Abstract
In most MANET clustering protocols, the clusterhead nodes take on a special role in managing routing information. However, the frequent changes of the clusterheads affect the performance of the routing protocol. Eventually, the clustering stability in MANET would be significantly affected. The route between two nodes changes constantly as the clusterhead set changes. Also, since the clusterhead has the recent routing information in the cluster-based routing protocol, a collapse of the cluster leads to loss those information that was stored at its clusterhead. To elect a new clusterhead, exchanging messages to reform the cluster which considered communication overhead are needed. The goal then would be to keep the average cluster residence time for such a node in a cluster as long as possible. This time is defined as the time a node remains associated with a given cluster not a given clusterhead. This can be done by deploying a secondary clusterhead for each clusterhead which we call here primary clusterhead. This secondary clusterhead, which is a regular member node, is identified and assigned by its primary to be the future leader of the cluster. Since the future clusterhead is known by the cluster members, the cluster leadership is transferred smoothly and the cluster is reformed immediately with no need to invoke the clustering algorithm. Hence, the smooth clusterhead transfer from a node to another aims at increasing the cluster residence time which sustains the stability of the network, decrease the clustering communication overhead and minimize the time spent by each node to join or to reform a cluster.