Telecommunications Techniques Corporation interceptor 147, Reference Manual, Page: 264 / 280

Understanding G.821 Performance Analysis
D-6
D
INTERCEPTOR 147 2 Mbit/s and Data Analyzer
D.4 DETERMINING DEGRADED
MINUTES
Degraded minutes (Deg Min) is an error analysis result
that is affected by available and unavailable time. Deg
Min is a count of the number of minutes during which an
average BER greater than 10
-6
occurs. The 1-minute
intervals are derived by removing Unavl Sec and SES
from the total test time and then consecutively grouping
the remaining seconds into blocks of 60. The average
BER is calculated for the block of 60 seconds and, if it is
greater than 10
-6
, the block is counted as a degraded
minute.
In the transition from available time to unavailable time,
the Deg Min result is unaffected. This is because a switch
to unavailable time requires 10 consecutive seconds each
with a BER greater than 10
-3
. Any second in available time
with a BER greater than 10
-3
is considered to be a severely
errored second and, therefore, not included in the
accumulation of seconds used to calculate Deg Min.
Moving from unavailable time to available time may
affect the Deg Min count. While in unavailable time, 10
consecutive seconds each with a BER less than 10
-3
are
required for the transition to available time. When this
happens, those 10 seconds are subtracted from the Unavl
Sec count and are added to the Avl Sec count. Since these
seconds are now considered to be a part of available time
and they are not SES, they are included in the calculation
of Deg Min.