rx rate issue

[Sebastian Gottschall]

Am 20.07.2016 um 13:03 schrieb Michal Kazior:
> On 20 July 2016 at 12:50, Sebastian Gottschall 
> <s.gottschall at dd-wrt.com> wrote:
>> Am 20.07.2016 um 12:23 schrieb Michal Kazior:
>>> On 20 July 2016 at 10:51, Sebastian Gottschall 
>>> <s.gottschall at dd-wrt.com>
>>> wrote:
>>>> Hello
>>>>
>>>> while hunting a link stability (packet transmission stop) issue i
>>>> discovered
>>>> a maybe cosmetic, but maybe als serious issue.
>>>> AP is a QCA9880 3x3 card configured as WDS AP
>>>> Station is a QCA9880 2x2 card configured as WDS STA
>>>>
>>>> the TX rate of the station matches to the rx rate of the AP.
>>>> but the RX rate of the station is wrong as it seems which may be a 
>>>> cause
>>>> of
>>>> the issue.
>>>> could this be a firmware bug on QCA9880?
>>>>
>>>> output of fw_stats
>>>>
>>>> WDS AP:
>>>>                Peer MAC address 40:a5:ef:85:4d:6f
>>>>                        Peer RSSI 12
>>>>                     Peer TX rate 175500
>>>>                     Peer RX rate 175500
>>>>                 Peer RX duration 0
>>>>
>>>>
>>>> WDS STA:
>>>>               Peer MAC address 40:a5:ef:51:49:db
>>>>                        Peer RSSI 13
>>>>                     Peer TX rate 175500
>>>>                     Peer RX rate 351000
>>>>                 Peer RX duration 0
> [...]
>>> Is this reproducible? Can you try setting a fixed tx bitrate (`iw
>>> wlanX set bitrates legacy-5 ht-mcs vht-mcs 1:4` to force vht mcs=4,
>>> nss=1) to see if it makes any difference? Perhaps rate-control and tx
>>> try-list/status are not parsed properly (for statistical purposes) in
>>> firmware which ends up with invalid peer-tx-rate on WDS AP.
>> lets try. can you correct the syntax? the following is not correct
>> iw dev ath1 set bitrates legacy-5 ht-mcs vht-mcs 1:4
>>
>> Usage:  iw [options] dev <devname> set bitrates [legacy-<2.4|5> 
>> <legacy rate
>> in Mbps>*] [ht-mcs-<2.4|5> <MCS index>*] [v
>> ht-mcs-<2.4|5> <NSS:MCSx,MCSy... | NSS:MCSx-MCSy>*] [sgi-2.4|lgi-2.4]
>> [sgi-5|lgi-5]
>>
>> Sets up the specified rate masks.
>> Not passing any arguments would clear the existing mask (if any).
> Ah, sorry, my bad.
>
>    iw dev ath1 set bitrates legacy-5 ht-mcs-5 vht-mcs-5 1:4
>
> (ht-mcs and vht-mcs were missing "-5" suffix)
>
> As a sidenote: The logic here is that you need to explicitly tell that
> you want empty set of legacy rates and empty set of HT rates and only
> a single VHT rate to be set (all explicitly for 5ghz band). This makes
> sure that FW rate control is ignored and a fixed rate is used for all
> data transmissions (and this should also build tx try-lists without
> any fancy retries/fallbacks to different rates).
after setting this setting on ap. i get the following results:

sta:
rx bitrate:     175.5 MBit/s VHT-MCS 4 80MHz VHT-NSS 1
                  Peer TX rate 234000
                   Peer RX rate 175500


AP:
         rx bitrate:     175.5 MBit/s VHT-MCS 4 80MHz VHT-NSS 1
                   Peer TX rate 263300
                   Peer RX rate 175500

this looks even more curious
>
> Michał
>


-- 
Mit freundlichen Grüssen / Regards

Sebastian Gottschall / CTO

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