Trouble shooting low rate MCS9 in 802.11ac

[Vu Hai NGUYEN]

Hi all,
I'm using ath10k with official firmware (10.1, 467-2-1), my module of wifi is Compex WLE900VX.
In theory MCS9 should give better rate than MCS 7.
But when running test with Iperf, I notice that if I force rate (using command "iw") to MCS9 or MCS8, 
the rate result from iperf are always lower than MCS 7 (even NSS1,2 or 3). 
Though I check RX rate report from "iw station dump" and it matches with the rate that I want to force.
You can see in the attached file a report of my test.
Any one has done the test and get better rate in MCS9 than in MCS7 with this wifi module ???

PS: The rate increases normally from MCS1 to MCS6.
Thanks,
NGUYEN Vu Hai
Acita-Sodielec
Route de Mayres - B.P. 9
12100 St GEORGES DE LUZENCON
FRANCE

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