link quality and noise level

Hi all,

I'm using the at76c503a driver on an iPAQ h5400 with the "familiar"
distribution.
I use the CVS version of the driver.
But when I execute iwconfig, link quality and noise level stay at 0 :
"Link Quality=3D0/0 Signal level=3D77/255 Noise level=3D0/0"

Do you know if there is a way to get these values ?
Maybe the firmware does not allow us to get this kind of information :-/
I don't know if there is an other solution than adding an other
wireless card ;-)

I'm trying to locate on a map several iPAQ using these values.

Thanks,
Jean-marie