SZ-DOC-W5-1.pdf LTU/NTU
Version: 1.5 Operating Manual
19 Revision: 2002-09-10
L
R
M
G
Local CRC error information
Remote CRC error information
CRC Monitor
CRC Generator
Optional
Mandatory
SN
SU
Storage for network side monitor
Storage for user side monitor
M
Digital Link
NT2
G
M
ET
L
R
R
L
TV3'
NT1
LT
M
M
G
SNSU
RX
TX
Figure 3-8: Digital Link with CRC Monitoring in the NT1
Depending on the distribution of NT1 and LT functionality, two set-ups are possible for option 1:
• The master is E1 configured transparent, AIS-generation on and AIS-detection off; the slave
is PRA NT1 & LT, CRC4 monitoring on.
• The master is PRA LT with CRC4 processing off; the slave is PRA NT1 with CRC4 monitoring
on.
3.3.3 Generation of CRC4 Error Notifications to the ET
For enhanced maintenance capabilities, CRC4 errors detected at the interface at the T reference
point may optionally be reported to the ET (see ETS 300 233 section 8.3 and table 4 of ITU-T
Rec. G.962 section B.5 and table B.2). CRC blocks in error detected at the T reference point of
the NT1 as well as CRC error indications received from the NT2/TE in the E-bits are reported to
the ET by using the Sa6-bits. An ET applying asynchronous detection of the Sa6-bits (no
synchronization of the Sa6-bits to the sub-multiframe) will misinterpret such CRC4 error reports
from the NT1 with other defect indications, e.g. loss of power at NT1 or FC4. Therefore, this Sa6-
bits indication can be disabled.
• If the CRC4 error notification in Sa6 is enabled, Sa6=0001 indicates an E-bit received from
the NT2/TE, Sa6=0010 indicates a CRC4 error detected at the T reference point of the NT1,
and Sa6=0011 indicates the simultaneous occurrence of both errors.
• If disabled, Sa6 is always 0000 in normal operation state.
As sending of Sa-bits requires regeneration of the CRC4 frames in the NT1, this option is only
activated when option 2 (Digital link with CRC processing in the NT1) is selected.
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