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Vehicle-based sensors can be used for traffic monitoring. These sensors are usually set with long sampling intervals to save communication costs and to avoid network congestion. In this paper, we are interested in understanding the traffic-monitoring performance that we can expect from such vehicle-based mobile sensor networks, despite the incomplete information provided. This is a fundamental problem to be addressed. A performance evaluation has been carried out in Shanghai, China, by utilizing the vehicle-based sensors installed in about 4000 taxies. Two types of traffic status-estimation algorithms, i.e., the link-based and the vehicle-based, are introduced and analyzed. The results show that estimations of the traffic status based on these imperfect data are reasonably accurate. Therefore, the feasibility of such an application is demonstrated.

In this paper, we present the characteristics of a vehicular ad hoc network (VANET), which is the Shanghai urban vehicular network (SUVnet). We construct a mobility model using the GPS data collected from more than 4000 taxis in Shanghai. The model is both realistic and large scale. Based on this model, network topology and connectivity of SUVnet are studied. Because of the sparse distribution and dynamic topology of SUVnet, simply utilizing the conventional mobile ad hoc network routing protocols in SUVnet may not achieve a satisfactory performance. Therefore, we apply the delay-tolerant network model to SUVnet and evaluate the epidemic routing protocols. We propose a new protocol, which is the distance aware epidemic routing (DAER), to improve the bundle delivery ratio. Results show that DAER performs well for a VANET. This paper provides a basis in studying a realistic urban VANET.

The existing vehicular sensors of taxi companies in most of cities can be used for traffic monitoring, however sensors are always set with a long sampling interval because of communication cost saving and network congestion avoidance. In this paper, we focus on the traffic data processing in vehicular sensor networks providing sparse and incomplete information. A performance evaluation study has been carried out in Shanghai by utilizing the sensors installed on 4000 taxis. Two types of traffic status estimation algorithms, the link-based and the vehicle-based, are introduced based on such data basis. The results from large-scale testing cases show that the traffic status can be fairly well estimated based on these imperfect data and we demonstrate the feasibility of such application in most of cities.

In performance studies of vehicular ad hoc networks (VANETs), the underlying mobility model plays an important role. Since conventional mobile ad hoc network (MANET) routing protocols do not work efficiently in vehicular environments due to the rapid topology changes, the Delay-Tolerant Network (DTN) model is often applied. In this paper, we construct a new mobility model, the Shanghai Urban Vehicular Network (SUVnet) model by using the GPS data from more than 4,000 taxis we have collected, and then investigate the performance of two kinds of DTN routing, the non-geographic pure epidemic routing and our newly-proposed geographic DTN routing, the Distance-Aware Epidemic Routing (DAER). We use the popular random waypoint mobility model and a more complex microscopic traffic simulator generated model for performance comparison. With the two considered DTN routing protocols, conventional mobility models tend to give higher performance results than SUVnet model, the presumably more realistic mobility model.

In this paper, we present the characteristics of trace data for a vehicular ad hoc network, the Shanghai Urban Vehicular Network (SUVnet). We construct a mobility model using the GPS data from more than 4,000 taxis collected in Shanghai city. Therefore, the model is both realistic and of large scale. Based on this model, the network topology, connectivity, and network performance of SUVnet are studied. The feasibility of an urban vehicular ad hoc network is discussed with a set of simulation results. This study provides a basis for a realistic urban vehicular mobile ad hoc network.