How to enable AO on iOS?

Hi epic,

I am currently working on a mobile project for iOS(new iPad). I’ve tried many ways to turn on the AO effect include Distance Field AO. Due to some solid limitations form project side only a movable directional light is allowed and CANNOT bake the lightmap, which means almost full dynamic. But surprisingly the stationary skylight is workable according to “not support” in docs.

I do want to know if there is a method can enable the AO effect on iOS?

Thanks,
Xu