CellularSystems Concept ¡ GSM ¢ IS-95 AdaptedfromJ.Schiller,“MobileCommunications”,Chapter4 WirelessNetworks:CellularSystems 1 CellularConcept Severalsmallcellsinsteadofasingletransmitter=>frequencyreuse:betterefficiency FixedChannelAllocation: ClusterofsizeN =i2+ij+j2;andD =sqrt(3N)R R cellradiusand D distanceatwhichafrequencycanbereusedwithacceptableinterference WirelessNetworks:CellularSystems 2 Examples WirelessNetworks:CellularSystems 3 CapacityinCellularSystems BlockingProbability(GradeOfService):ErlangB formula λ C = ( T ) / C! GOS £ C (λT )n / n! n=0 λ: callsarrivalrate;T:callsaverageduration(servicetime:1/µ) WirelessNetworks:CellularSystems 4 IncreasingCapacity Cellssplitting Sectoring:3sectoring(1200)or6sectoring WirelessNetworks:CellularSystems 5 GSM:Overview GSM¤ formerly:GroupeSpéciale Mobile(founded1982) ¥ now:GlobalSystemforMobileCommunication ¦ todaymanyprovidersallovertheworlduseGSM(morethan130 countriesinAmerica,Asia,Africa,Europe,Australia) § 500millionsubscribers WirelessNetworks:CellularSystems 6 PerformancecharacteristicsofGSM Communication¨ mobile,wirelesscommunication;supportforvoiceanddata services Totalmobility© internationalaccess,chip-cardenablesuseofaccesspointsof differentproviders Worldwideconnectivity onenumber,thenetworkhandleslocalization Highcapacity betterfrequencyefficiency,smallercells,morecustomerspercell Hightransmissionquality highaudioqualityandreliabilityforwireless,uninterruptedphone callsathigherspeeds(e.g.,fromcars,trains) Securityfunctions accesscontrol,authenticationviachip-cardandPIN WirelessNetworks:CellularSystems 7 DisadvantagesofGSM Thereisnoperfectsystem!! noend-to-endencryptionofuserdata nofullISDNbandwidthof64kbit/stotheuser electromagneticradiation abuseofprivatedatapossible roamingprofilesaccessible highcomplexityofthesystem(over5000pages) WirelessNetworks:CellularSystems 8 GSM:MobileServices GSMoffers severaltypesofconnections voiceconnections,dataconnections,shortmessageservice multi-serviceoptions(combinationofbasicservices) Threeservicedomains BearerServices Telematic Services SupplementaryServices bearerservices MS transit source/ TE MT GSM-PLMN network destination TE (PSTN,ISDN) network R,S Um (U,S,R) teleservices WirelessNetworks:CellularSystems 9 BearerServices Telecommunicationservicestotransferdatabetweenaccess points Specificationofservicesuptotheterminalinterface(OSIlayers 1-3) Differentdataratesforvoiceanddata(originalstandard) dataservice(circuitswitched) synchronous:2.4,4.8or9.6kbit/s asynchronous:300- 1200bit/s dataservice(packetswitched)! synchronous:2.4,4.8or9.6kbit/s " asynchronous:300- 9600bit/s WirelessNetworks:CellularSystems 10 TeleServicesI # Telecommunicationservicesthatenablevoicecommunication viamobilephones $ Allthesebasicserviceshavetoobeycellularfunctions,security measurementsetc. % Offeredservices& mobiletelephony primarygoalofGSMwastoenablemobiletelephonyofferingthe traditionalbandwidthof3.1kHz ' Emergencynumber commonnumber(911);mandatoryforallserviceproviders;freeof charge;connectionwiththehighestpriority(preemptionofother connectionspossible) ( Multinumbering severalISDNphonenumbersperuserpossible WirelessNetworks:CellularSystems 11 TeleServicesII Additionalservices) Non-Voice-Teleservices * group3fax + voicemailbox(implementedinthefixednetworksupportingthemobile terminals) , electronicmail(MHS,MessageHandlingSystem,implementedinthefixed network) - ... ShortMessageService(SMS) alphanumericdatatransmissionto/fromthemobileterminalusing the signalingchannel,thusallowingsimultaneoususeofbasicservicesand SMS WirelessNetworks:CellularSystems 12 Supplementaryservices / Servicesinadditiontothebasicservices,cannotbeoffered stand-alone 0 SimilartoISDNservicesbesideslowerbandwidthduetothe radiolink 1 Maydifferbetweendifferentserviceproviders,countriesand protocolversions 2 Importantservices3 identification:forwardingofcallernumber 4 suppressionofnumberforwarding 5 automaticcall-back 6 conferencingwithupto7participants 7 lockingofthemobileterminal(incomingoroutgoingcalls) 8 ... WirelessNetworks:CellularSystems 13 ArchitectureoftheGSMsystem GSMisaPLMN(PublicLandMobileNetwork)9 severalproviderssetupmobilenetworksfollowingtheGSM standardwithineachcountry : components; MS(mobilestation) < BS(basestation) = MSC(mobileswitchingcenter) > LR(locationregister) ? subsystems@ RSS(radiosubsystem):coversallradioaspects A NSS(networkandswitchingsubsystem):callforwarding,handover, switching B OSS(operationsubsystem):managementofthenetwork WirelessNetworks:CellularSystems 14 GSM:overview OMC,EIR, AUC HLR GMSC NSS fixednetwork with OSS VLR MSC MSC VLR BSC BSC RSS WirelessNetworks:CellularSystems 15 GSM:elementsandinterfaces radiocell BSS MS MS Um radiocell RSS BTS MS BTS Abis BSC BSC A MSC MSC NSS VLR VLR signaling ISDN,PSTN HLR GMSC PDN IWF O OSS EIR AUC OMC WirelessNetworks:CellularSystems 16 GSM:systemarchitecture radio networkand fixed subsystem switchingsubsystem partnernetworks MS MS ISDN PSTN MSC Um A BTS bis BSC BTS EIR SS7 HLR BTS VLR BSC ISDN BTS MSC A PSTN BSS IWF PSPDN CSPDN WirelessNetworks:CellularSystems 17 Systemarchitecture:radiosubsystem radio networkandswitching subsystem subsystem MS MS ComponentsC MS (MobileStation) D Um BSS (BaseStationSubsystem): consistingofE BTS Abis BSC MSC BTS (BaseTransceiverStation): BTS senderandreceiver F BSC (BaseStationController): controllingseveraltransceivers InterfacesG Um :radiointerface A H BTS Abis :standardized,openinterfacewith BSC MSC 16kbit/suserchannels BTS I A:standardized,openinterfacewith BSS 64kbit/suserchannels WirelessNetworks:CellularSystems 18 Systemarchitecture:networkandswitchingsubsystem network fixedpartner subsystem networks ComponentsJ MSC (MobileServicesSwitchingCenter): ISDN K IWF (Interworking Functions) PSTN MSC L ISDN (IntegratedServicesDigitalNetwork) M PSTN (PublicSwitchedTelephoneNetwork) EIR N PSPDN (PacketSwitchedPublicDataNet.) O CSPDN (CircuitSwitchedPublicDataNet.) SS7 HLR DatabasesP HLR (HomeLocationRegister) VLR Q VLR (VisitorLocationRegister) ISDN R EIR (EquipmentIdentityRegister) MSC PSTN IWF PSPDN CSPDN WirelessNetworks:CellularSystems 19 Radiosubsystem TheRadioSubsystem(RSS)comprisesthecellularmobilenetwork uptotheswitchingcenters S ComponentsT BaseStationSubsystem(BSS):U BaseTransceiverStation(BTS):radiocomponentsincludingsender, receiver,antenna- ifdirectedantennasareusedoneBTScancover severalcells V BaseStationController(BSC):switchingbetweenBTSs,controlling BTSs,managingofnetworkresources,mappingofradiochannels(Um) ontoterrestrialchannels(Ainterface) W BSS=BSC+sum(BTS)+interconnection X MobileStations(MS) WirelessNetworks:CellularSystems 20 GSM:cellularnetwork segmentationoftheareaintocells possibleradiocoverageofthecell idealizedshapeofthecell cell Y useofseveralcarrierfrequencies Z notthesamefrequencyinadjoiningcells [ cellsizesvaryfromsome300feetupto20milesdependingonuser density,geography,transceiverpoweretc. \ hexagonalshapeofcellsisidealized(cellsoverlap,shapesdependon geography) ] ifamobileuserchangescells^ handoveroftheconnectiontotheneighborcell WirelessNetworks:CellularSystems 21 BaseTransceiverStationandBaseStationController TasksofaBSSaredistributedoverBSCandBTS_ BTScomprisesradiospecificfunctions ` BSCistheswitchingcenterforradiochannels Functions BTS BSC Managementofradiochannels X Frequencyhopping(FH) X X Managementofterrestrialchannels X Mappingofterrestrialontoradiochannels X Channelcodinganddecoding X Rateadaptation X Encryptionanddecryption X X Paging X X Uplinksignalmeasurements X Trafficmeasurement X Authentication X Locationregistry,locationupdate X Handovermanagement X WirelessNetworks:CellularSystems 22 Mobilestation TerminalfortheuseofGSMservicesa Amobilestation(MS)comprisesseveralfunctionalgroups¨ MT(MobileTerminal):b offerscommonfunctionsusedbyallservicestheMSoffers c correspondstothenetworktermination(NT)ofanISDNaccess d end-pointoftheradiointerface(Um) TA(TerminalAdapter):e terminaladaptation,hidesradiospecificcharacteristics f TE(TerminalEquipment):g peripheraldeviceoftheMS,offersservicestoauser h doesnotcontainGSMspecificfunctions i SIM(SubscriberIdentityModule):j personalizationofthemobileterminal,storesuserparameters TE TA MT U R S m WirelessNetworks:CellularSystems 23 Networkandswitchingsubsystem NSSisthemaincomponentofthepublicmobilenetworkGSMk switching,mobilitymanagement,interconnectiontoothernetworks, systemcontrol l Componentsm MobileServicesSwitchingCenter(MSC) controlsallconnectionsviaaseparatednetworkto/fromamobile terminalwithinthedomainoftheMSC- severalBSCcanbelongto aMSC n Databases(important:scalability,highcapacity,lowdelay)o HomeLocationRegister(HLR) centralmasterdatabasecontaininguserdata,permanentandsemi- permanentdataofallsubscribersassignedtotheHLR(oneprovider canhaveseveralHLRs) p VisitorLocationRegister(VLR) localdatabaseforasubsetofuserdata,includingdataaboutalluser currentlyinthedomainoftheVLR WirelessNetworks:CellularSystems 24 MobileServicesSwitchingCenter TheMSC(mobileswitchingcenter)playsacentralroleinGSM switchingfunctions q additionalfunctionsformobilitysupport r managementofnetworkresources s interworkingfunctionsviaGatewayMSC(GMSC) t integrationofseveraldatabases u FunctionsofaMSCv specificfunctionsforpagingandcallforwarding w terminationofSS7(signalingsystemno.7) x mobilityspecificsignaling y locationregistrationandforwardingoflocationinformation z provisionofnewservices(fax,datacalls) { supportofshortmessageservice(SMS) | generationandforwardingofaccountingandbillinginformation WirelessNetworks:CellularSystems 25 Operationsubsystem TheOSS(OperationSubsystem)enablescentralizedoperation,