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1、TakingtheStingoutofCarrierSense:InterferenceCancellationforWirelessLANsDanielHalperinThomasAndersonDavidWetherallUniversityofWashingtonUniversityofWashingtonUniversityofWashingtonIntelResearchSeattleABSTRACThighperformancecommunication.Partly,thisisd
2、uetotheinherentcharacteristicsofwirelesscommunications,inAfundamentalproblemwithunmanagedwirelessnetworkswhichperformanceisheavilydependentonthedetailsofishighpacketlossratesandpoorspatialreuse,especiallytheenvironment.ButwirelessLANsalsoaddchaotictr
3、af-withburstytra?ctypicalofnormaluse.Toaddressthese?cpatterns,irregularandsometimesdynamictopologies,limitations,weexplorethenotionofinterferencecancella-heterogeneoushardware,devicesinseparateadministrativetionforunmanagednetworks—theabilityforasing
4、lere-domainsanddecentralizedcontrol.Theresultisthattra-ceivertodisambiguateandsuccessfullyreceivesimultane-ditionaltechniquesforallocatingresources,suchasTDMA,ousoverlappingtransmissionsfrommultipleunsynchronizedFDMA,CDMA,cannotreadilybeused.Instead,
5、wirelesssources.WedescribeapracticalalgorithmforinterferenceLANsrelyoncarriersense,inwhichadevicewilldefertoacancellation,andimplementitforZigBeeusingsoftwarera-transmissionalreadyinprogress.Nodessendwithamini-dios.Inthissetting,we?ndthatourtechnique
6、scanre-mumofdelaywhentheyhavedata,whileavoidingcollisionsducepacketlossrateandsubstantiallyincreasespatialreuse.thatwouldpotentiallycauseloss.Withcarriersensesettopreventconcurrentsends,ourap-Unfortunately,itiswell-knownthatcarriersensedoesnotproachr
7、educesthepacketlossrateduringcollisionsfromalwaysworkasintended.Hiddenterminalsarenodesthat14%to8%duetoimprovedhandlingofhiddenterminals.donotsenseeachother’stransmissions,eventhoughtheyConversely,disablingcarriersensereducesperformanceforinterfereat
8、anintendedreceivertopreventsuccessfuldecod-only7%ofallpairsoflinksandincreasesthedeliveryrateing.Exposedterminalsarenodesthatdosenseanddefertoforthemedianpairoflinksinourtestbedbyafactorof1.8eachother,eventhoughtheintendedreceiversarelocatedduetoimpr