Re: Client signal strength [was: Re: Re: Bat digest, Vol 1 #188 - 1 msg]

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On Wed, 15 Jan 2003, Chip Marshall wrote:

> On January 16, 2003, Marcos Biscaysaqu sent me the following:
> >  I have 2 freebsd access point runing with 20 costumers each someone
> > know if i can use the dstumbler on the freebsd access point to test the
> > signal level on the costumers, beacouse when i try to do that the Access
> > point crash.
>
> Doesn't wicontrol -l show signal strength? I went to look in the man
> page, but it doesn't seem to be mentioned much.
>

According to the wicontrol source it sure does. I took a look at
/usr/src/sys/dev/ic/if_wi_hostap.h to see where the signal/noise values
come from and it appears that they are set in wihap_data_input() from the
signal and noise values in the prism2 header as each packet from a given
station is processed. So, what 'wicontrol -l' will give you is the
signal/noise value for the last packet (and only the last packet) from the
station in question.

- From here on out is just my own conjecture and rambling. If you're
interested in it, read on. It may even be useful to somebody. :)

If you've ever spent any time looking at signal/noise values, you will
have noticed that a single packet's signal/noise value is not necessarily
representative of the overall quality of a connection to a station.

In an ideal world, there would be (and may be, anybody know?) a way to get
access from userspace to the incoming packets (including the prism2
header) in hostap mode in a similar fashion to monitor mode. Then, you
could write some pretty simple code to just monitor signal and noise
values on incoming packets and do some averaging or something to give a
more "real" idea of station signal quality.

One way that may work to get at least a better idea would be to make
repeated calls to the SIOCHOSTAP_GETALL ioctl (or SIOCHOSTAP_GET for just
a single station) and grab the values to build averages with. Kind of
like running 'wicontrol -l' a bunch and parsing out the info.


- -d

"You see, wire telegraph is a kind of a very, very long cat.
 You pull his tail in New York and his head is meowing in
 Los Angeles. Do you understand this? And radio operates
 exactly the same way: you send signals here, they receive
 them there. The only difference is that there is no cat. "

                                           --Albert Einstein


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