is your BTS is directly connected on ET? (Not DN2 between BTS and BSC)
if it is that case:
check your ET quality signal
ZYMO:ET,108;
A perfect PCM is:
0 CRC
0 Slips
100% EFS local and remote
LIKE THIS:
PCM STATISTICS
PERMANENT MEASUREMENT
UNIT START TIME
ET-52 2006-11-06 00:00
DISTURBANCES:
DISTTYPE COUNTER LIMITS (MS)
10-50 50-200 200-1000 1000-
NOINSGN 0 0 0 0
FALOST 0 0 0 0
AIS 0 0 0 0
REMOTE 0 0 0 0
FRAME ALIGNMENT SIGNAL ERRORS:
COUNTER LIMITS (ERRORS/ 5 SEC)
1-39 40-79 80-159 160-
0 0 0 0
SLIPS:
POSITIVE NEGATIVE
0 0
CRC PERFORMANCE MONITORING:
TOTAL AVAIL UNAVAIL
TIME TIME TIME
LOCAL END 14:17:22 14:17:22 00:00:00
REMOTE END 14:17:22 14:17:22 00:00:00
(%) EFS ES SES DM
LOCAL END 100.00 0.00 0.00 0.00
REMOTE END 100.00 0.00 0.00 0.00