Re: Using ath5k/ath9k radio for constant-tx noise source.

[Ben Greear <greearb@candelatech.com>]

On 10/22/2016 07:49 AM, Sebastian Gottschall wrote:
> atheros has a continues transmission mode which is used for power calibration in factory using the ART utility. its available on ath9k cards as well.
> once enabled no wifi connection is possible on the same frequency since it will break up all CSMA handling also with neighbor networks. its a nice
> feature for disconnecting all wifi networks in your area
> look for the called atheros / qca TESTMODE. its a simple register setting (enable, disable)

Hello,

I noticed recently that the carl9170 based system I was using can do a minimum
burst width of about 17us, which is not good enough for most RADAR emulation
settings (which often need 1us, 11us, etc).

So, I am back to thinking about trying this for ath9k, in hopes it can cycle
TX on/off faster.

So far, I have not found any useful info searching for TESTMODE in ath9k and madwifi code.

Do you have any more specific details about where I can find documents or source
code that uses the TX100 mode for ath9k?

Thanks,
Ben

>
> Am 15.09.2016 um 17:28 schrieb Zefir Kurtisi:
>> Hi Ben,
>>
>> On 09/15/2016 02:22 AM, Ben Greear wrote:
>>> On 08/20/2015 08:11 AM, Zefir Kurtisi wrote:
>>>> On 08/19/2015 09:07 PM, Ben Greear wrote:
>>>>> I have a commercial AP that is using a CM9 ath5k radio (evidently, I could be
>>>>> wrong)
>>>>> and it has the ability to do a constant transmit of raw noise (RF probe shows
>>>>> noise, but a monitor-port sniffer does not see any frames from the CM9).
>>>>>
>>>>> I don't know the low-level details of how it is doing this, but I suspect
>>>>> it is using something like madwifi for a driver.
>>>>>
>>>>> Does anyone know how this can be done with modern software and
>>>>> ath5k or ath9k NICs?
>>>>>
>>>>> Thanks,
>>>>> Ben
>>>>>
>>>> Maybe slightly related: some years ago when DFS became a topic and it was hard to
>>>> get hands on radar pattern generators, Christian Lamparter wrote a variant of the
>>>> carl9170 fw [1] which can generate radar pulses to test ath9k and other DFS radar
>>>> detectors. Pulses are generated by enabling txout at defined sampling intervals.
>>>>
>>>> It should be doable to mimic what you are looking for by generating a _very_ long
>>>> pulse.
>>> Sorry to revive such an old thread..but I'm back poking at this.
>>>
>> Whew, that year went by so incredibly fast ;)
>>
>>> I've used the modified carl9170 firmware to generate pulses, with
>>> the control being 'pulse-width' and 'pulse-interval'.
>>>
>>> This sort of works, and sometimes our ath10k in an isolation chamber reports
>>> a radar event.
>>>
>>> But, after some reading, I am thinking I need more control to better mimic
>>> a radar.
>>>
>>> If I understand things properly, I need something like this:
>>>
>>> A pulse event being:  pulse width, pulse period:  For instance 1us, 200us
>>> Then, I need to configure an amount of pulse events, maybe 10-30 consecutive pulse
>>> events.
>>> Then, I need a quiet period to mimic the radar sweeping full circle (15 seconds
>>> perhaps)
>>>
>>>  From what I can tell, the carl9170 modified firmware is missing the features
>>> to do this, though it should not be too difficult to add.
>>>
>> Yes, that's essentially it - the last step is even not needed if your goal is to
>> estimate DFS detection probabilities, since in the certification lab they usually
>> just repeatedly fire the radar pattern and count detection events.
>>
>> When I played with the modified carl9170 FW, I estimated that developing an solid
>> and reliable radar pattern pulse scheduler would take me 2-4 weeks, so being in a
>> hurry I ended up using an SDR (Ettus USRP N200, see [1]). I developed a pulse
>> scheduler to feed arbitrary patterns (covering those for DFS testing), which is
>> available in [2]. It has not been maintained ever since, but might help you as
>> starting point if you decide to go that route.
>>
>>> If someone has an idea whether the control above is appropriate, I'd
>>> appreciate feedback before I start hacking...
>>>
>>> This document seemed useful, for instance:
>>>
>>> https://dl.cdn-anritsu.com/en-en/test-measurement/files/Product-Introductions/Product-Introduction/mx370073a-el1200.pdf
>>>
>> We use the R&S SMBV100A [3], which we know is also used in some certification
>> labs. Unfortunately it is not exactly cheap - if you are not going to prepare your
>> product for certification, the SDR approach is affordable and good enough.
>>
>>> Thanks,
>>> Ben
>>>
>> Good luck,
>> Zefir
>>
>> [1] https://www.ettus.com/product/details/UN200-KIT
>> [2] https://github.com/zefir-kurtisi/USRP-Radar-Relay
>> [3]
>> https://www.rohde-schwarz.com/us/product/smbv100a-productstartpage_63493-10220.html
>>
>>
>
>


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com