[ath9k-devel] Question about Atheros AR9220

[ath9k-devel] Question about Atheros AR9220

[Mohammed Shafi Shajakhan]

Hi Wei Zhang,

i don't know, will ask some one internally who knows about it.
Cced ath9k-devel list.


On Saturday 03 March 2012 01:27 AM, Wei Zhang wrote:
> Hello, Mr. Mohammed,
>
>
>
> My name is Wei Zhang, I am a graduate student of Texas A&M University.
>
> Recently I'm working with MikroTik 433UAH router, which use a ath9k based NIC(Actually Atheros AR9220).
>
> As I know, some 802.11 NIC support 802.11-based modulation only, i.e. they can only sense 802.11 signal. However my project requires that the WiFi NIC could feel other 2.4G signals, like bluetooth or 802.15.4, as long as their signals are above the threshold. So I am wondering that if the hardware or even ath9k driver support the energy based modulation.
>
> Thank you.
>
>
>
> Best regards,
>
> Wei Zhang.
>
>
>
>


-- 
thanks,
shafi

[ath9k-devel] Question about Atheros AR9220

[Daniel Halperin]

Hi Wei,

You might try emailing Shravan Rayanchu and folks at Univ. Wisconsin. They
did something like this using AR9280 chips.

See the Airshark paper: http://pages.cs.wisc.edu/~suman/pubs/airshark.pdf

Dan

On Sun, Mar 4, 2012 at 9:03 PM, Mohammed Shafi Shajakhan <
mohammed@qca.qualcomm.com> wrote:

> Hi Wei Zhang,
>
> i don't know, will ask some one internally who knows about it.
> Cced ath9k-devel list.
>
>
> On Saturday 03 March 2012 01:27 AM, Wei Zhang wrote:
> > Hello, Mr. Mohammed,
> >
> >
> >
> > My name is Wei Zhang, I am a graduate student of Texas A&M University.
> >
> > Recently I'm working with MikroTik 433UAH router, which use a ath9k
> based NIC(Actually Atheros AR9220).
> >
> > As I know, some 802.11 NIC support 802.11-based modulation only, i.e.
> they can only sense 802.11 signal. However my project requires that the
> WiFi NIC could feel other 2.4G signals, like bluetooth or 802.15.4, as long
> as their signals are above the threshold. So I am wondering that if the
> hardware or even ath9k driver support the energy based modulation.
> >
> > Thank you.
> >
> >
> >
> > Best regards,
> >
> > Wei Zhang.
> >
> >
> >
> >
>
>
> --
> thanks,
> shafi
> _______________________________________________
> ath9k-devel mailing list
> ath9k-devel at lists.ath9k.org
> https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.ath9k.org/pipermail/ath9k-devel/attachments/20120304/87f1110e/attachment.htm 

[ath9k-devel] Question about Atheros AR9220

[Adrian Chadd]

Hi,

The hardware will detect a signal above that modulation level. What do
you need to do once it's detected that signal?


Adrian


On 4 March 2012 21:03, Mohammed Shafi Shajakhan
<mohammed@qca.qualcomm.com> wrote:
> Hi Wei Zhang,
>
> i don't know, will ask some one internally who knows about it.
> Cced ath9k-devel list.
>
>
> On Saturday 03 March 2012 01:27 AM, Wei Zhang wrote:
>> Hello, Mr. Mohammed,
>>
>>
>>
>> My name is Wei Zhang, I am a graduate student of Texas A&M University.
>>
>> Recently I'm working with MikroTik 433UAH router, which use a ath9k based NIC(Actually Atheros AR9220).
>>
>> As I know, some 802.11 NIC support 802.11-based modulation only, i.e. they can only sense 802.11 signal. However my project requires that the WiFi NIC could feel other 2.4G signals, like bluetooth or 802.15.4, as long as their signals are above the threshold. So I am wondering that if the hardware or even ath9k driver support the energy based modulation.
>>
>> Thank you.
>>
>>
>>
>> Best regards,
>>
>> Wei Zhang.
>>
>>
>>
>>
>
>
> --
> thanks,
> shafi
> _______________________________________________
> ath9k-devel mailing list
> ath9k-devel at lists.ath9k.org
> https://lists.ath9k.org/mailman/listinfo/ath9k-devel

[ath9k-devel] Question about Atheros AR9220

[Wei Zhang]

Thank you very much for the response.
Do you mean that the hardware can also detect other signal, even it's 
not a valid 802.11 one, say 802.15.4 if they are working in exactly the 
same channel(eg. 802.11 ch 11, 802.15.4 ch 23)?
I am just wondering if a WiFi hardware would do backoff when other 
non-802.11 signal with same frequency exsist.

Best regards,
Wei Zhang.

On 3/5/2012 1:11 AM, Adrian Chadd wrote:
> Hi,
>
> The hardware will detect a signal above that modulation level. What do
> you need to do once it's detected that signal?
>
>
> Adrian
>
>
> On 4 March 2012 21:03, Mohammed Shafi Shajakhan
> <mohammed@qca.qualcomm.com>  wrote:
>> Hi Wei Zhang,
>>
>> i don't know, will ask some one internally who knows about it.
>> Cced ath9k-devel list.
>>
>>
>> On Saturday 03 March 2012 01:27 AM, Wei Zhang wrote:
>>> Hello, Mr. Mohammed,
>>>
>>>
>>>
>>> My name is Wei Zhang, I am a graduate student of Texas A&M University.
>>>
>>> Recently I'm working with MikroTik 433UAH router, which use a ath9k based NIC(Actually Atheros AR9220).
>>>
>>> As I know, some 802.11 NIC support 802.11-based modulation only, i.e. they can only sense 802.11 signal. However my project requires that the WiFi NIC could feel other 2.4G signals, like bluetooth or 802.15.4, as long as their signals are above the threshold. So I am wondering that if the hardware or even ath9k driver support the energy based modulation.
>>>
>>> Thank you.
>>>
>>>
>>>
>>> Best regards,
>>>
>>> Wei Zhang.
>>>
>>>
>>>
>>>
>>
>> --
>> thanks,
>> shafi
>> _______________________________________________
>> ath9k-devel mailing list
>> ath9k-devel at lists.ath9k.org
>> https://lists.ath9k.org/mailman/listinfo/ath9k-devel

[ath9k-devel] Question about Atheros AR9220

[Adrian Chadd]

On 5 March 2012 09:40, Wei Zhang <charleyhuman@tamu.edu> wrote:
> Thank you very much for the response.
> Do you mean that the hardware can also detect other signal, even it's not a
> valid 802.11 one, say 802.15.4 if they are working in exactly the same
> channel(eg. 802.11 ch 11, 802.15.4 ch 23)?
> I am just wondering if a WiFi hardware would do backoff when other
> non-802.11 signal with same frequency exsist.

Hi,

I believe this is exactly what the specification says. There's a clear
channel access (CCA) threshold where the hardware won't consider the
medium "available" for transmitting on.

HTH,


Adrian

[ath9k-devel] Question about Atheros AR9220

[Daniel Halperin]

On Mon, Mar 5, 2012 at 11:12 AM, Adrian Chadd <adrian@freebsd.org> wrote:

> On 5 March 2012 09:40, Wei Zhang <charleyhuman@tamu.edu> wrote:
> > Thank you very much for the response.
> > Do you mean that the hardware can also detect other signal, even it's
> not a
> > valid 802.11 one, say 802.15.4 if they are working in exactly the same
> > channel(eg. 802.11 ch 11, 802.15.4 ch 23)?
> > I am just wondering if a WiFi hardware would do backoff when other
> > non-802.11 signal with same frequency exsist.
>
> Hi,
>
> I believe this is exactly what the specification says. There's a clear
> channel access (CCA) threshold where the hardware won't consider the
> medium "available" for transmitting on.
>
>
Not quite: There are many CCA modes in 802.11-2007,

The 802.11 ones: (15.4.8.4).

Mode 1: Energy detect above threshold. (Any energy will do)
Mode 2: Carrier detect. (Must have DSSS preamble)
Mode 3: Carrier detect and energy detect above threshold. (Must have DSSS
preamble)

Added in 802.11b (18.4.8.4):

Mode 4: Carrier detect with timer: (similar to mode 2 but for 802.11b
preambles)
Mode 5: Carrier detect and energy detect above threshold (similar to more 3
but for 802.11b preambles)

Finally, for 802.11g (19.3.5), the *only* mode used is:

Carrier detect and energy detect above threshold. This is similar to Mode 3
above, but for 802.11g.

So the standard says you have to see an 802.11-like signal; in practice
this is used. But there maybe a way to get the cards to do mode 1 instead.

Dan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.ath9k.org/pipermail/ath9k-devel/attachments/20120305/76628fb8/attachment.htm 

[ath9k-devel] Question about Atheros AR9220

[Adrian Chadd]

Hi,

You're likely much more versed in the nuances of the specification than I am. :)

My understanding of the AR_PHY_CCA_THRESH62 field is that it indeed is
the value that defines the -62 dBm CCA threshold, likely used for what
is termed "mode 1".

The other detection modes are likely engaged when the RX hardware has
successfully detected a preamble or started decoding a frame - it then
treats the medium as unavailable (as it's receiving.) This can be at a
_much lower_ power level.


Adrian

[ath9k-devel] Question about Atheros AR9220

[gtolon at inti.gob.ar]

Hi,

I'm also interested in this topic because i've been doing tests with 
interference with TP-Link (AR9285 chip), and i still don't understand 
completely what happens.

Using g mode, i ran iperf between two routers in channel 11. Then i used 
another router in channel 10, also running iperf with a PC. I used 
tcpdump to get the packets between routers in channel 11, and i can see 
that when the transmission in channel 10 is on, the data rate drops. I 
see a considerable amount of retransmitted packets, but that doesn't 
explain all the loss of performance with respect to the transmission 
without interference. I don't know if some packets are trasmitted but i 
can't see them because they are corrupted at the phy layer, or if 
they're not being transmitted because of CCA.

If ath9k implements a noise CCA, do you know how to be sure if it's 
being used. I've looked at iw survey dump, in channel busy time, but 
looking into the code it seems that it just reads a register value from 
the chip to get the number of busy cycles, so i don't know how it's 
determined.

Also, i 've done some tests with noise from a signal generator, in the 
same channel that the transmission between routers, and i observed that 
the transmission completely cuts with a calculated noise level of just 
-85 dbm (occupying the whole 20 MHz bandwith, FM modulation). I would 
expect a greater noise signal to prevent the routers to transmitt if it 
was due to CCA, or a condition where the transmission dropped little by 
little if it was due to transmitted packets damaged by the noise.

I've been doing these tests because sometimes i experience throughput 
drops and i would like to understand better the reasons behind, if it's 
because of wiphy signals in the some channel, in other channels, or just 
non wiphy noise signals. Thank you!

Gabriel



El 05/03/2012 04:55 p.m., Adrian Chadd escribi?:
> Hi,
>
> You're likely much more versed in the nuances of the specification than I am. :)
>
> My understanding of the AR_PHY_CCA_THRESH62 field is that it indeed is
> the value that defines the -62 dBm CCA threshold, likely used for what
> is termed "mode 1".
>
> The other detection modes are likely engaged when the RX hardware has
> successfully detected a preamble or started decoding a frame - it then
> treats the medium as unavailable (as it's receiving.) This can be at a
> _much lower_ power level.
>
>
> Adrian
> _______________________________________________
> ath9k-devel mailing list
> ath9k-devel at lists.ath9k.org
> https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>

[ath9k-devel] Question about Atheros AR9220

[Adrian Chadd]

Hi,

It's likely a mixture of both.

* The channel survey gives you an idea of what percentage of time the
NIC thinks the air is busy (RCCNT). RXCNT is the time spent _RX_ing
frames, even if they (a) fail FCS/CRC, or (b) aren't destined for it.
It's still decoding them. So, you can calculate a rough estimation of
the time spent doing "other" by taking RCCNT and subtracting RXCNT.
* You should see FCS/CRC errors pop up in RX frames. There's bits in
the RX descriptor that get set. There should be CRC error statistics
kept by the driver somewhere accessible by debugfs.


Adrian

[ath9k-devel] Question about Atheros AR9220

[gtolon at inti.gob.ar]

Thank you for the answer Adrian, i'll try with that. By the way, i've 
found in the code a register called RFCNT, i guess it's the RXCNT you 
mentioned.

Gabriel


El 20/03/2012 12:30 a.m., Adrian Chadd escribi?:
> Hi,
>
> It's likely a mixture of both.
>
> * The channel survey gives you an idea of what percentage of time the
> NIC thinks the air is busy (RCCNT). RXCNT is the time spent _RX_ing
> frames, even if they (a) fail FCS/CRC, or (b) aren't destined for it.
> It's still decoding them. So, you can calculate a rough estimation of
> the time spent doing "other" by taking RCCNT and subtracting RXCNT.
> * You should see FCS/CRC errors pop up in RX frames. There's bits in
> the RX descriptor that get set. There should be CRC error statistics
> kept by the driver somewhere accessible by debugfs.
>
>
> Adrian
>

[ath9k-devel] Question about Atheros AR9220

[manan]

 <gtolon <at> inti.gob.ar> writes:

> 
> Thank you for the answer Adrian, i'll try with that. By the way, i've 
> found in the code a register called RFCNT, i guess it's the RXCNT you 
> mentioned.
> 
> Gabriel
> 
> El 20/03/2012 12:30 a.m., Adrian Chadd escribi?:
> > Hi,
> >
> > It's likely a mixture of both.
> >
> > * The channel survey gives you an idea of what percentage of time the
> > NIC thinks the air is busy (RCCNT). RXCNT is the time spent _RX_ing
> > frames, even if they (a) fail FCS/CRC, or (b) aren't destined for it.
> > It's still decoding them. So, you can calculate a rough estimation of
> > the time spent doing "other" by taking RCCNT and subtracting RXCNT.
> > * You should see FCS/CRC errors pop up in RX frames. There's bits in
> > the RX descriptor that get set. There should be CRC error statistics
> > kept by the driver somewhere accessible by debugfs.
> >
> >
> > Adrian
> >
> 


Hi 

I want to know how we can change CCA mode in Atheros chipset and what is
default CCA mode in AR9220.
As I tested with different CCA threshold value but after making High CCA
threshold it is receiving all packets with lower rssi also, is this in CCA
mode 2 as Dan mentioned?

How to get CCA mode the atheros chip is using?


Thanks
manan