wpa_supplicant: signal strength

Dan Williams dcbw
Fri Aug 25 07:33:54 PDT 2006

On Fri, 2006-08-25 at 19:05 +0530, Pradeep Sengar wrote:
> Hi,
> I am having a wi-fi application to show the signal strength . From
> wpa_supplicant  I get the  RSSI value in dBm.  Now, the  dBm range is
> different for different AP's. How do I convert the signal strength
> value in a range?

It's different for every card.  Wireless Extensions specifies signal
strength in either RSSI or dBm, and the driver must specify a noise
floor in the same units.  If you're given dBm by the driver (or by
wpa_supplicant) you can use the noise floor as your lower value for the
range, but remember that the scale is not necessarily linear.

Furthermore, drivers these days are _very_ bad at reporting signal
strength in any standardized fashion, and drivers also have
discrepancies between a scanned AP's strength and the strength when
you're associated to that AP.

You may have to use WE directly rather than wpa_supplicant to get the
information you need.


> Regards 
> Pradeep
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