东南大学研究生英语雅思写作下学期大作业-豆柴文库

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OntheDelayofGeographicalCachingMethods
inTwo-TieredHeterogeneousNetworks






Abstract
Weconsiderahierarchicalnetworkthatconsistsofmobileusers,atwo-tieredcellularnetwork(namelysmallcellsandmacrocells)andcentralrouters,eachofwhichfollowsaPoissonpointprocess(PPP).Inthisscenario,smallcellswithlimited-capacitybackhaulareabletocachecontentunderagivensetofrandomizedcachingpoliciesandstorageconstraints.Moreover,weconsiderthreedifferentcontentpopularitymodels,namelyfixedcontentpopularity,distance-dependentandload-dependent,inordertomodelthespatio-temporalbehaviorofusers’contentrequestpatterns.Wederiveexpressionsfortheaveragedelayofusersassumingperfectknowledgeofcontentpopularitydistributionsandrandomizedcachingpolicies.Althoughthetrendoftheaveragedelayforallthreecontentpopularitymodelsisessentiallyidentical,ourresultsshowthattheoverallperformanceofcached-enabledheterogeneousnetworkscanbesubstantiallyimproved,especiallyundertheloaddependentcontentpopularitymodel.
Besides,Becauseofthelimitationofresearchconditions,thetotalnetworkdelay,networkcostandoptimizationofnetworkparametersarenotanalyzed.
Keywords:edgecaching,Poissonpointprocess,stochasticgeometry,mobilewirelessnetworks,5G

Introduction
Itisknownthatcontentcachingin5Gheterogeneouswirelessnetworksimprovesthesystemperformance,andisofhighimportanceinlimited-backhaulscenarios.Mostexistingliteraturefocusesonthecharacterizationofkeyperformancemetricsneglectingthebackhaullimitationsandthespatio-temporalcontentpopularityprofiles.Inthiswork,weanalyzethegainsofcachinginheterogeneousnetworkdeployment,andconsidertheaveragedelayasaperformancemetric.
Firstlyweusepassionpointprocess(PPP)methodtobuildthemodel.Thisheterogeneousnetworkconsistsofmobileterminals(users),cache-enabledsmallbasestations(SBSs),macrobasestations(MBSs)andcentralrouters.Inthisnetworksetting,ausermayexperiencedelaysduetodownlinktransmissions,backhaulandcaches.
Moreover,inordertocapturethespatio-temporalcontentaccesspatternsofusers,wesupposefixedcontentpopularity,