Page 904 - 5G Basics - Core Network Aspects

2 Transport aspects

After completion of the channel analysis and exchange phase, the transceiver shall proceed to showtime.

Figure 12-7 – Timeline of the initialization procedure

Each phase of initialization contains a number of tasks. The transition to the next phase of initialization shall
occur only after all tasks of the previous phase have been completed. A timeout period is defined for
completion of each phase to avoid suspension of the initialization procedure. Violation of the timeout or an
inability to complete any task of any phase results in aborting the activation process (unsuccessful
activation). The initialization procedure shall be aborted immediately after any of the following events is
discovered:

– Timeout of any phase;
– Missing or incomplete task during any phase;
– Violation of the task sequence or in communication protocol during any phase;
– Detection of more than 250 ms of unscheduled silence.

Each phase of initialization has an associated timeout counter. In all phases, the associated timeout counter
shall be started as the FTU enters the specific phase and shall be reset upon completion of the phase. The
following values for the timeouts shall be used:
– ITU-T G.994.1 handshake phase: As defined in [ITU-T G.994.1];
– Channel discovery phase:

– CD_time_out_1 seconds from the start of the channel discovery phase to the reception of O-
P-CHANNEL-DISCOVERY 1-1. The valid values for CD_time_out_1 during an initialization
starting with an ITU-T G.994.1 session are from five seconds to forty seconds in steps of five
seconds. The FTU-O shall support the default value of ten seconds, all other valid values are
optional. The FTU-R shall support the default value of ten seconds and shall support all other
valid values if the Spar 2 bit CD_time_out is set to ONE in the CLR message (see Table 12-15).
The value to be used during initialization starting with an ITU-T G.994.1 session is selected
during the ITU-T G.994.1 phase. During a fast retrain, the valid values for CD_time_out_1 are
from 1 to 40 seconds in steps of 1 second. The value to be used during a fast retrain shall be
indicated in O-MSG 1. All values shall be supported by the FTU-R if it indicates support of
additional values in ITU-T G.994.1;
– CD_time_out_2 seconds from the reception of O-P-CHANNEL-DISCOVERY 1-1 to the end of the
channel discovery phase. The valid values for CD_time_out_2 during an initialization starting
with an ITU-T G.994.1 session are from ten seconds to eighty seconds in steps of ten seconds.
The FTU-O shall support the default value of twenty seconds, all other valid values are
optional. The FTU-R shall support the default value of twenty seconds and shall support all
other valid values if the Spar 2 bit CD_time_out is set to ONE in the CLR message (see Table
12-15). The value to be used during initialization is selected during the ITU-T G.994.1 phase.
During a fast retrain, the valid values for CD_time_out_2 are from 1 to 80 seconds in steps of 1
second. The value to be used during a fast retrain shall be indicated in O-MSG 1. All valid
values shall be supported by the FTU-R if it indicates support of additional values in ITU-T
G.994.1.

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