VHT 160Mhz and nss related config.

[Sebastian Gottschall]

Am 11.02.2017 um 20:38 schrieb Ben Greear:
> On 02/11/2017 10:21 AM, Sebastian Gottschall wrote:
>> 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
>
> 160Mhz is really implemented as 80+80 internally it seems, so what I 
> meant is that
> 160Mhz or 80+80 both have the 2x2 restriction.
since i have a older fw source. can you give me a hint where you found a 
indication that its just 2x2?
>
> Stock ath10k driver doesn't set the rxnss_override, so the chip will 
> always be forced
> to send 1x1 at 160Mhz, so even if it associates and works at all, it 
> will probably not put
> many 160Mhz frames on air since the rate-ctrl should choose 3x3 or 4x4 
> 80Mhz as faster speeds.
sounds logic
>
> Thanks,
> Ben
>
>


-- 
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Sebastian Gottschall / CTO

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