Why is my wireless LAN suddenly transferring files so slowly?

[Papageno]

I can't figure it out. It used to transfer files at about 27 megabytes per second and now I'm lucky if I get 7. Nothing has changed that I can tell, apart from the fact that I updated the hosting PC's UEFI BIOS, and maybe installed a couple of Windows 11 updates. The receiving computer is running Windows 10 with the extended security updates till October sometime. The sending computer is plugged into the wireless AC router, and the receiving one has a USB-plugged in wifi (N) adapter.

Sometimes the transfer will just crap out with an unspecified network error--not too helpful. Anything I should check in the UEFI BIOS of the newer machine maybe? Or the network control panels on both computers?

 

[continuum]

Have your link rates changed at all?

 

[Papageno]

Have your link rates changed at all?

Thanks for the reply, but I'm not certain what that term means. Where in Windows 10 Pro (receiving PC) and Win 11 Home (sending one) would I check that? I haven't consciously done anything to either PC apart from install OS updates and on the sending one, the UEFI BIOS.

If the link below describes how I should check this on both machines, I will do that and report back. I know that nothing has changed in terms of hardware. All I can think is that somehow the wireless spectrum nearby is a lot more crowded/noisy suddenly.

https://www.tp-link.com/us/support/faq/2265/

 

[Kyuu]

If the link below describes how I should check this on both machines, I will do that and report back. I know that nothing has changed in terms of hardware. All I can think is that somehow the wireless spectrum nearby is a lot more crowded/noisy suddenly.

https://www.tp-link.com/us/support/faq/2265/

Yes that would be the link speed (PHY rate).

https://kb.netgear.com/19668/WiFi-Link-Rate-and-Transfer-Speed

 

[Papageno]

The wireless adapter on the receiving machine says it's 144.4 Mbps. This strikes me as low. Maybe it needs a new driver or something, because the specs say it should support up to 867 Mbps on the 5 GHz band.

 

[continuum]

Won't be the same, but what does an external speedtest ( www.speedtest.net or similar) show, run individually on each machine?

 

[Papageno]

@continuum I'll have to try that on the other machine (the one depending on wifi). On this one connected by ethernet cable to the router the Speedtest.net results are 658+ Mbps down and 42+ up.

I looked into downloading a new driver. The model of wireless adapter is a TP-Link Archer T4U Plus and does support Wireless AC after all. I found a new driver but it looks like it's using a much more recent Realtek one.

But after all is said and done I feel totally silly, because it turns out the stupid thing had at some point connected automatically to the 2.4 GHz band and not to the 5 GHz one. I corrected that and configured it so it wouldn't connect automatically to the 2.4 GHz band.

 

[Kyuu]

But after all is said and done I feel totally silly, because it turns out the stupid thing had at some point connected automatically to the 2.4 GHz band and not to the 5 GHz one. I corrected that and configured it so it wouldn't connect automatically to the 2.4 GHz band.

Yeah I was about to say, that 144.4 Mbps PHY rate rang a bell with me, which I then quickly confirmed:

Exactly the PHY rate one would expect with a 2x2 antenna on 20 MHz channels, which is what one would expect to see on a (good) 2.4 GHz connection.

 

[Paladin]

@continuum I'll have to try that on the other machine (the one depending on wifi). On this one connected by ethernet cable to the router the Speedtest.net results are 658+ Mbps down and 42+ up.

I looked into downloading a new driver. The model of wireless adapter is a TP-Link Archer T4U Plus and does support Wireless AC after all. I found a new driver but it looks like it's using a much more recent Realtek one.

But after all is said and done I feel totally silly, because it turns out the stupid thing had at some point connected automatically to the 2.4 GHz band and not to the 5 GHz one. I corrected that and configured it so it wouldn't connect automatically to the 2.4 GHz band.

That happens if you wander out of the effective 5Ghz range (which is much smaller than 2.4Ghz) or if something interferes or blocks the 5Ghz signal. Could be as simple as someone standing too close to one PC or the other, or near the router for a while, or moving a piece of furniture, putting something next to the router, bumping the antenna on the PC or router, etc. Wifi can be fragile.

 

[Papageno]

Aargh. Last night the same Windows 10 Pro machine lost Internet connectivity for no discernible reason. When I went over to it, logged into Windows etc. it identified the 5 GHz band (from it seemed to have spontaneously disconnected) as having "no Internet" even though the other, Ethernet-connected machine suffered no lack of connectivity. The USB3 connected wireless adapter's light on the Windows 10 machine was blinking slowly when I made my way over to it.

I couldn't get it to reconnect to the wireless network so I rebooted the machine and it connected again to the WLAN just fine.

 

[Paladin]

I would check for a driver and firmware update for the WiFi hardware.

 

[Papageno]

I would check for a driver and firmware update for the WiFi hardware.

Yeah, I looked into that last time around and there is a downloadable driver for the adapter but it's older than the Realtek driver it's using now. Still, the older driver is from the manufacturer (TP-Link).

 

[Paladin]

That might help, it is probably using the default one from Windows. You never know if the original one might work better.

 

[Papageno]

I’ve seen this happen - usually it’s not one thing but a combo. Biggest red flag: you’re sending from AC Wi-Fi to an N adapter. That alone can bottleneck hard, especially if interference increased.After BIOS/Windows updates, check NIC drivers mine got downgraded once and killed speeds. Also verify link speed in adapter settings (sometimes it drops). Try forcing 5 GHz on the router if possible.
The random dropouts sound like signal instability or power saving settings disable “allow computer to turn off device” in Device Manager.
Not 100% sure it’s BIOS-related, but I’d start with drivers + Wi-Fi limitations first.

Actually the adapter is supposed to support AC as well. Good idea though about checking the power saving settings.

 

[CatBus]

FWIW, I saw a reduction in wifi speeds on my Win11 machines that was so common that I implemented a workaround in my house. Basically, every time my machines went to sleep and woke back up, the wifi was hobbled -- it worked, but it was slow (but still faster than most people's internet connections, so this could be widespread and nobody notices but us WLAN speed measuring types). Disconnecting and reconnecting to the network got me full speed again. Turning airplane mode on and off also brought everything back full speed. This is all on intel NICs, multiple models, through years of driver updates at this point. I honestly have no idea if there's more to it, because the workaround was so easy that I stopped troubleshooting.

It's 2-step workaround. First, there's a policy in Windows to prevent the network from being disconnected when the machine sleeps while on AC power [Computer/System/Power Management/Sleep Settings/Allow Network Connectivity During Connected Standby (plugged in)]. I enabled that. There's also one for battery power, but it doesn't seem like a good idea, so I left that one alone. Instead, I made a script that restarts the wifi connection if it's on battery power, triggered by the event of the machine waking [System/Kernel-Power/Event 507].

The result: while I'm connected to AC power, I never have this problem anymore. When I'm on battery, it takes a little extra time for the wifi to come back, but when it does, it's always full speed.

I have no idea if this is related to the issue you're seeing, but thought I'd share. Not all wifi NICs have the option to disable "allow computer to turn off device", so this is what I have that seems to work everywhere for me.