차량간 통신을 위한 AODV 라우팅 프로토콜의 구현

Abstract

In order to realize Intelligent Transport System(ITS) without any road facilities, Inter-Vehicle Communication(IVC) is preferable. IVC makes it possible to exchange real-time information among vehicles without centralized infrastructure. The IVC network uses an ad hoc network, which consists of a set of vehicles that communicate through radio frequencies, without the use of a centralized administration. IVC exchanges various kinds of vehicular information in order to avoid collisions between vehicles and to ensure accurate automatic driving. IVC improves the traffic efficiency and traffic safety. In IVC, occurrence of a traffic accident should be immediately reported to the following vehicles to prevent secondary accident. And this information can also be transmitted through a vehicle-to-vehicle. The IVC systems rely on multi-hop broadcast to disseminate information to location beyond the transmission range. In the IVC networks, the topology changes frequently and the vehicles communicate between them using radio channel. To transmit broadcast message, IVC uses the ad hoc routing protocols. Among the ad hoc routing protocols, the AODV(Ad hoc On-Demand Distance Vector) routing protocol is used for the IVC network. However, the AODV routing protocol has the problems of the frequent link failure and delay of link recovery. In this paper, we propose the improved AODV routing protocol called MAODV(Modified AODV). The MAODV routing protocol uses a node distance table for fast link recovery. We use the Hello packet with location information to calculate the distance between source node and neighbors node. If node receives the Hello packet from neighbors node, node calculates the distance and stores which are far distance from source node. If link break occurs, upstream node transmits the Unicast RREQ(URREQ) packet to First_Priority_Node(FPN) in its node distance table. Using the URREQ packet can mitigate the overhead problem of the RREQ packet's broadcast. We confirm the throughput of the MAODV routing protocol compared with AODV using Qualnet ver.3.8 simulator. Simulation scenario composes 39 nodes in 6 line. The simulation results show that the MAODV routing protocol improves throughput by 32.3% relative to the AODV. The number of RREQ packets is reduced by 18% relative to the AODV. The number of RREP packets is reduced by 28.4% relative to the AODV. The number of RERR packets is reduced by 67.6% relative to the AODV. So the number of total routing packets is reduced by 32.3% relative to the AODV.