstrengthsarecloselycorrelated,whichisgenerallythecase open-looppowercontrolisnotasaccurateasclosed-loopapproach however,itcanreactmorequicklytorapidfluctuationsinsignalstrength,suchaswhenamobiledeviceemergesfrombehindalargebuilding thisfastresponseiscriticalinthereverselinkofaCDMAsysteminwhichasuddenincreaseinreceivedstrengthattheBSmaymaskoutallothersignalsPowerControl:BasicsPowerControl:Basics Closed-looppowercontrol: adjustingthesignalstrengthinthereversechannelbasedonsomemetricofperformanceinthatreversechannel,suchasreceivedsignalpowerlevel,receivedsignal-to-noiseratio,orreceivedbiterrorrate theBSmakesthepoweradjustmentdecisionandcommunicatesapoweradjustmentcommandtothemobiledeviceonacontrolchannel closed-looppowercontrolisalsousedtoadjustpowerintheforwardlink inthiscase,themobileprovidesinformationaboutreceivedsignalqualitytotheBS,whichthenadjuststransmittedpowerPowerControl:BasicsPowerControl:2G InIS-95,forwardlinkpowercontrolwasnotconsideredasimportantasthatrequiredbythereverselinkpowercontrol BasestationtransmitsalltheuserchannelscoherentlyinthesameRFcarrier Samefadingexperienced Thus,inIS-95,forwardlinkpowercontrolisslow Notfastthan50Hz TooslowtocopewithfastRayleighfadingPowerControl:3G 3GforwardlinkpowercontrolfunctionsaresimilartothereverselinkpowercontrolinIS-95 Atarateof800Hz Designobjectives: Highspeedforwardlinkpowercontrol Closedloopwithfasttimeresponse VariablepowerstepsizecontrolledbytheBS CancombatfastRayleighfading Ultimately,increasingcapacityontheforwardlinkcdma2000Evolutioncdma2000EvolutionMixingmorecdma2000(3G1X,3X)withcdmaOnecdma2000Architecturecdma2000Architecturecdma2000Architecture BSCandBTSprovideradioaccessnetworkfunction TheMSC/VLRandHLRarethemainentitiesofthecircuitswitchedcorenetwork OthersincludeAC,voicemail(VM),andmessagecenter(MC) Homeagent(HA)andforeignagent(FA)areformobileIPcdma2000Architecture:InternetAccesscdma20001XEV-DO Alsocalled“highdatarate”(HDR) Optimizedforpacketdataservices,withadecentralizedarchitecturebasedontheIPprotocol HDRoffersahigh-speedcost-effectivedatasolution Maximizethroughputsubjectedtoanacceptabledelay HDRoptimizesforwardlinkforpacketdatacdma20001XEV-DO:ForwardLink Basicunitistheair-linkframe Time-divisionmultiplexedfordifferentusers Transmittedatthelinkrate,rangingfrom38.4kbpsto2.4Mbps,dependingonchannelquality Employaschedulingalgorithmtodecideontime-slotallocationsandusersorderingcdma20001XEV-DO:ReverseLink Transmitsatdataratesrangingfrom9.6kbpsto153.6kbps Unlikeforwardlink,thereverselinkusesthebasicCDMAmechanism Multipleuserstransmitatthesametime Totalthroughputisabout250kbps,whichisabout1/5oftheforwardlinkthroughputcdma20001XEV-DOArchitecturecdma20001XEV-DO:ComparisonwithHSDPAcdma20001XEV-DV EV-DV(evolutionwithdataandvoice) Designedtodeliverreal-timecircuit-switchedvoiceservicesandhighdataratepacketservicesinthesameRFcarrier Deliversapeakdatarateof3.09Mbps Supportapplicationsthatrequiresimultaneousvoiceanddatatasks E.g.,havingavoiceconversationwhiledownloadingemailmessages Onlinegamingthatrequiresregulardatarates(e.g.,1.6kbpsatleast)andshortround-triptime(e.g.,<160ms)cdma2000DeploymentScenariosIntroduction EnablecomputerstomaintainInternetconnectivitywhilemovingfromoneInternetattachmentpointtoanother E.g.,aniPad-3Gusermovesfromonecellularnetworktoanother Mobile:user’spointofattachmentchangesdynamicallyandallconnectionsareautomaticallymaintaineddespitethechange Nomadic:user’sInternetconnectionisterminatedeachtimetheusermovesandanewconnectionisinitiatedwhentheuserdialsbackin New,temporaryIPaddressisassignedOperationofMobileIP Mobilenodeisassignedtoaparticularnetwork—homenetwork IPaddressonhomenetworkisstatic—homeaddress Mobilenodecanmovetoanothernetwork—foreignnetwork Mobilenoderegisterswithnetworknodeonforeignnetwork—foreignagent Mobilenodegivescare-ofaddresstoagentonhomenetwork—homeagentMobileIPScenarioMobileIPScenarioServerXtransmitsanIPdatagramdestinedformobilenodeA,withA’shomeaddressintheIPheader.TheIPdatagramisroutedtoA’shomenetwork.Atthehomenetwork,theincomingIPdatagramisinterceptedbythehomeagent.ThehomeagentencapsulatestheentiredatagraminsideanewIPdatagramwhichhastheA’scare-ofaddressintheheader,andretransmitsthedatagram.TheuseofanouterIPdatagramwithadifferentdestinationIPaddressisknownastunneling.ThisIPdatagramisroutedtotheforeignagent.TheforeignagentstripsofftheouterIPheader,encapsulatestheoriginalIPdatagraminanetwork-levelPDU(e.g.,aLANLLCframe),anddelivertheoriginaldatagramtoAacrosstheforeignnetwork.WhenAsendsIPtraffictoX,itusesX’sIPaddress.Inourexample,thisisafixedaddress;thatis,Xisnotamobilenode.EachIPdatagramissentbyAtoarouterontheforeignnetworkforroutingtoX.Typically,thisrouterisalsotheforeignagent.TheIPdatagramfromAtoXtravelsdirectlyacrosstheInternettoX,usingX’sIPaddress.MobileIPComponents Discovery:Amobilenodeusesadiscoveryproceduretoidentifyprospectivehomeagentsandforeignagents. Registration:Amobilenodeusesanauthenticatedregistrationproceduretoinformitshomeagentofitscare-ofaddress. Tunneling:TunnelingisusedtoforwardIPdatagramsfromahomeaddresstoacare-ofaddress.Discovery Mobilenodeisresponsibleforongoingdiscoveryprocess Mustdetermineifitisattachedtoitshomenetworkoraforeignnetwork Transitionfromhomenetworktoforeignnetworkcanoccuratanytimewithoutnotificationtothenetworklayer Mobilenodelistensforagentadvertisementmessages Comparesnetworkportionoftherouter'sIPaddresswiththenetworkportionofhomeaddressAgentAdvertisementMessageAgentSolicitation Foreignagentsareexpectedtoissueagentadvertisementmessagesperiodically Ifamobilenodeneedsagentinformationimmediately,itcanissueICMProutersolicitationmessage AnyagentreceivingthismessagewillthenissueanagentadvertisementMoveDetection MobilenodemaymovefromonenetworktoanotherduetosomehandoffmechanismwithoutIPlevelbeingaware Agentdiscoveryprocessisintendedtoenabletheagenttodetectsuchamove Algorithmstodetectmove: Useoflifetimefield:mobilenodeuseslifetimefieldasatimerforagentadvertisements Useofnetworkprefix:mobilenodechecksifanynewlyreceivedagentadvertisementmessagesareonthesamenetworkasthenode'scurrentcare-ofaddressCo-LocatedAddresses Ifmobilenodemovestoanetworkthathasnoforeignagents,orallforeignagentsarebusy,itcanactasitsownforeignagent Mobileagentusesco-locatedcare-ofaddress IPaddressobtainedbymobilenodeassociatedwithmobilenode'scurrentnetworkinterface Meanstoacquireco-locatedaddress: TemporaryIPaddressthroughanInternetservice,suchasDHCP Maybeownedbythemobilenodeasalong-termaddressforusewhilevisitingagivenforeignnetworkRegistrationProcess Mobilenodesendsregistrationrequesttoforeignagentrequestingforwardingservice Foreignagentrelaysrequesttohomeagent Homeagentacceptsordeniesrequestandsendsregistrationreplytoforeignagent ForeignagentrelaysreplytomobilenodeRegistrationOperationMessages Registrationrequestmessage Fields=type,S,B,D,M,V,G,lifetime,homeaddress,homeagent,care-of-address,identification,extensionsRegistrationOperationMessages Registrationreplymessage Fields=type,code,lifetime,homeaddress,homeagent,identification,extensionsRegistrationProcedure:Security MobileIPdesignedtoresistattacks Nodepretendingtobeaforeignagentsendsregistrationrequesttoahomeagenttodivertmobilenodetraffictoitself Agentreplaysoldregistrationmessagestocutmobilenodefromnetwork Formessageauthentication,registrationrequestandreplycontainauthenticationextension Fields=type,length,securityparameterindex(SPI),authenticatorMobileIPAuthenticationExtensionTypesofAuthenticationExtensions Mobile-home:providesforauthenticationofregistrationmessagesbetweenmobilenodeandhomeagent;mustbepresent Mobile-foreign:maybepresentwhenasecurityassociationexistsbetweenmobilenodeandforeignagent Foreign-home:maybepresentwhenasecurityassociationexistsbetweenforeignagentandhomeagentTunneling HomeagentinterceptsIPdatagramssenttomobilenode'shomeaddress Homeagentinformsothernodesonhomenetworkthatdatagramstomobilenodeshouldbedeliveredtohomeagent Datagramsforwardedtocare-ofaddressviatunneling DatagramencapsulatedinouterIPdatagramTunneling:AnExampleMobileIPEncapsulationOptions IP-within-IP:entireIPdatagrambecomespayloadinnewIPdatagram Original,innerIPheaderunchangedexceptTTLdecrementedby1 OuterheaderisafullIPheader Minimalencapsulation:newheaderisinsertedbetweenoriginalIPheaderandoriginalIPpayload OriginalIPheadermodifiedtoformnewouterIPheader Genericroutingencapsulation(GRE):developedpriortodevelopmentofMobileIPMobileIPEncapsulationOptionsMobileIPv6 TheenormousaddressspaceinIPv6allowsverysimpleaddressauto-configurationbymeansofStatelessAddressConfiguration(SAC).Becausethemobilenodecaneasilyobtainacollocatedcare-ofaddressbySAC,theforeignagentfunctionalityisnolongerneeded.Asaresult,theforeignagentiseliminatedfroMobileIPv6.ThisalsoimpliesthatallMobileIPv6care-ofaddre