车载Ad Hoc网络中基于移动网关的数据传输

摘要

由于车载Ad hoc网络拓扑的动态变化及车载节点的快速移动,应用现有传输方法在其上进行Internet接入点向移动车辆(Infrastructure-to-Vehicle,I2V)数据传输时成功率较低,而且传输延迟高、延迟抖动大.为了解决这一问题,文中利用公交车路线固定、运行特征可预测、节点及线路分布稠密等特性,将公交车作为移动网关( Mobile Gateway,MG),提出了一种新的基于MG转发的I2V数据传输方法(Mobile Gateway based Forwarding,MGF).文中首先将公路网模型化为状态-空间图,再运用马尔可夫决策方法建立了一种基于MG转发的I2V数据传输优化模型,然后通过对模型求解得出I2V数据传输的最优转发决策,最优转发决策指的就是每个状态下对应的最优动作序列,最后在目的车辆行驶轨迹上选取满足传输成功率阈值,并使I2V传输延迟最小的路口节点作为数据包与目的车辆的最优汇聚节点,即目标节点.应用MGF方法,MG节点将以最优概率转发序列向目标节点转发数据包.文中利用模拟平台对MGF方法的传输性能进行了评估,结果表明该方法在满足传输成功率阈值前提下,能够获得最小传输延迟期望.理论分析同样也证明了该方法的有效性.%The highly dynamic topology and the rapid movement of destination node pose special challenges to Infrastructure-to-Vehicle (I2V) data delivery in Vehicular Ad Hoc Networks (VANET). Current data delivery methods are with the strong delay, the large jitter of delay and low delivery ratio for I2V data delivery. The paper investigates how to effectively utilize the prominent characteristic of buses, and proposes Mobile Gateway (MG) based Forwarding (MGF) that buses are installed as MG to forward data packet. To solve the problem that the paper models road network as a probabilistic state-space graph, in which applies the value iteration algorithm for the markov decision processing model to derive the optimal forwarding policy, that means the optimal forwarding sequence. In order to improve the performance of data delivery, the paper selects an optimal rendezvous point of the packet and the destination vehicle as the target point while satisfying the required packet delivery probability. Through theoretical analysis and extensive experiments, it is shown that our design provides an efficient 12V data forwarding under a variety of vehicular traffic conditions.