G.821 Measurement Definitions

The following error parameters were developed for testing error performance of digital links in terms of performance parameters.

Errored Second (ES)

This is the number of seconds with at least one error.

Error Free Seconds (EFS)

This is the count of error free seconds since the beginning of the test. Error free seconds equals the total test time minus the number of errored seconds.

Available Seconds (AS)

This is the count of available seconds since the beginning of the test. Available seconds equals the total test time minus any unavailable seconds.

Severely Errored Seconds (SES)

This is the count of Severely Errored Seconds since the beginning of the test. A second with a bit error rate of 10-3 or higher is a severely errored second. Severely errored seconds are not counted during unavailable time. Loss of signal (LOS), loss of frame (LOF), and loss of pattern synchronization (LOP) are treated as severely errored seconds

Unavailable Seconds (UAS)

This is the count of UnAvailable Seconds that have occurred since the beginning of the test. Unavailable time begins at the onset of 10 consecutive severely errored seconds, and ends after 10 consecutive non‑severely errored seconds. The onset of unavailable seconds causes the SES count to be adjusted downward by 10. When unavailable time ends, the UAS count is adjusted downward by 10.

Degraded Minutes (DGRM)

This is the count of Degraded Minutes since the start of the test. A Degraded Minute occurs when a 10-6 bit error rate exists during 60 available, non‑severely bit errored seconds.

 

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