WLAN signal strength - good or bad ?

Werner Almesberger werner at openmoko.org
Mon Oct 6 19:09:44 CEST 2008

Andy Green wrote:
> I was saying maybe there is an easy patch there going into the IOCTL
> stuff that iwconfig uses and putting something more meaningful in this
> returned member.

Let's see ... for the AR6k, the code is here

What it does is that it only looks at the SNR, even though it often
calls it the RSSI [1], and the description of that function uses the
two almost interchangeably. The noise floor is just a hard-coded best
guess, as expected.

The chip does return the RSSI as well [2], but it just seems to do
exactly the same calculation as the driver, i.e., reported RSSI =
reported SNR - hard-coded noise.

[1] http://en.wikipedia.org/wiki/RSSI
[2] This is the data structure that comes from the chip:

So, short of actually trying to associate, this seems to be as much
information we can get.

- Werner

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