Cisco Systems 1600 Network Router User Manual


 
CiscoAironetAccessPointDeploymentGuide
CiscoSystems
Copyright©2012CiscoSystems,Inc.Allrightsreserved.
Page42of52
theIntelcardoropenacasewithIntelorthelaptopmanufacturerforapossibleremedy.DuringtheAP
3600 betatrials,Ciscoobserved differencesinperformancewithdifferentnotebooks usingtheIntel
6300card.
Note:Sometimesitcanbedifficulttoreliablymaintai na3SSlink,since
itiseasyfortheclientto
rateshiftoutofthe3SS mode.Theabilitytomaintain a3SSlinkvarieswith thequalityofthe
clientandthetestenvironment.
TheAP3600,withitsextraradioperband,canusetheextraredundantradiotobeamform(thanks
to
ClientLink2.0)andusesthistomaintaintheadvantageof3SSlinks.ClientLink2.0canalsoimprovethe
overallperformanceof802.11nclientsusingone,two,andthreespatialstreamsandlegacy.11a/g
clients.
BeamforminginClientLink1.0and2.0
ClientLink1.0wasfirstintroducedwiththeAP1250andtheAP1 140;itisamethodtocreateastronger
signalonthedownlinksidefor802.11a/gclientsbyhearingtheclientsontheuplinkandthenadjusting
thetransmittertimingsothesignalappearsmuchstrongeratthe
clientend.
Thisfeaturewaspreviouslyuserconfigurable.However,startingwith7.2 codestream,itisnowonby
defaultandisnotuserconfigurablebecausethereisnobenefittodisablingit.
TheAP3600fully supportsClientLink1.0for 802.11a/gclientsbuthasagreateradvantage,forit
also
supportsall802.11nclientsincludingone,two,andthreespatialstreamclients.Thiscapabilityiscalled
ClientLink2.0.Thereisadistinct advantagewithClientLink2.0overthe802.11nenhancedbeamforming
specification, because ClientLink 2.0 works with all clients today and does not require any client
soundingorsupport.(See
Figure55.)
Figure55:ClientLink2.0
Withbeamformingtechnology,changingthetimingoftwotransmitterscreatesastrongersignalforthe
receiver (for example,a client device).This is referredto as constructive interference. Ifthe opposite
happens,andthesignalscanceleachotherout,itiscalleddestructive
interference.(SeeFigure56.)
