Role-based multicast in highly mobile but sparsely connected ad hoc networks

We present an approach to multicasting messages among highly mobile hosts in ad hoc networks. We suggest a new definition of a role-based multicast that suits the special needs of inter-vehicle communication: rather than by explicit identification, a multicast group is defined implicitly by location, speed, driving direction and time. As an example, we study a road accident that is reported to nearby vehicles. We focus on sparse deployment of the system which is likely to occur soon after the system is introduced to the market. In this state, the resulting ad hoc network tends to be disconnected. We tailor the proposed algorithm to overcome this problem of network fragmentation. Simulations show us the quality of the proposed protocol by measuring how many vehicles inside a multicast area are informed in time under various conditions