简介:Forworkflow-basedservicecompositionapproach,therelationsbetweentheWebserviceQoSandenvironmentsareusuallynotconsidered,sothattheinformationaboutQoSforcompositeserviceselectionisinaccurate.Itmakestheselectedcompositeserviceinefficient,orevenunexecutable.Toaddressthisproblem,anovelservicecompositionapproachbasedonproductionQoSrulesisproposedinthispaper.Generally,itisverydifficulttodirectlyanalyzehowdifferentkindsofenvironmentfactorsinfluencetheWebserviceQoS.Weadopt'black-box'analysismethodofoptimizingcompositeservices,discoveringtheknowledgesuchas'theQoSofoneWebservicewillbehigherinspecificenvironments'.Inourapproach,theexecutioninformationofthecompositeserviceisrecordedintoalogfirst,whichwillbetakenasthebasisofthesubsequentstatisticalanalysisanddatamining.Then,thetimelyQoSvaluesoftheWebservicesareestimatedandtheproductionQoSrulesbeingusedtoqualitativelyexpressthedifferentperformancesoftheWebserviceQoSindifferentenvironmentsaremined.Atlast,weemploytheminedQoSknowledgeoftheWebservicestooptimizethecompositeserviceselection.Extensiveexperimentalresultsshowthatourapproachcanimprovetheperformanceofselectedcompositeservicesonthepremiseofassuringtheselectingcomputationcost.
简介:Inthispaper,basedonant-algorithm,weproposeaQoSmulticastroutingschemeinInternet.Wefirstdescribeant-algorithmmodelandgiveant-networkmodel,thenpresentanapproachusingant-algorithmtooptimizethemulticastrouteswithQoSconstaints.Finally,simulationshasbeenmadetoshowtheefficiencyoftheapproachintheenvironmentofOPNETsimulationsoftware,andthesimulationresultsshowthattheproposedapproachcanfindthebestoptimalmulticastrouteswhichcansatisfythedelay-boundedrequirementandavoidcongestednodesassoonaspossible.
简介:Athresholdsettingschemeisproposedbasedontheresourcemanagementandlimitedfeedbacktheoryinmultiuserorthogonalfrequencydivisionmultiplexing(OFDM)systems.Inadaptiveresourceallocation,thefactorsdenotingthequalityofservice(QoS)andfairnessarebothconsideredastheuserweight.Fromtheaspectoffeedbackoutageprobability,theproposedalgorithmsetsthethresholdforeachuserrelatedtoitsweight,whichbringsenoughfeedbacktotheuserwithgreaterweight.Analysisandsimulationresultsshowthat,comparedwiththethresholdignoringweights,theproposedschemehasmuchlowerfeedbackloadwhilewithbetterQoS.
简介:ThemaingoalofroutingsolutionsistosatisfytherequirementsoftheQualityofService(QoS)foreveryadmittedconnectionaswellastoachieveaglobalefficiencyinresourceutilization.InthispaperproposesasolutionbasedonHopfieldneuralnetwork(HNN)todealwithoneofrepresentativeroutingproblemsinuni-castrouting,i.e.themulti-constrained(MC)routingproblem.ComputersimulationshowsthatwecanobtaintheoptimalpathveryrapidlywithournewLyapunovenergyfunctions.
简介:介绍服务质量(QoS)的基本概念和Dynamips思科网络模拟软件,利用Dynamips模拟软件分别模拟仿真QoS常采用的PQ、CQ、CBWFQ、LLQ四种方式。分别从理论和实践两方面结合教学,可使学生对QoS获得深刻的理解。