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I'm performing some tests regarding 802.11e (WMM/WME) performance, and I'm getting some unwanted results.
Im using an Lynksys 1200ac with OpenWrt/LEDE installed as AP, and two PCs lets say PC1 and PC2, both PCs are using the same wireless card model.
The AP is operating 2.4Ghz band only in 802.11n mode.
In the next example I'm sending two similar streams (using iperf3 -u -b 0), the red one is a downlink stream (from AP to PC1) and the green one is an uplink stream (from PC2 to AP).
Red - Downlink stream (AP- PC1)| Green - Uplink stream (PC2->AP) Uplink vs Downlink Throughput test
From 15s to 45s Both streams are equal, from 50s to end the green(uplink stream) is marked as AC_VO.
I'm trying to find the reason why the downstream stream has so much more throughput than the uplink stream. Maybe the slottime is lower in AP thank in the clients? How can I check this?
Another question I have is regarding the capture that i made during this test,
As the AP is in 802.11n mode (where WMM support is mandatory) and WMM is enabled, it is supposedly using EDCA for channel access, but in the capture i have only a few RTS / CTS, and a lot of CF-End packets (shouldn't they only be sent when using PCF?)
Capture chunk showing an CF-end
The beacon frame from the AP showing the QOS control field: QOS control field
EDIT 1:
Red - Uplink stream (AP- PC2)| Green - Downlink stream (PC1->AP)
Paulo Ribeiro
Posted 2018-02-27T18:01:08.960
Reputation: 11
How did the average PHY rates for the two streams compare? I mean, if PC2 was farther from the AP than PC1, these results would be expected, because you’d expect PC2 to have to use a lower PHY rate. You haven’t given us enough information to rule that out. Also, was aggregation happening? – Spiff – 2018-02-27T20:33:45.667
I'm using 2 external usb wireless cards with a cable and they are side by side. The PC1 stream is being sent by other machine that is connected to the AP by Ethernet. Yes there is aggregation as you can see in the CF-end screenshot, aggregation is happening for the two streams, (there are Block Acks). – Paulo Ribeiro – 2018-02-28T01:49:55.900
What RSSI does PC1 see for the AP? What RSSI does the AP see for PC2? How fast does the uplink transfer go when the downlink transfer isn’t happening? When you say “side by side”, hopefully they are at least 2m apart. If not, move them 2m away from each other to they aren’t overloading each others’ front end and see if that makes a difference. – Spiff – 2018-02-28T02:20:02.977
When only uplink happening I get the whole bandwidth (same throughput as uplink +downlink ), I will post an image showing that. – Paulo Ribeiro – 2018-02-28T10:59:21.597
As you can see in the new plot I added between 40s and 50s there is only uplink stream and it is getting the whole bandwidth. – Paulo Ribeiro – 2018-02-28T12:19:31.983