rx rate issue

Sebastian Gottschall s.gottschall at dd-wrt.com
Wed Jul 20 03:50:50 PDT 2016

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
>>              Peer MAC address 40:a5:ef:51:49:db
>>                       Peer RSSI 13
>>                    Peer TX rate 175500
>>                    Peer RX rate 351000
>>                Peer RX duration 0
> Hmm.. Interesting. FWIW these are "last tx/rx rate". This isn't
> average nor anything fancy like that.
this is in sync yes. its also not that i just observed it for a second. 
this test installation is running here for a while
and while looking for the cause i observed this behavior.

> Can you compare that to `iw wlanX station dump`, please? It should
> report last rx bitrate at least (tx bitrate is broken so don't rely on
> that). The 175.5 and 351 seem to be both vht mcs index=4 but with
> differet nss values (1 or 2 spatial streams).
iw station dump shows the same rate

peer rx rate and iw dump is identical
Peer RX rate 526500
rx bitrate:     526.6 MBit/s VHT-MCS 6 80MHz VHT-NSS 2

Peer TX rate 234000

interesting here is that the TX rate on STA side matches to the RX rate 
on AP side, but not vice versa

> I do wonder at what rate frames are actually transmitted OTA.
> 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] 

Sets up the specified rate masks.
Not passing any arguments would clear the existing mask (if any).

> Michał

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
email: s.gottschall at dd-wrt.com
Tel.: +496251-582650 / Fax: +496251-5826565

More information about the ath10k mailing list