rx rate issue

Michal Kazior michal.kazior at tieto.com
Wed Jul 20 03:23:13 PDT 2016

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
>              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.

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).

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.


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