Page 644 - 5G Basics - Core Network Aspects

2 Transport aspects

The mapping of the CPRI signal into GFP-T is performed as specified in [ITU-T G.7041] with the following
parameters:
– each GFP-T frame contains data from a single CPRI signal
– when more than one CPRI clients are multiplexed, each CPRI signal is identified by a unique
Channel ID (CID) in the GFP extension header for a linear frame, see clause 6.1.2.1.3.2 of
[ITU-T G.7041]
– the GFP frame pFCS is not used.
Since this is a new client for GFP, it requires a new user payload identifier (UPI) code point from Table 6-3 of
[ITU-T G.7041]. Using 0xEC is suggested.

During a signal fail condition of the incoming CPRI client signal (e.g., in the case of a loss of input signal),
either:
– this failed incoming CPRI signal may be replaced by a stream of 10B blocks each carrying a link
fault indication as specified in clause 17.7.1.1 of [ITU-T G.709], which stream is then applied at the
GFP-T mapper, or
– the GFP-T signal may be replaced by a stream of GFP client signal fail (CSF) and GFP-idle frames as
specified in [ITU-T G.7041].

During either a signal fail condition of the incoming ODU2 signal (e.g., in the case of an ODU-AIS, ODU-LCK,
ODU-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. Each 10B block carries a link fault indication as a replacement signal for
the lost CPRI signal. The link fault 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.

It is recommended that the single error correction options specified in [ITU-T G.7041] be used for both the
extension header and the GFP-T superblocks.
As an example, with S=3 superblocks per GFP-T frame, the maximum number of CPRI clients that can be
mapped into an OPU2 is shown in Table 7-11:

Table 7-11 – The number of CPRI clients that can be mapped into an OPU2 using GFP-T
CPRI rate (Mbps) Max CPRI clients in an OPU2

614.4 (option 1) 18
1228.8 (option 2) 9
2457.6 (option 3) 4
3072.0 (option 4) 3
4915.2 (option 5) 2
6144.0 (option 6) 1

8 Multiple CPRI option 3, 4 or 5 signal mapping into ODU2r

Six [CPRI] option 3 signals, three [CPRI] option 4 signals or three [CPRI] option 5 signals into an OPUk
(k = 2r), which has a somewhat higher rate than ODU2, can be multiplexed and mapped using the following
method. Transporting these signals over more than a single OTU2r link is for further study.

8.1 OPU2r overhead description

The OPU2r overhead includes the payload structure identifier (PSI) including the payload type (PT), the
OPU2r multiframe identifier (OMFI) and client mapping specific overhead. The OPU2r PSI, PT and OMFI
overhead locations are shown in Figure 8-1.

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