Re: CVS-2-2 NMApplet empty bar explained

[Bill Moss <bmoss CLEMSON EDU>]

I have seen my card spike to -15 dBm when held next to an AP. The Cisco 
lookup table starts at -10 dBm. I agree that [-90, -20]. Is a good range 
to start with. I think the cards will all output biased values (+256) 
for qual-> level, max_qual->level, max_qual->noise but I could be wrong.

If agreement is ever reached on how to do the associated percentage 
calculation and the scanned percentage calculation, an appropriate patch 
could be submitted to each wireless driver project. The ipw2200 people 
seemed eager to have input on this issue. ipw2200.c is filled with TO DO 
and FIND A GOOD VALUE comments. The developers are just waiting for 
someone to bit the bullet.

Dan Williams wrote:

> On Fri, 2005-02-04 at 10:54 -0500, Bill Moss wrote:
>  
>
> > Take a look at the next message I sent about patching the NM 
> > nm_wireless_qual_to_percent function. If a driver does not report 
> > max_qual->level and max->qual->noise, make some good guess. The physical 
> > lower limit for what a card can do is about -96 dBm. The upper limit 
> > varies but is always less than -10 dBm. For the ipw2200, -20 dBm is 
> > about right. Percentage is at best a rough indicator and does not 
> > directly relate to a physical quantity so I don't think it matters that 
> > much to get it "exactly right". If the driver does not specify 
> > max_qual->level and max->qual->noise, how about setting
> >
> > max_qual->level to 221 (-35 dBm)
> > max_qual->noise to 161 (-95 dBm)
> >    
>
> I've seen mention of cards capable of receiving around -80 dBm down to
> -97 dBm.  I think around -90 dBm would be a good value there...
>
> I also don't think I've ever seen a card (out of my stack of 6 and a few
> more from friends and coworkers) that's been able to get above -20 dBm,
> so that might be a good starter value.
>
> We could also adjust this stuff on the fly (at least the upper bound
> here) and maybe move that down as low as -30dBm over time, though that
> gets more complicated.  I guess the answer would be "fix the driver" if
> people complained enough.  Sounds like a good idea though.  Thanks for
> the tip.
>
> Dan
>
>
>  

--
Bill Moss
Professor, Mathematical Sciences
Clemson University