Page 993 - 5G Basics - Core Network Aspects

Transport aspects 2

• within the latency bounds defined by the control parameter delay_max.

The control parameter delay_max during L2.1 shall be set to delay_max = max(2×TSF,
DELAYMAX). This setting allows at least two retransmission attempts with any selected value
of N.
• RFEC/NFEC ratio ≥ rnratio_min
• SNRM limited by autonomous SRA procedures within L2.1-RA-DSNRM ≤ SNRM ≤ L2.1-RA-USNRM
for all active data subcarriers
• SNRM_RMC ≥ MINSNRM-RMC for all RMC subcarriers.

Within the above constraints, for upstream, the FTU-O receiver shall select the values so as to minimize
power consumption in the following order:
1) While keeping the same RMC transmission schedule, adjust transmission parameters using SRA.

2) While keeping the same transmission parameters, perform L2TSA (trigger conditions see clause
13.2.1.4).Within the above constraints, for downstream, the FTU-R and FTU-O shall select the
values so as to minimize power consumption in the following order:
1) FTU-R: While keeping the same downstream RMC transmission schedule, adjust transmission
parameters using SRA.
2) FTU-O: While keeping the same downstream transmission parameters, perform L2TSA (trigger
conditions see clause 13.2.1.4).
NOTE 1 – Values for downstream and upstream should be selected with due attention to link robustness.
NOTE 2 – There is no change of transmit PSD during L2.1.
13.4.1.3.2 L2.1 operation procedures

To keep the data-related parameters in the required range, the FTUs shall apply the bit swapping
procedure defined in clause 13.2.1.2, or the SRA procedure defined in clause 13.2.1.1, or the FRA procedure
defined in clause 13.3.1.1, or the L2TSA procedure defined in clause 13.2.1.4. The FTU-O may initiate the
TIGA procedure, as defined clause 13.2.1.4. Upstream gi values may be changed by OLR procedures.
To keep the RMC-related transmission parameter in the required range, the FTUs shall apply the RPA
procedure, as defined in clause 13.2.1.3.
To support the mentioned OLR procedures, the values of relevant control parameters defined in
clause 13.4.1.5 shall be communicated to the FTU-R during initialization in O-MSG1 (see clause 12.3.4.2.1).

Fast retrain shall be applied according to the fast retrain policy (L2.1-FRpolicy = 0, see clause 12.1.4.2).
When the OLR procedures do not allow SNRM ≥ MINSNRM with an ETR ≥ L2.1_ETR_min to be maintained,
an L2.1_lom anomaly occurs. When the SNRM is equal to or greater than MINSNRM, an L2.1_lom anomaly
terminates. Upon an L2.1_lom anomaly occurring, the DRA may send a LinkState.Request primitive to exit
from the L2.1N link state to the L0 link state. If the line is in the L2.1B link state, the DRA may first send a
LinkState.Request primitive to transition from the L2.1B link state to the L2.1N link state, and then send a
LinkState.Request primitive to exit from the L2.1N link state to the L0 link state.

When the OLR procedures do not allow L2.1_EXIT_ETR equal to or greater than the L2.1_EXIT_ETR_min to
be maintained, an L2.1_low_EXIT_ETR anomaly occurs. When the L2.1_EXIT_ETR is equal to or greater than
the L2.1_EXIT_ETR_min, an L2.1_low_EXIT_ETR anomaly terminates. Upon an L2.1_low_EXIT_ETR anomaly
occurring, the DRA may send a LinkState.Request primitive to exit from the L2.1N link state to L0 link state.
If the line is in the L2.1B link state, the DRA may first send a LinkState.Request primitive to transition from
the L2.1B link state to the L2.1N link state, and then send a LinkState.Request primitive to exit from the
L2.1N link state to the L0 link state.

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