Subject: Re: atheros cards - no signal level info or am i doing something wrong?
To: David Young <>
From: Sam Leffler <>
List: current-users
Date: 01/15/2004 08:58:54
On Wednesday 14 January 2004 09:22 am, David Young wrote:
> On Wed, Jan 14, 2004 at 11:43:22AM +0100, Wojciech Puchar wrote:
> > i started atheros card (ath driver) fine. it works OK but receiver signal
> > level info gives always 0dB signal level and -149dB signal quality and
> > noise.
> -149 noise is an artifact of early mistakes in programming wiconfig; you
> can interpret it as "0". AFAIK, the Atheros hardware does not provide
> any noise figure. I don't precisely know why the signal level is 0,
> but see below.

There is code around to collect rssi from received frames and use it to 
calculate a "receiver signal level".  But as David says interpreting it based 
on Prism operating parameters is going to be confusing.  If you look at the 
madwifi code for Linux ( you'll find code to 
approximately convert from the rssi (given as dbm relative to the noise 
floor) to the prism-style signal quality metrics.  I've got this code in 
uncommitted changes for FreeBSD.

> > is it bug or lack of code?
> It depends what mode you run the interface in. You will probably not
> get an intelligible signal level report in ad hoc mode or in AP mode.

The numbers are real regardless of mode.  The question is what to return for a 
single value when operating in adhoc or ap operation.  The existing code 
averages over all stations when asked for a signal quality and operating in 
adhoc or ap mode.