As far as I can tell, there are two ways to do ns-3 MIPv6 simulations:
- using DCE: http://www.nsnam.org/~thehajime/ns-3-dce-umip/getting-started.html
- using a native UMIP implementation from http://eudl.eu/pdf/10.4108/ICST.SIMUTOOLS2010.8682 but I do not believe that it has been released.