Title: Timing characteristics of packet-based equipment clocks (frequency)

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Summary

• Packet-Based Equipment Slave Clock for Frequency (PEC-S-F)

• Designed primarily to supply frequency to cellular basestations

• Target output performance requirement: 16ppb frequency accuracy

• Specifies frequency accuracy, noise generation, noise tolerance, holdover, testing methods

Status

• Current version: 2nd. Edition, August 2017

• Download from: http://www.itu.int/ITU-T/recommendations/rec.aspx?rec=13320

Key Contents

• Frequency accuracy (free-run): 4.6 ppm

• Noise (wander) Generation:

Open

• Noise (PDV) Tolerance:

Open

• Holdover: based on G.812 Type III clock (Stratum 3E)

• Testing methods: Appendix I describes three methods of measuring the performance of slave clock:

  • PDV patterns based on flicker noise
    Measures clock performance using input PDV containing equal energy in every decade of
    frequency (i.e. flicker noise)

  • PDV patterns based on combined sinusoidal waveforms
    Measures clock performance using input PDV containing multiple frequencies simultaneously

  • PDV patterns based on a single sinusoidal waveforms
    Measures clock performance using PDV containing a sinusoidal modulation of the floor delay