Simulation of GPRS MS-BS Interface Using Ns-networ

SimulationofGPRSMS-BSInterfaceUsingns-NetworkSimulatorDualDegreePresentationbyRichaJain(96D07007)DepartmentofElectricalEngineering,IndianInstituteofTechnolgy,Mumbai,India.Outline•IntroductiontoGPRS•Aboutns-NetworkSimulator•ScopeoftheProject•Implementationdetails•Experiments•Concludingremarks..TheGeneralPacketRadioService•Packetswitchedradiotransmission•Suitedforburstyapplications(egInternet)•Dataratesupto170kbps•Re-usesGSMresources•Lowercallset-uptimes;cheaperGPRSArchitectureGPRSProtocolStackAboutns•Publicdomain•Eventdrivensimulator•Splitlanguage–OTclandC++•Nodesandlinks;routingalgorithms;queuingschemes•Protocols–TCP,UDP,IP•Trafficgenerators–CBR,Exponential,Pareto•Basicmobilitysupport.Asimplensscriptsetns[newSimulator]#Creatingtwonodessetn0[$nsnode];setn1[$nsnode]#Creatingalinkbtwnthenodes;propdelay=10ms;Droptail.$nsduplex-link$n0$n11Mb10msDropTail#Nodesthemselvesdon'tsend/rxdata.Createanagenttodososetcbr0[newAgent/CBR]$nsattach-agent$n0$cbr0#createsinksetnull0[newAgent/Null]$nsattach-agent$n1$null0#connectthetwoagents$nsconnect$cbr0$null0#Tellcbr0whentostartandstop$nsat0.5$cbr0start$nsat4.5$cbr0stop“$nsrunWirelessFeatures•Mobilenode(ad-hocnode)•Airinterface•Radiopropagationmodel•Adhocroutingprotocols•MobileIPStructureofawirelessnodeinnsSamplescriptforawirelesssimulation#Setuphierarchicalrouting.#Specifytopology.#Create‘God’#CreateaBaseStation$ns_node-config-adhocRoutingDSR-llTypeLL-macType802.11-ifqTypeDropTail-ifqLen100-antTypeOmniAntenna-propTypeTwoRayGround-phyTypeWirelessPhy-topoInstance$topo-wiredRoutingON-agentTraceON-routerTraceON-macTraceON-movementTraceOFF-channel$chan_SamplescriptforawirelesssimulationsetBS(0)[$ns_node1.0.0]$BS(0)random-motion0$BS(0)setX_1.0$BS(0)setY_2.0#createmobilenodesinthesamedomainasBS(0)$ns_node-config-wiredRoutingOFFsetnode_(0)[$ns_node1.0.1]$node_(0)base-station[AddrParamsaddr2id[$BS(0)node-addr]]#createandattachAgents–TCP/UDP/CBR::#includemovement..$ns_at10.0“$node(0)setdest200.0150.015.0:::ScopeoftheprojectWesimulatethenetworkstackfortheMS-BSinteractionandfocusonthehandlingofradioresources.GPRSAirinterface•TDMA•Uplink-downlinkskewof3slots•Physicalchannel=aslotonafrequency.•Logicalchannels–Broadcast/Control/Data.•Multiplexinglogicalchannelsontophysicalchannels•TransmissionburstsAradioblock(RLCPDU)01234567012345670123200bytesTDMAframesTransmissionovertheairinterface(inGPRS)FeaturesofourGPRSsimulator•TheSet-up•Asinglecell•ThewirelessnodenowhasLL,RLC,MACforGPRS.•Supportstrafficineitherdirection:MStoBSorBStoMS•BScantransmit/receiveonmultiplefrequenciesGPRSsimAirInterface/Channels•Separateuplink/downlinkfrequencies.•TDMAstructurewith8slotsperframe.•Uplink-downlinkskewof3slots.•Userdefinedoptions:-numberoffrequencies-numberofGPRSslotsperframe•Signalingchannel–slot0,onuplink/downlinkfrequency0.GPRSsimTransmissionandreceptionovertheair-interface•RLCPDUsizesetto50bytes=50bytestransmittedperslot.•Propagationdelaysetto0.•Timersmodeltransmissionandreception.•A‘radio’:switchedONduringtransmission/reception,OFFotherwise.GPRSsimSignalingforCallSet-UpandHandling•ResourceRequestMessage•fromMStoBS•ontheRandomAccesschannel(slot0,freq0)•lockIFQ•waitonlyoneTDMAframeforreply•ResourceReplyMessage•fromBStoMSonallottedchannel•updatevlr_tables•waittillMSreceivesreplybeforetransmittingGPRSsimSignaling….•ResourceReleaseMessage•fromMStoBS•onthededicatedslot•clearentries•laterrequestswillbetreatedonparwithfreshrequestsGPRSsimResourceHandling•SlotAllocation•firstfreeslotisalloted.•allocationsymmetriconuplinkanddownlink.•SlotRelease•MSinitiatesmessageonexpiryofslot_release_timer.•BSdeletesvlr_entriesonreceiptofmessage.•timervaluebasedonexperiments.GPRSsimDealingwithExceptions•Collisions•happenonlyontheRandomAccesschannel.•BSdropsallcollidingrequests.•eachMSwaitsoneTDMAframe,thenbacksoffforarandominterval.•Slotlevelerrors•errormodelintroduced.•usersmayinclude/not;userdefinedrate.•MultipleARPrequests•secondaryrequestsdropped.GPRSsimExperiments•Studyingtheaveragepacketdelay•Scenario•Observations•InferencesGPRSsimAveragepacketdelayforvariousdataratesGPRSsimAveragepacketdelayforvariousdataratesGPRSsimAveragepacketdelayvsdatagenerationratesGPRSsimSimulations…•Resourcereleasetimer•Scenario•Observations•Inferences•InteractionofLL/RLCandTCP’sARQ•GPRSvsGSMcapacityanalysisGPRSsimSummarizing….•AsimulatorfortheGPRSMS-BSinterfacewasdeveloped.•Featuresofthesimulatorweretested.•Experimentsontheaveragepacketdelay,slotreleasetimeretcwereperformed.