蜂窝系统切换技术中英文对照外文翻译文献

-PAGE54-中英文资料对照外文翻译 原文：HandoffinCellularSystemsCellularSystemDeploymentScenariosTheradiopropagationenvironmentandrelatedhandoffchallengesaredifferentindifferentcellularstructures.Ahandoffalgorithmwithfixedparameterscannotperformwellindifferentsystemenvironments.Specificcharacteristicsofthecommunicationsystemsshouldbetakenintoaccountwhiledesigninghandoffalgorithms.Severalbasiccellularstructures(e.g.,macrocells,microcells,andoverlaysystems)andspecialarchitectures(e.g.,underlays,multichannelbandwidthsystems,andevolutionaryarchitectures)aredescribednext.Integratedcordlessandcellularsystems,integratedcellularsystems,andintegratedterrestrialandsatellitesystemsarealsodescribed.MacrocellsMacrocellradiiareinseveralkilometers.Duetothelowcellcrossingrate,centralizedhandoffispossibledespitethelargenumberofMSstheMSChastomanage.Thesignalqualityintheuplinkanddownlinkisapproximatelythesame.ThetransitionregionbetweentheBSsislarge;handoffschemesshouldallowsomedelaytoavoidflip-flopping.However,thedelayshouldbeshortenoughtopreservethesignalqualitybecausetheinterferenceincreasesastheMSpenetratesthenewcell.Thiscellpenetrationiscalledcelldragging.Macrocellshaverelativelygentlepathlosscharacteristics.Theaveraginginterval(i.e.,thetimeperiodusedtoaveragethesignalstrengthvariations)shouldbelongenoughtogetridoffadingfluctuations.First-andsecond-generationcellularsystemsprovidewide-areacoverageevenincitiesusingmacrocells.Typically,aBStransceiverinamacrocelltransmitshighoutputpowerwiththeantennamountedseveralmetershighonatowertoilluminatealargearea.MicrocellsSomecapacityimprovementtechniques(e.g.,largerbandwidths,improvedmethodsforspeechcoding,channelcoding,andmodulation)willnotbesufficienttosatisfytherequiredservicedemand.Theuseofmicrocellsisconsideredthesinglemosteffectivemeansofincreasingthecapacityofcellularsystems.Microcellsincreasecapacity,butradioresourcemanagementbecomesmoredifficult.Microcellscanbeclassifiedasone-,two-,orthreedimensional,dependingonwhethertheyarealongaroadorahighway,coveringanareasuchasanumberofadjacentroads,orlocatedinmultilevelbuildings,respectively.Microcellscanbeclassifiedashotspots(serviceareaswithahighertrafficdensityorareasthatarecoveredpoorly),downtownclusteredmicrocells(contiguousareasservingpedestriansandmobiles),andin-building3-Dcells(servingofficebuildingsandpedestrians).Typically,aBStransceiverinamicrocelltransmitslowoutputpowerwiththeantennamountedatlamppostlevel(approximately5maboveground).TheMSalsotransmitslowpower,whichleadstolongerbatterylife.SinceBSantennashavelowerheightscomparedtothesurroundingbuildings,RFsignalspropagatemostlyalongthestreets.Theantennamaycover100–200mineachstreetdirection,servingafewcityblocks.Thispropagationenvironmenthaslowtimedispersion,whichallowshighdatarates.Microcellsaremoresensitivetothetrafficandinterferencethanmacrocellsduetoshort-termvariations(e.g.,trafficandinterferencevariations),medium/long-termalterations(e.g.,newbuildings),andincrementalgrowthoftheradionetwork(e.g.,newBSs).Thenumberofhandoffspercellisincreasedbyanorderofmagnitude,andthetimeavailabletomakeahandoffisdecreased.Usinganumbrellacellisonewaytoreducethehandoffrate.Duetotheincreaseinthemicrocellboundarycrossingsandexpectedhightrafficloads,ahigherdegreeofdecentralizationofthehandoffprocessbecomesnecessary.Microcellsencounterapropagationphenomenoncalledthecornereffect.Thecornereffectischaracterizedbyasuddenlargedrop(e.g.,20–30dB)insignalstrength(e.g.,at10–20mdistance)whenamobileturnsaroundacorner.Thecornereffectisduetothelossofthelineofsight(LOS)componentfromtheservingBStotheMS.Thecornereffectdemandsafasterhandoffandcanchangethesignalqualityveryfast.Thecornereffectishardtopredict.Alongmeasurementaveragingintervalisnotdesirableduetothecornereffect.MovingobstaclescantemporarilyhinderthepathbetweenaBSandanMS,whichresemblesthecornereffect.ReferencestudiesthepropertiesofsymmetricalcellplansinaManhattan-typeenvironment.Cellplansaffectsignal-to-interferenceratio(SIR)performanceintheuplinkanddownlinksignificantly.Symmetricalcellplanshavefournearestco-channelBSslocatedatthesamedistance.Suchcellplanscanbeclassifiedintohalf-square(HS),full-square(FS),andrectangular(R)cellplans.Thesecellplansaredescribednext.Half-SquareCellPlan—ThiscellplanplacesBSswithomnidirectionalantennasateachintersection,andeachBScovershalfablockinallfourdirections.Thiscellplanavoidsthestreetcornereffectandprovidesthehighestcapacity.ThiscellplanhasonlyLOShandoffs.Figure2showsanexampleofahalf-squarecellplaninamicrocellularsystem.Full-SquareCellPlan—ThereisaBSwithanomnidirectionalantennalocatedateveryotherintersection,andeachBScoversablockinallfourdirections.ItispossibleforanMStoexperiencethestreetcornereffectforthiscellplan.TheFScellplancanhaveLOSorNLOShandoffs.Figure3showsanexampleofafullsquarecellplaninamicrocellularsystem.RectangularCellPlan—EachBScoversafractionofeitherahorizontalorverticalstreetwiththeBSlocatedinthemiddleofthecell.Thiscellplancaneasilybeadaptedtomarketpenetration.FewerBSswithhightransmitpowercanbeusedinitially.Asuserdensityincreases,newBSscanbeaddedwithreducedtransmitpowerfromappropriateBSs.Thestreetcornereffectispossibleforthiscellplan.TheRcellplancanhaveLOSorNLOShandoffs.Figure4showsanexampleofarectangularcellplaninamicrocellularsystem.Macrocell/MicrocellOverlaysCongestionofcertainmicrocells,thelackofserviceofmicrocellsinsomeareas,andhighspeedofsomeusersaresomereasonsforhigherhandoffratesandsignalingloadformicrocells.Toalleviatesomeoftheseproblems,amixed-cellarchitecture(calledanoverlay/underlaysystem)consistingoflargesizemacrocells(calledumbrellacellsoroverlaycells)andsmall-sizemicrocells(calledunderlaycells)canbeused.Figure5illustratesanoverlaysystem.Themacrocell/microcelloverlayarchitectureprovidesabalancebetweenmaximizingthenumberofusersperunitareaandminimizingthenetworkcontrolloadassociatedwithhandoff.Macrocellsprovidewide-areacoveragebeyondmicrocellserviceareasandensurebetterintercellhandoff.Microcellsprovidecapacityduetogreaterfrequencyreuseandcoverareaswithhightrafficdensity(calledhotspots).Examplesofhotspotsincludeanairport,arailwaystation,oraparkinglot.Inlesscongestedareas(e.g.,areasbeyondacitycenteroroutsidethemainstreetsofacity)trafficdemandisnotveryhigh,andmacrocellscanprovideadequatecoverageinsuchareas.MacrocellsalsoservehighspeedMSsandtheareasnotcoveredbymicrocells(e.g.,duetolackofchannelsortheMSbeingoutofthemicrocellrange).Also,afterthemicrocellularsystemisusedtoitsfullestextent,theoverflowtrafficcanberoutedtomacrocells.Oneoftheimportantissuesfortheoverlay/underlaysystemisthedeterminationofoptimumdistributionofchannelsinthemacrocellsandmicrocells.Referenceevaluatesfourapproachestosharingtheavailablespectrumbetweenthetwotiers.Approach1usesTDMAformicrocellandCDMAformacrocell.Approach2usesCDMAformicrocellandTDMAformacrocell.Approach3usesTDMAinbothtiers,whileapproach4usesorthogonalfrequencychannelsinbothtiers.Theoverlay/underlaysystemhasseveraladvantagesoverapuremicrocellsystem:•TheBSsarerequiredonlyinhightrafficloadareas.Sinceitisnotnecessarytocoverthewholeserviceareawithmicrocells,infrastructurecostsaresaved.•Thenumberofhandoffsinanoverlaysystemismuchlessthaninamicrocellsystembecausefast-movingvehiclescanbeconnectedtotheoverlaymacrocell.•BothcallingfromanMSandlocationregistrationcaneasilybedonethroughthemicrocellsystem.Thereareseveralclassesofumbrellacells.Inoneclass,orthogonalchannelsaredistributedbetweenmicrocellsandmacrocells.Inanotherclass,microcellsusechannelsthataretemporarilyunusedbymacrocells.Inyetanotherclass,microcellsreusethechannelsalreadyassignedtomacrocellsanduseslightlyhighertransmitpowerlevelstocounteracttheinterferencefromthemacrocells.Withintheoverlay/underlaysystemenvironment,fourtypesofhandoversneedtobemanaged[19]:microcelltomicrocell,microcelltomacrocell,macrocelltomacrocell,andmacrocelltomicrocell.Referencedescribescombinedcellsplittingandoverlaying.Reuseofchannelsinthetwocellsisdonebyestablishinganoverlaidsmallcellservedbythesamecellsiteasthelargecell.Smallcellsreusethesplitcell’schannelsbecauseofthelargedistancebetweenthesplitcellandthesmallinnercell,whilethelargecellcannotreusethesechannels.Overlaidcellsareapproximately50percentmorespectrallyefficientthansegmenting(theprocessofdistributingthechannelsamongthesmall-andlargesizecellstoavoidinterference).Apracticalapproachforimplementationofamicrocellsystemoverlaidwithanexistingmacrocellsystemisproposedin.Thisreferenceintroduceschannelsegregation(aself-organizeddynamicchannelassignment)andautomatictransmitpowercontroltoobviatetheneedtodesignchannelassignmentandtransmitpowercontrolforthemicrocellsystem.Theavailablechannelsarereusedautomaticallybetweenmicrocellsandmacrocells.Aslightincreaseoftransmitpowerforthemicrocellsystemcompensatesforthemacrocell-to-microcellinterference.Simulationresultsindicatethatthelocaltrafficisaccommodatedbythemicrocellslaidundermacrocellswithoutanysignificantchannelmanagementeffort.ThemethodologyoftheGlobalSystemforMobileCommunications(GSM)-basedsystemisextendedtothemacrocell/microcelloverlaysystemin.Theuseofrandomfrequencyhoppingandadaptivefrequencyplanningisrecommended,anddifferentissuesrelatedtohandoffandfrequencyplanningforanoverlaysystemarediscussed.Fourstrategiesaredesignedtodetermineasuitablecellforauserforanoverlaysystem.Twostrategiesarebasedonthedwelltime(thetimeforwhichacallcanbemaintainedinacellwithouthandoff),andtheothertwostrategiesarebasedonuserspeedestimation.Aspeedestimationtechniquebasedondwelltimesisalsoproposed.ACDMAcellularsystemcanprovidefullconnectivitybetweenthemicrocellsandtheoverlayingmacrocellswithoutcapacitydegradation.Referenceanalyzesseveralfactorsthatdeterminethecellsize,thesofthandoff(SHO)zone,andthecapacityofthecellclusters.Severaltechniquesforoverlay-underlaycellclusteringarealsooutlined.ApplicationofCDMAtomicrocell/macrocelloverlayhavethefollowingmajoradvantages:•Aheterogeneousenvironmentcanbeilluminateduniformlybyusingadistributedantenna(withaseriesofradiatorswithdifferentpropagationdelays)whilestillmaintainingahigh-qualitysignal.•SHOobviatestheneedforcomplexfrequencyplanning.ReferencestudiesthefeasibilityofaCDMAoverlaythatcansharethe1850–1990MHzpersonalcommunicationsservices(PCS)bandwithexistingmicrowavesignals(transmittedbyutilitycompaniesandstateagencies).TheresultsofseveralfieldtestsdemonstratetheapplicationofsuchanoverlayforthePCSband.TheissueofuseofaCDMAmicrocellunderlayforanexistinganalogmacrocellisthefocusof.Itisshownthathighcapacitycanbeachievedinamicrocellattheexpenseofaslightdegradationinmacrocellperformance.ReferencefindsthattransmitandreceivenotchfiltersshouldbeusedatthemicrocellBSs.ItshowsthatkeyparametersforsuchanoverlayarethepowersoftheCDMABSandMStransmittersrelativetothemacrocellBSsandtheMSsservedbythemacrocells.Reference[25]studiesspectrummanagementinanoverlaysystem.Anewcellselectionmethodisproposed,whichusesthehistoryofmicrocellsojourntimes.Aproceduretodetermineanoptimumvelocitythresholdfortheproposedmethodisalsooutlined.Asystematicapproachtooptimalfrequencyspectrummanagementisdescribed.SpecialArchitecturesThereareseveralspecialcellulararchitecturesthattrytoimprovespectralefficiencywithoutalargeincreaseininfrastructurecosts.Someofthesestructures,discussedhere,includeanunderlay/overlaysystem(whichisdifferentfromtheoverlay/underlaysystemdescribedearlier)andamultichannelbandwidthsystem.Manycellularsystemsareexpectedtoevolvefromamacrocellularsystemtoanoverlay/underlaysystem.Astudythatfocusesonsuchevolutionisdescribedin[26].AMultiple-Channel-BandwidthSystem—Multiplechannelbandwidthscanbeusedwithinacelltoimprovespectralefficiency.Inamultiple-channel-bandwidthsystem(MCBS),acellhastwoorthreering-shapedregionswithdifferentbandwidthchannels[28].Figure7showsanMCBS.Assumethat30kHzisthenormalbandwidthforasignal.Now,forathree-ringMCBS,30kHzchannelscanbeusedintheoutermostring,15kHzchannelsinthemiddlering,and7.5kHzchannelsintheinnermostring.Theareasoftheseringscanbedeterminedbasedontheexpectedtrafficconditions.Thus,insteadofusing30kHzchannelsthroughoutthecell,differentbandwidthchannels(e.g.,15kHzand7.5kHz)canbeusedtoincreasethenumberofchannelsinacell.TheMCBSusesthefactthatawide-bandwidthchannelrequiresalowercarrier-to-interferenceratio(C/I)thananarrow-bandwidthchannelforthesamevoicequality.Forexample,C/Irequirementsfor30kHz,15kHz,and7.5kHzchannelbandwidthsare18dB,24dB,and30dB,respectively,basedonsubjectivevoicequalitytests[28].Ifthetransmitpoweratacellciteisthesameforallthebandwidths,awidechannelcanservealargecellwhileanarrowchannelcanservearelativelysmallcell.Moreover,sinceawidechannelcantolerateahigherlevelofco-channelinterference(CCI),itcanaffordasmallerD/Rratio(theratioofco-channeldistancetocellradius).Thus,intheMCBSmorechannelsbecomeavailableduetomultiple-bandwidthsignals,andfrequencycanbereusedmorecloselyinagivenserviceregionduetodifferentC/Irequirements.IntegratedWirelessSystemsIntegratedwirelesssystemsareexemplifiedbyintegratedcordlessandcellularsystems,integratedcellularsystems,andintegratedterrestrialandsatellitesystems.Suchintegratedsystemscombinethefeaturesofindividualwirelesssystemstoachievethegoalsofimprovedmobilityandlowcost.IntegratedTerrestrialSystems—Terrestrialintersystemhandoffmaybebetweentwocellularsystemsorbetweenacellularsystemandacordlesstelephonesystem.ExamplesofsystemsthatneedintersystemhandoffsincludeGSM–DigitalEuropeanCordlessTelephone(DECT),CDMAinmacrocells,andTDMAinmicrocells.WhenacallinitiatedinacellularsystemcontrolledbyanMSCentersasystemcontrolledbyanotherMSC,intersystemhandoffisrequiredtocontinuethecall[29].InthiscaseoneMSCmakesahandoffrequesttoanotherMSCtosavethecall.TheMSCsneedtohavesoftwareforintersystemhandoffifintersystemhandoffistobeimplemented.CompatibilitybetweentheconcernedMSCsneedstobeconsidered,too.Thereareseveralpossibleoutcomesofanintersystemhandoff[29]:•Along-distancecallbecomesalocalcallwhenanMSbecomesaroamer.•Along-distancecallbecomesalocalcallwhenaroamerbecomesahomemobileunit.•Alocalcallbecomesalongdistancecallwhenahomemobileunitbecomesaroamer.•Alocalcallbecomesalong-distancecallwhenaroamerbecomesahomemobileunit.ThereisagrowingtrendtowardserviceportabilityacrossdissimilarsystemssuchasGSMandDECT[30].Forexample,itisnicetohaveintersystemhandoffbetweencordlessandcellularcoverage.Cost-effectivehandoffalgorithmsforsuchscenariosrepresentasignificantresearcharea.Thisarticleoutlinesdifferentapproachestoachievingintersystemhandoff.SimulationresultsarepresentedforhandoffbetweenGSMandDECT/WideAccessCommunicationsSystem(WACS).ThepapershowsthataminoradjustmenttotheDECTspecificationcangreatlysimplifytheimplementationofanMScapableofintersystemhandoffbetweenGSMandDECT.IntegratedTerrestrialandSatelliteSystems—Inanintegratedcellular/satellitesystem,theadvantagesofsatellitesandcellularsystemscanbecombined.Satellitescanprovidewideareacoverage,completionofcoverage,immediateservice,andadditionalcapacity(byhandlingoverflowtraffic).Acellularsystemcanprovideahigh-capacityeconomicalsystem.Someoftheissuesinvolvedinanintegratedsystemarediscussedin[31].Inparticular,theproceduresofGSMareexaminedfortheirapplicationtotheintegratedsystems.Thefuturepubliclandmobiletelecommunicationsystem(FPLMTS)willprovideapersonaltelephonesystemthatenablesapersonwithahandheldterminaltoreachanywhereintheworld[32].TheFPLMTSwillincludelowEarthorbit(LEO)orgeostationaryEarthorbit(GEO)satellitesaswellasterrestrialcellularsystems.WhenanMSisinsidethecoverageareaofaterrestrialcellularsystem,theBSwillactasarelaystationandprovidealinkbetweentheMSandthesatellite.WhenanMSisoutsidetheterrestrialsystemcoveragearea,itwillhaveadirectcommunicationlinkwiththesatellite.Differentissuessuchassystemarchitecture,callhandling,performanceanalysisoftheaccess,andtransmissionprotocolsarediscussedin[32].Thetwohandoffscenariosinanintegratedsystemaredescribedbelow.HandofffromtheLandMobileSatelliteSystemtotheTerrestrialSystem—Whileoperating,theMSmonitorsthesatellitelinkandevaluatesthelinkperformance.Thereceivedsignalstrengths(RSSs)areaveraged(e.g.,overa30stimeperiod)tominimizesignalstrengthvariations.IftheRSSfallsbelowacertainthresholdNconsecutivetimes(e.g.,N=3),theMSbeginsmeasuringRSSfromtheterrestrialcellularsystem.Iftheterrestrialsignalsarestrongenough,handoffismadetotheterrestrialsystem,providedthattheterrestrialsystemcanservetheMS.HandofffromtheTerrestrialSystemtotheLandMobileSatelliteSystem—WhenanMSisgettingservicefromtheterrestrialsystem,theBSsendsanacknowledgerequest(calledpage)atpredefinedintervalstoensurethattheMSisstillinsidethecoveragearea.IfanacknowledgerequestsignalfromtheMS(calledpageresponse)isnotreceivedattheBSforNconsecutivetimes,itishandedofftothelandmobilesatellitesystem(LMSS).Reference[33]focusesonpersonalcommunicationsystemswithhierarchicaloverlaysthatincorporateterrestrialandsatellitesystems.Thelowestlevelinthehierarchyisformedbymicrocells.Macrocellsoverlaymicrocellsandformthemiddlelevelinthehierarchy.Satellitebeamsoverlaymacrocellsandconstitutethetopmosthierarchylevel.Twotypesofsubscribersareconsidered,satellite-onlyanddualcellular/satellite.Callattemptsfromsatellite-onlysubscribersareservedbysatellitesystems,whilecallattemptsfromdualsubscribersarefirstdirectedtotheservingterrestrialsystemswiththesatellitestakingcareoftheoverflowtraffic.Ananalyticalmodelforteletrafficperformanceisdeveloped,andperformancemeasuressuchastrafficdistribution,blockingprobability,andforcedterminationprobabilityareevaluatedforlow-speedandhigh-speedusers.HandoffEvaluationMechanismsThreebasicmechanismsusedtoevaluatetheperformanceofhandoffalgorithmsincludetheanalytical,simulation,andemulationapproaches.Thesemechanismsaredescribedhere.TheAnalyticalApproachThisapproachcanquicklygiveapreliminaryideaabouttheperformanceofsomehandoffalgorithmsforsimplifiedhandoffscenarios.Thisapproachisvalidonlyunderspecifiedconstraints(e.g.,assumptionsabouttheRSSprofiles).Actualhandoffproceduresarequitecomplicatedandarenotmemoryless.Thismakestheanalyticalapproachlessrealistic.Forreal-worldsituations,thisapproachiscomplexandmathematicallyintractable.Someoftheanalyticalapproachesappearingintheliteraturearebrieflytouchedonbelow.

译文：蜂窝系统切换技术蜂窝系统部署方案其无线电传播环境和相关切换的难度是在于针对不同的单元结构。在不同的系统环境中，固定参数切换算法不能发挥优势，。而通信系统的具体特点，应考虑而设计的切换算法是：几个基本的单元结构（如宏蜂窝，微单元，并覆盖系统）及（如：特殊结构，多通道带宽系统和演化架构）是描述将来。集成的无线和蜂窝系统，蜂窝系统集成，综合地面卫星系统也作了相关说明。宏单元宏的定义是达数公里半径。由于低单元传输率，集中式切换是可能的，尽管大量的各成员国已进行了海安管理。但是在上行和下行信号质量大约是相同的。考虑基地台之间的过渡区，大切换计划应允许一些延迟，以避免信号不稳定。然而，延误应足够短，以保持信号的质量，应对新的穿透移动台单元的干扰增加。这被称为的“单元拖动”。宏单元有相对平缓的路径损耗特性。在平均间隔（即使用一段时间的平均信号强度变化）应得到足够长的波动减少衰退。第一代和第二代蜂窝系统，即在城市大面积的报道。通常，在收发器宏单元传输与高输出功率的天线安装在塔高数米，覆盖大片区域。微单元某些技术的提高（例如，更大的带宽，编码，改进方法，语音信道编码和调制）将不足以满足需要的服务需求。无线资源管理目前变得更加困难，因此微单元增加容量的能力被认为是增加单元系统的一个最有效的手段。微单元可分为一，二，或了三维，取决于他们是否沿着道路或公路这些区域进行覆盖，如相邻道路，或在多层建筑物内分别编号。微单元可分为焦点（与通信密度较高或覆盖不足地区服务的地区），市中心聚集微单元（行人和手机间的相邻地区服务），并在建设3–D单元（在职办公大楼和行人）。通常，在一个微蜂窝系统收发天线传输与低输出功率在路灯水平（大约离地面5米）。安装的移动台转送保持低功耗，从而延长电池寿命。使天线具有比周围的建筑物更低的高度，射频信号的天线大多集中在街区.信号发射有可能包括在每个街道方向100-200米，服务几个街区。此传播环境具有较低的时间分散，这使得可以提高数据速率。微单元比宏单元通信更敏感。由于短期变化（如干扰，交通和干扰变化），中/长期变化（如新的建筑物），以及无线网络（例如，新的增量增长基地台）。每单元交接数目增加了一个数量级，以及可利用的时间作出交替下降。利用中转单元是其中一个不错方法，以减少切换率。由于微蜂窝接口要处理预期的高增长的通信负荷，让切换过程中的权限下放程度较高成为一个必要。微单元遇到阻塞现象称为拐角效应。拐角效应的特点是围绕一个角落移动时信号处理突然大幅下降（例如，在20-30分贝信号强度（例如）在10-20米的距离）时。由于从服务基站组件到移动台的视线丢失（LOS）。拐角效应需要一个更快的切换和可以快速提高的信号质量。角落里的效果是很难预测。测量平均间隔的不可取是由于拐角效应。运动障碍可以暂时阻碍之间的信号传递，这类似于一个角落效应.参考了在曼哈顿式的环境对称单元计划的研究。单元计划影响的信号来干扰比（SIR）的上行和下行的性能显着。对称单元计划同时距离基地台有四个最近的交流路径。这种单元计划可以分为半平方米（房协），全方（财经事务），和矩形（R）的单元计划。这些单元是描述未来的计划。半广场单元计划此单元格计划在每个路口基站全向天线的，并且每个微蜂窝占地50份在所有范围的四个方向。此单元格计划避免了街角的效果，并提供最高的容量。此计划是穿透单元交接。图2显示了一半的系统计划，其中在一平方单元微孔为例1。全区域单元计划有其他的十字路口位于每个天线与全方位微蜂窝，微蜂窝的每块覆盖在所有四个方向。这是可能的移动台体验这个单元街道拐角效应的计划。计划的全方位单元可以有一个例子，一个全方位的单元计划计划在微孔视角。从楼院或矩形单元的非视距切换。图3显示了每一个微蜂窝学位包括一小部分的水平或垂直的街道正中，及位于微蜂窝该单元格。此单元格图可以很容易地适应市场的需要。较少的基地台发射功率高，可用于初步。随着用户密度的增加，可以添加新的基地台与基地台发射功率降低适当。街道拐角效应是可能的这个单元的计划。计划的R单元可以有非视距或视线交接。图4显示矩形系统单元中的微孔计划的一个例子。宏/微小区覆盖微单元会拥塞缺乏某种服务的某些地区，而有些用户的切换率过高等一些原因会令微单元负载[13]。为了减轻这些问题，一些单元的混合单元结构（称为覆盖/衬底系统重叠）伞组成的大面积单元或宏单元（称为）和小尺寸微单元（称为衬底单元）都可以使用。图5显示了一覆盖系统。在宏蜂窝/微蜂窝覆盖架构中提供了一个切换最大化之间的平衡，每个单位面积的用户数量和减少社区间的网络控制与负荷相关的切换。超出微蜂窝覆盖面积宏单元提供广泛的服务领域，并确保做得更好[14]。微小区的提供能力利用和覆盖的地区，高密度的通信区（调用）有较大的频率点。例如机场，火车站或停车场。在不太拥挤的通信需求地区（如城市以外地区的主要街道中心或市外）不是很高，宏单元可以提供足够的覆盖面等方面的研究。宏单元也为各成员国和高速微单元所覆盖地区的不足（例如，由于缺乏渠道或范围的移动台正在走出微单元）。此外，在微孔系统用于溢出的通信其最充分的程度是可以路由到宏小区。覆盖/衬垫系统是宏单元和微单元测定的最佳分配的渠道[15]。参考文献[16]两层之间的计算方法有四种共享的可用频谱。方法1用于宏区域的TDMA和CDMA微蜂窝。方法2用于宏区域的CDMA和TDMA微蜂窝。爱他们使用在这两个层次的TDMA中，且在这两个办法的第4层采用正交频渠道。覆盖/衬底系统微蜂窝系统的一些优势[17]：•基地台只在需要高流量负荷的地区使用。因为它不是必需的，使该地区与微单元全程服务，同时基础设施的成本节省。•在系统的覆盖的数目远远低于宏微蜂窝系统，因为在快速移动的车辆可连接到覆盖。•调用移动台和通信位置可以很容易地做到通过微蜂窝系统。伞单元有几类[17]。第一类在正交渠道分布微单元和巨单元之间。另一个类在微通道使用，微循环利用的巨单元的渠道已经可以处理发射功率稍高的水平分配，抵消了宏单元的干扰。在环境中覆盖/衬底系统中，有4种切换需要管理[19]：微单元，以微蜂窝，微蜂窝向宏，宏向宏，微蜂窝和宏蜂窝。参考文献[20]描述了单元分裂和结合覆盖。单元再利用