Trouble shooting low rate MCS9 in 802.11ac

Vu Hai NGUYEN vh.nguyen at
Tue Aug 26 01:32:23 PDT 2014

>So probably the air condition you have forces the rate control to pick
>MCS7 as the most suitable rates.

>>>In open AP mode (bridge), CUS223 HW (not WLE900VX however) and on
>>>AP135 platform (customized openwrt SW + bleeding edge of
>>>ath10k/wireless subsystem souces - private backports tarball).. for
>>>UDP (last time I measured) I have around 820Mpbs for UCP both ways and
>>>720Mbps TCP.
>> This is in NSS3 -MCS9? Did you get better or worse rate if you clear the mask
>> (iw wlanX set bitrates) cause if I don't config rate, from AP to STA I have the best rate
>> (ie same as MCS7) but from STA to AP my rate is much lower than MCS7 (240 Mbps
>> vs 370 Mbps in TCP).

>Yes, NSS-3; Over the RF-cables I'm easily able to get MCS9 rates
>transmitions without any forced settings (the rate control is picking
>the highest rates).

Hi Bartosz,
I connect 2 antennas on my 2 devices together by a RF-cables with an attenuator around -60dBm, config 
each device to use one antenna and force rate to NSS1. But the TCP through put of MCS7 (230 Mbps) is 
always slightly higher than MCS8 (210Mbps) and 9 (190Mbps).
Can you give me some detail about your RF-cables test-bed? (for example which attenuator did you use?,etc...)
Thank you in advance.

Route de Mayres - B.P. 9

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