Specifications

Watson TDM
Operating Manual
Watson-TDM-Manual-W.doc
Version 2.0-01
3-14
Revision: 2008-02-07
Digital Link with CRC Monitoring in the NT1 (Option 4)
CRC4 multiframe alignment and checksum words are not regenerated in both di-
rections, i.e. data will be transmitted without changes in both directions. However,
blocks with CRC4 errors received from the NT2/TE and the ET will be detected
and monitored by the G.826 performance management functions of the modems.
When loss of signal or loss of frame alignment is detected at either side, AIS is
transmitted at the opposite side.
The detection of events and the state information are still valid as in normal PRA
operation mode (option 4).
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
T V3'
NT1
LT
M
M
G
SNSU
RX
TX
Figure 3-13: Digital Link with CRC Monitoring in the NT1
Depending on the distribution of NT1 and LT functionality, two configurations 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.
3.3.2 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. CRC block errors de-
tected at the T reference point of the NT1 and CRC error indications received
from the NT2/TE in the E-bits are reported to the ET using the Sa6-bits. An ET
applying asynchronous detection of the Sa6-bits (no synchronization of the Sa6-
bits to the sub-multiframe) will mistake such CRC4 error reports from the NT1 for