Research On Routing Protocol Based On Road Constraint For VANET

VANET(Vehicular Ad-hoc Network)is a hot topic of wireless network field.Its target is establishing communication by vehicle to vehicle or vehicle to infrastructure.The route of communication is determined by routing algorithm.However,the routing algorithms of traditional static network are no longer applied for VANET because of the high mobility of vehicles in VANET environment.Therefore,new routing algorithms should be proposed to transmit data packets.There are still many challenges to propose a routing algorithm suitable for complex traffic environment.Firstly,vehicles move too fast,which makes communication link between vehicles get worse.Secondly,network topology changes frequently because of the high mobility of vehicles,thus single hop communication link between vehicles can not maintain the transmission of data packet depended on multi hop communication link.Finally,communication between vehicles must be within the scope of their communication,thus long-distance data transmission is not reliable and has long-time delay because of the opportunistic communication between vehicles.According to the characteristics of VANET,it has been shown that the routing protocol based on geographical position is more suitable for VANET.However,the main consideration of the current routing scheme are geographical position of vehicles,driving direction of vehicles and so on.Less consideration of traffic restrictions on vehicles and the habits of drivers is mode to select route.In the actual traffic environment,vehicles don't move randomly but move along with streets.Therefore,road constraint plays an important role in the excavation of vehicle trajectory.In this paper,we proposed a routing algorithm based on GPSR protocol and road constraint to make a better performance for transmitting data packets.First of all,we analyzed the fracture of communication link.Secondly,we proposed heuristic rule of routing based on road constraint.And then,we built a motion model with trajectory of vehicles.Finally,we proposed different routing algorithms according to whether the next hop forwarding vehicles are in the intersection or not.In this paper,we used NS2 to build our experimental environment.We first improved code based on GPSR in NS2 and coded the routing algorithm with C++.Then we make recompilation with new code in NS2.We used SUMO to simulate traffic information and put it into Tcl script in NS2.Finally,we analyzed the trace files.To contrast communication performance of packet delivery fraction,end-to-end delay and packet throughput with GPSR protocol,our program has been improved in terms of effectiveness and efficiency.