WiFi DELL XPS 13 9360 keeps disconnecting with QCA6174 802.11ac Wireless Network Adapter

I would disable wifi power management with

sudo sed -i 's/wifi.powersave = 3/wifi.powersave = 2/' /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf

Change the encryption on the wireless router to WPA2 only with no WEP, TKIP or plain WPA, depending on the router it may be called WPA2-PSK, WPA2-AES or WPA2 Personal.

Reinstall the linux-firmware package

sudo apt-get install --reinstall linux-firmware

Reboot

I think I fixed it. The problem probably originated from my router settings. When I changed from 802.11n+g+b to 802.11n+g the connection seems stable. Although over time I changed quite a lot of setting in Ubuntu and my router, this seemed to do the trick.

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Edit 1/7/17: Later I found another crucial option which I had to uncheck in order to get it to work. In my Fritzbox router it is called:

Wireless LAN coexistence enabled

In heavily used wireless environments the available channel width is divided among the participants in the best way possible.

I think this option sometimes changes the bandwidth of the signal. When this happens the connection is lost between my laptop and the router. In the /var/log/syslog file I also saw something like: bandwidth changed, connection lost, if I recall correctly.