| Mobile Ad Hoc Network(MANET) has its own characteristics which is very suitable for communication among vehicles. Vehicular Ad Hoc Network(VANET) which is based on MANET has no central node, and it is a self-organizing network with topology changing rapidly. The routing protocols of traditional MANET can’t satisfy the demands of VANET’s special environment, so, designing a protocol that can deliver message timely and reliably has become hot spot and difficulty.This paper analyzes the current situation of related fields at home and abroad, combining with GPSR(Greedy Perimeters Stateless Protocol), comes up with a new improved routing protocol which is more suitable for vehicular environment, here are the research:This paper studies the nodes’ mobility models, analyzes some classical vehicular mobility models and their theory, focuses on the study of mobility model based on traffic flow which is used by this paper.For the situation where there is no obstacle models in normal simulation, this paper bring forward a simple and convenient obstacle realization algorithm. It can simulate the situation where communication radio is blocked by obstacles effectively and make the simulation results of simulation scenarios with obstacle models closer to reality.Traditional GPSR isn’t fit with the special condition of VANET in city environment well. For this, this paper proposes crossroad priority algorithm, which adds road information, classified nodes information based on original GPSR. It takes different forwarding policies for different nodes, converting geographical restraint to forwarding advantage, and improves the delivery ratio.Traditional GPSR ignores nodes’ direction of movement, On the other hand, the position prediction algorithm proposed by this paper take advantage of nodes’ direction of movement. The nodes can predict its next hop node in advance, lower the odds of routing loophole, and improve the delivery ratio.Lastly, this paper establishs a union simulation platform of VANET, tests and verifies the performance of improved GPSR by simulation. Three comparing tests are completed to show the performance of protocols in different conditions. The simulation result shows that the delivery ratio of improved GPSR increases 20% compared with traditional GPSR in urban environment. The delay keeps almost unchanged. So this protocol is suitable for the occasion that demands high reliability and low delay. |
