Araki Daichi, Yoshihiro Takuya
Graduate School of Systems Engineering, Wakayama University, 930 Sakaedani, Wakayama 640-8510, Japan.
Faculty of Systems Engineering, Wakayama University, 930 Sakaedani, Wakayama 640-8510, Japan.
Sensors (Basel). 2019 Jun 14;19(12):2688. doi: 10.3390/s19122688.
Vehicular Ad hoc NETworks (VANET) has been well studied for a long time as a means to exchange information among moving vehicles. As vehicular networks do not always have connected paths, vehicular networks can be regarded as a kind of delay-tolerant networks (DTNs) when the density of vehicles is not high enough. In this case, packet delivery ratio degrades significantly so that reliability of networks as an information infrastructure is hardly held. Past studies such as SADV (Static-node Assisted Data dissemination protocol for Vehicular networks) and RDV (Reliable Distance-Vector routing) showed that the assistance of low-cost unwired static nodes located at intersections, which work as routers to provide distance-vector or link-state routing functions, significantly improves the communication performance. However, they still have problems: SADV does not provide high-enough delivery ratio and RDV suffers from traffic concentration on the shortest paths. In this paper, we propose MP-RDV (Multi-Path RDV) by extending RDV with multiple paths utilization to improve performance against both of those problems. In addition, we apply a delay routing metric, which is one of the major metrics in this field, to RDV to compare performance with the traffic-volume metric, which is a built-in metric of RDV. Evaluation results show that MP-RDV achieves high load-balancing performance, larger network capacity, lower delivery delay, and higher fault tolerance against topology changes compared to RDV. As for routing metrics, we showed that the traffic-volume metric is better than the delay one in RDV because delay measurement is less stable against traffic fluctuation.
车载自组织网络（VANET）作为移动车辆间交换信息的一种方式，已经被深入研究了很长时间。由于车载网络并不总是有连接路径，当车辆密度不够高时，车载网络可被视为一种容延迟网络（DTN）。在这种情况下，数据包传输率会显著下降，以至于作为信息基础设施的网络可靠性难以维持。诸如SADV（车载网络静态节点辅助数据分发协议）和RDV（可靠距离向量路由）等以往的研究表明，位于交叉路口的低成本无线静态节点作为路由器提供距离向量或链路状态路由功能，能显著提高通信性能。然而，它们仍存在问题：SADV的传输率不够高，而RDV存在最短路径上流量集中的问题。在本文中，我们通过扩展RDV以利用多条路径来提出MP - RDV（多路径RDV），以解决这两个问题。此外，我们将延迟路由度量（该领域的主要度量之一）应用于RDV，以便与RDV的内置度量——流量度量进行性能比较。评估结果表明，与RDV相比，MP - RDV实现了高负载均衡性能、更大的网络容量、更低的传输延迟以及更高的抗拓扑变化容错能力。至于路由度量，我们表明在RDV中流量度量比延迟度量更好，因为延迟测量对流量波动的稳定性较差。
