| Vehicular Ad-Hoc Network (VANET) is a kind of special Ad-Hoc network. It can not only be used in traffic safety, but also in navigation and intelligent transportation. VANET will also be widely used in entertainment, news, video conference and other entertainment consulting services in the future. While with the reality that automobiles are always moving in high speed, communication range of Road-Side Units (RSU) is limited and the RSUs are sparse distributed, that they cannot cover the whole data transmission process. In this thesis, a kind of solution is designed to solve the problem of communication range limitation and the problem that large file transfer cannot be completed in a transmission period. Generally, when data download is not completed in an RSU communication range, a group of coming-by automobiles is chosen to carry the rest data, and the rest data relay sent to users, as a result, the problem that data communication will be lost when vehicles are not in the RSU communication area.Regional compensation method is adopted in this thesis. Data assistant download will be conducted while the automobile is within the communication range. Compared to other network, the dynamic characteristics of the car is very obvious. While clustering during the motion process, the vanet is not stable, in order to reduce the difficulty of the analysis model, at first, designing of a cluster algorithm based on communication delay. The vehicle will be divided into multi-level network, using this method reduce network complexity. Based on the algorithm, introducing the vehicle driving behavior into the model, the GPSR routing strategies are improved so as to be applicable to cooperation download. Based on the vehicle’s position, velocity, acceleration and other information, combining the behavior prediction, the vanet could obtain a higher probability of future vehicle location. On basis of the above, vehicle maintenance time of link between the cars will be forecasted, and the best cooperation download vehicles would be found. In order to improve the success rate of data transmission, this thesis analysis of delay of the packet arrival rate, to find the bottleneck of data transmission. Then, based on the all, adjusting data packets priority to deliver the packet that taken by the leaving vehicle. Finally, through the simulation analysis, show that the scheme can effectively improve the success rate of data transmission, reducing the transmitting delay.Research in this thesis mainly concentrates on three aspects:1. Based on urban traffic situation, combining driving behavior analysis method of traffic flow theory, automobile behavior is predicted with the automobile driving characteristics and road condition data. Future trend of a automobile can be get, and the most appropriate assistant automobile is chosen;2. Time consumed in data transmission during automobiles is analyzed, and grouping and routing algorithm based on time length is established;3. Information scheduling management theory is introduced to set transmission priority, manage the communication information in whole so as to complete information transfer task as much as possible. |
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