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Proceedings ArticleDOI

An algorithm for WSN clock synchronization: Uncertainty and convergence rate trade off

06 Jul 2009-pp 74-79
TL;DR: A synchronization algorithm based on a linear controller is used to dynamically compensate both mutual offsets and drifts of the clock associated with the nodes of a WSN, which explicitly takes into account the inter-node communication latencies.
Abstract: -Achieving tight time synchronization between wireless sensor network (WSN) nodes is essential to coordinate the activities of different devices. In this paper, a synchronization algorithm based on a linear controller is used to dynamically compensate both mutual offsets and drifts of the clock associated with the nodes of a WSN. This approach, compared with other existing solutions based on control theory, explicitly takes into account the inter-node communication latencies. Furthermore, it presents on optimal (fastest convergence) controller in the case of full visibility among nodes. In the case of noise in both the clock measurements and the clock drifts, a controller that reduces the noise effect on the synchronization accuracy is also proposed and compared to the optimal one. In all cases, the correct operation of the algorithm has been proved through simulations.
Citations
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Proceedings ArticleDOI
13 May 2012
TL;DR: A consensus-based synchronization algorithm is used to compensate dynamically both time offsets and clock frequency skews, thus driving all WSN clocks towards a common time scale.
Abstract: Time synchronization in wireless sensor networks (WSN) is essential to schedule communication and distributed measurement tasks. In this paper a consensus-based synchronization algorithm is used to compensate dynamically both time offsets and clock frequency skews, thus driving all WSN clocks towards a common time scale. The proposed approach does not require either the election of a master node as a time reference for the whole network, or a specific synchronization protocol. Some simulation results show that the algorithm converges within a reasonable time, regardless of timestamping jitter, random communication latencies and incomplete node visibility.

4 citations


Cites background from "An algorithm for WSN clock synchron..."

  • ..., the expected clock evolution), a second-order system is needed [18], [19]....

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Journal ArticleDOI
TL;DR: The result indicates that error accumulation is lower in the optimized algorithm, the synchronization overhead is significantly reduced and the RBRS algorithm can improve the synchronization accuracy and reduce energy consumption significantly, which is conducive to extend the life of the network.
Abstract: Based on the study of RBS algorithm in wireless sensor network, an improved algorithm named RBRS is presented, to solve the time synchronization problem of multi hop networks. On the basis of RBS, the broadcast group and least square linear regression methods were used to realize entire network time synchronization in the algorithm. Synchronization error and overhead with the existing improved BRS are compared in the article. The result shows that the algorithm has certain superiority in many algorithms, which is suitable for light and low power consumption network load. Through an emulation with the matlab software, the result indicates that error accumulation is lower in the optimized algorithm, the synchronization overhead is significantly reduced and can realize the time synchronization of the whole network. A time synchronization algorithm based on RBRS algorithm is proposed for multi-hop and the low power consumption. A variable period synchronization method is introduces in the algorithm: in line with Bias maximum a posterior estimation principle, the maximum phase offset is estimated to determine the synchronization period, which can reduce the number of node synchronization, and with the least square linear regression method, the periodic fitting clock offset. The Simulation in matlab indicate that RBRS algorithm can improve the synchronization accuracy and reduce energy consumption significantly, which is conducive to extend the life of the network.

3 citations

01 Jan 2013
TL;DR: This dissertation presents the proposal, implementation, and evaluation of a new architecture for the framework C-MAC, enabling a greater reuse of its software components, providing greater configurability and, consequently, supporting a wider range of applications.
Abstract: Wireless sensor networks are highly dependent on medium access control protocols to make effective use of the few resources available on sensor nodes. Nevertheless, most of the optimizations proposed by existing protocols focus on specific segments of the design space. What is considered an optimization by one class of applications can represent a strong limitation for others. A protocol aiming at covering a large fraction of the application universe for sensor networks must feature configuration or adaptation mechanisms. Therefore, the Configurable Medium Access Control (C-MAC) was created (WANNER; OLIVEIRA; FROHLICH, 2007). C-MAC is realized as a framework of medium access control strategies that can be combined to produce application-specific protocols. Through this paradigm, application programmers can create new communication services on demand and experiment with different communication parameters, collecting metrics to identify and adjust the protocol to match their applications’ requirements. Nonetheless, C-MAC original architecture provides low reuse of software components, hindering its configurability. This dissertation presents the proposal, implementation, and evaluation of a new architecture for the framework C-MAC. Through the analysis of the different categories of MAC protocols for sensor networks, common characteristics and specificities of these protocols were identified and used in the development of the new C-MAC. Thus, the proposed architecture enables a greater reuse of its software components, providing greater configurability and, consequently, supporting a wider range of applications.
References
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Journal ArticleDOI
09 Dec 2002
TL;DR: Reference Broadcast Synchronization (RBS) as discussed by the authors is a scheme in which nodes send reference beacons to their neighbors using physical-layer broadcasts, and receivers use their arrival time as a point of reference for comparing their clocks.
Abstract: Recent advances in miniaturization and low-cost, low-power design have led to active research in large-scale networks of small, wireless, low-power sensors and actuators. Time synchronization is critical in sensor networks for diverse purposes including sensor data fusion, coordinated actuation, and power-efficient duty cycling. Though the clock accuracy and precision requirements are often stricter than in traditional distributed systems, strict energy constraints limit the resources available to meet these goals.We present Reference-Broadcast Synchronization, a scheme in which nodes send reference beacons to their neighbors using physical-layer broadcasts. A reference broadcast does not contain an explicit timestamp; instead, receivers use its arrival time as a point of reference for comparing their clocks. In this paper, we use measurements from two wireless implementations to show that removing the sender's nondeterminism from the critical path in this way produces high-precision clock agreement (1.85 ± 1.28μsec, using off-the-shelf 802.11 wireless Ethernet), while using minimal energy. We also describe a novel algorithm that uses this same broadcast property to federate clocks across broadcast domains with a slow decay in precision (3.68 ± 2.57μsec after 4 hops). RBS can be used without external references, forming a precise relative timescale, or can maintain microsecond-level synchronization to an external timescale such as UTC. We show a significant improvement over the Network Time Protocol (NTP) under similar conditions.

2,537 citations

Proceedings ArticleDOI
03 Nov 2004
TL;DR: The FTSP achieves its robustness by utilizing periodic flooding of synchronization messages, and implicit dynamic topology update and comprehensive error compensation including clock skew estimation, which is markedly better than that of the existing RBS and TPSN algorithms.
Abstract: Wireless sensor network applications, similarly to other distributed systems, often require a scalable time synchronization service enabling data consistency and coordination. This paper describes the Flooding Time Synchronization Protocol (FTSP), especially tailored for applications requiring stringent precision on resource limited wireless platforms. The proposed time synchronization protocol uses low communication bandwidth and it is robust against node and link failures. The FTSP achieves its robustness by utilizing periodic flooding of synchronization messages, and implicit dynamic topology update. The unique high precision performance is reached by utilizing MAC-layer time-stamping and comprehensive error compensation including clock skew estimation. The sources of delays and uncertainties in message transmission are analyzed in detail and techniques are presented to mitigate their effects. The FTSP was implemented on the Berkeley Mica2 platform and evaluated in a 60-node, multi-hop setup. The average per-hop synchronization error was in the one microsecond range, which is markedly better than that of the existing RBS and TPSN algorithms.

2,267 citations

Book
01 Jan 1987
TL;DR: Discrete-time control systems, Discrete- time control systems , مرکز فناوری اطلاعات و ا�ل squares رسانی, کسورزی.
Abstract: Discrete-time control systems , Discrete-time control systems , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

2,098 citations


"An algorithm for WSN clock synchron..." refers background in this paper

  • ...Such a discrete time system, dubbed as dead beat in control literature, reaches the desired value after two steps, since the closed loop system is of the second order [12]....

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Journal ArticleDOI
01 Jul 2000
TL;DR: In this paper, the authors introduce the concept of hybrid systems and some of the challenges associated with the stability of such systems, including the issues of guaranteeing stability of switched stable systems and finding conditions for the existence of switched controllers for stabilizing switched unstable systems.
Abstract: This paper introduces the concept of a hybrid system and some of the challenges associated with the stability of such systems, including the issues of guaranteeing stability of switched stable systems and finding conditions for the existence of switched controllers for stabilizing switched unstable systems. In this endeavour, this paper surveys the major results in the (Lyapunov) stability of finite-dimensional hybrid systems and then discusses the stronger, more specialized results of switched linear (stable and unstable) systems. A section detailing how some of the results can be formulated as linear matrix inequalities is given. Stability analyses on the regulation of the angle of attack of an aircraft and on the PI control of a vehicle with an automatic transmission are given. Other examples are included to illustrate various results in this paper.

1,647 citations


"An algorithm for WSN clock synchron..." refers background or methods in this paper

  • ...In general, the performance of a switching system may be so severely lowered that even stability may be destroyed, although each compounding closed loop system is asymptotically stable [11]....

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  • ...In this way, referred to as an average dwell time approach in switching system literature [11], the rate of γk changes is lowered down to ensure global stability....

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27 Sep 2004
TL;DR: A protocol is provided in this standard that enables precise synchronization of clocks in measurement and control systems implemented with technologies such as network communication, local computing, and distributed objects.
Abstract: A protocol is provided in this standard that enables precise synchronization of clocks in measurement and control systems implemented with technologies such as network communication, local computing, and distributed objects. The protocol is applicable to systems communicating via packet networks. Heterogeneous systems are enabled that include clocks of various inherent precision, resolution, and stability to synchronize. System-wide synchronization accuracy and precision in the sub-microsecond range are supported with minimal network and local clock computing resources. Simple systems are installed and operated without requiring the management attention of users because the default behavior of the protocol allows for it.

1,428 citations