I've recently moved to a new place, where I share a WiFi connection with other tenants (meaning I have no access to the router or the direct external Internet connection, which however I know is fiber optic, very fast and stable). I didn't use WiFi at my old place; so, when I moved here, I purchased a cheap USB WiFi receiver dongle for my PC (a desktop running Windows 8.1 Pro, full configuration in the signature below). It worked fine for a few days, then my connection started getting terribly slow (dial-up speeds or worse) and unstable.
However, my cell phone always connects to the WiFi network flawlessly, and I noticed that my PC's connection was likewise fast and stable when instead of using the dongle, I shared my phone's WiFi access through its USB cable. So, I resorted to using that. Fine, except that it's inconvenient when I need to leave the PC connected and go somewhere else taking my phone - that's what cell phones are made for, after all. (Just for the record, my phone is a mid-range LG model, running Android 4.4.2 KitKat.)
Thinking that maybe it was because of a bad dongle (it was a nondescript brandless Chinese thingy), I bought a fancy new D-Link one with the fastest 802.11n support. Again, it worked very well for a couple of days, then my connection became slow and unstable again - but great when I use the phone and the respective USB cable (you bet I'm using them now). The nature of the problem varies, too - sometimes DNS, but mostly Windows shows nothing wrong, yet it doesn't work. Windows' network problem-solving wizard usually can find nothing, but occasionally it finds a "bad gateway," fixes it, and the problem goes away for a few minutes, then it's back. The same happens when I disconnect and reconnect - it's briefly fixed, then it's slow and unstable again. On rare occasions, the connection becomes "Limited," but mostly Windows shows it as "Connected" - that is, Windows thinks it's normal, but it isn't.
I've tried all possible workarounds I found on the Web, from a plethora of netsh and ipconfig commands to ensuring energy saving doesn't turn the dongle off, to thoroughly uninstalling and reinstalling the dongle's drivers (using both D-Link's and Microsoft's drivers), and so on. Some of the solutions even work - for a few minutes, then my connection gets slow and shaky again.
Since I changed my dongle to a good one from a reliable brand and the same problem happened after a while, I think we can rule out that component. My USB ports are fine, everything else works great on them (and yes, I've tried changing the dongle's USB port - even to a USB 3.0 port, to no avail). Like I said above, I have no access to the router, but even if I had, my phone works well and the other tenants have no connectivity problems either, so I think we can rule that out as well. The problem is certainly with Windows. I use Comodo Firewall, but I've disabled it and re-enabled it, uninstalled and reinstalled it, and that had no effect on the problem.
From what I could find in my searches,, it appears Windows 8.1 is very problematic for WiFi, but on the other hand, here it always detects the WiFi network right away and establishes the connection promptly - but after that, the connection works erratically. I'm puzzled and I don't know what else to do - I seem to have tried just about everything possible. For now, I'm working around the problem by using my phone, but I don't want to depend on it for that - like I said, it's called a mobile phone for a reason, and I don't want it almost permanently hooked to my PC with a cable.
What can I do? Thanks for any help.