SDH frame structure
...................................................................................................................................................................................................................................
This section provides detailed information on the locations and functions of various
overhead bytes for each of the following SDH path and line sections:
•
Regenerator Section
•
Multiplex Section
•
Path
Section overhead
The following table identifies the location and function of each regenerator section
overhead byte.
Bytes
Function
A1, A2
Frame alignment A1 = 1111 0110 ; A2 = 0010 1000 ; These
fixed-value bytes are used for synchronization.
B1
BIP-8 parity test
Regenerator section error monitoring; BIP-8 :
Computed over all bits of the previous frame after scrambling; B1 is
placed into the SOH before scrambling;
BIP-X: (Bit Interleaved Parity X bits) Even parity, X-bit code;
first bit of code = even parity over first bit of all X-bit sequences;
B2
Multiplex section error monitoring; BIP-24 :
B2 is computed over all bits of the previous STM-1 frame except for
row 1 to 3 of the SOH (RSOH); B2 is computed after and placed
before scrambling;
Z0
Spare bytes
D1 - D3 (=
DCC
R
) D4 -
D12 (= DCC
M
)
Data Communication Channel (network management information
exchange)
E1
Orderwire channel
E2
Orderwire channel
F1
User channel
K1, K2
Automatic protection switch
K2
MS-AIS/RDI indicator
S1
Synchronization Status Message
M1
REI (Remote Error Indication) byte
NU
National Usage
An SDH overview
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365-312-847R4.0
Issue 4, November 2006
Lucent Technologies - Proprietary
See notice on first page
A-9
