毕设外文原文及译文.docx

毕设外文原文及译文.docx

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毕设外文原文及译文

北京联合大学毕业设计（论文）任务书

题目：

OFDM调制解调技术的设计与仿真实现

专业：

通信工程指导教师：

张雪芬

学院：

信息学院学号：

2011080331132

班级：

1101B姓名：

徐嘉明

一、外文原文

EvolutionTowards5GMulti-tierCellularWirelessNetworks:

AnInterferenceManagementPerspective

EkramHossain,MehdiRasti,HinaTabassum,andAmrAbdelnasser

Abstract—Theevolvingfifthgeneration（5G）cellularwirelessnetworksareenvisionedtoovercomethefundamentalchallengesofexistingcellularnetworks,e.g.,higherdatarates,excellentend-to-endperformanceanduser-coverageinhot-spotsandcrowdedareaswithlowerlatency,energyconsumptionandcostperinformationtransfer.Toaddressthesechallenges,5Gsystemswilladoptamulti-tierarchitectureconsistingofmacrocells,differenttypesoflicensedsmallcells,relays,anddevice-to-device（D2D）networkstoserveuserswithdifferentquality-of-service（QoS）requirementsinaspectrumandenergy-efficientmanner.Startingwiththevisionsandrequirementsof5Gmulti-tiernetworks,thisarticleoutlinesthechallengesofinterferencemanagement（e.g.,powercontrol,cellassociation）inthesenetworkswithsharedspectrumaccess（i.e.,whenthedifferentnetworktierssharethesamelicensedspectrum）.Itisarguedthattheexistinginterferencemanagementschemeswillnotbeabletoaddresstheinterferencemanagementprobleminprioritized5Gmultitiernetworkswhereusersindifferenttiershavedifferentprioritiesforchannelaccess.Inthiscontext,asurveyandqualitativecomparisonoftheexistingcellassociationandpowercontrolschemesisprovidedtodemonstratetheirlimitationsforinterferencemanagementin5Gnetworks.Openchallengesarehighlightedandguidelinesareprovidedtomodifytheexistingschemesinordertoovercometheselimitationsandmakethemsuitablefortheemerging5Gsystems.

IndexTerms—5Gcellularwireless,multi-tiernetworks,interferencemanagement,cellassociation,powercontrol.

I.INTRODUCTION

Tosatisfytheever-increasingdemandformobilebroadbandcommunications,theIMT-Advanced（IMT-A）standardshavebeenratifiedbytheInternationalTelecommunicationsUnion（ITU）inNovember2010andthefourthgeneration（4G）

wirelesscommunicationsystemsarecurrentlybeingdeployedworldwide.ThestandardizationforLTERel-12,alsoknownasLTE-B,isalsoongoingandexpectedtobefinalizedin2014.Nonetheless,existingwirelesssystemswillnotbeabletodealwiththethousand-foldincreaseintotalmobilebroadbanddata[1]contributedbynewapplicationsandservicessuchaspervasive3Dmultimedia,HDTV,VoIP,gaming,e-Health,andCar2xcommunication.Inthiscontext,thefifthgeneration（5G）wirelesscommunicationtechnologiesareexpectedtoattain1000timeshighermobiledatavolumeperunitarea,

10-100timeshighernumberofconnectingdevicesanduserdatarate,10timeslongerbatterylifeand5timesreducedlatency[2].Whilefor4Gnetworksthesingle-useraverage

datarateisexpectedtobe1Gbps,itispostulatedthatcelldatarateoftheorderof10Gbpswillbeakeyattributeof5Gnetworks.

5Gwirelessnetworksareexpectedtobeamixtureofnetworktiersofdifferentsizes,transmitpowers,backhaulconnections,differentradioaccesstechnologies（RATs）that

areaccessedbyanunprecedentednumbersofsmartandheterogeneouswirelessdevices.Thisarchitecturalenhancementalongwiththeadvancedphysicalcommunicationstechnologysuchashigh-orderspatialmultiplexingmultiple-inputmultiple-output（MIMO）communicationswillprovidehigheraggregatecapacityformoresimultaneoususers,orhigherlevelspectralefficiency,whencomparedtothe4Gnetworks.Radioresourceandinterferencemanagementwillbeakeyresearchchallengeinmulti-tierandheterogeneous5Gcellularnetworks.Thetraditionalmethodsforradioresourceandinterferencemanagement（e.g.,channelallocation,powercontrol,cellassociationorloadbalancing）insingle-tiernetworks（evensomeofthosedevelopedfortwo-tiernetworks）maynotbeefficientinthisenvironmentandanewlookintotheinterferencemanagementproblemwillberequired.

First,thearticleoutlinesthevisionsandrequirementsof5Gcellularwirelesssystems.Majorresearchchallengesarethenhighlightedfromtheperspectiveofinterferencemanagementwhenthedifferentnetworktierssharethesameradiospectrum.Acomparativeanalysisoftheexistingapproachesfordistributedcellassociationandpowercontrol（CAPC）isthenprovidedfollowedbyadiscussionontheirlimitationsfor

5Gmulti-tiercellularnetworks.Finally,anumberofsuggestionsareprovidedtomodifytheexistingCAPCschemestoovercometheselimitations.

II.VISIONSANDREQUIREMENTSFOR5GMULTI-TIER

CELLULARNETWORKS

5Gmobileandwirelesscommunicationsystemswillrequireamixofnewsystemconceptstoboostthespectralandenergyefficiency.Thevisionsandrequirementsfor5Gwirelesssystemsareoutlinedbelow.

·Datarateandlatency:

Fordenseurbanareas,5Gnetworksareenvisionedtoenableanexperienceddatarateof300Mbpsand60Mbpsindownlinkanduplink,respectively,in95%oflocationsandtime[2].Theend-to-endlatenciesareexpectedtobeintheorderof2to5milliseconds.Thedetailedrequirementsfordifferentscenariosarelistedin[2].

·Machine-typeCommunication（MTC）devices:

Thenumberoftraditionalhuman-centricwirelessdeviceswithInternetconnectivity（e.g.,smartphones,super-phones,tablets）maybeoutnumberedbyMTCdeviceswhichcanbeusedinvehicles,homeappliances,surveillancedevices,andsensors.

·Millimeter-wavecommunication:

Tosatisfytheexponentialincreaseintrafficandtheadditionofdifferentdevicesandservices,additionalspectrumbeyondwhatwaspreviouslyallocatedto4Gstandardissoughtfor.Theuseofmillimeter-wavefrequencybands（e.g.,28GHzand38GHzbands）isapotentialcandidatetoovercometheproblemofscarcespectrumresourcessinceitallowstransmissionatwiderbandwidthsthanconventional20MHzchannelsfor4Gsystems.

·MultipleRATs:

5Gisnotaboutreplacingtheexistingtechnologies,butitisaboutenhancingandsupportingthemwithnewtechnologies[1].In5Gsystems,theexistingRATs,includingGSM（GlobalSystemforMobileCommunications）,HSPA+（EvolvedHigh-SpeedPacketAccess）,andLTE,willcontinuetoevolvetoprovideasuperiorsystemperformance.Theywillalsobeaccompaniedbysomenewtechnologies（e.g.,beyond

LTE-Advanced）.

·Basestation（BS）densification:

BSdensificationisaneffectivemethodologytomeettherequirementsof5Gwirelessnetworks.Specifically,in5Gnetworks,therewillbedeploymentsofalargenumberoflowpowernodes,relays,anddevice-to-device（D2D）communicationlinkswithmuchhigherdensitythantoday’smacrocellnetworks.

Fig.1showssuchamulti-tiernetworkwithamacrocelloverlaidbyrelays,picocells,femtocells,andD2Dlinks.Theadoptionofmultipletiersinthecellularnetworkarchitecturewillresultinbetterperformanceintermsofcapacity,coverage,spectralefficiency,andtotalpowerconsumption,providedthattheinter-tierandintratier

interferencesarewellmanaged.

·Prioritizedspectrumaccess:

Thenotionsofbothtrafficbasedandtier-basedPrioriti

-eswillexistin5Gnetworks.Traffic-basedpriorityarisesfromthedifferentrequirementsoftheusers（e.g.,reliabilityandlatencyrequirements,energyconstraints）,whereasthetier-basedpriorityisforusersbelongingtodifferentnetworktiers.Forexample,withsharedspectrumaccessamongmacrocellsandfemtocellsinatwo-tiernetwork,femtocellscreate“deadzones”aroundtheminthedownlinkformacrousers.Protectionshould,thus,beguaranteedforthemacrousers.Consequently,themacroandfemtousersplaytheroleofhigh-priorityusers（HPUEs）andlowpriorityusers（LPUEs）,respectively.Intheuplinkdirection,themacrocellusersatthecelledgetypicallytransmitwithhighpowerswhichgenerateshighuplinkinterferencetonearbyfemtocells.Therefore,inthiscase,theuserprioritiesshouldgetreversed.AnotherexampleisaD2Dtransmissionwheredifferentdevicesmayopportunisticallyaccessthespectrumtoestablishacommunicationlinkbetweenthemprovidedthattheinterferenceintroducedtothecellularusersremainsbelowagiventhreshold.Inthiscase,theD2DusersplaytheroleofLPUEswhereasthecellularusersplaytheroleofHPUEs.

·Network-assistedD2Dcommunication:

IntheLTERel-12andbeyond,focuswillbeonnetworkcontrolledD2Dcommunications,wherethemacrocellBSperformscontrolsignalingintermsofsynchronization,beaconsignalconfigurationandprovidingidentityandsecuritymanagement[3].Thisfeaturewillextendin5Gnetworkstoallowothernodes,ratherthanthemacrocellBS,tohavethecontrol.Forexample,consideraD2Dlinkatthe

celledgeandthedirectlinkbetweentheD2DtransmitterUEtothemacrocellisindeepfade,thentherelaynodecanberesponsibleforthecontrolsignalingoftheD2D

link（i.e.,relay-aidedD2Dcommunication）.

·Energyharvestingforenergy-efficientcommunication:

Oneofthemainchallengesin5Gwirelessnetworksistoimprovetheenergyefficiencyofthebattery-constrainedwirelessdevices.Toprolongthebatterylifetimeaswellastoimprovetheenergyefficiency,anappealingsolutionistoharvestenergyfromenvironmentalenergysources（e.g.,solarandwindenergy）.Also,energycanbeharvestedfromambientradiosignals（i.e.,RFenergyharvesting）withreasonableefficiencyoversmalldistances.ThehavestedenergycouldbeusedforD2Dcommunicationorcommunicationwithinasmallcell.Inthiscontext,simultaneouswirelessinformationandpowertransfer（SWIPT）isapromisingtechnologyfor5Gwirelessnetworks.However,practicalcircuitsforh