A Reliable Geocast Routing Protocol for Vehicular Ad Hoc Networks

In addition to safety applications, new Vehicular Ad-Hoc Network (VANET) applications such as onboard entertainment and traffic management are rapidly being developed. This has made geocast, i.e. the transmission of data over a geographic area, an important research topic. Often geocast is done over wide and distant areas, which can result in significant overhead. In this paper, existing VANET routing protocols are investigated from a geocast perspective. To address the shortcomings of these methods in addressing both overhead and packet delivery ratio issues in geocast routing, two enhanced mechanisms are introduced based on the AODV routing protocol. Unicast routing is employed in the proposed protocols to transmit data to the destination region, and then flooding is used within the region for data dissemination. Furthermore, rateless coding and link layer notifications are used to improve the delivery ratio. The proposed methods are compared with existing flooding based geocast routing and Inter Vehicle Geocast (IVG) routing. Results are presented for an urban environment in terms of delay, overhead, and message delivery. These results show that the proposed approach significantly reduces the overhead and increases the delivery ratio with a minimal increase in delay.