Page 990 - 5G Basics - Core Network Aspects

2 Transport aspects

Entry into L2.1 shall be initiated by the FTU-O. Upon reception of a LinkState.request (L2.1N or L2.1B)
primitive from the γ-O interface (see Table 8-3), the FTU-O shall complete or terminate all OLR procedures
and send to the FTU-R an L2.1-Entry-Request eoc command, which includes relevant parameters for
upstream transmission and the constraint for the FTU-R to determine the downstream transmission
parameters during L2.1, sourced by the FTU-O (see clause 11.2.2.16). The L2.1 entry procedure is jointly
coordinated by the FTU-O and the VCE.
Upon reception of this L2.1-Entry-Request eoc command, the FTU-R shall respond within a time consistent
with the timeout value specified in Table 11-3 by sending either an L2.1-Entry-Confirm eoc response with
the downstream transmission parameters, if the L2.1-Entry-Request eoc command is accepted, or an
L2.1-Entry-Reject eoc response with the appropriate reason code, as defined in Table 11-48.6 (see
clause 11.2.2.16).
The FTU-R shall reject the L2.1-Entry-Request eoc command with reason code "invalid parameters" if using
the requested downstream value of L2_PSDR in conjunction with the requested schedule of RMC symbol
transmission cannot provide the required bit rate described in the L2.1 entry policy.
The FTU-R shall reject the L2.1-Entry-Request eoc command with reason code "wait for RPA" if the
implementation of the L2.1-Entry-Request requires a reconfiguration of the downstream RMC (e.g., to
provide sufficient SNRM-RMC after the requested PSD reduction, see Table 11-48.1). Within 100 ms after
rejecting the L2.1-Entry-Request, the FTU-R shall send an OLR request type 4 (RPA) to reconfigure the RMC.
The value of CNTSF indicated in this RPA command shall not exceed the current superframe count by more
than 16. After the completion of the RPA procedure, or if no RPA request is received before the timeout,
the FTU-O may send another L2-Entry-Request command.

The FTU-O shall not initiate an L2.1 entry procedure before all running OLR procedures have been
completed (i.e., either rejected or accomplished). After sending an L2.1-Entry-Request eoc command, the
FTU-O shall reject all Type 1 and Type 2 OLR requests from the FTU-R, until the end of the L2.1 entry
procedure using the corresponding reject OLR request response with reason code "wait". After reception of
an L2.1-Entry-Request eoc command, the FTU-R shall not send any Type 1 or Type 2 OLR requests until the
end of the L2.1 entry procedure.
NOTE – Type 1 and type 2 OLR requests are rejected because the final bit loading is determined by the parameters
negotiated during the L2.1 entry procedure.
After reception of an L2.1-Entry-Confirm eoc response, the FTU-O shall send an RMC L2-TRNS command
indicating at which superframe count the transition from L0 to L2.1 shall occur. This superframe count shall
be jointly coordinated by the FTU-O and the VCE consistent with the L0  L2.1 transition time, as defined
in clause 12.1.1 and is the same for both upstream and downstream. The parameters conveyed in the
L2.1-Entry-Request eoc command and L2.1-Entry-Confirm eoc response shall be applied by both FTUs
starting from the first RMC symbol of the indicated superframe, in the upstream and in the downstream,
respectively. Once these parameters have been applied, the link is in the L2.1N or L2.1B link state, and the
FTU-O shall respond to the DRA over the γ-O interface (see Table 8-3) with a LinkState.confirm (L2.1N or
L2.1B) primitive within the time shown in Table 12-1.

If the FTU-R does not receive the L2-TRNS command within 1 s after transmission of the L2.1-Entry-Confirm
eoc response has finished, it shall consider that the L0  L2.1 transition has failed and shall continue to
operate in L0. If the FTU-O receives no response to an L2.1-Entry-Request eoc command within the timeout
specified in Table 11-3, or upon reception of an L2.1-Entry-Reject eoc response, the L2.1 entry procedure
shall be considered as failed, and the FTU-O shall respond to the DRA over the γ-O interface (see Table 8-3)
with a LinkState.confirm (FAIL) primitive within the time shown in Table 12-1. If the L2.1 entry criteria are
still met, the DRA may send a new LinkState.request (L2.1N or L2.1B) primitive to the FTU-O, for which the
FTU-O shall send a new L2.1-Entry-Request eoc command to the FTU-R.
13.4.1.2.1 L2.1 entry policy

The method used by the transceivers to select the values of RMC transmission schedule, transmission and
framing parameters described in this clause is vendor discretionary. However, the selected values shall
meet all of the following constraints.

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