Research On Routing Protocol In Urban Vehicluar Ad Hoc Network

The increasingly serious traffic congestion, road accident, traffic pollution and energy consumption have become the worldwide problems. Intelligent Transportation Systems (ITS) which intergrates intellectualization, informatization and networking has generally been regarded as the fundamental way to resolve the current traffic problems. As one of the most important parts of ITS, the vehicular ad hoc network (VANET) has become one of the research hotspots of many countries currently. Vehicular ad hoc network is a mobile wireless network which is used in road traffic networks. Based on the existing wireless communication network, signal and information processing technology, sensor and detection technology and road infrastructure, VANET has made intervehicular communications (IVC) and road-vehicle communications (RVC) come true. Along with the recent development in vehicular ad hoc network, a number of attractive applications such as traffic information query, cooperative collision warning and real-time traffic information disseminations have emerged. The comfort applications such as on-vehicle chat, Internet access, distributed games, chats, music downloads can lift the vehicle driving pleasure.Due to the high mobility of vehicles, frequent change in network topology, channel fading, Doppler effect, etc., VANET research is facing enormous challenges. Despite many scholars have conducted extensive research in data transmission and routing and so on and achieved the desired results, the design of relatively stable routing continues to face new challenges due to the unique characteristics and diverse applications of VANET. At present, routing for the freeway scene has been received wide attention, but routing for urban with more complex communication condition is seldom studied. Therefore, we focus on the design of city routing protocol for vehicular ad hoc network. The main contents and contributions of this dissertation are as follows:1. We describe the concept of VANET based on the self-organizing network and analyze the vehicular ad hoc network structure, characteristics and protocol framework. Then we describe some typical application of VANET and the related key technology. Furthermore we summarize the research status of routing protocol. Based on these, we analyse the difficulty of routing research currently. We also point out the main problems and the development trend of the city routing strategy design.2. Connectivity is the premise of reliable service provided by network routing protocol. We model the connectivity probability and time-delay based on the characteristics of city road network. Based on the traffic flow information we provide the method for connectivity and delay of connection-oriented and connectionless communication. The experimental results verify the correctness of proposed model analysis.3. Vehicle local cluster routing strategy is proposed. We analyse the vehicle cluster characteristics around intersections or accident spots. The methods of cluster and cluster maintenance for hotspots are proposed. Through the cooperation of cluster head and cluster members the effective data forwarding performance is achieved. The experiment results verify that the local cluster routing performs better than the existing classic VANET routing protocols.4. We propose two-scale routing protocol to resolve the blindness of data packet dissemination in networks. With the help of location service system, the macro-scale routing based on connectivity provides optimal macroscopic routes for the source node and the destination node. The micro-scale routing chooses the best next hop for the current node based on the macro-scale routing.5. The radio signal sharply degrades behind corners of intersections. We introduce a data dissemination strategy assisted by vehicle queues. The optimal route composed of successive roads for the source node and the destination node is chosen based the connectivity model in chapter2. The dynamic queue head helps to avoid the frequent link breakage, which ensures the data smooth delivery at the corner.6. Multipath routing has better network performance compared to single path routing in certain conditions. We propose an improved multi-path routing strategy, which can be realized as the additional support for the routing strategy in chapter5. The multipath routing can further improves the network performance.