A New Methodology for Handling Empty Zone Problem over Mobile Ad Hoc Network

Group communications are important in Mobile Ad hoc Networks (MANET). Multicast is an efficient method for implementing group communications. However, it is challenging to implement multicast packet forwarding over a dynamic topology. Researchers propose a novel Efficient Geographic Multicast Protocol (EGMP). A network wide zone based bi-directional tree is constructed to achieve more efficient multicast delivery. The position information is used to guide the zone structure building, multicast tree construction and multicast packet forwarding which efficiently reduces the overhead for route searching and tree structure maintenance. Several strategies have been proposed to further improve the efficiency of the protocol, for example introducing the concept of zone depth for building an optimal tree structure and integrating the location search of group members with the hierarchical group membership management. Finally, researchers design a scheme to handle empty zone problem faced by most routing protocols using a zone structure. The scalability and the efficiency of EGMP are evaluated through simulations. The simulation results demonstrate that EGMP has high packet delivery ratio and low control overhead and multicast group joining delay under all test scenarios and is scalable to both group size and network size. EGMP has significantly lower control overhead, data transmission overhead and multicast group joining delay.