windows 10 1607 ~ 1909
wireless driver 18.40.x ~ 126.96.36.199 (the latest)
It happens with all microsoft, oem provided and intel official drivers.
router : asus rt-ac86u, all firmware versions.
There are two symptoms.
First, when the laptop is connected to the router 5Ghz wifi that has no clients for a long time, it is connected at 866/433Mbps.
Second, if the laptop is left idle for tens of minutes or hours, the wifi download speed drops to a low speed.
There are two symptoms as above, and I solved them by changing the MIMO Power Save Mode to Static SMPS mode in the wireless driver settings.
The weird thing is that the setup works differently than intel's description of smps settings.
Problems occur in all of Auto SMPS, Dynamic SMPS, and No SMPS, and there is no problem only in Static SMPS.
I was able to find a related article on this static smps in hp korea, reddit and microsoft community.
I can't find a lot of related reports, but there seems to be a serious problem with the SMPS settings of the Intel driver.
I would appreciate it if you check.
I thought it was fixed because the problem didn't recur for 2 days.
However, the slowdown just happened again.
I am suffering from this problem.
Reconnecting the wireless connection temporarily fixes it, but I hope Intel releases a driver that fixes the problem.
Edit:I am using 500Mbps/500Mbps service. And I usually get 400+mbps/400+mbps speed test results.
In the above speedtest result, even though the upload is a 866Mbps link, only 200Mbps appears, so it seems that only one antenna is used for upload.
So, I guess that one of the two antennas goes to deepsleep mode and the other one is operating in low power receive and full power transmit mode due to some powersave setup problem.