Unicast Assisted GeoBroadcast in Urban Vehicular Ad-Hoc Networks

摘要

The development of Intelligent Transportation Systems (ITS) aims to enable the Vehicle-to-X (V2X) communication to deal with the road traffic and road safety problems, and to support the comfort applications. Vehicles move fast in Vehicular Ad-hoc Networks (VANETs) and are constrained by the layout of the roads. Furthermore, in urban areas, vehicles are facing the shadowing effects of buildings. These characteristics make the V2X communications in urban VANETs more challenging. According to European Telecommunications Standards Institute (ETSI) standards for ITS, communication between different communication endpoints might be realized by geoBroadcast. But performing geoBroadcast arises the broadcast storm problem that needs to be tackled. In this work, we introduce Unicast-Assisted GeoBroadcast (UAG) that selects several target positions within the geo-region and geoUnicasts a copy of the message from the source vehicle to each target position. UAG makes sure that these copies take different routes towards the geo-region to increase the chance of reaching it. Afterwards, some of the vehicles located in the geo-region are selected to broadcast the message within the geo-region. UAG applies the intersection-based or the road-based approach to select the target positions. Moreover, UAG implements the forwarding-zone breathing based on the road topology of the geo-region and its neighborhood, in order to increase the reachability. We compare our proposed protocol with simple flooding and Urban Geocast based on Adaptive Delay (UGAD), and show that UAG performs better in terms of reachability and scalability.