Re: Passive Scanning Bugreport

On Thursday 03 August 2006 09:18, Zhu Yi wrote:

> Yes, I tried your patch. I can always get a scan completed notification
> when the STA is associated. It could be either a succesfully scan
> completed notification or a scan abort notification depending on the
> dwell time and the DTIM setting from my AP (Asus WL-500g-X).
>
> passive_dwell	DTIM	scaned_channels		found_APs
> 120ms		1	1 (abort)		1
> 30ms		1	5~11 (abort)		1~7
> 120ms		10	23 (successfully)       13
> 30ms		10	23 (successfully)       9
>
> >From above results, set the dwell time to 120ms is more reasonable
>
> because the default beacon interval is 100ms. Otherwise we are likely to
> lose the beacon frames because we are not stay long enough on each
> channel. On the other hand, because some APs set the default DTIM value
> to a relative short period, we are unlikely to get the full scan result
> when the STA is associated. I think this is OK since we are already
> associated so we don't care much about other APs. Otherwise we should
> use the active scan.
I followed your advice and set the passive dwell time to 120ms. With my 
Fujitsu-Siemens laptop everything works fine. However, I have another 
question about the DTIM interval. If I get it right, the DTIM timer defines 
how often a DTIM frame is send out by the AP. If I miss a DTIM frame the scan 
will be aborted by the ipw_handle_missed_beacon function. Is this correct?
Why do we abort a scan after we missed a DTIM frame? It is already missed, so 
why not accomplishing the running scan?

I have another question: If I activate the rtap feature and wiretap this 
interface I see a lot of beacons sent out on neighboring channels. Lets say I 
am associated to channel 8, I still see beacons from an access point using 
channel 6. I guess this is due to the overlapping of 802.11b/g channels, 
isn't it? Do you have more information about this phenomena? How many 
channels can be reached? Does the power measurement of the wireless network 
card still work if I receive a beacon from an neighbor channel?

My last question for today :-): Do we have a timetable for the next release of 
the driver?

Greetings,
Thomas

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