ch_6_wireless_mobile_network

6:WirelessandMobileNetworks6-1Chapter6WirelessandMobileNetworksComputerNetworking:ATopDownApproachFeaturingtheInternet,3rdedition.JimKurose,KeithRossAddison-Wesley,July2004.Anoteontheuseofthesepptslides:We’remakingtheseslidesfreelyavailabletoall(faculty,students,readers).They’reinPowerPointformsoyoucanadd,modify,anddeleteslides(includingthisone)andslidecontenttosuityourneeds.Theyobviouslyrepresentalotofworkonourpart.Inreturnforuse,weonlyaskthefollowing:Ifyouusetheseslides(e.g.,inaclass)insubstantiallyunalteredform,thatyoumentiontheirsource(afterall,we’dlikepeopletouseourbook!)Ifyoupostanyslidesinsubstantiallyunalteredformonawwwsite,thatyounotethattheyareadaptedfrom(orperhapsidenticalto)ourslides,andnoteourcopyrightofthismaterial.Thanksandenjoy!JFK/KWRAllmaterialcopyright1996-2006J.FKuroseandK.W.Ross,AllRightsReserved6:WirelessandMobileNetworks6-2Chapter6:WirelessandMobileNetworksBackground:#wireless(mobile)phonesubscribersnowexceeds#wiredphonesubscribers!computernets:laptops,palmtops,PDAs,Internet-enabledphonepromiseanytimeuntetheredInternetaccesstwoimportant(butdifferent)challengescommunicationoverwirelesslinkhandlingmobileuserwhochangespointofattachmenttonetwork6:WirelessandMobileNetworks6-3Chapter6outline6.1IntroductionWireless6.2Wirelesslinks,characteristicsCDMA6.3IEEE802.11wirelessLANs(“wi-fi”)6.4CellularInternetAccessarchitecturestandards(e.g.,GSM)Mobility6.5Principles:addressingandroutingtomobileusers6.6MobileIP6.7Handlingmobilityincellularnetworks6.8Mobilityandhigher-layerprotocols6.9Summary6:WirelessandMobileNetworks6-4Elementsofawirelessnetworknetworkinfrastructurewirelesshostslaptop,PDA,IPphonerunapplicationsmaybestationary(non-mobile)ormobilewirelessdoesnotalwaysmeanmobility6:WirelessandMobileNetworks6-5Elementsofawirelessnetworknetworkinfrastructurebasestationtypicallyconnectedtowirednetworkrelay-responsibleforsendingpacketsbetweenwirednetworkandwirelesshost(s)inits“area”e.g.,celltowers802.11accesspoints6:WirelessandMobileNetworks6-6Elementsofawirelessnetworknetworkinfrastructurewirelesslinktypicallyusedtoconnectmobile(s)tobasestationalsousedasbackbonelinkmultipleaccessprotocolcoordinateslinkaccessvariousdatarates,transmissiondistance6:WirelessandMobileNetworks6-7Characteristicsofselectedwirelesslinkstandards384Kbps56Kbps54Mbps5-11Mbps1Mbps802.15802.11b802.11{a,g}IS-95CDMA,GSMUMTS/WCDMA,CDMA2000.11p-to-plink2G3GIndoor10–30mOutdoor50–200mMidrangeoutdoor200m–4KmLongrangeoutdoor5Km–20Km6:WirelessandMobileNetworks6-8Elementsofawirelessnetworknetworkinfrastructureinfrastructuremodebasestationconnectsmobilesintowirednetworkhandoff:mobilechangesbasestationprovidingconnectionintowirednetwork6:WirelessandMobileNetworks6-9ElementsofawirelessnetworkAdhocmodenobasestationsnodescanonlytransmittoothernodeswithinlinkcoveragenodesorganizethemselvesintoanetwork:routeamongthemselves6:WirelessandMobileNetworks6-10WirelessLinkCharacteristicsDifferencesfromwiredlink….decreasedsignalstrength:radiosignalattenuatesasitpropagatesthroughmatter(pathloss)interferencefromothersources:standardizedwirelessnetworkfrequencies(e.g.,2.4GHz)sharedbyotherdevices(e.g.,phone);devices(motors)interfereaswellmultipathpropagation:radiosignalreflectsoffobjectsandtheground,arrivingaddestinationatslightlydifferenttimes….makecommunicationacross(evenapointtopoint)wirelesslinkmuchmore“difficult”6:WirelessandMobileNetworks6-11WirelessnetworkcharacteristicsMultiplewirelesssendersandreceiverscreateadditionalproblems(beyondmultipleaccess):ABCHiddenterminalproblemB,AheareachotherB,CheareachotherA,CcannotheareachothermeansA,CunawareoftheirinterferenceatBABCA’ssignalstrengthspaceC’ssignalstrengthSignalfading:B,AheareachotherB,CheareachotherA,CcannotheareachotherinterferingatB6:WirelessandMobileNetworks6-12CodeDivisionMultipleAccess(CDMA)usedinseveralwirelessbroadcastchannels(cellular,satellite,etc)standardsunique“code”assignedtoeachuser;i.e.,codesetpartitioningalluserssharesamefrequency,buteachuserhasown“chipping”sequence(i.e.,code)toencodedataencodedsignal=(originaldata)X(chippingsequence)decoding:inner-productofencodedsignalandchippingsequenceallowsmultipleusersto“coexist”andtransmitsimultaneouslywithminimalinterference(ifcodesare“orthogonal”)6:WirelessandMobileNetworks6-13CDMAEncode/Decodeslot1slot0d1=-111111-1-1-1-Zi,m=di.cmd0=111111-1-1-1-11111-1-1-1-11111-1-1-1-slot0channeloutputslot1channeloutputchanneloutputZi,msendercodedatabitsslot1slot0d1=-1d0=111111-1-1-1-11111-1-1-1-11111-1-1-1-11111-1-1-1-slot0channeloutputslot1channeloutputreceivercodereceivedinputDi=SZi,m.cmm=1MM6:WirelessandMobileNetworks6-14CDMA:two-senderinterference6:WirelessandMobileNetworks6-15Chapter6outline6.1IntroductionWireless6.2Wirelesslinks,characteristicsCDMA6.3IEEE802.11wirelessLANs(“wi-fi”)6.4CellularInternetAccessarchitecturestandards(e.g.,GSM)Mobility6.5Principles:addressingandroutingtomobileusers6.6MobileIP6.7Handlingmobilityincellularnetworks6.8Mobilityandhigher-layerprotocols6.9Summary6:WirelessandMobileNe