基于弱状态的车载网数据转发策略

针对车载网（VANET）中车辆高度移动性、拓扑变化动态性等特点所导致的数据转发失败问题，提出一种基于弱状态协议（WSR）下的数据包传输算法——WSFD，实现交通控制中心（TCC）到目标车辆之间的高效数据传输。首先，车辆控制中心将收集到的数据包发送给位于目的车辆方向的接入点（AP）；然后，接入点在其通信范围内将数据包转发给某车辆，同时数据包携带上目标车辆位置信息；其次，每次接收到数据包的车辆对比自身所持有的映射，筛选出对于目标车辆位置信息确定性最大的映射与数据包携带的位置信息对比以确定下一步转发方向。若映射置信度较大，则将数据包方向修正为向此映射对应的地理区域中心移动，同时数据包更新包中所携带的目标车辆信息，反之则维持原方向不变。最后经过多次转发修正数据包传输方向，逐渐逼近目标车辆所在的区域，完成最终的数据交付。在30 km×30 km方形区域的数据传输实验中，与TSF与GPSR算法相比，WSFD在数据包的传输延迟上普遍降低至5 s以下，且将数据包投递率提高至0.92。实验结果表明，WSFD能准确高效地传输数据包，在增强了驾驶员的人身安全性同时有效缓解了交通堵塞。

Data forwarding strategy based on weak state in vehicular Ad Hoc network

To avoid the failure of data forwarding, brought by some characteristics of Vehicular Ad Hoc Networks (VANET), uniform distribution of vehicles, frequent network partition and mergence, etc., a new data delivery method based on Weak State Routing (WSR) from Traffic Control Center (TCC) to driving vehicles, called Weak State Forwarding (WSFD), was introduced in VANET. Firstly, a data packet collected by TCC was delivered to an Access Point (AP) along the direction of the destination vehicle. Secondly, the data packet was forwarded to the destination vehicle by AP within its communication range, at the same time, the location information of destination vehicle was carried by the data packet. Then, after comparing all the mapping information owned by the vehicle which received the data packet, the most deterministic map information was chosen by the vehicle and compared to the location information carried by the data packet so as to ensure the next forwarding direction. If the confidential level was quite high, the data packet was revised to move towards the mapping's corresponding central area, meanwhile, the information of destination vehicle carried by the data packet was updated. Otherwise, the original direction would be kept. Lastly, through several times' forwarding and revising, the data packet would be gradually approached to the area where the destination vehicle located, and the whole data delivery would be finally completed. Compared with Trajectory-based Statistical Forwarding for multihop infrastructure-to-vehicle data delivery (TSF) and Greedy Perimeter Stateless Routing (GPSR) algorithm, the WSFD algorithm could reduce the delivery delay to 5 seconds or less and elevate the delivery rate to 0.92 or more generally in the experiment of data transmission in 30 km*30 km square area. The experimental results show that the WSFD algorithm can improve safety of drivers and alleviate the traffic jam effectively.