VHT 160Mhz and nss related config.

[Sebastian Gottschall]

Am 11.02.2017 um 18:58 schrieb Ben Greear:
> On 02/10/2017 08:37 PM, Adrian Chadd wrote:
>> On 10 February 2017 at 20:22, Sebastian Gottschall
>> <s.gottschall at dd-wrt.com> wrote:
>>> i really can't believe this. if this is true the  160 mhz mode would 
>>> not
>>> make any sense.
>>> the maximum tx / rx rate for 4x4 vht80 and 2x2 vht160 is identical. so
>>> vht160 would not increase performance in any way
>>
>> Well, if it can also do 2x2 MU-MIMO at 160MHz then it can be a
>> perfectly fine STA to a 4x4 160MHz MU-MIMO chip that can actually
>> transmit 2x2 rates to different MU-MIMO peers.
>>
>> That's the outstanding question I have - is it like, 2x2 MU only, or
>> is it say, 2 concurrently different spatial stream 2x2 MU? Ie, can you
>> have 2 peers, different VHT spatial groups (or 4 peers, 1 spatial
>> group each) all going at the same time?
>>
>> I'm .. not even sure how you're supposed to cleanly negotiate that you
>> can do 4NSS in VHT80 but 2NSS in VHT160 to a peer... that only makes
>> sense if you're doing lots of 1NSS and 2NSS MU-MIMO peers..
>
> I think using the max-rx-rate logic might could imply this, but I am 
> not sure
> many drivers fill this out properly.
>
> Looks like a mess waiting to happen to me.
>
> Even if you can do 1x1 160Mhz MU-MIMO to two stations, and I am not 
> certain you
> can since in 80Mhz you can only do a 1x1 and a 2x2 (not two 2x2).
>
> So, from what I know currently, 80+80 is not that useful on the 9984 
> NIC...
never tried 80+80 since i need to enhance the channel logic alot in my 
firmware code to handle it. would be great enough if vht160 would work 
as expected and i'm not sure right now if it really works, even if the 
interface initialized correctly it assocs only with vht80
>
> Thanks,
> Ben
>
>>
>>
>> -adrian
>>
>>>
>>> Am 10.02.2017 um 23:58 schrieb Ben Greear:
>>>>
>>>> So, it appears that the ath10k QCA9984 4x4 160Mhz chip can do 4x4 
>>>> MIMO at
>>>> VHT80, but
>>>> it can do only 2x2 MIMO at VHT160/80+80.
>>>>
>>>> When configuring a peer, we need to tell the firmware the number of
>>>> spatial streams
>>>> of the peer at VHT160 and at VHT80 and lower.  They are not the same
>>>> value.
>>>>
>>>> I cannot think of any standard way to get this information based on 
>>>> VHT
>>>> capabilities
>>>> and such.  Currently, one could just assume VHT160 NSS is 1/2 of 
>>>> the VHT80
>>>> NSS,
>>>> but that is unlikely to be true for all vendors.
>>>>
>>>> Any ideas?
>>>>
>>>> Thanks,
>>>> Ben
>>>>
>>>
>>>
>>> -- 
>>> Mit freundlichen Grüssen / Regards
>>>
>>> Sebastian Gottschall / CTO
>>>
>>> NewMedia-NET GmbH - DD-WRT
>>> Firmensitz:  Berliner Ring 101, 64625 Bensheim
>>> Registergericht: Amtsgericht Darmstadt, HRB 25473
>>> Geschäftsführer: Peter Steinhäuser, Christian Scheele
>>> http://www.dd-wrt.com
>>> email: s.gottschall at dd-wrt.com
>>> Tel.: +496251-582650 / Fax: +496251-5826565
>>>
>>>
>>> _______________________________________________
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>>
>
>


-- 
Mit freundlichen Grüssen / Regards

Sebastian Gottschall / CTO

NewMedia-NET GmbH - DD-WRT
Firmensitz:  Berliner Ring 101, 64625 Bensheim
Registergericht: Amtsgericht Darmstadt, HRB 25473
Geschäftsführer: Peter Steinhäuser, Christian Scheele
http://www.dd-wrt.com
email: s.gottschall at dd-wrt.com
Tel.: +496251-582650 / Fax: +496251-5826565