无线通信与网络ppt课件.ppt

《无线通信与网络ppt课件.ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、CellularWirelessNetworksChapter10CellularNetworkOrganizationUsemultiplelow-powertransmitters(100Worless)AreasdividedintocellsEachservedbyitsownantennaServedbybasestationconsistingoftransmitter,receiver,andcontrolunitBandoffrequenciesallocatedCellssetupsuchthata

2、ntennasofallneighborsareequidistant(hexagonalpattern)FrequencyReuseAdjacentcellsassigneddifferentfrequenciestoavoidinterferenceorcrosstalkObjectiveistoreusefrequencyinnearbycells10to50frequenciesassignedtoeachcellTransmissionpowercontrolledtolimitpoweratthatfre

3、quencyescapingtoadjacentcellsTheissueistodeterminehowmanycellsmustintervenebetweentwocellsusingthesamefrequencyApproachestoCopewithIncreasingCapacityAddingnewchannelsFrequencyborrowing–frequenciesaretakenfromadjacentcellsbycongestedcellsCellsplitting–cellsinare

4、asofhighusagecanbesplitintosmallercellsCellsectoring–cellsaredividedintoanumberofwedge-shapedsectors,eachwiththeirownsetofchannelsMicrocells–antennasmovetobuildings,hills,andlamppostsCellularSystemOverviewCellularSystemsTermsBaseStation(BS)–includesanantenna,ac

5、ontroller,andanumberofreceiversMobiletelecommunicationsswitchingoffice(MTSO)–connectscallsbetweenmobileunitsTwotypesofchannelsavailablebetweenmobileunitandBSControlchannels–usedtoexchangeinformationhavingtodowithsettingupandmaintainingcallsTrafficchannels–carry

6、voiceordataconnectionbetweenusersStepsinanMTSOControlledCallbetweenMobileUsersMobileunitinitializationMobile-originatedcallPagingCallacceptedOngoingcallHandoffAdditionalFunctionsinanMTSOControlledCallCallblockingCallterminationCalldropCallsto/fromfixedandremote

7、mobilesubscriberMobileRadioPropagationEffectsSignalstrengthMustbestrongenoughbetweenbasestationandmobileunittomaintainsignalqualityatthereceiverMustnotbesostrongastocreatetoomuchcochannelinterferencewithchannelsinanothercellusingthesamefrequencybandFadingSignal

8、propagationeffectsmaydisruptthesignalandcauseerrorsHandoffPerformanceMetricsCellblockingprobability–probabilityofanewcallbeingblockedCalldroppingprobability–probabilitythata