Page 1199 - 5G Basics - Core Network Aspects

Transport aspects 2

– An OPU3 1.25G tributary slot occupies 3.125% of the OPU3 payload area. It is a structure with 119
columns by 128 (32  4) rows (see Figures 19-2 and 19-8) plus a tributary slot overhead (TSOH).
The thirty-two OPU3 1.25G TSs are byte interleaved in the OPU3 payload area and the thirty-two
OPU3 TSOHs are frame interleaved in the OPU3 overhead area.

An OPU3 2.5G tributary slot "i" (i = 1,2,..16) is provided by two OPU3 1.25G tributary slots "i" and "i+16" as
illustrated in Figure 19-2.
The tributary slot overhead (TSOH) of OPU3 tributary slots is located in column 16 plus column 15, rows 1,
2 and 3 of the OPU3 frame.
The TSOH for a 2.5G tributary slot is available once every 16 frames. A 16-frame multiframe structure is
used for this assignment. This multiframe structure is locked to bits 5, 6, 7 and 8 of the MFAS byte as shown
in Table 19-2 and Figure 19-2.

The TSOH for a 1.25G tributary slot is available once every 32 frames. A 32-frame multiframe structure is
used for this assignment. This multiframe structure is locked to bits 4, 5, 6, 7 and 8 of the MFAS byte as
shown in Table 19-2 and Figure 19-2.

MFAS Multi- Column
bits frame
(4)5678 row Frame 1 ..... 15 16 17 18 ..... 31 32 33 34 ..... 47 48 49 50 ..... 3823 3824
row
1 1
2 2
(0)0000 TSOH TS1 ..... ..... ..... .....
3 3
4 4
5 1
6 2
(0)0001 TSOH TS2 ..... ..... ..... .....
7 3
8 4

.....
61 1
62 2
(0)1111 TSOH TS16 ..... ..... ..... .....
63 3
64 4
65 1 1
66 2 2
(1)0000 TSOH TS1 or TS17 ..... ..... ..... .....
67 3 3
68 4 4

..... .....
125 61 1
126 62 2
(1)1111 TSOH TS16 or TS32 ..... ..... ..... .....
127 63 3 1 2 15 16 17 18 31 32 1 2 31 32 1.25G TS#
128 64 4 1 2 15 16 1 2 15 16 1 2 15 16 2.5G TS#
G.709-Y.1331(12)_F19-2

Figure 19-2 – OPU3 tributary slot allocation

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