Research On Cooperative Collision Avoidance And Communication Scheme Based On Dynamic Grouping

Traffic safety and efficient communication are two important areas in the research of VANET,and they complement each other. Efficient communication provides a timely road information for vehicles, ensuring traffic safety, simultaneously, it also meets the needs of passengers to obtain network information. On the other hand, vehicle safety is the premise to ensure the stability of the communication. In this paper, we take vehicle dynamic grouping mechanism as the starting point to improve the communication efficiency as well as provide efficient service of collision warning.Firstly, we study the conception and operation mechanism of dynamic grouping carefully, for the shortcomings of which the corresponding solutions are proposed:in order to avoid cars join and leave a group frequently in a short time, a delayed response mechanism is proposed to reduce the dynamic changes of grouping,thus lower the network overhead; for warning message may not be timely sent to the car that just joined the group, we put forward a scheme to extend the effective time of warning message to avoid collision; in order to reduce the probability of occurrence of warning message delay caused by excessive vehicle density,we optimized the Location-based Backoff Scheme by adding the factor of vehicle density;finally,we restricted the length of the group to further reduce the network overhead.Then combined with the advantage of vehicle information sharing mechanism within a group, we proposed a kind of communication scheme based on the group which target vehicle belongs to. The vehicle can determine whether the target vehicle which communicate with is in the same group. If it is, it means that the target vehicle is not too far away, and they can use stable V2V multi hop routing to communicate with each other; otherwise,the vehicle will utilize the roadside base station to communicate among groups. We use a network communication technology based on SDN in the base station forwarding mode:SD-VCPS, and optimize the routing strategy utilizing grouping features:updating all the vehicle information of a group in the data center at every communication. This optimization scheme can effectively reduce the delay in frequent communication, improving the communication efficiency.The simulation results show that,the optimized early warning scheme can effectively reduce the network overhead and improve the success rate. The proposed communication scheme got obvious improvement in the packet loss rate,and the optimized routing scheme reduced the time to switch the base station, thus further reducing the delay of packets.