Should the classical variance be used as a basic measure in standards metrology?

Allan, David W.

doi:10.1109/tim.1987.6312761

Cited by 195 publications

(150 citation statements)

References 20 publications

Supporting

Mentioning

148

Contrasting

Unclassified

Order By: Relevance

“…A (t 0 ) counts for the original speed difference between two clocks at t 0 ; the integration part η(u)du accumulates real-time environmental impacts during t. In practice, the value of σ η can be obtained from empirical literatures [33][14] [35] or system profiling before network deployments [16] [34].…”

Section: Clock Drift Modelingmentioning

confidence: 99%

PSR: Practical synchronous rendezvous in low-duty-cycle wireless networks

Huang

Yun

Zhong

et al. 2013

2013 Proceedings IEEE INFOCOM

View full text Add to dashboard Cite

Abstract-Low-duty-cycle radio operations have been proposed for wireless networks facing severe energy constraints. Despite energy savings, duty-cycling the radio creates transient-available wireless links, making communication rendezvous a challenging task under the practical issue of clock drift. To overcome limitations of prior work, this paper presents PSR, a practical design for synchronous rendezvous in low-duty-cycle wireless networks. The key idea behind PSR is to extract timing information naturally embedded in the pattern of radio duty-cycling, so that normal traffic in the network can be utilized as a "free" input for drift detection, which helps reduce (or even eliminate) the overhead of traditional time-stamp exchange with dedicated packets or bits. To prevent an overuse of such free information, leading to energy waste, an energy-driven adaptive mechanism is developed for clock calibration to balance between energy efficiency and rendezvous accuracy. PSR is evaluated with both test-bed experiments and extensive simulations, by augmenting and comparing with four different MAC protocols. Results show that PSR is practical and effective under different levels of traffic load, and can be fused with those MAC protocols to improve their energy efficiency without major change of the original designs. I. INTRODUCTIONIn wireless networks with severe energy constraints, e.g., wireless sensor networks [1], low-duty-cycle radio operations have been proposed as one of the major techniques to elongate the network lifetime [5], since the radio can be a main source of energy consumption [13]. Basically, the RF module of a node stays active only for a small percentage of time during each duty-cycle period (e.g., 1%), while keeps in low-energy sleep/off mode for the rest of the time [5][28]. Low-duty-cycle radio activity has been favorable in applications such as environment monitoring (e.g., Redwood [3], GreenOrbs [9]), animal observation (e.g., Great Duck Island [10]), civil structure surveillance (e.g., Mine [11]), etc. In all those applications, low-duty-cycle networking provides a nice trade-off between service quality and energy cost; however, it also brings about transient-available radio links that are essentially at odd with highly efficient communication. This is because in low-dutycycle networks, two nodes located within each other's radio range can communicate only when both of them are active simultaneously for transmitting (TX) and receiving (RX) [12]. A problem called communication rendezvous [17].Many smart ideas have been proposed for the rendezvous task in low-duty-cycle wireless networks. They usually function at the MAC layer and can be categorized into two general classes: (i) asynchronous [5]

show abstract

Section: Clock Drift Modelingmentioning

confidence: 99%

PSR: Practical synchronous rendezvous in low-duty-cycle wireless networks

Huang

Yun

Zhong

et al. 2013

2013 Proceedings IEEE INFOCOM

View full text Add to dashboard Cite

show abstract

“…It can be seen that Allan deviation of beat frequency obtained with the Tesa laser against the frequency comb describes the typical behaviour with white noise common in the caesium and rubidium time/frequency standards [11,12]. However, the stability of HP5517D and HP5519A lasers (Fig.…”

Section: Resultsmentioning

confidence: 86%

“…8) at the longer averaging times is degraded. In particular, the stability plot has a t [11,12] slope (time = t) beyond 250 s that corresponds to the drift (i.e., about 5.6 Â 10 À9 at 5000 s). Evaluating the compatibility coefficient C, using the formula…”

Section: Resultsmentioning

confidence: 99%

Realisation of the metre by using a femtosecond laser frequency comb: applications in optical frequency metrology

Samoudi

2017

Int. J. Metrol. Qual. Eng.

View full text Add to dashboard Cite

Abstract. The appearance of the frequency comb technology, awarded the Nobel Prize in Physics 2005, has enormously revolutionized the metrology of optical frequencies, eliminating the need for complicated frequency chains. By direct linking to the unit of time, the second, through frequency standards (Cs, Rb), by using femtosecond mode-locked lasers and frequency comb technology, the Spanish Centre of Metrology (CEM) has established a new way of practical realisation of the National Standard of Length, the metre. By stabilising and characterising two free parameters -the repetition frequency f r and the offset frequency f 0 , the frequency comb generator thereby was successfully put into operation. After such realization, the accuracy of the length unit will be increased in two orders of magnitude, that is 2 Â 10 À13 instead of 2.1 Â 10 À11 . In this paper we present the results of applying comb generator to the absolute measurement of the three Zeeman stabilized He-Ne lasers operating at 633 nm with a nominal frequency of 473.612 THz. A comparison of these results with those obtained by the current system based on standard iodine stabilized lasers is in good compatibility. A treatment for the evaluation of measurement uncertainty of laser frequency in calibration using a comb in accordance with Guide of Uncertainty Measurement ISO/BIPM is also presented.

show abstract

“…To study the stability of the system as well as the note beat we have used the Allan variance analysis [11,12]. For a set of N frequency measurements, the Allan variance is defined as…”

Section: Stability Of the Systemmentioning

confidence: 99%