Page 1178 - 5G Basics - Core Network Aspects

2 Transport aspects

Table 17-5 – Replacement signal for sub-1.238G clients

Client signal Replacement signal Bit-rate tolerance (ppm)

STM-1 Generic-AIS 20
STM-4 Generic-AIS 20
1000BASE-X Link Fault 100
FC-100 NOS 100
SBCON/ESCON NOS 200

DVB-ASI Generic-AIS 100
SDI Generic-AIS For further study

17.7.1.1 1000BASE-X transcoding
The 1000BASE-X signal (8B/10B coded, nominal bit rate of 1 250 000 kbit/s and a bit-rate tolerance up to
100 ppm) is synchronously mapped into a 75-octet GFP-T frame stream with a bit rate of 15/16  1 250
000 kbit/s 100 ppm (approximately 1 171 875 kbit/s 100 ppm). This process is referred to as "timing
transparent transcoding (TTT)". The 15/16  1 250 000 kbit/s 100 ppm signal is then mapped into an OPU0
by means of the generic mapping procedure as specified in clause 17.7.1 and Annex D.
For 1000BASE-X client mapping, 1-bit timing information (C1) is not needed, so OPU0 JC4/JC5/JC6 OH value
will be fixed to all-0s.
The mapping of the 1000BASE-X signal into GFP-T is performed as specified in [ITU-T G.7041] with the
following parameters:
– Each GFP-T frame contains one superblock
– The 65B_PAD character is not used
– GFP idle frames are not used
– The GFP frame pFCS is not used.
During a signal fail condition of the incoming 1000BASE-X client signal (e.g., in the case of a loss of input
signal), either:
– This failed incoming 1000BASE-X signal is replaced by a stream of 10B blocks, with a bit rate of 1
250 000 kbit/s 100 ppm, each carrying a link fault indication as specified in [IEEE 802.3], which
stream is then applied at the GFP-T mapper, or
– The GFP-T signal is replaced by a stream of GFP client signal fail (CSF) and GFP-idle frames as
specified in [ITU-T G.7041] with a bit rate of 15/16 x 1 250 000 kbit/s 100 ppm.
During either
– A signal fail condition of the incoming ODU0/OPU0 signal (e.g., in the case of an ODU0-AIS, ODU0-
LCK, ODU0-OCI condition), or
– Incoming CSF frames as specified in [ITU-T G.7041].
The GFP-T de-mapper process generates a stream of 10B blocks, with each block carrying a link fault
indication as specified in [IEEE 802.3] as a replacement signal for the lost 1000BASE-X signal.
NOTE – The Ethernet link fault indication is a stream of repeating /C1/C2/C1/C2/ … ordered sets, where
C1 = /K28.5/D21.5/D0.0/D0.0/ and C2 = /K28.5/D2.2/D0.0/D0.0/. This character stream is then processed by the GFP-
T mapper process in the same manner as if it were the received 8B/10B data stream, mapping it into GFP-T
superblocks for transmission.
17.7.1.2 FC-100

During a signal fail condition of the incoming FC-100 signal (e.g., in the case of a loss of input signal), this
failed incoming FC-100 signal is replaced by an NOS primitive sequence as specified in [b-INCITS 470].

NOTE – The NOS primitive sequence ordered set is defined as /K28.5/D21.2/D31.5/D5.2/.

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