Page 1263 - 5G Basics - Core Network Aspects

Transport aspects 2

Table D.1 – OPUk, ODTUk.ts and ODTUCn.ts GMP parameter values

GMP CBR client into OPUk ODUj into OPUk (ODTUk.ts) ODUk into OPUCn (ODTUCn.ts)
parameter
(for selected OPU1: 0 to +15
clients) OPU2: 0 to +63
OPU3: 0 to +255
OPU4: 0 to +639

D.3 Cm(t) encoding and decoding
Cm(t) is encoded in the ODTUk.ts justification control bytes JC1, JC2 and JC3 specified in clause 19.4 for the
14-bit count and clause 20.4 for the 10-bit count field.
Cm(t) is an L-bit binary count of the number of groups of m OPU payload bits that carry m client bits; it has
values between Floor(Cm,min) and Ceiling(Cm,max), which are client specific. The Ci (i=1..L) bits that comprise
Cm(t) are used to indicate whether the Cm(t) value is incremented or decremented from the value in the
previous frame, that is indicated by Cm(t-1). Tables D.2 and D.3 show the inversion patterns for the Ci bits of
Cm(t-1) that are inverted to indicate an increment or decrement of the Cm(t) value. Table D.2 shows the
inversion patterns for the 14-bit count and Table D.3 shows the inversion patterns for the 10-bit count. An
"I" entry in the table indicates an inversion of that bit.

The bit inversion patterns apply to the Cm(t-1) value, prior to the increment or decrement operation that is
signalled by the inversion pattern when |Cm(t) – Cm(t-1)| ≤ 2 (except Cm(t) – Cm(t-1) = 0). The incremented
or decremented Cm(t) value becomes the base value for the next GMP overhead transmission.
– When 0 < Cm(t) – Cm(t-1) ≤ 2, indicating an increment of +1 or +2, a subset of the Ci bits containing
Cm(t-1) is inverted as specified in Table D.2 or Table D.3 and the increment indicator (II) bit is set to
1.

– When 0 > Cm(t) – Cm(t-1) ≥ -2, indicating a decrement of -1 or -2, a subset of Ci bits containing Cm(t-
1) is inverted as specified in Table D.2 or Table D.3 and the decrement indicator (DI) bit is set to 1.

– When the value of Cm(t) is changed with a value larger than +2 or –2 from the value of Cm(t-1),
both the II and DI bits are set to 1 and the Ci bits contain the new Cm(t) value. The associated CRC
in JC3 verifies whether the Cm(t) value has been received correctly.
– When the value of Cm(t) is unchanged from the value of Cm(t-1), both the II and DI bits are set to 0.
The above encoding process is illustrated in Figure D.6.

Table D.2 – 14-bit Cm(t) increment and decrement indicator patterns

C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 II DI Change

U U U U U U U U U U U U U U 0 0 0
I U I U I U I U I U I U I U 1 0 +1
U I U I U I U I U I U I U I 0 1 –1
U I I U U I I U U I I U U I 1 0 +2
I U U I I U U I I U U I I U 0 1 –2
binary value 1 1 More than
+2/–2
NOTE
– I indicates inverted Ci bit
– U indicates unchanged Ci bit

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