Hi Tim,

I know this will probably be in your write-up, but I am curious if you are sniffing the traffic to verify that OFDMA is actually happening by pinning the aid to the monitor interface and using a wireshark display filter radiotap.he.data_1.ppdu_format==0x2 to see the HE_MU frames. From my testing it is not something that is automatically in use all the time...it is used as needed per each AP's decision algorithm. I seem to be able to cause OFDMA to happen sometimes when using small payloads with bursty traffic and periods of quiet, but it is not something that I can turn on and just say OFDMA is happening.

Also, in my flent tcp_download vs tcp_upload tests I see similar latency values that are both relatively low. I will have to run the rtt_fair_var to see how it compares.

Nice use of flent! Looking forward to your write-up.

Isaac

On Wed, Apr 29, 2020 at 2:40 PM Tim Higgins <tim@smallnetbuilder.com> wrote:

Hi all,

I finally have my testbed working the way I want and am starting to run tests to see if OFDMA does anything useful.

This will all be covered in detail in an upcoming SmallNetBuilder article. But I wanted to sanity check something with this esteemed group.

The tests are basically the flent rtt_fair_var up and down tests ported to the octoScope platform I use for WiFi testing.
The initial work was done on flent, with a lot of hand-holding from Toke. (Thank you, Toke!)

Using 4 Intel AX200 STAs on Win10. iperf3 is running traffic using TCP/IP with unthrottled bandwidth. I've taken Bjørn's idea and have each STA using a different DSCP priority level, but with TCP/IP traffic, not UDP. I'm sticking to using CS0-7 equivalents and confirmed that the iperf3 --dscp values properly translate to the intended WiFi priority levels. Each STA has a different priority, either CS0,3,5 or 6 (best effort, excellent effort, video and voice).

Ping is used to measure latency and always runs from AP to STA. Only TCP/IP traffic direction is reversed between the down and uplink tests.

One thing that jumps out immediately is that uplink latencies are *much* lower than downlink, with either OFDMA on or off. Attached are three examples. The CDFs are average latency of the 4 STAs.

The NETGEAR R7800 is a 4x4 AC Qualcomm-based. I'm using this as a baseline product.

The NETGEAR RAX15 is 2x2 AX Broadcom-based. You can see what I mean when I say OFDMA doesn't help.

Does this much difference between up and downlink latency pass the sniff test?

===
Tim

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