Hello Gaetan,
you can also give a look to ros_rt_wmp, is node that allows to use a
different core in each node and the communication is managed (via wifi) by
the RT-WMP protocol.
It supports mobility and multi-hop.
Topic in a node can be replicated in other nodes without the need for
sharing the core.

Yo can find documentation at http://www.ros.org/wiki/ros-rt-wmp

Tell me if you need help.

Best Regards,
 Danilo