Efficient Broadcasting in Manets Using Directional Antennas

Broadcast has been widely used in mobile ad hoc networks (MANETs) as a communication means to disseminate information to all reachable nodes. However, the conventional broadcast scheme that broadcast packets omni directionally suffers from several drawbacks: excessive amount of redundant traffic, exaggerated interference/contention among neighboring nodes, and limited coverage (as a result of contention/collision). This is termed as the broadcast storm problem. In this paper, we address this problem in MANETs with the use of directional antennas. We propose a broadcast protocol called directional broadcast protocol (DBP) to alleviate broadcast storm problem in ad hoc networks using directional antennas. Compared with omni directional scheme DBP uses minimum number of forward nodes to relay the broadcast packet, while the number of forward directions that each forward node uses in transmission is significantly reduced. With lower broadcast redundancy, DBP is more bandwidth and energy efficient. DBP is based on neighbor discovery information and does not rely on location or angle-of –arrival information. Two special cases of DBP are discussed: the first one preserves shortest path in reactive routing discoveries; the second one uses both directional transmission and reception mode to minimize broadcast redundancy. An extensive simulation study using ns2.30 shows that DBP significantly outperforms the omni directional broadcast protocols.