nm_ap_get_strength question

[Franco Miceli <fmiceli plan ceibal edu uy>]

I have a question about the method nm_ap_get_strength. The method reports values of 88 - 90 for signal levels of -50 dBm (as reported by iwlist sc).
My question is, what does strength report? A quality measurement? If so, what is the math behind its calculation?

The reason I'm asking this is because while iwlist reports differences in signal level of 20 dB, strength reports differences of only 4 (unit missing).

Thank you all for your attention.

Cheers

2010/6/5 Dan Williams <dcbw redhat com>

On Thu, 2010-05-27 at 05:56 +0200, Frederik Nnaji wrote:
> On Tue, May 25, 2010 at 18:45, Franco Miceli
> <fmiceli plan ceibal edu uy> wrote:
>         Therefore we want to to make some changes to the NM code in
>         order to take into consideration other factors such as: SNR,
>         loss %, etc.
>
>
> will you considered working on a UI for manually selecting and
> configuring a symbolic visual representation of known APs currently
> within range/sight?
> This would also help with GeoLocation, since it could use "strength"
> to approximate My position by the nearness of a known AP currently
> within sight.

We've thought about strength for a while, but in the end it doesn't work
very well.  There are simply too many things that can affect AP signal
strength to use it as a reliable measure of where you are.  It's better
to use *more than one* AP and triangulate to get better accuracy than
just 100m radius of one AP's known location.  Using only one AP, if
somebody turns on a microwave or uses a 2.4GHz DECT phone, suddenly it
looks like you're 30 meters farther away from the AP than you were 10
seconds ago...

Dan

-- 
Ing. Franco Miceli
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