On evaluating the trade-offs between broadcasting and multicasting in ad hoc networks

Dissemination of information to multiple recipients is of importance in many ad hoc networks applications. Towards this, multicasting in ad hoc networks has received a lot of attention. Most multicast protocols require the creation and maintenance of a structure (such as a tree or a mesh) for distribution of information to the group members. In contrast, broadcast schemes are simple schemes which aim to distribute the information to all or a fraction of the nodes in the network without having such a structural framework. While the creation/maintenance of the structure could potentially be cumbersome and heavyweight, multicast does offer benefits in terms of restricting the number of nodes that perform rebroadcasts. We argue that it is not a given that multicast is a better choice for group communications in all possible scenarios and that there could be circumstances wherein the use of a simple broadcast based technique would be more advantageous. In order to support this claim, we study various scenarios to evaluate and quantify the trade-offs between broadcasting and multicasting. In particular we perform simulation experiments by choosing the On-Demand Multicast Routing Protocol and the Simple Broadcast Algorithm respectively, as candidate protocols for multicasting and broadcasting. These protocols have been shown to be the elite protocols in their classes in prior work. The results from our studies demonstrate that multicasting is preferable only under conditions of moderate mobility and with multicast group sizes smaller than 40%.