Two-clocks synchronization for networked sensors

Fernández‐Madrigal, Juan‐Antonio; Martínez-Tenor, Ángel

doi:10.1109/icsens.2014.6985431

Cited by 2 publications

(5 citation statements)

References 11 publications

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“… Differences detected in execution times of the algorithms when exposed to different scenarios are not highly significant, but in the case of geometrical methods, they are slightly more efficient in the number of polygon vertices in symmetric communication scenarios. Another result is that the number of vertices is kept around tenths, corroborating a hypothesis stated in [ 20 ]. The total amount of uncertainty in geometrical algorithms, either measured as polygon areas or diagonals (

and

), and also the isolated amount of uncertainty in

and

(which is not only produced by the geometrical algorithms), or, in other words, the inaccuracy of the algorithms, is smaller in scenarios with shorter round-trip times and with faster communications compared to the execution times in

.…”

Section: Statistical Analysis Of Methods and Systemssupporting

confidence: 85%

“…Differences detected in execution times of the algorithms when exposed to different scenarios are not highly significant, but in the case of geometrical methods, they are slightly more efficient in the number of polygon vertices in symmetric communication scenarios. Another result is that the number of vertices is kept around tenths, corroborating a hypothesis stated in [20].…”

supporting

confidence: 83%

“…The geometrical algorithm presented in [ 20 ], that can be abbreviated as DGP for Direct Geometrical Pairwise synchronization, shows similar features in the estimation of

and

as that of Berthaud’s, but it runs a more computationally efficient procedure due to its direct work on the

plane. One of the first “direct” geometrical approaches was [ 19 ], that reported a nice statistical solution in the form of maximum likelihood estimator, however without hard guarantees and under the assumption of a very particular form for the probability distribution of the communication delays (exponential), specifically aimed at wireless sensor networks.…”

Section: Related Work and Synchronization Methodsmentioning

confidence: 99%

“…That relation, although appearing in the literature under several forms and names, can be formalized with two quantities: the relative drift, that we denote as

, which relates the deviations of the frequencies of both clocks from their nominal values, and the relative offset,

, that reflects the difference between their starting times—their zero-time timestamps—conveniently adjusted by their drifts. Formally, the two-clock synchronization problem can be stated as,

where it can be shown that [ 20 ],

being the following the basic parameters of the problem formulation:

are the nominal clock periods of both devices;

are the actual clock periods;

are the universal time moments when both devices started their respective clocks;

is the error produced by using discrete timestamps. …”

Section: Introductionmentioning

confidence: 99%

“…Thus, a less restricted approach is needed which is applicable to pairwise systems. The DGP method that we include in this study does not require any particular form for the delays distribution and includes hard guarantees along with the estimates [20].…”

mentioning

confidence: 99%

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Characterization, Statistical Analysis and Method Selection in the Two-Clocks Synchronization Problem for Pairwise Interconnected Sensors

Fernández‐Madrigal

Navarro

Asenjo

et al. 2020

Sensors

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Time synchronization among sensor devices connected through non-deterministic media is a fundamental requirement for sensor fusion and other distributed tasks that need a common time reference. In many of the time synchronization methods existing in literature, the estimation of the relation between pairs of clocks is a core concept; moreover, in applications that do not have general connectivity among its devices but a simple pairwise topology, such as embedded systems, mobile robots or home automation, two-clock synchronization is actually the basic form of the time estimation problem. In these kinds of applications, especially for critical ones, not only the quality of the estimation of the relation between two clocks is important, but also the bounds the methods provide for the estimated values, and their computational effort (since many are small systems). In this paper, we characterize, with a thorough parameterization, the possible scenarios where two-clock synchronization is to be solved, and then conduct a rigorous statistical study of both scenarios and methods. The study is based on exhaustive simulations run in a super-computer. Our aim is to provide a sound basis to select the best clock synchronization algorithm depending on the application requirements and characteristics, and also to deduce which ones of these characteristics are most relevant, in general, when solving the problem. For our comparisons we have considered several representative methods for clock synchronization according to a novel taxonomy that we also propose in the paper, and in particular, a few geometrical ones that have special desirable characteristics for the two-clock problem. We illustrate the method selection procedure with practical use-cases of sensory systems where two-clock synchronization is essential.

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and

), and also the isolated amount of uncertainty in

and

.…”

Section: Statistical Analysis Of Methods and Systemssupporting

confidence: 85%

“…Differences detected in execution times of the algorithms when exposed to different scenarios are not highly significant, but in the case of geometrical methods, they are slightly more efficient in the number of polygon vertices in symmetric communication scenarios. Another result is that the number of vertices is kept around tenths, corroborating a hypothesis stated in [20].…”

supporting

confidence: 83%

“…The geometrical algorithm presented in [ 20 ], that can be abbreviated as DGP for Direct Geometrical Pairwise synchronization, shows similar features in the estimation of

and

as that of Berthaud’s, but it runs a more computationally efficient procedure due to its direct work on the

Section: Related Work and Synchronization Methodsmentioning

confidence: 99%

“…That relation, although appearing in the literature under several forms and names, can be formalized with two quantities: the relative drift, that we denote as

, which relates the deviations of the frequencies of both clocks from their nominal values, and the relative offset,

, that reflects the difference between their starting times—their zero-time timestamps—conveniently adjusted by their drifts. Formally, the two-clock synchronization problem can be stated as,

where it can be shown that [ 20 ],

being the following the basic parameters of the problem formulation:

are the nominal clock periods of both devices;

are the actual clock periods;

are the universal time moments when both devices started their respective clocks;

is the error produced by using discrete timestamps. …”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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