Share USB modem dongle Internet over WiFi
You can try to use special Software to start a Hotspot. The easiest solution for myself is ap-hotspot.
A broader description of it can be found under the following link. http://www.webupd8.org/2013/06/how-to-set-up-wireless-hotspot-access.html
It installs Hostapd on your Laptop, directly via a PPA. After that just start it with the following command.
sudo ap-hotspot start
and also restart or stop it this way.