Cisco Systems BeamforminginClientLink1.0and2.0

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CiscoAironetAccessPointDeploymentGuide 
CiscoSystems
Copyright©2012CiscoSystems,Inc.Allrightsreserved.
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theIntelcardoropenacasewithIntelorthelaptopmanufacturerforapossibleremedy.DuringtheAP
3600betatrials,CiscoobserveddifferencesinperformancewithdifferentnotebooksusingtheIntel
6300card.
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Note:Sometimesitcanbedifficulttoreliablymaintaina3SSlink,sinceitiseasyfortheclientto
rate‐shiftoutofthe3SSmode.Theabilitytomaintaina3SSlinkvarieswiththequalityofthe
clientandthetestenvironment.
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TheAP3600,withitsextraradioperband,canusetheextraredundantradiotobeamform(thanksto
ClientLink2.0)andusesthistomaintaintheadvantageof3SSlinks.ClientLink2.0canalsoimprovethe
overallperformanceof802.11nclientsusingone,two,andthreespatialstreamsandlegacy.11a/g
clients.
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BeamforminginClientLink1.0and2.0
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ClientLink1.0wasfirstintroducedwiththeAP1250andtheAP1140;itisamethodtocreateastronger
signalonthedownlinksidefor802.11a/gclientsbyhearingtheclientsontheuplinkandthenadjusting
thetransmittertimingsothesignalappearsmuchstrongerattheclientend.
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Thisfeaturewaspreviouslyuserconfigurable.However,startingwith7.2codestream,itisnowonby
defaultandisnotuserconfigurablebecausethereisnobenefittodisablingit.
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TheAP3600fullysupportsClientLink1.0for802.11a/gclientsbuthasagreateradvantage,foritalso
supportsall802.11nclientsincludingone,two,andthreespatialstreamclients.Thiscapabilityiscalled
ClientLink2.0.ThereisadistinctadvantagewithClientLink2.0overthe802.11nenhancedbeamforming
specification,becauseClientLink2.0workswithallclientstodayanddoesnotrequireanyclient
soundingorsupport.(SeeFigure55.)
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Figure55:ClientLink2.0
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Withbeamformingtechnology,changingthetimingoftwotransmitterscreatesastrongersignalforthe
receiver(forexample,aclientdevice).Thisisreferredtoasconstructiveinterference.Iftheopposite
happens,andthesignalscanceleachotherout,itiscalleddestructiveinterference.(SeeFigure56.)
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