Higher latency on upload under poor signal conditions

[Michael Yartys]

Hi

I decided to run some 8-stream TCP tests at the edge of the range of my WiFi network, and I noticed that I get higher latency when I run an upload compared to a download. The latency when downloading is pretty steady at right above 30 ms, and when I run the upload it hovers around 80-100 ms. I think I know why this happens, but I would like to read the opinion of the mailing list.

My test setup is a NETGEAR R7800 running OpenWrt with fq_codel'd WiFi and a laptop with an Intel 7260 ac wireless card. The laptop reports an average signal strength of about -77 dBm, while the router has a much harder time hearing the laptop at -98 dBm signal strength with a noise floor of -109 dBm.

I suspect this extra latency is due to buffering because the laptop has to retransmit a lot of frames due to how poorly the router hears it. Is this correct?

The associated flent files are attached.

Michael
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