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Fine-grained network time synchronization using reference broadcasts
, 2002
"... Permission is granted for noncommercial reproduction of the work for educational or research purposes. ..."
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Cited by 764 (28 self)
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Permission is granted for noncommercial reproduction of the work for educational or research purposes.
Time Synchronization in Wireless Sensor Networks
, 2003
"... OF THE DISSERTATION University of California, Los Angeles, 2003 Professor Deborah L. Estrin, Chair active research in large-scale networks of small, wireless, low-power sensors and actuators. Time synchronization is a critical piece of infrastructure in any dis- tributed system, but wirel ..."
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Cited by 254 (10 self)
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OF THE DISSERTATION University of California, Los Angeles, 2003 Professor Deborah L. Estrin, Chair active research in large-scale networks of small, wireless, low-power sensors and actuators. Time synchronization is a critical piece of infrastructure in any dis- tributed system, but wireless sensor networks make particularly extensive use physical world. However, while the clock accuracy and precision requirements are often stricter in sensor networks than in traditional distributed systems, energy and channel constraints limit the resources available to meet these goals.
Wireless Sensor Networks: A New Regime for Time Synchronization
- IN PROCEEDINGS OF THE FIRST WORKSHOP ON HOT TOPICS IN NETWORKS (HOTNETS-I
, 2002
"... Wireless sensor networks (WSNs) consist of large populations of wirelessly connected nodes, capable of computation, communication, and sensing. Sensor nodes cooperate in order to merge individual sensor readings into a high-level sensing result, such as integrating a time series of position measurem ..."
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Cited by 201 (9 self)
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Wireless sensor networks (WSNs) consist of large populations of wirelessly connected nodes, capable of computation, communication, and sensing. Sensor nodes cooperate in order to merge individual sensor readings into a high-level sensing result, such as integrating a time series of position measurements into a velocity estimate. The physical time of sensor readings is a key element in this process called data fusion. Hence, time synchronization is a crucial component of WSNs. We argue that time synchronization schemes developed for traditional networks such as NTP [21] are ill-suited for WSNs and suggest more appropriate approaches.
Clock synchronization for wireless sensor networks: A Survey
- Ad Hoc Networks (Elsevier
, 2005
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SECTOR: secure tracking of node encounters in multi-hop wireless networks
- In ACM Workshop on Security of Ad Hoc and Sensor Networks (SASN
, 2003
"... In this paper we present SECTOR, a set of mechanisms for the secure verification of the time of encounters between nodes in multi-hop wireless networks. This information can be used notably to prevent wormhole attacks (without requiring any clock synchronization), to secure routing protocols based o ..."
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Cited by 164 (22 self)
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In this paper we present SECTOR, a set of mechanisms for the secure verification of the time of encounters between nodes in multi-hop wireless networks. This information can be used notably to prevent wormhole attacks (without requiring any clock synchronization), to secure routing protocols based on last encounters (with only loose clock synchronization) , and to control the topology of the network. SECTOR is based primarily on distance-bounding techniques, on one-way hash chains and on Merkle hash trees. We analyze the communication, computation and storage complexity of the proposed mechanisms and we show that, due to their efficiency and simplicity, they are compliant with the limited resources of most mobile devices.
Simple, Accurate Time Synchronization for Wireless Sensor Networks
, 2003
"... Time synchronization is important for any distributed system. In particular, wireless sensor networks make extensive use of synchronized time in many contexts (e.g. for data fusion, TDMA schedules, synchronized sleep periods, etc.). Existing time synchronization methods were not designed with wirele ..."
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Cited by 142 (1 self)
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Time synchronization is important for any distributed system. In particular, wireless sensor networks make extensive use of synchronized time in many contexts (e.g. for data fusion, TDMA schedules, synchronized sleep periods, etc.). Existing time synchronization methods were not designed with wireless sensor networks in mind, and need to be extended or redesigned. Our solution centers around the development of a deterministic time synchronization method relevant for wireless sensor networks. The proposed solution features minimal complexity in network bandwidth, storage and processing and can achieve good accuracy. Highly relevant for sensor networks, it also provides tight, deterministic bounds on both the offsets and clock drifts. A method to synchronize the entire network in preparation for data fusion is presented. A real implementation of a wireless ad-hoc network is used to evaluate the performance of the proposed approach.
Global clock synchronization in sensor networks
- IEEE Transactions on Computers
"... Abstract—Global synchronization is important for many sensor network applications that require precise mapping of collected sensor data with the time of the events, for example, in tracking and surveillance. It also plays an important role in energy conservation in MAC layer protocols. This paper de ..."
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Cited by 137 (1 self)
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Abstract—Global synchronization is important for many sensor network applications that require precise mapping of collected sensor data with the time of the events, for example, in tracking and surveillance. It also plays an important role in energy conservation in MAC layer protocols. This paper describes four methods to achieve global synchronization in a sensor network: a node-based approach, a hierarchical cluster-based method, a diffusion-based method, and a fault-tolerant diffusion-based method. The diffusion-based protocol is fully localized. We present two implementations of the diffusion-based protocol for synchronous and asynchronous systems and prove its convergence. Finally, we show that, by imposing some constraints on the sensor network, global clock synchronization can be achieved in the presence of malicious nodes that exhibit Byzantine failures. Index Terms—Sensor networks, fault tolerance. æ
Time synchronization in sensor networks: A survey
- IEEE Network
, 2004
"... Time synchronization is an important issue in multihop ad hoc wireless networks such as sensor networks. Many applications of sensor networks need local clocks of sensor nodes to be synchronized, requiring various degrees of precision. Some intrinsic properties of sensor networks, such as limited re ..."
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Cited by 125 (0 self)
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Time synchronization is an important issue in multihop ad hoc wireless networks such as sensor networks. Many applications of sensor networks need local clocks of sensor nodes to be synchronized, requiring various degrees of precision. Some intrinsic properties of sensor networks, such as limited resources of energy, storage, computation, and bandwidth, combined with potentially high density of nodes make traditional synchronization methods unsuitable for these networks. Hence, there has been an increasing research focus on designing synchronization algorithms specifically for sensor networks. This article reviews the time synchronization problem and the need for synchronization in sensor networks, then presents in detail the basic synchronization methods explicitly designed and proposed for sensor networks. As advances in technology have enabled the development of tiny low-power devices capable of performing sensing and communication tasks, sensor networks have emerged and received the attention of many
A scalable synchronization protocol for large scale sensor networks and its applications
- IEEE Journal on Selected Areas in Communications,vol.23,no.5,pp
"... Abstract—Synchronization is considered a particularly difficult task in wireless sensor networks due to its decentralized structure. Interestingly, synchrony has often been observed in networks of biological agents (e.g., synchronously flashing fireflies, or spiking of neurons). In this paper, we pr ..."
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Cited by 69 (4 self)
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Abstract—Synchronization is considered a particularly difficult task in wireless sensor networks due to its decentralized structure. Interestingly, synchrony has often been observed in networks of biological agents (e.g., synchronously flashing fireflies, or spiking of neurons). In this paper, we propose a bio-inspired network synchronization protocol for large scale sensor networks that emulates the simple strategies adopted by the biological agents. The strategy synchronizes pulsing devices that are led to emit their pulses periodically and simultaneously. The convergence to synchrony of our strategy follows from the theory of Mirollo and Strogatz, 1990, while the scalability is evident from the many examples existing in the natural world. When the nodes are within a single broadcast range, our key observation is that the dependence of the synchronization time on the number of nodes is subject to a phase transition: for values of beyond a specific threshold, the synchronization is nearly immediate; while for smaller, the synchronization time decreases smoothly with respect to. Interestingly, a tradeoff is observed between the total energy consumption and the time necessary to reach synchrony. We obtain an optimum operating point at the local minimum of the energy consumption curve that is associated to the phase transition phenomenon mentioned before. The proposed synchronization protocol is directly applied to the cooperative reach-back communications problem. The main advantages of the proposed method are its scalability and low complexity. Index Terms—Communication systems, distributed algorithms, distributed feedback oscillators, sensor networks, synchronization. I.
