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AP signal quality reporting

Unanswered Question
Dec 17th, 2006
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Hi,


When we do a show assoc etc on a 1232 AP,

we get figures back showing signal strength in the region of 70 and signal quality around 35.

What is the reference for these figures?

Is it 70 as in 0 bad 100 good, or is it 70db, where 60 is a stronger signal than 70.

And how does the 35 get measured.

Any help much appreciated.

Thanks

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Loading.

Speed...MinSig..MinSNR

54......-71.....25

36......-73.....18

24......-77.....12

12/11...-82.....10

6/5.5...-89.....08

2.......-91.....06

1.......-94.....04


-70 is a weaker signal than -60 in reference to signal strength. SNR of 25 is greater than an SNR of 15.


The SNR is the ratio between your desired signal and noise.

rwakelin Mon, 12/18/2006 - 15:39
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OK...

So you are saying that the signal strength that is reported is db, and the signal quality that is reported is actually SNR?

john.preves Tue, 12/19/2006 - 09:57
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Not necessarily, Signal quality is usually some sort of useless percentage of what, nobody at Cisco can answer. SNR on the other hand is Signal to Noise ratio. This is a quantifiable number that refers to where your signal is in reference to where the noise is. SNR is measured in dB as well. If your noise is -88dBm and you signal is -65dBm, then your SNR is -23dB (which is good depending on what your doing with it, voice would probably work depending on whose it is etc...)the lower the number the SNR is the closer your signal is to the noise. Think of your car driving around until the radio station starts to drop off. If it's a really good song you will put up with the static so long as it isn't unbearable. When it becomes unbearable you will find something else to listen to.


Think of -25 to -30 as very good (depending again on environment etc..just a guide not a rule), -18 to -20 ok, (VoIP might be giving you problems but your data probably still works) and anything lower than that is pushing it.


This is not to say that signal quality is useless altogether, it must be looked at in conjunction with signal strength and SNR and the environment it is in etc... in order to give you a picture of what you have or what you think you have anyway...

rwakelin Tue, 12/19/2006 - 13:49
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Thanks for all that.

I'm aware of what all the acronyms are, etc.

What I'm trying to find out is what these numbers are supposed to represent on this piece of equipment. The Cisco documentation is NOT helpful, and the outputs from the commands are not discussed at all.

So I'll try again.


Is the signal strength measurement in dB or

"cisco power"? The command output does not have db after it, but that is not definitive.

Perhaps it is RSSI?

Is the signal quality a qualititive measurement (again Cisco specific) or is it a SNR figure (perhaps in dB)?

Thanks

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