Research And Optimization On Broadcast Algorithm Of Vehicle Ad Hoc Network

In recent years, with the development of transportation technology, transportation has become more and more important in people’s life. VANET (Vehicle Ad hoc network) has also become a focus research field in ITS (Intelligent Transportation System), most research of ITS focus on the method to solve the problem of safety and efficiency in transportation, a lot of research projects associated are also carried out in many countries all around the world, many world-renowned automobile manufacturer and research institutions in developed countries are also concerned about DSRC standard of V2V communication, and continue to explore new solutions for them. The most effective and commonly used broadcast in vehicle communication has also become a hot research field.In this paper we analyzed the shortcomings of existing VANET broadcast protocols and proposed an optimized ODAM-C broadcast algorithm based on ODAM broadcast routing algorithm, which is a traditional distance-based broadcast algorithm. The main contributions of this paper are as follows:(1) We noticed that in some certain scenarios, the collision and interference caused by simultaneous transmission of broadcast packets from sending nodes will lead to a decrease of transmission efficiency in ODAM algorithm. In ODAM-C algorithm we choose the next hop relay node by the method of calculating the vector angle between source sending node and forward node, and by this way we reduce the interference of broadcast packets from simultaneous transmission nodes and ensure the reliability of data transmission.(2) Traditional broadcast protocols in VANET will forward the received broadcast packets immediately without any judgments, this may usually cause broadcast storm phenomenon and result in the loss of large number of broadcast transmission packets. In ODAM-C algorithm we solve this problem by expanding the storage capacity of node and increase the link redundancy relatively. In this way ODAM-C could reduce the communication interference between nodes effectively and improve the data transmission reliability in broadcast, and reduce the probability of broadcast storm in network at the same time.In the fourth chapter of this paper, we also finished the simulation experiments in three network scenarios with different vehicle node density on NS2platform. We simulated the broadcast transmission process of WPBM algorithm, ODAM algorithm and ODAM-C algorithm and compare the end-to-end delay, network link redundancy and packet delivery rate of three algorithms in different scenarios. Experimental results show that, two improved method including the judgment of forward angle between forward nodes and expansion of node storage capacity based on traditional ODAM broadcast algorithm has improved the transmission performance of ODAM algorithm. Compared with traditional WPBM broadcast algorithm and ODAM broadcast algorithm, packet delivery rate of ODAM-C has been improved effectively in three network scenarios.