| With the popularity of vehicles and the rapid development of wireless communication technology, inter-vehicle communication has become an urgent requirement for urban development and people’s lives, so the Vehicular Ad hoc NETworks(VANETs) come into being. As an important part of intelligent transportation system (ITS), it can bring inestimable benefits for various applications such as road safety, traffic management,in-vehicle infotainment and so on. It has received widespread attention from organizations, academia, industry. In order to make the full use of VANETs, there are many problems need to be addressed. Routing algorithm as the basis of data forwarding has become a hot topic in the research of VANETs.Due to the high mobility of the nodes in the VANETs, network topology changes frequently, then network partition and link interruption often occur. Those features make the absence of end-to-end links among nodes, also makes the VANETs and the delay tolerant network (DTN)have much in common. As a result, more and more researchers are beginning to apply the mechanism of Delay Tolerant Network (DTN) to the VANETs for better performance. "store-carry-forward" mechanism is a technology which proposed to solve the network partition problem in sparse VANETs scenario.Based on the summary of existing protocols of VANETs, this paper proposes a delay tolerant routing algorithm in VANETs. First, the algorithm uses the concept of two-hop selected node degree to estimate the network connectivity around the node. Then network state is divided into connect mode and DTN mode. Based on the forwarding characteristics of different mode, different forwarding metrics are proposed respectively. In addition, according to the relationship between the Three-phase traffic theory and the network stability, this paper defines a new metric called Flow State Differentiation as an important factor in the next hop selection. Finally, we validated our new VANET delay routing algorithm by simulation. |
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