Browsing by Author "Gu, Yu"
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Item Sleipnir: A Versatile Extremely Low Duty-Cycle Sensor Network(2009-10-07) Gu, Yu; He, TianWireless Sensor Network (WSN) is a new information paradigm based on the collaboration of a large number of self-organized sensing nodes that can be used for applications such as assisted living, infrastructure protection and scientific exploration. Along with advantages such as low-cost and low-profile, sensor networks are severely resource constrained, especially in terms of energy supply due to its small-form-factor. However, many sensor network based applications require a lifetime that can span tens of years. In order to bridge the gap between limited energy supply and long-term operation requirement, we then have to build extremely low duty-cycle sensor networks where sensor nodes stay in a dormant state for most of the time. In this thesis research, we initiate the first systematic research in this frontier under a wide spectrum of design space, including static, dynamic and mobile networks.Item Sleipnir: a versatile extremely low duty-cycle sensor network.(2010-06) Gu, YuWireless Sensor Network (WSN), is a new information paradigm based on the collaboration of a large number of self-organized sensing nodes. With the increasing demand of cyber-physical interaction, wireless sensor networks have emerged as one of key technologies for many promising applications such as assisted living, military surveillance, infrastructure protection and scientific exploration. Sensor networks are acclaimed to be low-cost, low-profile, and easy to deploy. These attractive advantages, however, imply the resources available to individual nodes are severely limited. Although it is highly possible that the constraints on computation and storage disappear along with the fast development of fabrication techniques, the energy constraint is unlikely to fade away quickly. On the other hand, many sensor network based applications require a lifetime that ranges from several months to tens of years. In order to bridge the gap between limited energy supply and long-term operation requirement of applications, we then have to build extremely low duty-cycle sensor networks where during the operation of sensor applications, sensor nodes activate very briefly and stay in a dormant state for a very long period of time. In this dissertation research, we initiate the first systematic research for low-duty-cycle sensor networks, including a generic sensing architecture, a novel data forwarding scheme for intermittently connected networks and an energy synchronized communication middleware for energy-harvesting sensor networks. The goal of this dissertation research is to provide better understanding of how to build practical and efficient extremely low duty-cycle sensor networks and support those long-term applications such as structure monitoring, traffic control and so on. We hope, toward the very end, this dissertation research can assist the transition of sensor network technology from a research concept to a general-purpose technology available for use for a wide variety of research, government and industry purposes.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 Travel Prediction-based Data Forwarding for Sparse Vehicular Networks(2011-07-28) Xu, Fulong; Guo, Shuo; Jeong, Jaehoon; Gu, Yu; Cao, Qing; Liu, Ming; He, TianVehicular Ad Hoc Networks (VANETs) represent promising technologies of cyber-physical systems for improving driving safety and communication mobility. Due to the highly dynamic driving patterns of vehicles, effective packet forwarding, especially for time sensitive data, has been a challenging research problem. Previous works forward data packets mostly utilizing statistical information about road network traffic, which becomes much less accurate when vehicles travel in sparse network as highly dynamic traffic introduces large variance for these statistics.With the popularity of on-board GPS navigation systems, individual vehicle trajectories become available and can be utilized for removing the uncertainty in road traffic statistics and improve the performance of the data forwarding in VANETs. In this paper, we propose Travel Prediction based Data-forwarding (TPD), in which vehicles share their trajectory information to achieve the low delay and high reliability of data delivery in multi-hop carry-and-forward environments. The driven idea is to construct a vehicle encounter graph based on pair-wise encounter probabilities, derived from shared trajectory information. With the encounter graph available, TPD optimizes delivery delay under a specific delivery ratio threshold, and the data forwarding rule is that a vehicle carrying packets always selects the next packet-carrier that can provide the best forwarding performance within the communication range. Through extensive simulations we demonstrate that TPD significantly outperforms existing schemes of TBD and VADD with more than 5% more packets delivery while reducing more than 40% delivery delay.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 VISA: Virtual Scanning Algorithm for Dynamic Protection of Road Networks(2008-08-22) Jeong, Jaehoon; Gu, Yu; He, Tian; DuHung-Chang, DavidThis paper proposes a Virtual Scanning Algorithm (VISA), tailored and optimized for road network surveillance. Our design uniquely leverages upon the facts that (i) the movement of targets (e.g., vehicles) is confined within roadways and (ii) the road network maps are normally known. We guarantee the detection of moving targets before they reach designated protection points (such as temporary base camps), while maximizing the lifetime of the sensor network. The main idea of this work is virtual scan - waves of sensing activities scheduled for road network protection. We provide design-space analysis on the performance of virtual scan in terms of lifetime and average detection delay. Importantly, to our knowledge, this is the first work to study how to guarantee target detection while sensor network deteriorates, using a novel hole handling technique. Through theoretical analysis and extensive simulation, it is shown that a surveillance system, using our design, sustains orders-of-magnitude longer lifetime than full coverage algorithms, and as much as ten times longer than legacy duty cycling algorithms.