Trouble shooting low rate MCS9 in 802.11ac

Bartosz Markowski bartosz.markowski at
Tue Aug 26 01:55:08 PDT 2014

On 26 August 2014 10:32, Vu Hai NGUYEN <vh.nguyen at> wrote:
>>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.

I have a custom made QCA programmable attenuator and besides this
nothing facy: 2.4GHz and 5GHz RF cables (Nm connectors, u.fl cables +
adaptors etc.)


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