Page 896 - 5G Basics - Core Network Aspects

2 Transport aspects

Table 12-5 – FTU-R state definitions

State name Description

R-SHOWTIME Steady state entered to transmit user data;
(mandatory) Online reconfigurations occurs within this state;
Upon conditions satisfying the fast-retrain policy (FRpolicy), transitions to the R-INIT/TRAIN
state;
When link transition to L3 state is granted, the FTU-R transitions to the R-SILENT state;
The FME reports the FTU-R performance parameters to the ME and to the FTU-O (via
indicator bits).
12.1.3 Initialization procedures

The ITU-T G.9701 initialization procedures comprise 3 phases:
– ITU-T G.994.1 handshake phase,
– Channel discovery phase, and

– Channel analysis and exchange phase.
During the ITU-T G.994.1 handshake phase of the initialization procedure, the FTUs exchange capability lists
and agree on a common mode for training and operation using the ITU-T G.994.1 protocol. A successful
completion of the ITU-T G.994.1 handshake phase will lead to the channel discovery phase of initialization.
Failure of the ITU-T G.994.1 handshake phase leads the FTU back to the SILENT state and leads the link back
to the L3 state. The handshake procedure is described in clause 12.3.2 and [ITU-T G.994.1].
During the channel discovery and channel analysis and exchange phases of initialization, the FTUs train
their respective transceivers after identifying the common mode of operation. During these phases, the
transceivers identify channel conditions, exchange and optimize parameters for showtime operation using
the applied CIpolicy, etc. After successful completion of the initialization procedure, the FTUs transition to
the SHOWTIME state (showtime). Upon unsuccessful completion of the initialization procedure, the FTUs
return to the SILENT state and the link returns to the L3 state. The initialization phases are described in
clauses 12.3.3 and 12.3.4.

12.1.4 Deactivation, reinitialization, persistent link defects and high_BER events
12.1.4.1 Deactivation

The deactivation procedure allows an orderly shutdown of the link. The FTUs shall follow the procedures
described in clause 12.1.2 to transition the link from the L0 state to the L3 state.
The link enters the L3 state when the FTU leaves the SHOWTIME state. The FTU-O transitions from the
O-SHOWTIME state to the O-SILENT state via the O-DEACTIVATING1 state. The FTU-R transitions from the
R-SHOWTIME state to the R-SILENT state directly. The transition can be initiated by either the local or the
remote FTU (see clauses 11.2.2.12 and 12.1.2). The deactivation criterion is vendor discretionary.

12.1.4.2 Fast retrain
When the fast retrain policy (FRpolicy) triggers a fast retrain at the FTU-O (see Figure 12-4), the FTU-O shall
transition from the O-SHOWTIME state via the O-DEACTIVATING2 state to the O-INIT/TRAIN state.
In the O-INIT/TRAIN state, the FTU-O executes the part of the initialization sequence, starting from the
QUIET 1 stage (clauses 12.3.3 and 12.3.4). When the initialization sequence is completed, the FTU-O
transitions back to the O-SHOWTIME state. If the initialization sequence is aborted (per conditions defined
in clause 12.1.1), then the FTU-O transitions to the O-SILENT state (see Figure 12-4).

When a fast retrain is triggered at the FTU-R (see Figure 12-5) according to the fast retrain policy, the FTU-R
shall transition from the R-SHOWTIME state to the R-INIT/TRAIN state.

In the R-INIT/TRAIN state, the FTU-R executes the part of the initialization sequence starting from QUIET 1
stage (clauses 12.3.3 and 12.3.4). When the initialization sequence is completed, then the FTU-R transitions

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