Forwarder Smart Selection Protocol for Limitation of Broadcast Storm Problem

In this paper we introduce a novel routing protocol for efficiently broadcasting packets in vehicular ad hoc networks, while limiting multiple copies of the same packet, and avoiding collisions. In high-congested traffic scenarios, the increase of packet collisions and medium contentions among vehicles affects the inter-vehicular communications, and causes a degradation of quality-of-service (QoS). The effect also results in a very high number of message copies and collisions within the vehicular network. This is the well-known broadcast storm problem. Our proposed technique, namely 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 interest". 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 urban and highway scenarios. The limitation of the broadcast storm problem, as provided by SRB, is expressed in terms of a reduction of number of next-hop forwarders. The effectiveness of SRB has been also compared to (i) the traditional broadcast protocol, since in respect of traditional broadcasting, the main strengths of SRB are the efficiency of detecting clusters and selecting forwarders in a fast way, as well as (ii) a content-based dissemination approach, due to its ability to determine clusters of vehicles having common interests.