Page 891 - 5G Basics - Core Network Aspects

Transport aspects 2

Upon a guided power management (r:_L3_request, see clause 11.2.2.12), the FTU-R shall transition back to
the R-SILENT state. Upon a fast retrain triggered by fast-retrain policy (see clause 12.1.4), the FTU-R shall
transition to the R-INIT/TRAIN state.
When the FTU-O transitions from the O-SHOWTIME state to the O-DEACTIVATING2 state, the FTU-R detects
a fast-retrain policy trigger (see clause 12.1.4.2). Upon detecting a fast-retrain policy trigger, the FTU-R shall
transition immediately to the R-INIT/TRAIN state.

When the FTU-O transitions from the O-INIT/TRAIN state to the O-DEACTIVATING1 state, the FTU-R detects
a failure in the training. Upon detecting a failure in the training, the FTU-R shall transition immediately to
the R-SILENT state, followed by the R-INIT/HS state and shall start transmission of R-TONES-REQ (see [ITU-T
G.994.1]) within one second.
When the FTU-R transitions from the R-SHOWTIME state to the R-INIT/TRAIN state, the FTU-O detects a
fast-retrain policy trigger (see clause 12.1.4.2). Upon detecting a fast-retrain policy trigger, the FTU-O shall
transition immediately to the O-DEACTIVATING2 state, followed by the O-INIT/TRAIN state. The FTU-O shall
further transition from the O-DEACTIVATING2 state to the O-INIT/TRAIN state after the VCE updates the
FEXT cancellation coefficients among the lines in the O-SHOWTIME state. The ME indicates the readiness by
o:_fast-retrain primitive.

When the FTU-R transitions from the R-INIT/TRAIN state to the R-SILENT state, the FTU-O detects a failure
in the training. Upon detecting a failure in the training, the FTU-O shall transition immediately to the O-
DEACTIVATING1 state. The FTU-O shall transition from the O-DEACTIVATING1 state to the O-SILENT state
when it receives the o:_reinitialization primitive from the ME.
NOTE – While the FTU-O is in the O-DEACTIVATING1 state, the VCE updates the coefficients among the showtime
lines. The ME indicates its readiness to continue with the reinitialization by issuing an o:_reinitialization primitive.
In the O-SILENT state, the FTU-O shall monitor for R-TONES-REQ (FTU-R initiated handshake). Upon
detection of R-TONES-REQ, the FTU-O shall transition to O-INIT/HS state. If the FTU-O receives an
o:_L0_request from the ME while in the O-SILENT state (FTU-O initiated handshake), it shall transition to
the O-INIT/HS state. The FTU-O shall transmit C-TONES within one second after transitioning to the
O-INIT/HS state.

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