in synaptic package manager go to settings, go to settings>repositories and chose other software tab.
Add the following repository: ppa:voria/ppa
click reload on the main package manager screen then search for samsung
check the boxes by samsung-tools AND samsung-backlight
click apply and load the packages. close package manager and reboot
in the terminal run:
sudo gedit /lib/udev/rules.d/95-keyboard-force-release.rules
in the samsung section you will see a line with *N130*|*N140* etc. add |*N150* there
also do the same for:
sudo gedit /lib/udev/rules.d/95-keymap.rules
substitute your model for N150 above if it isnt already there.
The first part loads the samsung tools and backlight utility. this will also get some of your other function keys working. you can see the mappings in system>samsung tools preferences.
The second part gets the mappings working for the fn-up and fn-down keys. it also keeps the fn-keys from going crazy by forcing them to release after being pressed.