Performance Monitoring; Phase Measurements; Mtie Calculations - Symmetricom TimeProvider 1000 User Manual

Performance Monitoring

The TimeProvider can monitor and qualify all enabled input signals based on phase
measurements. It measures the phase differences between the inputs and the
output of the corrected clock. From these phase measurements, the TimeProvider
computes frequency offset and wander of the input signals. Wander is reported in
terms of Maximum Time Interval Error (MTIE) and Time Deviation (TDEV) and
creates phase, MTIE, TDEV, and Fractional Frequency Offset (FFOFF) reports.
Performance data is automatically gathered on all enabled or monitored inputs.
Using MTIE and FFOFF data, the TimeProvider qualifies inputs based on these
metrics. User-specified thresholds can be set to disqualify inputs and generate
corresponding alarms, causing the TimeProvider to switch references or enter the
Holdover mode.
For more information on performance monitoring, see
Monitoring, on page 108. The TimeProvider TL1 Reference Guide contains a
section describing the TL1 commands related to performance monitoring.

Phase Measurements

The IOC measures and transfers 1-second phase data with 100 ns resolution from
each enabled input to the IMC every 10 seconds. This phase data is averaged to a
1 ns resolution, which is used to produce a 1-minute phase data sample. The 1 ns
data sample is the basis for MTIE, TDEV, and FFOFF calculations. The phase data
is not used to qualify an input reference source.
TL1 commands are available to display the 60 most recent phase data (at 100 pS
resolution) measurements, the previous 86400 1 ns data averages, and the
previous 10080 samples of 1-minute 1 ns-resolution data.

MTIE Calculations

MTIE is a measure of the relative noisiness of an input signal that relates to
frequency offsets and phase transients. The TimeProvider automatically calculates
MTIE for each enabled input from the 600 most recent 1-second phase updates.
From this calculation, you can retrieve MTIE values for 1, 5, 10, 50, 100, and
500-second windows. You can set an alarm threshold for each of these windows; if
the MTIE value exceeds this threshold and the alarm level is set to Minor or higher,
the TimeProvider generates an alarm.
You can use the automatic MTIE calculations to qualify each input with user-defined
qualification thresholds. If an input exceeds the threshold, then the input reference
automatically switches to the next-best input.
097-58001-02 Revision C – August 2005
Chapter 1 Overview of the TimeProvider
Performance Monitoring
Using Performance
TimeProvider User's Guide 25