NIRANJAN
Regional Telecom Training Center
MYSORE
NBP/RTTC-MYSORE
SDH Framing Structure
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SDH Framing Structure
Overhead (PDH)
TU-12
2 Mbit/s
TU-12
VC-12
C-12
TUG-2 TUG-2 TUG-2
TU-12
TU-12 TUG-2
TUG-3 TUG-2 TUG-2 TUG-2
Pointer (PTR) Stuff
TU-12
TU-12
P RSOH
O VC-4
TUG-3
AU Pointer
H
STM-1
AU-4
VC-4
MSOH
TUG-3
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SDH ALARMS
• LOS : When NE is unable to receive signal
from other NE , due to fiber break , Tx failure
of other NE,etc .It triggers Loss Of Signal
• LOS is Physical Layer Alarm
• There is no byte in SDH frame to indicate LOS. Its the
transreceiver (SFP) which detects the in coming signal.
• If no light coming to SFP it gives LOS to processor or the
controlling device.
Also when u get BER of orde 1 in 1000 results in LOS
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LOS-Loss Of Signal
AIS-Alarm Indication Signal
RDI-Remote Defect Indication
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Probable Causes
ALARM PROBABLE CAUSE
1) STM -N Port loss of
signal OF cable break
Rx optical power beyond thrushhold limit
(local eqpt)
TX forced off (Forced Laser Off at distant
end)
Distant ADM/TM/REG module fault
Distant end power failure
Local RX faulty
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SDH ALARMS
• LOF : Assuming that signal is present .
• Next job is to identify STM-1 frame by means
of Nx 6 bytes FAW ( 3 bytes of A1 and
3bytesA2 bytes of RSOH) .
• Else it triggers Loss Of Frame
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LOF-Loss Of Frame
AIS-Alarm Indication Signal
RDI-Remote Defect Indication
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AU-LOP
THE NEXT STEP IS TO FIND WHERE THE VC-4S ARE LOCATED
RELATIVE TO THE FAW.
THIS IS ESTABLISHED BY READING THE ADMIN UNIT (AU)
POINTER TO LOCATE THE J1 BYTE IN THE VC-4 POH.
IF A SENSIBLE POINTER CANNOT BE FOUND, A LOSS OF
POINTER (LOP) ALARM IS RAISED AT THE AU LEVEL.
THIS IS USUALLY REFERRED TO AS AN AU-LOP,
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LOP-Loss Of Pointer
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TU-LOP
The next step is to locate and read the Tributary
Unit (TU) pointer
for the specified TU.
If a sensible pointer cannot be found,
then a LOP alarm is raised at the TU level
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LOP-Loss Of Pointer
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AIS (Alarm Indication Signal)
LOS, LOF, and LOP alarms will render the whole
signal unusable.
In this case, the missing or corrupted signal is
replaced by an AIS consisting of continuous binary
1s.
This will produce AIS alarms on all equipment
downstream of the fault
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AIS-Alarm Indication Signal
RDI-Remote Defect Indication
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AIS-Alarm Indication Signal
LOS-Loss Of Signal
RDI-Remote Defect Indication
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AIS-Alarm Indication Signal
RDI-Remote Defect Indication
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AIS-Alarm Indication Signal
RDI-Remote Defect Indication
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FERF- Far End Reporting Failure
RAI-Remote Alarm Indication
The NE detecting the fault also sends an indication to the
distant (sending) end that an alarm has been raised.
This raises a FERF alarm at the appropriate level at the
transmitting NE.
Thus, a fault at the MS level will produce an MS-FERF.
At the VC-4 level, it will produce a VC-4 FERF on some
equipment, HO-FERFs.
Some SDH elements refer to a remote alarm indication at
some levels in the hierarchy.
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HO FERF- Far End Reporting Failure
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LO FERF- Far End Reporting Failure
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BIP-Bit Interleaving Parity
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TIM-Trace Identifier Mismatch
AIS-Alarm Indication Signal
RDI-Remote Defect Indication
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BIP-Bit Interleaving Parity
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EXC-Excessive Bit Error rate( > 10x E-3)
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BIP-Bit Interleaving Parity
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RDI-Remote Defect Indication
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REI-Remote Error Indication
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DEG-Degradation
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UNEQ- UNEQuipped
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TIM-Trace Identifier Mismatch
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BIP-Bit Interleaving Parity
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RDI-Remote Defect Indication
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REI-Remote Error Indication
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DEG-Degradation
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EXC-Excessive Bit Error rate( > 10x E-3)
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PLM-Path Load Mismatch
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TIM-Trace Identifier Mismatch
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RDI-Remote Defect Indication
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REI-Remote Error Indication
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DEG-Degradation
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EXC-Excessive Bit Error rate( > 10x E-3)
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PLM-Path Load Mismatch
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UNEQ- UNEQuipped
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LOM-Loss Of Multi frame
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ERROR MONITORING
B1 byte is used to check for errors in the RS.
B2 byte is used to check for errors in the MS.
B3 byte is used to check for errors in the VC-4 path.
V5 byte is used to check for errors in the VC-12 path.
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BIP-Bit Interleaving Parity
B1,B2,B3 & B5 bytes are used for Error Detection in
specific section and path .
This is based upon BIP detection mechanism
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