Vehicular Ad hoc Network (VANET) is a subset of Mobile Ad hoc Network (MANET). VANET is a self-organized information system composed of vehicles (and possibly additional infrastructure) capable of short-range communication through the device called On Board Unit (OBU). There is a wide range of possible application areas of VANETs, including warning systems, collision avoidance/notification, autonomous vehicles, and traffic optimization. VANETs rely heavily on broadcast transmission. When a vehicle rebroadcasts a message, it is highly likely that the neighboring vehicles have already received it, and these results in a large number of redundant messages. This affects inter-vehicle communications, since redundant rebroadcasts, contention and collisions can be largely increased as the number of vehicles increases. Broadcasting packets may lead to frequent contention and collisions in transmission among neighboring vehicles this problem is referred as the broadcast storm problem. The main goal of Selective Reliable Broadcast protocol (SRB), is intended to limit the number of packet transmissions. Through an opportunistic vehicle selection, packets are retransmitted towards a next hop, in order to strongly reduce the number of forwarder vehicles, while preserving an acceptable level of QoS. SRB belongs to the class of broadcast protocols, as well as cluster-based approaches. It exploits the partitioning behavior, as typical from vehicular ad hoc networks, in order to automatically detect vehicular clusters, intended as “zones of interestâ€. Packets will be then forwarded only to selected vehicles, opportunistically elected as cluster-heads. SRB performances have been assessed in different vehicular scenarios, mostly realistic environments, such as highway scenarios.
