wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

18-10 Industrial Communication Systems
NTP
θ C
θ R
Phase
detector
V d
Clock filter
VS
VFO
Loop filter
x
V c
Clock adjust
y
Predictor
FIGURE 18.7 NTP clock discipline (NTPClockDiscipline.pdf). (Redrawn from Mills, D., IEEE/ACM Trans.
Netw., 6(5), 505, 1998.)
x
Phase
correct
y PLL
PLL predict
V S
y
Frequency
y adj
Σ
y FLL
FLL predict
FIGURE 18.8 NTP phase and frequency prediction functions (NTPPredictionFunctions.pdf). (Redrawn from
Mills, D., IEEE/ACM Trans. Netw., 6(5), 505, 1998.)
prediction (Figure 18.8). The phase-locked loop (PLL) predicts a frequency offset as integral of V S τ, whereas
the frequency-locked loop (FLL) use an exponential average of V S /τ. These two values are combined via a
simple summarization. It has to be specifically noted that the averaging interval of these two components is
chosen with respect to the Allan-intercept, in order to gain an optimal behavior of the structure.
References
[Anceaume1997] Anceaume, E. and Puaut, I.A., Taxonomy of clock synchronization algorithms, Campus
Universitaire de Beaulieu, Rennes Cedex, France, 1997, 25 pp.
[Brennan2005] Brennan, R.W., Christensen, J.H., Gruver, W.A., Kotak, D.B., Norrie, D.H., and van
Leeuwen, E.H., Holonic manufacturing systems: A technical overview, in The Industrial Information
Technology Handbook, Part II (Industrial Information Technology), Section 7 (Integration
Technologies), Chapter 106, CRC Press, Boca Raton, FL, 2005, 106-1–106-15.
[Eidson2005] Eidson, J. C., The application of IEEE 1588 to test & measurement systems, White Paper
Agilent, Agilent Laboratories, Palo Alto, CA, December 2005, pp. 9–13.
[Eidson2006] Eidson, J.C., Measurement, Control, and Communication Using IEEE 1588, Springer,
London, U.K., 2006.
[Gaderer2004] Gaderer, G. and Sauter, T., Strategies for clock synchronization in powerline networks, in
Proceedings of the 3rd International Workshop on Real-Time Networks in Conjunction with the 16th
Euromicro International Conference on Real-Time Systems, Catania, Italy, 2004.
© 2011 by Taylor and Francis Group, LLC