Page 1144 - 5G Basics - Core Network Aspects

2 Transport aspects

The OTUk contains one instance of OTU BEI/BIAE overhead. The OTUCn contains n instances of the OTU
BEI/BIAE overhead, numbered 1 to n (BEI/BIAE #1 to BEI/BIAE #n).
NOTE – The BIAE indication of an OTUCn is transported n times (ie. in OTUC SM # 1 to SM #n) and detected in OTUC
SM #1 only.

Table 15-1  OTU SM BEI/BIAE interpretation

OTU SM BEI/BIAE
BIAE BIP violations
bits 1 2 3 4
0 0 0 0 false 0
0 0 0 1 false 1
0 0 1 0 false 2
0 0 1 1 false 3
0 1 0 0 false 4
0 1 0 1 false 5
0 1 1 0 false 6
0 1 1 1 false 7

1 0 0 0 false 8
1 0 0 1, 1 0 1 0 false 0
1 0 1 1 true 0
1 1 0 0 false 0
to
1 1 1 1

15.7.2.1.5 OTUk SM incoming alignment error overhead (IAE)

A single-bit incoming alignment error (IAE) signal is defined to allow the S-CMEP ingress point to inform its
peer S-CMEP egress point that an alignment error in the incoming signal has been detected.

IAE is set to "1" to indicate a frame alignment error, otherwise it is set to "0".
The S-CMEP egress point may use this information to suppress the counting of bit errors, which may occur
as a result of a frame phase change of the OTUk at the ingress of the section.

15.7.2.1.6 OTU SM reserved overhead (RES)
For section monitoring of the OTUk, two bits in the SM overhead are reserved (RES) for future international
standardization. They are set to "00".
For section monitoring of the OTUCn, 12 bits in the SM overhead in the OTU frame structures #2 to #n are
reserved for future international standardization. The value of these bits is set to "0".

15.7.2.1.7 OTUCn SM status (STAT)
For section monitoring, three bits are defined as status bits (STAT). They indicate the presence of a
maintenance signal or if there is an incoming alignment error at the source S-CMEP, (see Table 15-2).

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