In this paper, we present and visit the limitation of reference point group mobility model. It assumes that nodes in the same group always stay together throughout the simulation process. However, in many real life applications, the nodes’s movement within a group is not always common. In particular, in a military operation, initially there is only one group. With multiple missions assigned to it, the group may be divided into a number of subgroups with each subgroup moving to a different location for accomplishing its task. A subgroup may be further divided into smaller groups or merge with other subgroups after completing its task. Therefore, in many scenarios it is necessary for a group to partition itself into smaller groups or a number of smaller groups to merge. Some recent researches present mobility models, which model possible group partitioning and group merging. We call this kind of mobility model a reference region group mobility model for ad hoc networks.