【作者】 杜昱宏；

【导师】 秦华标；

【作者基本信息】 华南理工大学 ， 电路与系统， 2010， 硕士

【摘要】 进入21世纪以来,汽车逐渐成为人们日常生活的主要交通工具。汽车数量的增长也产生了一系列社会问题,甚至带来负面影响。车载自组网作为智能交通系统的重要组成部分,能够有效改善交通安全状况,提高道路通行效率,降低能源消耗,最大限度地提高车辆的安全和效率。其中,城市是车载自组网最重要的应用场景,本文针对城市车载网的多跳路由技术进行了一些研究。车载自组网是一类特殊的移动自组网,二者之间存在较大差异,故不能把移动自组网的路由协议直接应用到车载自组网。因此,本文所采取的研究方法是:首先,比较分析了移动自组网和车载自组网的移动模型,提出了一种新的基于地图的城市移动模型CTM,该模型采用了真实的道路形状,并模拟了车流量不均衡的特征。然后本文将CTM和移动自组网的常用移动模型进行了仿真,其中包括网络连通率、节点密度以及链路持续时间等。结果定量地说明了车载自组网与移动自组网的差异:一方面车载自组网拓扑变化频繁,端到端路由路径生存时间短;另一方面网络存在分割,部分节点某些时刻不存在到目的节点的路径。然后,本文针对这些特征设计了一种新的城市车载网多跳路由协议CDVR。该协议将城市多跳路由划分成路段路由和路口路由两个部分,车辆在路段上行驶时采用基于地理位置的贪婪算法,而当车辆行驶到路口时根据道路的连通度进行转发。最后,本文利用NS2平台对AODV,GPSR,Epidemic和CDVR协议进行了比较,仿真结果说明:在城市车载网中,CDVR的多跳路由性能优于其它三种协议。在网络快速变化和存在分割的情况下,CDVR能够达到较高的发送成功率和较低的传输延迟,并且CDVR的控制负载很轻,协议可扩性强,能够适用于大规模的车载自组网应用。更多还原

【Abstract】 Since the beginning of the 21st century,car has been a major transportation in our daily life. However the growing number of cars also produced a series of social problems, even bringing negative effects. Since the vehicle ad hoc network (VANET) is an important part of the intelligent transportation system, it can greatly improve the road safety and traffic efficiency, also reducing energy consumption. City is the most important scenario for VANET application, so this paper has done some research on multi-hop routing problem for urban vehicle ad hoc network.VANET is a special kind of mobile ad hoc network (MANET), but we can’t apply the routing protocol of MANET directly to the VANET because these two kinds of networks are quite different. Accordingly, our methodologies are as below: First, we analyses and comprises the mobility models of both MANET and VANET. In this paper, we present a new map-based urban mobility model called CTM. CTM adopts the real road shape according to the digital map and implements the uneven distribution of vehicles among roads. Then, a series of network metrics are proposed including the ratio of network connectivity, node density, link duration, etc, and we simulate the RWP, Manhattan and CTM model respectively based on these metrics. Results show two main differences between MANET and VANET: In the one hand, the topology of VANET changes frequently and the life of the end-to-end path is short. In another hand, VANET has segmentation, which sometimes results in the missing path from source to destination. Motivated by this, we design a new urban multi-hop routing protocol called CDVR to solve the above problem. CDVR divides the routing into two modes, road routing and intersection routing. When car is on the road, the protocol chooses greedy algorithm to forward the data based on the geographical position. When car is arriving at the intersection, the protocol forwards the data based on the connectivity of road. Finally, we use NS2 to simulate and analysis the protocol of AODV, GPSR, Epidemic and CDVR. Results show that in VANET the routing performance of CDVR is more superior to the other three protocols. CDVR can achieve high data delivery ratio and low transmission delay under the network of rapid changing and segmentation, and also CDVR is lightweight and scalable which promises large-scale applications of VANET.更多还原