Trouble shooting low rate MCS9 in 802.11ac

[Michal Kazior]

On 17 July 2014 12:40, Vu Hai NGUYEN <vh.nguyen at actiasodielec.fr> wrote:
> Hi all,

Hi,


> 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 ???

The higher the MCS rate the more symbols are packed up per baud which
means it is more susceptible to interference and corruption.

You probably don't have an environment clean enough to pull off MCS8
and MCS9 and you end up with a lot of retransmissions.

If you're sure you have a clean environment then try putting your
devices (or them antenna) at different angles against each other and
different distances.


Michał