无线通信系统第2章

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1、TheCellularConcept：SystemDesignFundamentals7/3/20211CellularNetworks7/3/20212CellshapeCircle:Equilateraltriangle:Square:Hexagon:7/3/20213Cellularcoveragerepresentation7/3/20214Macrocelllarge,coveringawidearerangeofseveralhundredkilometres(km)totenkmmostlydeployedinruralandsparselypopul

2、atedareasMicrocellmediumcell,coverageareasmallerthaninmacrocellsrangeofseveralhundredmetrestoacoupleofmetresdeployedmostlyincrowdedareas,stadiums,shoppingmallsPicocellsmall,coveringaverysmallarearangeofseveraltensofmetreslowpowerantennas,indoorThesizeofacell7/3/202157/3/20216Basestatio

3、ntransmittersInhexagonalcells,basestationstransmittersareeither:centre-excited,basestationisatthecentreofthecelledge-excited,basestationat3ofthe6cellverticescentre-excitededge-excited7/3/20217CellularcoveragerepresentationCcanbeusedasameasureofcapacity7/3/20218Amobilecommunicationsyste

4、musesafrequencyreusefactorof1/7and416channelsavailable.If21channelsareallocatedascontrolchannels,computeitssystemcapacity.Assumeachannelsupports8usersChannelsavailableforallocation=416-21=395ChannelNumberofacell=395/7=57Numberofsimultaneoususerspercell=8x57=456Numberofsimultaneoususers

5、insystem=7x456=3192Example17/3/20219Ifatotalof33MHzofbandwidthisallocatedtoaparticularFDDcellulartelephonesystemwhichusestwo25kHzsimplexchannelstoprovidefullduplexvoiceandcontrolchannels,computethenumberofchannelsavailablepercellifasystemusesfour-cellreuse.If1MHzoftheallocatedspectrumi

6、sdedicatedtocontrolchannels,determineanequitabledistributionofcontrolchannelsandtrafficchannelsineachcellforeachofthesystem.Example27/3/202110Methodoflocatingco-channelcells7/3/202111ChannelAssignmentStrategiesThreeassignmentapproachesFixedandstatic(mostcommon)DynamicHybridFixedchannel

7、assignmentallchannelsinacellcouldbeinuseallthetimenewcallsarethenblocked(nochannelsleft)maybesolvedbyborrowingsparechannelsfromnearbycells7/3/202112DynamicchannelassignmentMSCallocatesfrequencieswhenacallismadeProvideshighchannelutilisationTodothisitneedsreal-timeinformationonchannel