After installing Ubuntu 16.10 I occasionally had problems with WiFi after waking up from sleep.
But of course there’s a workaround (credit to Joakim Koed on askubuntu.com and the solution).
sudo bash -c 'cat >/etc/systemd/system/wake-up.service <<EOF [Unit] Description=Restart networkmanager at resume After=suspend.target After=hibernate.target After=hybrid-sleep.target [Service] Type=oneshot ExecStart=/bin/systemctl restart network-manager.service [Install] WantedBy=suspend.target WantedBy=hibernate.target WantedBy=hybrid-sleep.target EOF' sudo systemctl enable wake-up.service