Research Of Multi-hop Routing In Urban Vehicular Ad Hoc Network

Since the beginning of the 21st century,car has been a major transportation in our daily life. However the growing number of cars also produced a series of social problems, even bringing negative effects. Since the vehicle ad hoc network (VANET) is an important part of the intelligent transportation system, it can greatly improve the road safety and traffic efficiency, also reducing energy consumption. City is the most important scenario for VANET application, so this paper has done some research on multi-hop routing problem for urban vehicle ad hoc network.VANET is a special kind of mobile ad hoc network (MANET), but we can't apply the routing protocol of MANET directly to the VANET because these two kinds of networks are quite different. Accordingly, our methodologies are as below: First, we analyses and comprises the mobility models of both MANET and VANET. In this paper, we present a new map-based urban mobility model called CTM. CTM adopts the real road shape according to the digital map and implements the uneven distribution of vehicles among roads. Then, a series of network metrics are proposed including the ratio of network connectivity, node density, link duration, etc, and we simulate the RWP, Manhattan and CTM model respectively based on these metrics. Results show two main differences between MANET and VANET: In the one hand, the topology of VANET changes frequently and the life of the end-to-end path is short. In another hand, VANET has segmentation, which sometimes results in the missing path from source to destination. Motivated by this, we design a new urban multi-hop routing protocol called CDVR to solve the above problem. CDVR divides the routing into two modes, road routing and intersection routing. When car is on the road, the protocol chooses greedy algorithm to forward the data based on the geographical position. When car is arriving at the intersection, the protocol forwards the data based on the connectivity of road. Finally, we use NS2 to simulate and analysis the protocol of AODV, GPSR, Epidemic and CDVR. Results show that in VANET the routing performance of CDVR is more superior to the other three protocols. CDVR can achieve high data delivery ratio and low transmission delay under the network of rapid changing and segmentation, and also CDVR is lightweight and scalable which promises large-scale applications of VANET.