Dell has been pushing fixes for the Dell XPS Developer Edition to upstream projects to make them available to all new releases of Linux distributions, but one thing that isn't quite working with the latest Ubuntu 16.04 is resuming WIFI after suspend. It's easily fixed with a little Systemd service.
Add this Systemd Unit file to restart the network manager after suspend:
sudo vim /etc/systemd/system/wifi-resume.service
Press i for insert mode and paste this content to the file:
[Unit] Description=Resume WIFI After=suspend.target [Service] Type=oneshot ExecStart=/bin/systemctl restart NetworkManager.service [Install] WantedBy=suspend.target
Then press ESC to exit insert mode and type :wq to save and quit.
If you're on an older version of Ubuntu then the NetworkManager service may be named network-manager.service. In that case adjust the reference to the service in the Unit file above.
Refresh Systemd's configuration files:
sudo systemctl daemon-reload
Enable the wifi-resume service:
sudo systemctl enable wifi-resume.service