Hi Ben,
I enjoyed watching your graph already a few times now ;-)
I have a few questions related to your experiment:
-about the setup, the cards have 3x3 MIMO so the attenuator has probably
also three channels which are attenuated in parallel?
-based on the datasheet of the QCA9880 VHT80_MCS9 reception should break
around -68dBm. On your graph it breaks around -52dBm, which is not
within the described tolerances. Do you have any idea what could be
causing this? Is the noise level higher than expected? Or did I made the
wrong conclusions? I will try to verify on our setup.
-my million dollar question to you is related to the approx. 810Mbps UDP
goodput :-) I already did some experiments over 3 coax cables, I noticed
the same UDP goodput as over the air, which is around 640Mbps. Watching
the sniffer I've noticed MCS=9, Data rate=1299.9 Mbps and block ACKs
every (in avg.) 10 frames. So what is the key to the higher goodput?
-related to the hot signal, without having proof I've noticed that it
is easier to have higher goodputs with a low tx-power set, like 1 dBm.
But probably more related to our setup... Which tx-power did you use
during your experiments? Would you be able to get the same results
(point break around -52dBm) with another tx-power set?
Thanks,
Bart
On 07/26/2014 01:15 AM, Ben Greear wrote:
Some time back, I ran some tests, and someone (sorry, can't remember or find
the email)
suggested my signal might be too hot. I was using a 30 db fixed attenuator
inline with the SMA
cables.
I set up a test today with E5 processor system as station, and a fast i7
processor
system as AP, with the two systems cabled through our variable attenuator.
Open authentication,
channel 149, other wifi equipment in area on 5ghz was (mostly) idle or powered
down.
Kernel is 3.14.13+, latest ath10k CT (10.1.467 based) firmware on both systems
(though I don't think that matters much for throughput tests). 10 virtual
stations
configured on station machine, but only one was actively doing traffic.
Here is a udp download v/s rx-signal graph as the attenuator is stepped from 0
to 95.5
db attenuation in .5 db steps.
http://www.candelatech.com/pdfs/ath10k_atten_vs_throughput.pdf
The rx-signal axis is the left hand side. The green graph is the station's (ie
netdev)
rx bps, the black is UDP goodput.
It seems ath10k (WLE900VX) has no real trouble with hot signals, and runs best
between
-15 and -52 rx signal level (as reported by the station device).
Our systems are not perfectly isolated, so the maximum attenuation is around
-85.
Enjoy,
Ben
--
Bart Jooris
Department of Information Technology
Internet Based Communication Networks and Services (IBCN)
Ghent University - iMinds
Gaston Crommenlaan 8 (Bus 201), B-9050 Gent, Belgium
E-mail: [email protected]
M: +32 474 59 53 42
Tel. +32 9 33 14900
Fax +32 9 33 14899
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