Research On Routing Protocol For VANET In Urban Environments

VANET is a kind of network that makes use of ad hoc network to providevehicular communications. It is made of vehicles and roadside units that are installedwith wireless communication devices. It is introduced to improve traffic condition andtransportation safety. With the continuous development of VANET technology,VANET routing protocol design is one of the key research issues of VANET.This thesis presents a dynamic Routing-Tree based Data Forwarding (RTDF)scheme, which focuses on road networks with a parking lot that is required frequentlysome time. First, we developed a packet delivery overhead model, which is used tocalculate the ratio between the overhead of parking lot broadcasting messages to buildrouting-tree and the overhead of letting vehicle discover routes itself. If the number ofinquiries the parking lot received during a period of time is more than this ratio, theparking lot will broadcast messages to build a routing-tree. Then, we designed acollaborative information maintenance method to maintain the routing information ateach intersection. This method consists of two parts. One part is a distance level basedbroadcasting method in network layer; the other part is an adaptive backoffmechanism in MAC layer. And we defined a criterion to tell intersections when tostop maintaining the routing-tree. At last, we introduced how to deliver data to theparking lot using the built routing-tree and further optimized the improved flooding.We use the vehicular mobility model generator MOVE and network simulatorNS-2to compare the performance of RTDF and AODV. In order to have a faircomparison, we modified the flooding to directional flooding in the process of routecreation in AODV. Then we compared the performance of RTDF and AODV onpacket delivery overhead, packet delivery delay, and packet delivery ratio. Simulationresults show that RTDF performs better than AODV in all the three metrics.