Hi -
Dynamic occlusion is not handled on mobile. You will want to use Precomputed Visibility Volumes around your playable areas. Then you can build lighting and it will use the cell size to handle occlusion on your devices.
There isn’t a whole lot in the way of documentation for Unreal Engine 4 at the moment, but the documentation from UDK/UE3 is still fairly accurate with using this system. There are a couple of things that are no in UE4 that is demoed in this page, but it can still help you get it setup and working properly.
https://udn.epicgames.com/Three/PrecomputedVisibility.html
I hope this helps.
Tim