WLAN signal strength - good or bad ?
Werner Almesberger
werner at openmoko.org
Mon Oct 6 11:05:32 CEST 2008
Andy Green wrote:
> BTW A lot of confusion is caused by this 4/94 type report in iwconfig,
> if there is no valid information driven by bit error rate floating
> around for that maybe an interesting patch would be to take the dBm
> figure and say add 100 to it or something and report / 100, so at least
> the figure here is sane.
All the numbers I posted were the "signal level" reported by iwlist.
The reported noise level was -95dBm in all cases, so the baseline
was the same, according to iwlist.
Is that what you meant ?
I've written a little script to summarize the output of iwlist scan:
http://svn.openmoko.org/developers/werner/bin/wlanscan
Some more results: local time 06:30, 13C, humidity 87%, sorted by
ESSID for easier comparison.
Laptop:
08 9noB -94/-95 dBm WEP
02 ALTAMIRANO -90/-95 dBm open
07 Amazonas Cafe -83/-95 dBm open
09 EDIFIER -84/-95 dBm WPA
12 LAORACION -94/-95 dBm WPA
13 TAXON OFFICE -92/-95 dBm WPA
11 The Newcastle Group -93/-95 dBm WPA
06 UOL-PIOLA -90/-95 dBm open
03 Universidad -79/-95 dBm WEP
05 canzani -84/-95 dBm open
10 linksys -84/-95 dBm WPA
04 villar_1 at buenosaireslibre.org -104/-95 dBm open
01 xyz -48/-95 dBm WEP
Neo 1, on the bench, partially unshielded:
04 Marin -95/-95 dBm WEP
03 Universidad -87/-95 dBm WEP
01 jose -90/-95 dBm WPA
02 xyz -56/-95 dBm WEP
Neo 2, next to the laptop:
08 BaseSR -93/-95 dBm WEP
10 CBSHOME -93/-95 dBm WEP
01 EDIFIER -90/-95 dBm WPA
05 FT25250 -93/-95 dBm open
04 FT66245 -95/-95 dBm open
07 Marin -85/-95 dBm WEP
03 UOL-PIOLA -88/-95 dBm open
09 Universidad -89/-95 dBm WEP
02 jose -83/-95 dBm WPA
06 xyz -41/-95 dBm WEP
The noise level is probably simply meaningless. My laptop seems to
particularly like the nodes of the local free WLAN project
(buenosaireslibre.org). For the villar_1 node, I got reports ranging
from (plus !) 47/-95dBm to -189/-95dBm. I'll throw dice the next
time ;-)
So ... it seems that we're not doing so poorly overall in terms of
access point detection. Association and DHCP were also fine with the
open nodes.
- Werner
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