I have a Windows 10 PC, with an ASUS Wireless PCE-AC51 adapter.
Problem: The wifi connection is extremely slow and often breaks down entirely. When it breaks down, it doesn't lose radio contact with the router downstairs, but rather the Internet no longer gets through. With "slow" I mean about 15-20 Mbps (OOKLA Speedtest). My Internet Plan lists 300 Mbps.
Windows Network Diagnostics is usually able to fix the problem (which is: "the default gateway is not available"), but that last only a while. Then the problem starts again. Anyway, the speed remains always slow.
As said, the router is located one floor down in the building, but none of the other wifi-devices in the room (like my smartphone and tablet) has this problem. They all seem to enjoy the full 300 Mbps, without any interruptions. This leads me to conclude that the problem is located within the PC.
However, when I open the ASUS Wireless PCE-AC51 adapter in the Windows Device Manager, it says that "it works properly". I also made sure that the driver for the adapter is up-to-date. Windows is automatically updated.
I'm at a loss. Please advise.
21 Answer
I've got Windows 10 32bit with ASUS PCE-AC51, with a similar problem.
I managed to slightly improve the speed in this way:
I've inserted the network card better in the slot.
I've uninstalled every application and drivers related to the network card: "asus a51" "realtek" or similar,
I've manually installed the latest Windows 10 drivers via "Device Manager" (no Drivers setup.exe).
Nonetheless there's a lot of people in Internet with similar problems in Windows 10 and ASUS PCE-AC51, I advice you to try to install another network card. I eventually solved by changing my network card. See those links and the related comments:
