[Make-wifi-fast] AX latency testing

Bob McMahon bob.mcmahon at broadcom.com
Mon Dec 16 16:05:06 EST 2019

iperf 2.0.13 and iperf 2.0.14a <https://sourceforge.net/projects/iperf2/>
(currently in development) have support for end/end or write to read
latencies in both mean/min/max/stdev and histogram formats. It does require
realtime clock sync which can be done if a few ways.  There is also support
for clock_nanosleep() based burst scheduling.

We use programmable attenuators to affect the distances and programmable
phase shifter to affect the channel mixing or MIMO mixing.

Don't know if any of this helps or not.


On Mon, Dec 16, 2019 at 12:54 PM Tim Higgins <tim at smallnetbuilder.com>

> On 12/16/2019 12:59 PM, Toke Høiland-Jørgensen wrote:
> Tim Higgins <tim at smallnetbuilder.com> <tim at smallnetbuilder.com> writes:
> Hi all,
> Dave Täht suggested that I post the discussion we've started to this broader
> group.
> I've been spending the past few months trying to develop methods to verify one
> of the key promises of OFDMA; improved efficiency.
> The tests have mostly focused on trying to see improvement in total throughput
> using various traffic mixes using four OFDMA STAs.
> I've been using Samsung S10e's as STAs and primarily iperf3 TCP/IP and UDP
> traffic.  I did some work with the Intel AX200 as a STA using both Windows 10
> and Linux for RvR testing and found the Linux driver basically broken for
> uplink. (See the Win10/Linux comparison in the RAX40 section ofhttps://www.smallnetbuilder.com/wireless/wireless-reviews/33220-wi-fi-6-performance-roundup-five-routers-tested?start=1
> FWIW, Johannes was debugging some TCP issues on Intel 802.11ax the other
> day, and was getting ~1.4Gbps of throughput:https://lore.kernel.org/linux-wireless/90485ecbfa2a13c4438b840c8a9d37677e833ea5.camel@sipsolutions.net/T/
> So I guess maybe there are improvements coming in that space?
> TH: Yes, I'm monitoring that thread. I'm about to try a 5.2.14 kernel with
> this patch
> https://patchwork.kernel.org/patch/11253471/
> I think there are others in the works. Hope the end product will be
> available in a backport.
> So, for now, I'm limited to using the Samsung S10 as STAs.
> ANYWAY, I haven't been having much luck finding total throughput gains, so
> thought I'd bang my head against a different wall for awhile, which brings me
> to latency.
> My initial work was pretty simple, just running pings to four OFDMA STAs with
> OFDMA on/off on the AP, which showed no improvement. That's once I realized
> the large ping times and variation I was seeing initially was due to
> aggressive power-save kicking in on the STAs with no traffic running. So I
> also tried various TCP rates starting at 1 Mbps per STA to keep the STA awake.
> Coincidentally, Dave reached out the other day and suggested I look at the
> toolsets used for the make-wifi-fast project.
> I've spent a few hours looking at the flent and rrul sites and  I'm interested
> in exploring using the tools/techniques used for the make-wifi-fast work to
> date to see if AX adds anything to the latency improvement party.  If anyone
> is willing to provide some pointers on the proper use of the tools, I'd
> appreciate it.
> I think the Flent batch file used to run the tests are part of the data
> file at the bottom of this page:https://www.cs.kau.se/tohojo/airtime-fairness/
> TH: Thanks for the reference, I'll look into that
> The setup I was using had a server that ran the tests, which was one
> Ethernet hop from the AP. The clients were passive, run running
> 'netserver' so the server could run 'netperf' against each of them. This
> flips up/down in the tests but otherwise works fairly well. I used a
> separate (wired) control network for telling the clients to
> connect/disconnect...
> More details about the setup here:https://blog.tohojo.dk/2017/11/building-a-wireless-testbed-with-wires.html
> TH: Again, thanks.
> For example, I didn't see mention of the bitrates used for the traffic streams
> in the tests. Do I just tell each stream to run full blast (1 Gbps)?
> Well for TCP tests, yeah. The only UDP tests I did were flood tests,
> where I just had iperf blasting away at way above the link rate, then
> measured how many packets made it through.
> TH: Got it. Blast away on both TCP and UDP. Not sure how that will work
> with OFDMA trying to split that bandwidth into multiple RUs that have
> smaller bandwidth, but guess I'll find out.
> Also, since most implementations of (consumer at least) OFDMA require multiple
> STAs to trigger OFDMA frames, I could use some help understanding whether
> multiple streams should be applied per STA, or spread among the 4 STAs I'm
> using in my testing.
> Why not just try both and see what works? :)
> TH: Why didn't I think of that? :) OK.
> Also (2), has anyone used Android STAs for make-wifi-fast testing?
> Nope. But if you can get netperf cross-compiled it should be simple
> enough to run 'netserver' on them, I would think?
> TH: Unfortunately, that requires more skills than I have. Maybe someone
> else on this list has already done it?
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