Page 1243 - 5G Basics - Core Network Aspects

Transport aspects 2

JC4, JC5 and JC6 fields plus bits 1 and 2 in the JC1, JC2 and JC3 fields, two reserved bits and a 1-bit odd
parity (OP) field which contains an error check code over bit 1 in the JC4 and JC5 fields.

The value of 'm' in Cm is 128'ts' (number of tributary slots occupied by the ODTUCn.ts).
The value of 'n' represents the timing granularity of the GMP Cn parameter, which is also present in CnD.
The value of n is 8.
The value of Cm controls the distribution of groups of '16ts' ODUk data bytes into groups of '16ts'
ODTUCn.ts payload bytes. Refer to clause 20.5 and Annex D for further specification of this process.
The value of CnD provides additional 'n'-bit timing information, which is necessary to control the jitter and
wander performance experienced by the ODUk signal.
The value of Cn (i.e., number of client n-bit data entities per OPUCn multiframe) is computed as follows:
Cn(t) = m  Cm(t) + (CnD(t) – CnD(t–1)). Note that the value CnD is effectively an indication of the amount of
data in the mapper's virtual queue that it could not send during that multiframe due to it being less than a
2M-byte word. For the case where the value of CnD in a multiframe 't' is corrupted, it is possible to recover
from such error in the next multiframe 't+1'.

20.4.4 OPUCn multiframe identifier overhead (OMFI)
An OPUCn multiframe identifier (OMFI) byte is defined in row 4, column 16 of the OPUC #1 to #n overhead
(Figure 20-10). The value of bits 4 to 8 of the OMFI byte will be incremented each OPUCn frame to provide
a 20 frame multiframe for the multiplexing of ODUk signals into the OPUCn.
NOTE 1 – It is an option to align the OMFI = 0 position with MFAS = 0 position every 1280 (the least common multiple
of 20 and 256) frame periods.
NOTE 2 – OMFI must be copied in all n OPUC instances at the source, and only 1 need to be processed at the sink.

OMFI OH Byte
1 2 3 4 5 6 7 8

. .
Fixed to 0 Fixed to 0 Fixed to 0 0 0 0 0 1
0 0 0 0 0
0 0 0 1 0
0 0 0 1 1
0 0 1 0 0
0 0 1 0 1
0 0 1 1 0 OMFI sequence
0 0 1 1 1
0 1 0 0 0
0 1 0 0 1
0 1 0 1 0
0 1 0 1 1
.
0 1 1 0 0
.
0 1 1 0 1
0 1 1 1 0
0 1 1 1 1
1 0 0 0 0
1 0 0 0 1
1 0 0 1 0
1 0 0 1 1
0 0 0 0 0
0 0 0 0 1

Figure 20-10 OPUCn multiframe identifier (OMFI) overhead

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