[ath9k-devel] ath9k: signal level of rxed probe req.

[Lukasz <zmielony@poczta.onet.pl>]

On 06/22/2012 08:42 AM, Holger Schurig wrote:
>> Is there any way to filter out frames received on other channels (so I only
>> receive frames from channel on which my AP is configured)?
>
> No, there isn't. Suppose the probe request was sent on channel 10. And
> your AP is on channel 11. Then your AP actually really receives the
> probe request on channel 11. Those channels are overlapping, after
> all. Also, then "received channel" information in some wiretap header
> (available on some monitoring interface) would also indicate channel
> 11.
>
> You may use a heuristics: then you receive probe requests, record
> their mac, signal level and a time stamp. If you get another probe
> requets from the same MAC and the time is similar to what you already
> have, then use the higher signal. That will work because a probing
> client usually probes on different frequencies within a short timespan
> (around 100 ms per channel).
>

Actually I'm doing it this way now. The problem is that different devices use 
different scan interval, also time of channel switch doesn't seem to be constant 
(even for the same device). And it sometimes happens that not all frames are 
being received by AP. So it's quite tricky to find out good filter timing.

Anyway, I think I will have to improve my current filtering implementation :)

Thank you for answers!

with regards,
Lukasz