Many of you have faced issue of wifi connection when you suspend your laptop and resume on Ubuntu 16.04 LTS, specifically after upgrade from Ubuntu 14.04 LTS to Ubuntu 16.04 LTS, I have found this from Ubuntu Forums, Thought to share with you so that It will be helpful for you guys.
16.04 runs on systemd. Try the following:
sudo systemctl restart network-manager.service
If this works, you can create a script to automate it.
Open a terminal and type the following:
sudo nano /etc/systemd/system/wifi-resume.service
Now paste the script in there with a right click. Exit with CTRL + X and press Y to save. Now to activate it:
sudo systemctl enable wifi-resume.service
#/etc/systemd/system/wifi-resume.service #sudo systemctl enable wifi-resume.service [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
Reference Taken from : http://askubuntu.com/questions/761180/wifi-doesnt-work-after-suspend-after-16-04-upgrade