基于泊松分布到达率的蜂窝网络阻塞业务的多变量概率综合(IJWMT-V8-N4-2)

I.J.WirelessandMicrowaveTechnologies,2018,4,14-39PublishedOnlineJuly2018inMECS()DOI:10.5815/ijwmt.2018.04.02Availableonlineat–Kenya.Received:23April2018;Accepted:25May2018;Published:08July2018AbstractCellularnetworksarecharacterizedbymobilityinwhichsubscribersmovefreelywithinthecoveragearea.Sincetheradiospectrumisascarceresource,theavailablebandwidthisdividedbyusingacombinationofTime-andFrequency-DivisionMultipleAccess(TDMA)CodeDivisionMultipleAccess(CDMA)andFrequencyDivisionMultipleAccess(FDMA).Forcommunicationprocesstosucceed,thesubscribermustbeallocatedsomefrequencyband(FDMA),atimeslot(TDMA)orpseudorandombinarysequencethatmodulatesthecarrier(CDMA).Withtheincreasingnumberofusers,theseresourcesmaybecomeunavailable,leadingtonewcallblockingorhandovercallblocking.ErlangBandErlangChavebeenusedinthepasttomodelteletrafficblockinginPublicSwitchedTelephoneNetwork(PSTN).Unfortunately,ErlangBisonlyidealwhensubscribersdonotperformcallre-attemptsaftertheirinitialcallsareblocked.Ontheotherhand,ErlangCmodelisapplicableonlyinnetworkswherequeuingisappliedandcaneasilyleadtohigherblockingrateswhenthenumberofusersishigh.Thisisbecauseittakesintoconsiderationthenumberofinstancesinthequeueaswellastheresourcesunderuse.Inthispaper,teletrafficblockingprobabilitiesthattakeintoaccountadditionalcellularnetworkconceptssuchasthenumberofmobilestations,callretries,channelsreservation,overlaysandunderlays,uservelocity,relativemobility,callpriority,callarrivalratesandsignaltointerferenceplusnoiseratio(SINR)weresynthesized.ThesimulationresultsshowedthatthedevelopedteletrafficblockingprobabilitiesweresuperiortotheconventionalErlangBandErlangCastheyconsidernewconceptsthatexistincellularnetworksthatwerenotenvisionedintraditionalPSTN.IndexTerms:Blockingprobability,gradeofservice,qualityofservice,teletraffic.©2018PublishedbyMECSPublisher.Selectionand/orpeerreviewunderresponsibilityoftheResearchAssociationofModernEducationandComputerScience*Correspondingauthor.E-mailaddress:MultivariateProbabilisticSynthesisofCellularNetworksTeletraffic15BlockingwithPoissonianDistributionArrivalRates1.IntroductionInGSM,anetworkconsistsofanumberofradiocellsinwhicheachcellisassignedabandoffrequenciesforsendingandreceivingdata.Atthecenterofeachcellisbasetransceiverstation(BTS)whichismadeupofatransmitter,receiverandcontrolunit.Toavoidinterference,neighboringcellsareallocateddifferentfrequencies[1].Unfortunately,asthenumberofsubscriberswithinabasestationincrease,thetraffictheygeneratesoarsuptoapointwheretherearenofreetimeslotsorfrequencychannelstobeassignedtonewcalls.Thisleadstoblockingofeithernewcallsorhandedovercalls.Accordingto[2],tooffergoodQualityofservice(QoS),GSMnetworkoperatorsstrivetoeffectivelyutilizetheiravailableresourcesandthesecallsforeffectualnetworkdesignandnetworkplanning.Callblockingprobability,whichdefinestheprospectofnetworkservicesbeingdeprivedoftosubscriberduetothenon-availabilityofradioresources,istheprincipalfactoremployedforefficientnetworkdesignandnetworkplanning.Handedovercallsaremoresensitivetoblockingthannewcallssinceblockingcausesforcedterminationofalreadyestablishedcallswhichbecomesannoying.Whenasubscribermakesarequestforahandover,thenetworkmustassignresourcestobeusedinroutingthecalltonextbasetransceiverstation.Insituationswherethehandoverfailstooccurattherighttime,theQoSdropsbelowthesetthresholdlevelandthesubscribercallisterminatedandthisconstitutehandoffcallblocking.Otherparametersinvolvedinthehandoverdecisionincludecellblockingprobability,callcompletionprobability,probabilityofunsuccessfulhandover,handoverblockingprobability,rateofhandover,interruptiondurationandhandoverdelay.Intheirstudy,[3]explainthatapartfromunavailabilityoftimeorfrequencychannel,lowlevelofsystemconfigurationandhightrafficratescanalsoleadtocallblocking.OneofthesalientfeaturesofGSMismovementofcustomerswithinthecoveragearea.Thesemobilitypatternsusuallyvarycontinuouslyduetofactorssuchasrushhours,duringwhichhotspotsconsistingofabiggerthanaveragenumberofuserstravelalongahighway.Consequently,thisbiggernumberofsubscribersbringsforthalargerfreshcallarrivalrate.Theseusersmakingcallswhileintransitthroughthecellularnetworkprovokehandoversthatoccurwhenacallisrelocatedfromthecoverageareaofacellintothecoverageareaofaneighboringcell.Itispossibleforsomesubscriberswhosehandoversareblockedtoattemptre-establishingtheirconnection.Regrettably,solongastherearenofreeresourcesinthetargetedcell,theseredialsareboundtobeblocked,furtheraddingtothecallblockingprobability.A.TeletrafficModelsTeletrafficmodelshaveanabilityofsimulatingreal-lifeconditionsandassuch,anumberofmodelshavebeencreatedsoastoapproximateblockingprobabilitiesthatassistnetworkengineersindimensioning.As[4]d