Browsing by Author "Hung-Chang Du, David"
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Item TBD: Trajectory-Based Data Forwarding for Light-Traffic Vehicular Networks(2008-11-24) Jeong, Jaehoon; Guo, Shuo; Gu, Yu; He, Tian; Hung-Chang Du, DavidThis paper proposes a Trajectory-Based Data Forwarding (TBD) scheme, tailored for the data forwarding in light-traffic vehicular ad-hoc networks. We consider the scenarios in which Internet access points are sparsely deployed to receive the roadside reports of time-critical information such as driving accident or hazard. Since the Internet access points have limited communication coverage, a vehicular ad-hoc network is needed to forward data packets to the access points. State-of-the-art schemes have demonstrated the effectiveness of their data forwarding strategies by exploiting known vehicular traffic statistics (e.g., densities and speeds) in such a network. These results are encouraging, however, further improvements can be made by taking advantage of the growing popularity of GPS-based navigation systems. This paper presents the first attempt to investigate how to effectively utilize vehicles' trajectory information in a privacy-preserving manner. In our design, the trajectory information is combined with the traffic statistics to improve the performance of data forwarding in road networks. Through theoretical analysis and extensive simulation, it is shown that our design outperforms the existing scheme in terms of both the data delivery delay and packet delivery ratio, specially under light-traffic situations.Item TSF: Trajectory-based Statistical Forwarding for Infrastructure-to-Vehicle Data Delivery in Vehicular Networks(2010-03-12) Jeong, Jaehoon; Guo, Shuo; Gu, Yu; He, Tian; Hung-Chang Du, DavidWe consider the scenarios where Internet access points are sparsely deployed in road networks to provide individual vehicles with customized road condition information for the driving safety, such as holes and bumps along their trajectories. Due to the limited communication coverage, vehicular ad-hoc networks are used to support the multi-hop data forwarding. State-of-the-art schemes have demonstrated their effectiveness in the data forwarding from vehicles to stationary points (e.g., Internet access points). However, they are not designed for the reverse data forwarding from Internet access points to vehicles, a much more challenging problem because of the mobility of the packet destination. This paper proposes a data forwarding scheme called Trajectory-based Statistical Forwarding (TSF), tailored for the infrastructure-to-vehicle data delivery in vehicular networks. TSF forwards packets over multi-hop to a selected target point where the vehicle is expected to pass by. Such a target point is selected optimally to minimize the packet delivery delay while satisfying the required packet delivery probability. The optimality is achieved analytically by utilizing the packet's delivery delay distribution and the destination vehicle's travel delay distribution. To our knowledge, this paper presents the first attempt to investigate how to effectively utilize the destination vehicle's trajectory to compute such an optimal target point. Through theoretical analysis and extensive simulation, it is shown that our design provides an efficient data forwarding under a variety of vehicular traffic conditions.Item Wireless Sensor Networks with Energy Efficient Organization(2002-12-08) Cardei, Mihaela; MacCallum, David; Cheng, Xiaoyan; Min, Manki; Jia, Xiaohua; Li, Deying; Du, Ding-Zhu; Hung-Chang Du, DavidA critical aspect of applications with wireless sensor networks is network lifetime. Battery-powered sensors are usable as long as they can communicate captured data to a processing node. Sensing and communications consume energy, therefore judicious power management and scheduling caneffectively extend the operational time. One important class of wireless sensor applications consists of deployment of large number of sensors in an area for environmental monitoring. The data collected by the sensors is sent to a central node for processing. In this paper we propose an efficient method to achieve energy savings by organizing the sensor nodes into a maximum number of disjoint dominating sets (DDS) which are activated successively. Only the sensors from the active set are responsible for monitoring the target area and for disseminating the collected data. All other nodes are into a sleep mode, characterized by a low energy consumption. We define the maximum disjoint dominating sets problem and we design a heuristic that computes the sets. Theoretical analysis and performance evaluation results are presented to verify our approach.