“…dis(cur_RA(x), cur_RA(y)): The distance between mobile users x and y. Therefore, dis(x,y)= dis(cur_RA(x), cur_RA(y)) When calculating the location management cost, as in [1,3], we consider the following related costs in location update and the lookup procedure: L: The cost of following a link in the tree of the location databases, i.e., sending a message to the parent or the child node of a location database. U: The cost of a database update.…”