Fundamental Limits on Synchronizing Clocks Over Networks

Freris, Nikolaos M.; Graham, Steve; Kumar, P. R.

doi:10.1109/tac.2010.2089210

Cited by 183 publications

(105 citation statements)

References 16 publications

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“…The main result is that while estimating the clock skew between two nodes is possible, it is impossible to determine the clock offset for pairwise synchronization, unless the delays in two-way message communication are symmetric, i.e., d AB = d BA . The same result was later extended in [60] for the network case. Recently, timestamp-free synchronization algorithms were reported in [61,62] to avoid the overhead brought by timestamp exchanges.…”

Section: Conclusion and Open Problemssupporting

confidence: 56%

“…Based on the two-way message exchange system model described in Section 2.2, this paper surveyed the most representative pairwise and fully-distributed clock synchronization algorithms from a statistical signal processing viewpoint. The interested reader is referred to [59][60][61][62][63] for references based on other system models. Specifically, similar to Equation (2), [59] adopted a two-way message exchange mechanism where no random delay is considered and the fixed portion of delays is different for the uplink and downlink (i.e., replace d in Equation (2) by d AB and d BA ).…”

Section: Conclusion and Open Problemsmentioning

confidence: 99%

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An Overview of a Class of Clock Synchronization Algorithms for Wireless Sensor Networks: A Statistical Signal Processing Perspective

Jeske

Serpedin

2015

Algorithms

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Recently, wireless sensor networks (WSNs) have drawn great interest due to their outstanding monitoring and management potential in medical, environmental and industrial applications. Most of the applications that employ WSNs demand all of the sensor nodes to run on a common time scale, a requirement that highlights the importance of clock synchronization. The clock synchronization problem in WSNs is inherently related to parameter estimation. The accuracy of clock synchronization algorithms depends essentially on the statistical properties of the parameter estimation algorithms. Recently, studies dedicated to the estimation of synchronization parameters, such as clock offset and skew, have begun to emerge in the literature. The aim of this article is to provide an overview of the state-of-the-art clock synchronization algorithms for WSNs from a statistical signal processing point of view. This article focuses on describing the key features of the class of clock synchronization algorithms that exploit the traditional two-way message (signal) exchange mechanism. Upon introducing the two-way message exchange mechanism, the main clock offset estimation algorithms for pairwise synchronization of sensor nodes are first reviewed, and their performance is compared. The class of fully-distributed clock offset estimation algorithms for network-wide synchronization is then surveyed. The paper concludes with a list of open research problems pertaining to clock synchronization of WSNs.

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Section: Conclusion and Open Problemssupporting

confidence: 56%

Section: Conclusion and Open Problemsmentioning

confidence: 99%

An Overview of a Class of Clock Synchronization Algorithms for Wireless Sensor Networks: A Statistical Signal Processing Perspective

Jeske

Serpedin

2015

Algorithms

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“…Example 3: Consider the system (8) and (9) satisfying Assumption 1, with T 1 = 3 and T 2 = 7 andτ = (δ , 0) ∈ [0, 1) × 0. Then, n 1 = 7, n 2 = 3 and D = 21.…”

Section: Further Reduction Of the Time-domainmentioning

confidence: 99%

“…As mentioned there, clocks synchronization over networks has fundamental limitations [8] and GPS synchronization may be vulnerable against malicious attacks [12]. In this context [19] addresses the problem of how large the clock offset between actuator and sensor can be, without compromising the existence of a stabilizing linear time-invariant controller.…”

Section: Introductionmentioning

confidence: 99%

Stability analysis for systems with asynchronous sensors and actuators

Fiacchini¹,

Morărescu²

2016

2016 IEEE 55th Conference on Decision and Control (CDC)

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Abstract-The paper provides computation-oriented necessary and sufficient conditions for the global exponential stability of linear systems with asynchronous sensors and actuators. Precisely, we focus on continuous-time linear systems whose state undergoes finite jumps referred to as impulsions. The impulsions are of two types: those related to input updates and those related to measurement updates. We assume that impulsions of each type occur periodically but the periods may be different and the clocks at the sensor and at the actuator are not synchronized. We first show that the analysis can be reduced to a finite time domain. Based on that, we provide necessary and sufficient conditions for the global exponential stability of systems belonging to the class under study. An example illustrates numerically the proposed results.

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“…The problem of time synchronization in WSNs has attracted a great deal of attention; it represents a challenge, having in mind multi-hop communications, unpredictable packet losses and high probability of node failures. There are numerous approaches to time synchronization in WSNs starting from different assumptions, e.g., Freris et al (2011Freris et al ( , 2009Carli et al (2011);Xia and Cao (2011);Ganeriwal et al (1999); Elson et al (2002). An important class of time synchronization algorithms is based on full distribution of functions, when there are no reference nodes and when all the nodes run the same algorithm, such as in, e.g., Simeone et al (2008); Solis et al (2006).…”

Section: Introductionmentioning

confidence: 99%

Distributed Time Synchronization in Lossy Wireless Sensor Networks

Stanković

Johansson

2012

IFAC Proceedings Volumes

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In this paper a new distributed time synchronization algorithm is proposed for lossy wireless sensor networks with noisy local clock readings and inter-node communications. The algorithm is derived in the form of two asynchronous recursions of stochastic gradient type providing estimates of the parameters used to compensate drifts and offsets of the local clocks. A special modification of the algorithm for drift compensation based on instrumental variables is introduced in the case of internal measurement noise. It is proved that the proposed algorithm provides asymptotic synchronization in the sense that all the equivalent drifts, as well as all the equivalent offsets, converge in the mean square sense and with probability one to the same random variables.

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Fundamental Limits on Synchronizing Clocks Over Networks

Cited by 183 publications

References 16 publications

An Overview of a Class of Clock Synchronization Algorithms for Wireless Sensor Networks: A Statistical Signal Processing Perspective

An Overview of a Class of Clock Synchronization Algorithms for Wireless Sensor Networks: A Statistical Signal Processing Perspective

Stability analysis for systems with asynchronous sensors and actuators

Distributed Time Synchronization in Lossy Wireless Sensor Networks

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