Page 1333 - 5G Basics - Core Network Aspects

Transport aspects 2

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3) The coefficients of R(x) are considered to be a 16-bit sequence, where x is the most significant
bit.
4) This 16-bit sequence is the CRC-16 where the first bit of the CRC-16 to be transmitted is the
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0
coefficient of x and the last bit transmitted is the coefficient of x .
The demapper process performs steps 1-3 in the same manner as the mapper process, except that here,
the M(x) polynomial of step 1 includes the CRC-16 bits in received order, and has degree 87. In the absence
of bit errors, the remainder shall be 0.
9.2.8 FlexO management communications channel (FCC)
An 896-bit (112 bytes) field per multi-frame is provided for a FlexO interface management communications
channel. These are allocated across all 8 frames of the multi-frame. This provides a clear channel, and the
format and content of the management channel is outside the scope of this recommendation.
NOTE – The FCC is intended for interface management functions and is not a generic communications channel.

The FCC field is located in all frames, in overhead bytes 13 to 26. If unused, the management channel shall
be filled with all-0s prior to scrambling. The FCC bytes provide a communication channel per FlexO interface
with an approximate bandwidth of 17.98 Mbit/s.

Figure 9-8  FCC transmission order

9.2.9 FlexO reserved overhead (RES)
123.5 bytes of the FlexO overhead area in the FlexO multi-frame structure are reserved for future
international standardization. These bytes/bits are located in frame 1/byte 5, frame 2/bytes 4, 5, 6, frames
3 to 8/bytes 3 to 6 and frames 1 to 8/bytes 29 to 40. These bytes/bits are set to all-0s prior to scrambling.

9.2.10 OTN Sync Message Channel (OSMC)

A 128-bit (16 bytes) field per multi-frame is provided for an OTN synchronization message channel. These
are allocated across all eight frames of the multi-frame. This field provides a clear channel, to transport
SSM and PTP messages.
The OSMC is only defined on the first FlexO interface (lowest PID value) of a FlexO group. The OSMC field is
located in all frames, in overhead bytes 27 and 28. If unused, the OTN synchronization message channel
bytes shall be filled with all-0s prior to scrambling. The OSMC bytes are combined to provide a messaging
channel, as illustrated in Figure 9-9, with an approximate bandwidth of 2.56 Mbit/s per 100G interface.

Figure 9-9  OSMC transmission order

The SSM and PTP messages within a FlexO interface are encapsulated into GFP-F frames as specified into
[ITU-T G.7041]. PTP event messages are timestamped and after encapsulation into GFP-F frames, inserted
into the OSMC as specified in clause 9.2.9.1. GFP-F encapsulated SSM messages (and PTP non-event

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