[ath9k-devel] scanning all the channels from phy interface continuously

[ath9k-devel] scanning all the channels from phy interface continuously

[abhinav narain]

hi,
  I am creating a phy interface for each wlan0,wlan1 and sniffing packets.
This seems to give me packets ( i see most of them) on the frequency wlan0
is set...
Is there a way i can sniff on all the channels, continuously ?
If so, any hints how to do it ?
I hope it doesnt effect the performance of the AP or will it ?


-Abhinav
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[ath9k-devel] scanning all the channels from phy interface continuously

[Adrian Chadd]

Hi,

You can't do that. You have to do a channel change into each channel
and then receive some frames. You can't operate in multiple
simultaneous channels on an Atheros NIC.

And yes, scanning will negatively impact performance.



adrian

[ath9k-devel] scanning all the channels from phy interface continuously

[abhinav narain]

Okay. I had my doubts about that already :-)

On Tue, May 22, 2012 at 3:00 AM, Adrian Chadd <adrian@freebsd.org> wrote:

> Hi,
>
> You can't do that. You have to do a channel change into each channel
> and then receive some frames. You can't operate in multiple
> simultaneous channels on an Atheros NIC.
>
> And yes, scanning will negatively impact performance.
>
>
>
> adrian
>
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[ath9k-devel] scanning all the channels from phy interface continuously

[Mohammed Shafi]

On Tue, May 22, 2012 at 8:03 PM, abhinav narain
<abhinavnarain10@gmail.com> wrote:
> Okay. I had my doubts about that already :-)

just curious are there proprietary sniffers that can do this stuff ?

>
>
> On Tue, May 22, 2012 at 3:00 AM, Adrian Chadd <adrian@freebsd.org> wrote:
>>
>> Hi,
>>
>> You can't do that. You have to do a channel change into each channel
>> and then receive some frames. You can't operate in multiple
>> simultaneous channels on an Atheros NIC.
>>
>> And yes, scanning will negatively impact performance.
>>
>>
>>
>> adrian
>
>
>
> _______________________________________________
> ath9k-devel mailing list
> ath9k-devel at lists.ath9k.org
> https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>



-- 
thanks,
shafi

[ath9k-devel] scanning all the channels from phy interface continuously

[abhinav narain]

They can !
 There are some in the market, Spectrum Expert/Spectrum Analyzer are two of
them
I suppose.

-Abhinav

On Tue, May 22, 2012 at 12:15 PM, Mohammed Shafi
<shafi.wireless@gmail.com>wrote:

> On Tue, May 22, 2012 at 8:03 PM, abhinav narain
> <abhinavnarain10@gmail.com> wrote:
> > Okay. I had my doubts about that already :-)
>
> just curious are there proprietary sniffers that can do this stuff ?
>
> >
> >
> > On Tue, May 22, 2012 at 3:00 AM, Adrian Chadd <adrian@freebsd.org>
> wrote:
> >>
> >> Hi,
> >>
> >> You can't do that. You have to do a channel change into each channel
> >> and then receive some frames. You can't operate in multiple
> >> simultaneous channels on an Atheros NIC.
> >>
> >> And yes, scanning will negatively impact performance.
> >>
> >>
> >>
> >> adrian
> >
> >
> >
> > _______________________________________________
> > ath9k-devel mailing list
> > ath9k-devel at lists.ath9k.org
> > https://lists.ath9k.org/mailman/listinfo/ath9k-devel
> >
>
>
>
> --
> thanks,
> shafi
>
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[ath9k-devel] scanning all the channels from phy interface continuously

[Adrian Chadd]

Off the top of my head:

* do fast channel change hacks and just change channels quickly. The
trouble here is you may miss out on some rather important periodic
signals (and insert "nyquist sampling theorem" here, for trying to
sample periodic changes in signal levels.) But for most people (and
for most spectrum analysers), this is what you do. You just do it very
quick.

* Operate your radio in a larger bandwidth mode and do scanning. This
works fine if you're doing straight spectral scan (as you may as well
do it in 40MHz channel chunks, rather than lots of 20MHz channel
chunks..) but not if you're scanning to try and find actual data
frames.

* You could just custom build something that samples an 80 or 160MHz
wide channel. Again, that's likely fine for doing air profiling, but
decoding frames will be another story. And if you have multiple,
concurrent frames coming in (ie something on channel 1, something on
channel 4, something on channel 6, all overlapping) then you'd have to
do some rather heavy math to decode those simultaneously. It's
possible (I've read a couple of papers on the topic) but it's likely
something you'd spin on an FPGA board, make work, then spin into an
ASIC.

* .. or you just buy four NICs, put them in one box, and combine them
whilst doing fast channel change. You can then decode frames on all
four, on different channels. Of if you're evil - decode frames on two,
and put the other two into spectral scan mode.

2c,


Adrian

[ath9k-devel] scanning all the channels from phy interface continuously

[J. C. Jones]

Hi,

I sorta-kinda asked this question before, but does anyone know of any 802.11
chips that have independent transmit/receiver paths? 

-Wabbit

-----Original Message-----
From: ath9k-devel-bounces@lists.ath9k.org
[mailto:ath9k-devel-bounces at lists.ath9k.org] On Behalf Of Adrian Chadd
Sent: Tuesday, May 22, 2012 2:00 AM
To: abhinav narain
Cc: ath9k-devel at lists.ath9k.org
Subject: Re: [ath9k-devel] scanning all the channels from phy interface
continuously

Hi,

You can't do that. You have to do a channel change into each channel and
then receive some frames. You can't operate in multiple simultaneous
channels on an Atheros NIC.

And yes, scanning will negatively impact performance.



adrian
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