Research On Data Dissemination Algorithm For Vehicular Ad-hoc Network

A very promising direction in intelligent transportation system is the applications based on vehicular ad-hoc networks (VANET). Through information sharing between vehicles via VANET, the efficiency and safety of transportation system can be improved and the existing road network can give full play of its role. The high mobility of vehicles, the complex distribution of road networks and the time property of traffic peak hours lead to the highly uneven and dynamic topology of VANET. The information sharing algorithms used for traditional mobile ad-hoc networks aren't fit for VANET.To solve the problem of information sharing in VANET, an efficient data dissemination algorithm is proposed. In addition, the framework of an information dissemination and query platform on VANET is explored. The main research issues in the thesis include: the analysis of the performance of IEEE 802.11 broadcast protocol; the ranking algorithm based on the concept of supply and demand; an efficient traffic information dissemination algorithm based on VANET; the security model of VANET; the framework of an information dissemination and query platform on VANET. Some innovative contributions of the thesis are enumerated as follows:1. Based on the performance analysis model of IEEE 802.11 broadcast under saturation conditions, two broadcast algorithms are proposed: the broadcast algorithm with maximized throughput and the broadcast algorithm with maximized value.Unlike in previous works, the influence of the data frame length on network performance and the hidden terminal problem in multihop wireless networks are taken into consideration in the model. The throughput range for reliable broadcast in both local area network and multihop wireless networks are calculated using the model. Based on the results, the broadcast algorithm with maximized throughput and the broadcast algorithm with maximized value are proposed. The two broadcast algorithms can improve the performance of IEEE 802.11 broadcast.2. The ranking algorithm based on the concept of supply and demand is proposed for VANET. Borrowing the concept of supply and demand in economics, the supply of information is defined as the percentage of the nodes in the system that had already received the information and the demand of information is the quantitative evaluation of the importance and the value of the information. The ranking algorithm evaluates the importance of information based on the supply of and demand for the information by all the nodes in the network. The algorithm is used to calculate the rank of information for efficient dissemination.3. An efficient traffic information dissemination algorithm based on VANET-- ETDAR is proposed.ETDAR is designed for the complex road network condition. It can be used as the framework for the information dissemination algorithms based on VANET. Simulation and field test show that the performance and the generality of ETDAR are better than the existing traffic information dissemination algorithms.