Page 1192 - 5G Basics - Core Network Aspects

2 Transport aspects

– The p OH blocks are interleaved in the order #1, #2 to #p. The p ni-1 padding blocks are interleaved
in the order #1, #2 to #p. The p sub-calendar blocks (of length n1, n2 to np) are interleaved in the
order #1, #2 to #p.
NOTE 1 – An Ethernet error control block is a 66B control block (sync header = 10) with a block type of 0x1E and the
other eight 7-bit characters equal to 0x1E.
NOTE 2 – The remaining m-p 100G FlexE signals – out of an m × 100G FlexE group signal – are carried via other
ODUflex signals carried in other ODUCn/OTUCn/OTSiA signals.
NOTE 3 – Values of p and n (in FlexEp-n) supported and the subset of the p×20 calendar slots that are included in the
FlexEp-n mapped into the OPUflex are vendor specific and outside the scope of this Recommendation.

Figure 17-20 – Full/partial rate FlexE signal interleaving

The 66b block stream of the FlexE partial rate (sub)group signal shall be scrambled after rate adaptation
and before mapping into the OPUflex. In the reverse operation, following termination of the OPUflex signal,
the 66 block stream will be descrambled before being passed to the FlexE deinterleaving, depadding and
decrunching process.
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A self-synchronizing scrambler with generator polynomial 1+ x +x shall be used, that is identical to the
scrambler specified in clause 49.2.6 [IEEE 802.3]. 66b block stream scrambling is required to provide
security against false 66b block delineation (as the two sync header bits bypass the scrambler), the 66b
codewords replicating the OTU and ODU frame alignment signal and the 66b codewords combined with the
OTU scrambler pattern used for the interface replicating the OTU and ODU frame alignment signal.
The FlexE partial rate (sub)group signal (with up to 100 ppm bit-rate tolerance) is mapped into the
OPUflex as per the encoding and stuffing distribution described below. The OPUflex payload bit rate is
100GE_bit_rate × 240/239 × n/20 kbit/s ± 100 ppm, with n = n1 + n2 + .. + np. The ODUflex bit rate is
100GE_bit_rate × 240/238 × n/20 kbit/s ± 100 ppm.
On the transmit side, the stuffing is inserted as 16-byte blocks and systematically controlled using a 15 bit
sigma-delta as:
100GE_rate × (16k-1)/16k × n × 1024/(1+20×1023) = 100GE_rate × n/20 × 240/238 × 238/239 × (4×238-3-
s)/(4×238) → s = 3373/23384 (Numerator=3373, Denominator=23384)
This encoding uses a bitsynchronous generic mapping procedure (BGMP) for the distribution and encoding
of the stuffing. The GMP is operated in a special mode, where the Cm value does not come from a
synchronizer but is generated deterministically, and ∑CnD is unused (Cn = Cm).

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