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1、TalkingAboutWLANtechnology：802.11xXuShuminInternationalSchool,Class2009215102,09212759BeijingUniversityofPostandTelecommunicationEmail:jp092759@bupt.edu.cnPage1of9lAbstractInjustthepastfewyears,wirelessLANshavecometooccupyasignificantnicheinthelocalareanetworkmark
2、et.Increasingly,organizationsarefindingthatwirelessLANsareanindispensableadjuncttotraditionalwiredLANs,tosatisfyrequirementsformobility,relocation,adhocnetworking,andcoverageoflocationsdifficulttowire.lKeyWords:WLAN;IEEE802.11;Telecommunicationl1.IntroductionAsthe
3、namesuggests,aWirelessLocalAreaNetwork(WLAN)isonethatmakesuseofawirelesstransmissionmedium.Itisquiteconvenientdatatransmissionsystem,whichhasbeenusingRadioFrequency(RF)toreplacethetraditionalCoaxialthatformtheLocalAreaNetwork(LAN),makestheWLANusesimpleaccessarchit
4、ectureallowsuserstopassthroughit.Page2of9l2.WirelessLANTechnologyWirelessLANsaregenerallycategorizedaccordingtothetransmissiontechniquethatisused.AllcurrentwirelessLANproductsfallintooneofthefollowingcategories(Table1).u2.1Infrared(IR)LANs:AnindividualcellofanIRLA
5、Nislimitedtoasingleroom,becauseinfraredlightdoesnotpenetrateopaquewalls.n2.1.1StrengthsandWeaknessThespectrumforinfraredisvirtuallyunlimited,whichpresentsthepossibilityofachievingextremelyhighdatarates.Inaddition,infraredsharessomepropertiesofvisiblelightthatmakei
6、tattractiveforcertaintypesofLANconfigurations.Anotherstrengthofinfraredisthattheequipmentisrelativelyinexpensiveandsimple.However,theinfraredmediumalsoexhibitssomedrawbacks.Manyindoorenvironmentsexperienceratherintenseinfraredbackgroundradiation,fromsunlightandind
7、oorlighting.n2.1.2TransmissionTechniquesTherearethreealternativetransmissiontechniquescommonlyusedforIRdatatransmission:thetransmittedsignalcanbefocusedandaimed(asinaremoteTVcontrol);itcanberadiatedomnidirectionally;oritcanbereflectedfromalightcoloredceiling.Direc
8、ted-beamIRcanbeusedtocreatepoint-to-pointlinks.Inthismode,therangedependsontheemittedpowerandonthedegreeoffocusing.Anomnidirectionalconfigurationinvolve
