Power levels / HostAP documentation

Leonardo Pereira Santos lsantos
Thu Oct 30 05:17:09 PST 2003

Hash: SHA1

If you take a look at the prism2_ap_get_sta_qual function(hostap_ap.c), lines 
2473 and 2474 :

qual[count].level = HFA384X_LEVEL_TO_dBm(sta->last_rx_signal);
qual[count].noise = HFA384X_LEVEL_TO_dBm(sta->last_rx_silence);

Than, looking at the iwlib.c file of wireless tools package, lines 950 to 986, 
it uses the stats from the driver to display the information about, among 
other things, the link quality:

  if(has_range && (qual->level != 0))
      /* If the statistics are in dBm */
      if(qual->level > range->max_qual.level)
	  /* Statistics are in dBm (absolute power measurement) */
		  "Quality:%d/%d  Signal level:%d dBm  Noise level:%d dBm%s",
		  qual->qual, range->max_qual.qual,
		  qual->level - 0x100, qual->noise - 0x100,
		  (qual->updated & 0x7) ? " (updated)" : "");
	  /* Statistics are relative values (0 -> max) */
		  "Quality:%d/%d  Signal level:%d/%d  Noise level:%d/%d%s",
		  qual->qual, range->max_qual.qual,
		  qual->level, range->max_qual.level,
		  qual->noise, range->max_qual.noise,
		  (qual->updated & 0x7) ? " (updated)" : "");
      /* We can't read the range, so we don't know... */
      sprintf(buffer, "Quality:%d  Signal level:%d  Noise level:%d%s",
	      qual->qual, qual->level, qual->noise,
	      (qual->updated & 0x7) ? " (updated)" : "");

You can get all these values from hostap's proc entry. One note here: with 
wireless extensions 16, iwspy is supposed to get stats using a standard ioctl 
call? I didn't try with hostap 0.1.1, but 0.0.4 I only got "not statistics to 
display". Should this work? I had to write a cgi to display the link 
statistics and the only way I found was to parse the /proc entry and use the 
signal and silence values as in the iw_print_stats function.
Another question is that the ap displays link quality like 26/92, while the 
client show a link of 92/92 and they are 1 m apart. Does anyone has any clue 
why this happens? And sometimes I get link qualities of 230/92, or other 
greater and 92 values. This also happens with a we 15 kernel with hosatap 

Thanks a lot!

On Wednesday 29 October 2003 22:24, mike-hostap at tiedyenetworks.com wrote:
> Howdy,
> 	First, thanks for HostAP.
> 	The Makefile for hostap has some depmod -ae statements in it which
> won't work in my enviroment because the machine building it doesn't run
> the kernel that it's being compiled against. Would it be possible to
> either remove these from the Makefile, or include a conditional so that
> these can be avoided when someone knows that it's going to fail?
> 	Secondly, with respect to powerlevels and somesuch, I don't see
> anywhere this is discussed. In /proc/net/hostap/wlanxx/ I find
> files with the mac addresses of the associated stations and
> looking at them I see a statement such as:
> last_rx: silence=164 signal=177 rate=110
> 	The rate paramater is pretty obvious, but what about the other
> two? I don't necessarilly need dbm or milliwatts and realise that
> these numbers can be subjective - the question is, what do the numbers
> represent from the hardware's perspective and can I derive signal
> level and linq quality information from them?
> 	Lastly, I get some strange messages from time to time of the form:
> klogd: handle_ap_item - addr3(BSSID) xx:xx:xx:xx:xx:xx not own MAC
> 	Where xx:xx:xx:xx:xx:xx is the mac address of the router on the
> ethrnet interface directly behind the AP. I looked at the code where this
> message is generated but I can't determine if it means that the ap
> received a frame on the wireless side with a bogus mac address or what.
> Any ideas?
> Mike-
> _______________________________________________
> HostAP mailing list
> HostAP at shmoo.com
> http://lists.shmoo.com/mailman/listinfo/hostap

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On a quiet night, you can hear Windows reboot.

Leonardo Pereira Santos
Engenheiro de Projetos
PD3 Tecnologia
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(51) 3337 1237

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