Wifi gets disconnected automatically

First, check the settings in the router. WPA2-AES is preferred; not any WPA and WPA2 mixed mode and certainly not TKIP. Second, if your router is capable of N speeds, you may have better connectivity with a channel width of 20 MHz in the 2.4 GHz band instead of automatic 20/40 MHz, although it is likely to affect N speeds. I also have better luck with a fixed channel, either 1, 6 or 11, rather than automatic channel selection. Also, be certain the router is not set to use N speeds only; auto B, G and N is preferred. In some cases, auto B and G may also be helpful. After making these changes, reboot the router.

Next, I recommend that your regulatory domain be set explicitly. Check yours:

sudo iw reg get

If you get 00, that is a one-size-maybe-fits-all setting. Find yours here: http://en.wikipedia.org/wiki/ISO_3166-1_alpha-2 Then set it temporarily:

sudo iw reg set IS

Of course, substitute your country code if not Iceland. Set it permanently:

gksudo gedit /etc/default/crda

Use nano or kate or leafpad if you don't have the text editor gedit. Change the last line to read:

REGDOMAIN=IS

Proofread carefully, save and close the text editor.

Next, I'd set IPv6 to Ignore in Network Manager: http://docs.fedoraproject.org/en-US/Fedora/18/html/Installation_Guide/images/netconfig/network-connections-ipv6-ignore.png This example is for ethernet, but you want wireless.

If these changes do not help, please try:

sudo -i
echo "options rt2800pci nohwcrypt=Y"  >  /etc/modprobe.d/rt2800pci.conf
modprobe -r rt2800pci && modprobe rt2800pci
exit

If these changes are still not helpful, let's compile the newest version of the driver. Download this package to your desktop: https://www.kernel.org/pub/linux/kernel/projects/backports/2015/11/15/backports-20151115.tar.gz Right-click it and select 'Extract Here.' Now, back to the terminal:

sudo apt-get install linux-headers-generic build-essential
cd ~/Desktop/backports-20151115
make defconfig-wifi
make
sudo make install

Reboot, unload ndiswrapper and tell us if there is any improvement.

sudo modprobe -r ndiswrapper
sudo modprobe rt2800pci

If these changes are helpful, remove ndiswrapper:

sudo apt-get purge ndiswrapper-utils-1.9
sudo apt-get purge ndiswrapper

The native driver rt2800pci may be blacklisted. Please check:

sudo gedit /etc/modprobe.d/blacklist.conf

If it is, remove the line blacklist rt2800pci, save and close the text editor.

Also, you have compiled the driver for your currently running kernel only. When Update Manager installs a newer linux-image, after the requested reboot, recompile:

cd ~/Desktop/backports-20151115
make clean
make defconfig-wifi
make
sudo make install 

Please retain the file and these instructions for that time.

I had similar experiences with another Ralink network interface. The problem is Linux's wireless driver support, which is not very good. You can try a different kernel and you might be lucky, but there is no guarantee that it will fix the problem. I had best experience with Intel wifi cards, they seem to be more stable.