Specifications

RF Auto-Tuning Overview
RoamAbout Mobility System Software Configuration Guide 11-3
Power Tuning
Bydefault,theswitchevaluatesthescanresultsforpossiblepowerchangesevery300seconds(5
minutes),andraisesorlowersthepowerlevelifneeded.
IfRFAuto‐Tuningdeterminesthatapowerchangeisneededonaradio,MSSrampsthepowerup
ordownuntilthenewpowe r
levelisreached.Ramp‐uporramp‐downofthepoweroccursin
1dBmincrements,atregulartimeintervals.Thedefaultintervalis60secondsand isconfigurable.
Thepowerrampamount(1 dBmperinterval)isnotconfigurable.
Channel Tuning
Bydefault,theswitchevaluatesthescanresultsforpossiblechannelchangesevery3600seconds
(1hour).MSSusesthefollowingparameterstodeterminewhethertochangethechannelona
radio:
•Presenceofactivesessions.
•Bydefault,iftheradiohasactivesessions,MSSdoesnotchangethechannel.If
theradiodoes
nothaveanyactivesessions,MSSusestheremainingparameterstodeterminewhetherto
changethechannel.Receivedsignalstrengthindica tion(RSSI)
•Amountofnoiseonthechannel
• Packetretransmissioncount,whichistherateatwhichtheradioreceivesretransmitted
packets.
• Utilization,calculatedbasedonthenumberofmulticast
packetspersecondthataradiocan
sendonachannelwhilecontinuouslysendingfixed‐sizeframesoveraperiodoftime.
•Phyerrorcount,whichisthenumberofframesreceivedbytheAPradiothathavephysical
layererrors.AhighnumberofPhyerrorscanindicatethepresence
ofanon‐802.11device
usingthesameRFspectrum.
• ReceivedCRCerrorcount.AhighnumberofCRCerrorscanindicateahiddennodeorco‐
channelinterference.
Thethresholdsfortheseparametersarenotconfigurable.RF Auto‐Tuningalsocanchangea
radio’schannelwhenthechanneltuningintervalexpires,
ifachannelthathaslessdisturbanceis
detected.Disturbanceisbasedonthenumberofneighborstheradiohasandeachneighbor’sRSSI.
AradioalsocanchangeitschannelbeforethechanneltuningintervalexpirestorespondtoRF
anomalies.AnRFanomalyisasuddenmajorchangein
theRFenvironment,suchassudden
majorinterferenceonthechannel.
Bydefault,aradiocannotchangeitschannelmoreoftenthanevery900seconds,regardless ofthe
RFenvironment.ThischannelholddownavoidsunnecessarychangesduetoverytransientRF
changes,suchasactivationofamicrowaveoven.