[Rick Murphy]

On Nov 16, 2015, at 4:08 AM, Peter Mackenzie wrote:

Hi All,

Sorry for how long it has taken me to share my test results with you, I have been crazy busy here.

Please find attached a very quick write up of my first controlled test. Although I have written a short conclusion section. I’m trying to not draw to many conclusion at this stage and would like to do some more tests.

Thanks
Peter

[Rick Murphy]

On Oct 24, 2015, at 8:12 AM, Chuck Lukaszewski [mailto:clukaszewski@arubanetworks.com] wrote:

Rick,

Had a really long week here, will reply more tomorrow.

Very nice test design and results. Appreciate you checking out my claim here.

-cl

[Rick Murphy]

On Oct 23, 2015, at 11:23 AM, Devin Akin [mailto:Devin.Akin@DivDyn.net] wrote:

Rick,

You need to practice being more thorough. 😀 hehe.

Nice work on this! I agree that this test supports Chuck’s assertion.

Thanks a ton for the effort!

Devin

[Rick Murphy]

On Oct 22, 2015, at 1:14 PM, Rick wrote:

Attached find my preliminary test results using a platform similar to what Chuck described in his first message. Please, share your comments and let me know if you spot any flaws or inaccuracies in my procedure. I want to run another set of tests (different location, different vendor equipment, different band, and lower RSSI) before committing one way or the other on this.

I would like to know if anyone else has achieved similar results.

Rick

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[Rick Murphy]

On Oct 1, 2015, at 6:32 PM, Devin Akin [mailto:Devin.Akin@DivDyn.net] wrote:

I’m definitely on board with this now…and it makes me want to cry a little. 🙁 Let’s hope that 802.11ax includes some fun new parts and pieces to improve this situation.

A huge thanks to Chuck for such thorough and helpful work!

#GoTwitter!

Devin

[Rick Murphy]

On Oct 1, 2015, at 8:40 PM, Peter Mackenzie [mailto:pmackenzie@marquest.com]wrote:

Hi Chuck,

Thanks for your response. I’m not sure I explained myself very well, I agree with you CCA is set to busy as a direct result of sensing a valid carrier.

My point was, if you force RXS -82dBm then my understanding is you would not leave the first (idle) state of the RX state machine. I agree once the RX state machine has stated there is no way off unless an error occurs.

From all the evidence it looks like you are right on this one, I just wanted to keep the alternative argument there until we test. Also I like playing “Devils advocate” a bit.

Thanks
Peter

Sent from my iPhone

[Rick Murphy]

On Oct 1, 2015, at 11:10 PM, Chuck Lukaszewski [mailto:clukaszewski@arubanetworks.com]wrote:

No, you have it backwards. CCA is set to busy as a direct result of sensing a valid carrier signal, not the other way around. “Carrier signal” means that valid L-STF / L-LTF training fields (TFs) immediately prior to the L-SIG are detected. This happens at the hardware RX sensitivity (RXS) level. These are shown in red boxes below.

Once the TFs are detected successfully, then CCA is asserted. This occurs immediately before the L-SIG is decoded (orange box).

My understanding is that the RX state machine really begins when the first L-STF is detected (really there is no other way it can work).

The Perahia and Stacey book on 11ac is the definitive work on the subject, if you have not read it buy a copy today. Every CWNE should be thoroughly familiar with it.

The only way not to enter the state machine is to administratively set the RXS level to a higher value than the hardware supports, such that the TFs are never heard. Once the TFs are in, the radio has already set its AGC, timing and done channel estimation for phase correction. In other words, the roller coaster has left the platform and you can’t get off unless there’s an accident.

For example you could force RXS to -82 dBm which would override the hardware value for any data rates that could otherwise be decoded below. This would force the HW to behave in the way Devin was arguing it should.

Here is an example of a typical RXS table for one of our currently shipping APs. Note these values are per chain. We will successfully decode legacy OFDM 6 Mbps rate at -93 dBm!!!

[Rick Murphy]

On Oct 1, 2015, at 8:44 PM, Peter Mackenzie [mailto:pmackenzie@marquest.com] wrote:

Unless you never enter the RX state machine. The trigger which kick starts the RX state machine is CCA=busy. So if CCA remains idle because the receive level is less then -82dBm, my question is can you continue to, or have you already, receive(d) enough to report stats e.g. receive signal level.

I have not had any time yet to research if the premise above carries any wait, I just wanted to throw it into the mix.

Thanks
Peter

Sent from my iPhone

[Rick Murphy]

On 1 Oct 2015, at 05:52, Rick Murphy wrote:

I keep returning to paragraph 1 on slide 3. That seems to verify Chuck’s premise. Also, I have not found any exceptions to Chuck’s claim that there is no way to exit the RX state machine based on CCA once a valid preamble has begun decoding. I will attempt to test this in the next couple of weeks in our lab.

Rick

[Rick Murphy]

On Sep 30, 2015, at 11:08 PM, Devin Akin wrote:

See attached. This is a GREAT read about this topic.

Devin

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[Rick Murphy]

On Sep 29, 2015, at 9:24 AM, Devin Akin wrote:
Looking up who Ron Porat and Jianhan Lin are, and the fact that they are requesting the -82dBm (@20MHz) limit tells me that it’s likely that the -82dBm limit isn’t already in place. 🙁

Devin

[Rick Murphy]

On Sep 28, 2015, at 10:25 PM, Devin Akin wrote:

Hi Chuck,

I read this, and I believe you’re right on how to test it. We’ll test this as soon as possible, and update each other via this email thread.

I really appreciate you articulating this so well. I didn’t know that it had been motioned (#34) to clarify what happens below -82dBm. That seems like good news if it’s adopted….or at least I hope so.

The state machine was way over my barely-adequate head, so I’ll have to take your word for that part. 🙂

Devin

[Rick Murphy]

On Sep 28, 2015, at 11:30 AM, Rick Murphy wrote:

Chuck,

You’ve made a very good case for this but I will dig a little deeper before adding my comments. Thanks for including me.

Rick Murphy

On Sep 28, 2015, at 10:47 AM, Chuck Lukaszewski wrote:

…adding Coleman to the thread…

[Rick Murphy]

On Sep 27, 2015, at 11:56 PM, Peter Mackenzie [mailto:pmackenzie@marquest.com] wrote:

Thank you for starting this thread Chuck. I won’t be back in the office for two weeks, but I hope to start some testing when I’m back. I will share progress and results when I have something.

Thanks
Peter Mackenzie

Sent from my iPhone

[Rick Murphy]

On Sep 27, 2015, at 11:36 PM, Ronald van Kleunen ronald@globeron.com> wrote:

Hi Chuck,

Thank you to put this together offline first. I have sent COD a linkedin msg. I believe the @cwne.com domain does not exist anymore (?)
(I remember something reading about this). I am back online on Tue. (boarding flight now).

Ronald van Kleunen

[Author]

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