Limited area broadcast for warning message delivery over vehicular ad-hoc networks

Vehicular ad hoc networks have been developed in consideration of advancing driving safety. In driving-safety applications, rapid dissemination of warning messages is highly demanded to avoid accidents involving incoming vehicles. Broadcast transmission is considered the most appropriate technique to spread warning messages because it can simultaneously reach all neighboring nodes within a transmission range using only a brief wireless media access. However, blindly broadcasting redundant messages may severely overcrowd wireless media channels and provoke transmission collisions; this is known as the broadcast storm problem. In order to reduce broadcast redundancy, broadcasting must be intelligently controlled. Simultaneously, an intelligent broadcast scheme should aim to reduce the number of hops needed to arrive at a destination, to achieve smaller propagation delay. In this paper, we observed the behavior of a few broadcast schemes and found that their performances can be explained as limiting a space to control the number of contentions in broadcasting. From the observation, we propose a limited area-based (LAB) scheme to achieve a shorter propagation time as well as a smaller number of redundant broadcast messages. The proposed scheme can maintain a proper collision rate to obtain a faster propagation time by adjusting the size of an area in which broadcasting nodes belong. Performance evaluation results from simulation show that the proposed scheme is feasible and reasonable.