ContentionforULOFDMADate:2014-12-10Slide1MarvellAuthors:
UseCasesforContention-BasedULOFDMASomeSTAsmayhavelowpowerandtheSTAsneedtousebandwidthlowerthan20MHztoreachtheAP,e.g.doassociationwiththeAP.TheAPcanallocatesomeULOFDMAPPDUforSTAstodoassociationwiththeAPbycontention.ArguablyrobustMCS(duplicaten*26tonesinfullbandwidth)withnormalassociationcansolvetheproblem.AnAPmaynotknowwhichSTAsshouldbepolledforbufferinformationreport.TheAPcanallocatesomeULOFDMAPPDUforSTAstoreporttheirbufferinformationthroughcontention.ArguablynormalULOFDMAwhichmayneedhelpfromrobustMCScanalsodothejob.AnAPmaytriggermultiplepowersaveSTAstotransmitPS-PollthroughcontentionOFDMA.Inthetriggerframe,nospecificSTAsareindicated.ArguablynormalPS-PollwhichmayneedhelpfromrobustMCScandothesamework.Observation:if11axacceptscontention-basedOFDMA,contention-basedOFDMAshouldbeoptionalfeature.Slide2
MethodtoContendtheSubchannelDistributedcontentionEachSTAcancreatearandomnumberperUMCWwhichisrestrictedbyUMCWmin(ULOFDMACWmin),UMCWmax(ULOFDMACWmax).IfUMCWisUMCWmax,UMCWissettoUMCWminafterselectingtherandomnumberperUMCW.AfterasuccessfulcontentionOFDMAtransmission,UMCWischangedtoUMCWmin.AfteranunsuccessfulcontentionOFDMAtransmission,theUMCWisdoubleduntilUMCWmax.AfterreceivingaSYNCforcontentionOFDMA,therandomnumberisdecreasedby1.TheSTAwith0randomnumberrandomlyselectasubchanneltotransmittheframeCentralizedcontention.TheAPindicatesacontentionthresholdwhichissmallerthanMAX_THRESHOLDinthetriggerframeorBeaconforthecontentionofOFDMAsubchannel.TheselectionofthecontentionthresholdisbasedonthecollisionofthecontentionFODMAorothercriteria.ASTAcreatearandomnumberwhichisin[0,MAX_THRESHOLD].Iftherandomnumberissmallerthanthecontent