Delay-based Geocast Routing Protocol for Message Dissemination in Vehicular Highway Networks

Geocast routing in vehicular ad-hoc networks has become an area of interest for researchers as it is an essential part of ITS (intelligent transport system). Many vehicular applications require geocast i.e. fast and reliable warning message dissemination to particular regions. Several proposed approaches, consider a geocast region as a circular area with a center point and a radius. However, in case of VANETs, only road segments should be considered as geocast regions to deliver the safety information efficiently for many scenarios such as accidents, deviations and congestion. In this paper, we propose a map-aware delay based novel geocast routing protocol to ensure reliable delivery of warning messages to all nearby vehicles on different road segments. Our approach is robust and scalable over highly mobile and dynamic vehicular conditions with low rebroadcast overhead. Roads are selected as geocast regions based on the road probabilities calculated using number of lanes around each intersection. Moreover, using the neighbor knowledge, a circle of forwarders is selected and messages are rebroadcasted by assigning certain delays to vehicles to avoid unnecessary rebroadcasts. Vehicles use two different modes for message forwarding to safeguard message delivery to all vehicles present in the geocast regions. We evaluate our approach through extensive and realistic simulations and results show that our routing algorithm achieves high packet delivery ratio and low packet rebroadcast ratio for highway scenario compared with existing geocast routing method.