Performance evaluation and improvement of broadcasting algorithms in ad hoc networks

Summary form only given. Efficient broadcasting protocol design is an important issue in mobile ad hoc networks, because the broadcasting technique has been widely used in various applications involving route searching and message distribution. A problem with the original broadcasting protocol flooding is the excessive retransmissions that cause packet collisions and lead to bandwidth reduction. Various improved techniques have been proposed in the literature to alleviate this problem, while most of them are designed for networks with static topology, and their performance is often compared by means of numerical simulations. Recently, we have constructed mathematical models for several broadcasting protocols in one-dimensional and two-dimensional topology, and have proposed the close-form expressions to clearly reveal some new relationships between performance metrics and network parameters. In another recent contribution, we have also taken a preliminary step to address the mobility issue. That is, we intend to improve the existing broadcasting protocols, which do not perform very well under highly-mobile situations. Our proposed mobility-sensitive mechanisms adaptively increase broadcast redundancy when the nodal mobility is detected. Neighbor information, instead of location information, is employed in one of our algorithms, which has been shown preferable in ad hoc networks when node locations are not available. As a third research effort we have carried out, we recently focus on the design of broadcasting protocols with a specific application: route searching. In on-demand ad hoc routing protocols, route searching is an essential part in network layer to establish a path between a pair of nodes that wish to exchange information. Based on the observation that unnecessary retransmissions can be further reduced by combining various broadcasting protocols with some specific features of route searching, we propose a method to reduce redundancy after the required route is found. The simulations have shown the efficiency of this technique on improving protocol performance in terms of the decreased number of nodes that receive the broadcasted packet.