Structural Damage Detection Robust Against Time Synchronization Errors

Structural Damage Detection based on Wireless Sensor Networks Can Be Affected Significantly by Time Synchronization Errors among Sensors. Precise Time Synchronization of Sensor Nodes Has Been Viewed as Crucial for Addressing This Issue. However, Precise Time Synchronization over a Long Period of Time is Often Impractical in Large Wireless Sensor Networks Due to Two Inherent Challenges. First, Time Synchronization Needs to Be Performed Periodically, Requiring Frequent Wireless Communication among Sensors at Significant Energy Cost. Second, Significant Time Synchronization Errors May Result from Node Failures Which Are Likely to Occur during Long-Term Deployment over Civil Infrastructures. in This Paper, a Damage Detection Approach is Proposed that is Robust Against Time Synchronization Errors in Wireless Sensor Networks. the Paper First Examines the Ways in Which Time Synchronization Errors Distort Identified Mode Shapes, and Then Proposes a Strategy for Reducing Distortion in the Identified Mode Shapes. Modified Values for These Identified Mode Shapes Are Then Used in Conjunction with Flexibility-Based Damage Detection Methods to Localize Damage. This Alternative Approach Relaxes the Need for Frequent Sensor Synchronization and Can Tolerate Significant Time Synchronization Errors Caused by Node Failures. the Proposed Approach is Successfully Demonstrated through Numerical Simulations and Experimental Tests in a Lab. © 2010 IOP Publishing Ltd

Time synchronization in wireless sensor networks

Time synchronization is basic requirements for various applications in wireless sensor network, e.g., event detection, speed estimating, environment monitoring, data aggregation, target tracking, scheduling and sensor nodes cooperation. Time synchronization is also helpful to save energy in WSN because it provides the possibility to set nodes into the sleeping mode. In wireless sensor networks all of above applications need that all sensor nodes have a common time reference. However, most existing time synchronization protocols are likely to deteriorate or even be destroyed when the WSNs attack by malicious intruders. The recently developed maximum and minimum consensus based time synchronization protocol (MMTS) is a promising alternative as it does not depend on any reference node or network topology. But MMTS is vulnerable to message manipulation attacks. In this thesis, we focus on how to defend the MMTS protocol in wireless sensor networks under message manipulation attacks. We investigate the impact of message manipulation attacks over MMTS. Then, a Secured Maximum and Minimum Consensus based Time Synchronization (SMMTS) protocol is proposed to detect and invalidate message manipulation attacks

A distributed scheme to detect wormhole attacks in mobile wireless sensor networks

Due to mostly being unattended, sensor nodes become open to physical attacks such as wormhole attack, which is our focus in this paper. Various solutions are proposed for wormhole attacks in sensor networks, but only a few of them take mobility of sensor nodes into account. We propose a distributed wormhole detection scheme for mobile wireless sensor networks in which mobility of sensor nodes is utilized to estimate two network features (i.e. network node density, standard deviation in network node density) through using neighboring information in a local manner. Wormhole attack is detected via observing anomalies in the neighbor nodes’ behaviors based on the estimated network features and the neighboring information. We analyze the performance of proposed scheme via simulations. The results show that our scheme achieves a detection rate up to 100% with very small false positive rate (at most 1.5%) if the system parameters are chosen accordingly. Moreover, our solution requires neither additional hardware nor tight clock synchronization which are both costly for sensor networks

A Time Synchronization Protocol for TDMA Based Wireless Sensor Networks

학위논문 (석사)-- 서울대학교 대학원 : 전기공학부, 2013. 8. 이정우.There has been much interest in wireless sensor networks recently, due to their diverse range of possible applications. Although there have been much research in MAC layer protocols for wireless sensor networks, these works are mainly focussed on the power savings and efficiencies of the protocols. For sensor networks which are in-situ and do not require much flexibility, such as a battery management system, energy is not always the most important factor, but rather reliability and scalability (where sensing periods are known). As such, a traditional TDMA protocol can be considered as a good option. Time synchronization in wireless sensor networks have also been considered by many academics, but work related to time synchronization in TDMA networks have been much less popular. In this thesis, a time synchronization protocol for TDMA based wireless sensor networks is proposed, Propagating Chain Time Synchronization. Propagating Chain Time Synchronization is a novel protocol for synchronizing TDMA based networks. The scheme achieves improved synchronization errors compared to traditional beacon synchronization methods, through skew correction estimated from chained two-way message exchanges, which employ piggybacking and overhearing.1 Introduction 1 1.1 Wireless Sensor Networks 1 1.1.1 Challenges in Designing Wireless Sensor Networks 2 1.2 Thesis Motivation 7 1.2.1 Wireless Sensor Networks in Battery Management Systems 7 2 Time Synchronization 10 2.1 Overview 10 2.2 Models of Clock Synchronization 11 2.2.1 Typical Synchronization Errors 13 2.3 Related Work 14 2.3.1 Sender-Receiver Synchronization 14 2.3.2 Receiver-Receiver Synchronization 16 2.3.3 Receiver-Only Synchronization 17 2.3.4 Clock Skew Estimation and Correction 18 2.3.5 Clock Synchronization in TDMA Based Networks 19 3 Propagating Chain Time Synchronization for TDMA Based Wireless Sensor Networks 21 3.1 Overview 21 3.2 System Model 21 3.2.1 Basic Assumptions 22 3.2.2 Topology 22 3.2.3 Chained Synchronization 23 3.2.4 Overhearing and Piggybacking 24 3.2.5 Propagating Skew Correction 28 4 Theoretical Error Analysis 31 4.1 System Models 31 4.2 Node Clock Modelling 32 4.3 TSF 34 4.4 Chained Synchronization 36 4.5 Two-Way Message Exchange Synchronization Error 38 5 Simulation 42 5.1 Simulation Parameters 42 5.2 Simulation Results 46 6 Conclusion 52 Bibliography 54Maste

Fundamentals of Large Sensor Networks: Connectivity, Capacity, Clocks and Computation

Sensor networks potentially feature large numbers of nodes that can sense their environment over time, communicate with each other over a wireless network, and process information. They differ from data networks in that the network as a whole may be designed for a specific application. We study the theoretical foundations of such large scale sensor networks, addressing four fundamental issues- connectivity, capacity, clocks and function computation. To begin with, a sensor network must be connected so that information can indeed be exchanged between nodes. The connectivity graph of an ad-hoc network is modeled as a random graph and the critical range for asymptotic connectivity is determined, as well as the critical number of neighbors that a node needs to connect to. Next, given connectivity, we address the issue of how much data can be transported over the sensor network. We present fundamental bounds on capacity under several models, as well as architectural implications for how wireless communication should be organized. Temporal information is important both for the applications of sensor networks as well as their operation.We present fundamental bounds on the synchronizability of clocks in networks, and also present and analyze algorithms for clock synchronization. Finally we turn to the issue of gathering relevant information, that sensor networks are designed to do. One needs to study optimal strategies for in-network aggregation of data, in order to reliably compute a composite function of sensor measurements, as well as the complexity of doing so. We address the issue of how such computation can be performed efficiently in a sensor network and the algorithms for doing so, for some classes of functions.Comment: 10 pages, 3 figures, Submitted to the Proceedings of the IEE

Self-Synchronization in Duty-cycled Internet of Things (IoT) Applications

In recent years, the networks of low-power devices have gained popularity. Typically these devices are wireless and interact to form large networks such as the Machine to Machine (M2M) networks, Internet of Things (IoT), Wearable Computing, and Wireless Sensor Networks. The collaboration among these devices is a key to achieving the full potential of these networks. A major problem in this field is to guarantee robust communication between elements while keeping the whole network energy efficient. In this paper, we introduce an extended and improved emergent broadcast slot (EBS) scheme, which facilitates collaboration for robust communication and is energy efficient. In the EBS, nodes communication unit remains in sleeping mode and are awake just to communicate. The EBS scheme is fully decentralized, that is, nodes coordinate their wake-up window in partially overlapped manner within each duty-cycle to avoid message collisions. We show the theoretical convergence behavior of the scheme, which is confirmed through real test-bed experimentation.Comment: 12 Pages, 11 Figures, Journa