My quest to disable Wi-Fi background scan on the ASUS PCE-AC88 AC3100 card
My computer is, unfortunately, not in the same room as my modem. And up until recently, I was using ethernet-over-powerline adapters. It’s fairly “old” technology and depends a lot on the quality of the wiring in your walls. I went through three models of those adapters until I found one that would allow me to actually reach the complete bandwidth offered by my phone line.
I eventually did find that model, but slowly, problems started creeping it. I didn’t think much of it at first, but a constant 5% packet loss showed up in Dota 2. I figured it was just the servers themselves. But then the speeds started to plummet unless I turned unplugged and replugged either adapter. And in the end, that ended up not working anymore.
Well, time to go back to Wi-Fi connection then! The other alternatives was to either move my office to the living room (not gonna happen), or to lay down a good 20 meters of Ethernet cable and trip all over it in the hallway (unlikely to happen, but honestly, I’m strongly considering it now).
I started looking for adapters. I actually did had a dongle lying around from about 6 years ago. Unfortunately, it caused blue screens of death, I assume because it didn’t have proper drivers for Windows 10.
First, I bought the TP-Link Archer T9E AC1900. It was pretty good, seemed to have no problems, and allowed me to reach about 95% of my speed capacity. However, its driver has an awful problem: the speed starts to plummet after some time (usually a day of uptime). The two solutions are to “restart” the card by clicking on the Wi-Fi tile toggle in the network list (merely disconnecting and reconnecting does not work), or just reboot your computer. Using generic drivers from the chipset manufacturer did not alleviate the issue; in fact, it made the first solution, which was already sometimes unreliable, not work at all: the card would freeze altogether, and a reboot would be the only option.
I returned that one and went for the most expensive one I could find! It ended up being the Asus PCE-AC88 AC3100. It is very very fast. It’s actually the first time I’m completely maxing out my connection; neither ethernet-over-powerline or any previous Wi-Fi solutions that I’d used actually unlocked its full potential.
However, there is one problem (hey, look, we’re finally getting to the actual topic of this post). Every five minutes, exactly 300 seconds, there would be a short spike in latency and/or packet loss.
This software is called PingPlotter, it’s very neat, and thankfully it offered a 15-day trial version. I’ve set it to ping my router every 100 milliseconds. The spikes generally reach 250 to 400 ms in latency, and last about 300 ms.
It’s not a big deal, but it was disappointing that a 100 € card with such blazing speeds ended up having this problem when the other one, with an actually crippling issue, didn’t suffer from it.
This is caused by Windows (or the driver) scanning for Wi-Fi networks in the background. If you search for that on Google, you’ll see a lot of people have the same issue on other cards. See, though, most other cards have had the decency to offer a driver-level setting that would stop background scans. The PCE-AC88 does not!
This is what opening the list of Wi-Fi networks, triggering a full scan, looks like:
It’s mind-blowingly bad, but I can understand that since it’s a full scan, and thankfully, the 5 minute spikes are nothing like that so you could totally bear with them. But I still wanted to look for a fix!
There’s this piece of software called WLAN Optimizer, which does a bunch of behind-the-scenes voodoo magic to disable background scans, and/or enable settings that could prevent them. Unfortunately, it did not help at all!
Then I ended up trying a few crazy things, and here’s one that surprisingly worked... it actually touches the same thing that WLAN Optimizer does, but does so differently.
If I restarted Windows 10′s WLAN AutoConfig service, the system tray would display the wireless icon with a red X, as if the adapter was unavailable. Yet I was connected! It’s like Schrödinger’s Wi-Fi.
The WLAN AutoConfig service is responsible for quite a lot of things that are related to wireless connectivity, but as far as I understand, what WLAN Optimizer does is that it pauses or interrupts it in a specific way so that opening the network list would not display any access points. But it’s... still kinda running? I’m not 100% sure.
Anyway, doing this by itself did not solve the issue, and another thing I tried in tandem with that, toggling on Flight Mode, ended up making the spikes happen in a much worse fashion, every 45 to 60 seconds!
Instead, after the service was restarted, I turned WLAN Optimizer back on, with only the “stop background scan” and “streaming mode on” settings.
And guess what... it works! No more spikes.
Constant 2ms latency to my router over 6 hours!
However, one thing I experienced shortly before writing this post was explorer.exe crashing and restarting (lol). This restored the wireless icon back to normal and broke the fix... until I just applied it again. Go figure!
You can restart the WLAN AutoConfig service using a batch file, too!
net stop WLANSVC net start WLANSVC PAUSE
I’m wondering if maybe the whole thing is caused by the Windows UI wanting to refresh the signal strength and having to scan for it or something... I’m thinking of investigating that, and a couple of other potential avenues that might make the fix easier to apply or more reliable. I’m worried that this fix is little more than an exploit, using a bug to fix another one.
I wrote to ASUS Support but I’m not hopeful to get a reply, let alone a driver fix.
