蜂窝网结构wikipedia

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1、CellularnetworkFromWikipedia,thefreeencyclopediaTopofacellularradiotowerAcellularnetworkisaradionetworkdistributedoverlandareascalledcells,eachservedbyatleastonefixed-locationtransceiverknownasacellsiteorbasestation.Whenjoinedtogetherthesecellsprovideradiocoverageoverawidegeogr

2、aphicarea.Thisenablesalargenumberofportabletransceivers(e.g.,mobilephones,pagers,etc.)tocommunicatewitheachotherandwithfixedtransceiversandtelephonesanywhereinthenetwork,viabasestations,evenifsomeofthetransceiversaremovingthroughmorethanonecellduringtransmission.Cellularnetwork

3、sofferanumberofadvantagesoveralternativesolutions:■increasedcapacity■reducedpoweruse■largercoveragearea■reducedinterfereneefromothersignalsAnexampleofasimplenon-telephonecellularsystemisanoldta)

4、ncommunicatedirectlywitheachtaxi.Contents[hide]1Theconcept2Cellsignalcncoding3Frequencyreuse1Directionalanlennas5Broadcastmessagesandpaging6Movementfromcelltocel1andhandover7Exampleofacellularnetwork:themobi1ephonenetwork7.1Structureofthemobi1ephonecellularnetwork7.2Cellularhan

5、doverinmobilephonenetworks7.3Cellularfrequencychoiceinmobi1ephonenetworks7.4Coveragecomparisonofdifferentfrequencics8Seealso9References[editiTheconceptExampleoffrequencyreusefactororpattern1/4Inacellularradiosystem,alandareatobesuppliedwithradioserviceisdividedintoregularshaped

6、cells,whichcanbehexagonal,square,circularorsomeotherirregularshapes,althoughhexagonalcellsareconventional.Eachofthesecellsisassignedmultiplefrequencies（斥・fQ）whichhavecorrespondingradiobasestations.Thegroupoffrequenciescanbereusedinothercells,providedthatthesamefrequenciesarenot

7、reusedinadjacentneighboringcellsasthatwouldcausecochannelinterferenee.Theincreasedcapacityinacellularnetwork,comparedwithanetworkwithasingletransmitter,comesfromthefactthatthesameradiofrequencycanbereusedinadifferentareaforacompletelydifferenttransmission.Ifthereisasingleplaint

8、ransmitter,onlyonetransmissioncanbeusedonanygivenfrequ