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SZ-DOC-W5-1.pdf LTU/NTU
Version: 1.5 Operating Manual
17 Revision: 2002-09-10
L
R
M
G
Local CRC error information
Remote CRC error information
CRC Monitor
CRC Generator
Optional
Mandatory
Digital Link
NT2
G
M
ET
L
R
R
L
TV3'
NT1
LT
L
R
L
R
G
M
G
M
M
G
RX
TX
Figure 3-6: Digital Link with CRC Processing in the NT1
CRC4 is generated towards the NT2/TE and towards the ET and monitored at both sides of the
NT1. When a block with a CRC4 error is received from the NT2/TE, CRC4 error information is
transmitted towards the NT2/TE (via E-bits) and optionally towards the ET (via Sa6-bits). When a
block with a CRC4 error is received from the ET, error information is transmitted towards the ET
(via E-bits). CRC4 errors detected at the T reference point of the NT2/TE are reported to the NT1
(via E-bits) and optionally towards the ET (via Sa6-bits). CRC4 errors detected at the V3 reference
point of the ET are reported to the NT1 (via E-bits). Loopback 1 and 2 control facilities and
monitoring of defect conditions are implemented according to ETS 300 233.
Depending on the distribution of NT1 and LT functionality, two set-ups are possible for option 2:
The master is E1 configured transparent, AIS-generation on and AIS-detection off; the slave
is PRA NT1 & LT, CRC4 processing on.
The master is PRA LT with CRC4 monitoring on; the slave is PRA NT1 with CRC4 processing
on.
3.3.2.3 Digital Link with CRC Processing in the LT and NT1 (Option 3)
In this mode, the NT1 behaves like in option 2. The LT is not transparent, but has CRC4
generation and monitoring in both directions. This option is not possible when using combined
NT1 & LT mode, the set-up for option 3 is:
The master is PRA LT with CRC4 processing on; the slave is PRA NT1 with CRC4 processing
on.
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