A Study On Broadcasting With Low Overhead In MANET

In Ad hoc networks, broadcasting is a fundamental and effective data dissemination mechanism, especially in route discovery in on-demand route protocols. Broadcasting is important and widely used, which is also main part of overhead in MANET. The main approach for broadcasting is flooding where a mobile node blindly rebroadcasts the first received broadcasting packet. Although flooding ensures a complete coverage, in reality, flooding may generate many redundant rebroadcasted packets and consume lots of resources. It may cause contention and collision at the same time, especially in dense networks, which is known as broadcast storm problem. To reduce the broadcast storm problem and routing overhead, the number of forwarding nodes should be restricted.Firstly, this paper introduces two kinds of structures in Ad hoc network. Then we show that the main resource of overhead is broadcasting on the basis of analyzing the cause of routing overhead. To reduce redundant packet forwarding generated by flooding, a variety of broadcasting techniques are presented.Secondly, this paper proposes a novel broadcasting algorithm named low overhead geometric broadcasting scheme, which is based on probabilistic-based algorithm and distance-based algorithm to reduce routing overhead in Ad hoc networks. As one of the widely used reliable broadcast algorithms, the connected dominating sets(CDS) algorithm can minimize the number of forwarding nodes but have a very high communication overhead due to its dependency on 1-hop neighborhood information and 2-hop neighborhood information. Considering GPS information is hard to acknowledge in reality, the algorithm we proposed reduces the requirement for input information. In this approach, we calculate the distance between a sender and a receiver for every duplicate packet to set a reasonable rebroadcast probability. Node sets a delay timer when it receives a broadcast packet for the first time. If a node receives a duplicate packet before the timer expires, it will set a reasonable rebroadcast probability based on the distance between the transmitter and receiver. Our approach only needs distance information to adjust to a rebroadcast probability based on duplicate packets, which can significantly reduce redundant retransmissions so as to reduce the routing overhead, and also can improve the routing performance.In order to evaluate the performance of proposed algorithm, we apply the proposed idea to plane Ad hoc network in this paper based on OPNET Modeler platform. We evaluate the protocol under different node density, mobility speed and transmission radius scenarios. Simulation results show that compared with probabilistic-based algorithm and CDS algorithm, the proposed broadcast scheme lessens broadcasting redundancy effectively with a high packet delivery ratio so as to improve the network performance.