Page 999 - 5G Basics - Core Network Aspects

Transport aspects 2

the L2.2 link state by the L2.2-Entry-Request eoc command (see clause 11.2.2.16, Table 11-48.1), and shall
be kept during the entire session in the L2.2 link state.

The value of X shall be set the same for upstream and downstream. The downstream RMC symbol shall
only be sent during the sync frame of a superframe. The time position of the upstream RMC symbols
relative to the downstream RMC symbols shall be delayed by floor(X×MSF/2) logical frames plus the time
period between the upstream and downstream RMC symbol positions of the same logical frame.

The PSD reduction (relative to the L0 link state) and the set of active subcarriers in RMC symbols at the
transition to the L2.2 link state shall not change (it shall stay the same as in the L2.1 link state whence the
transition was performed).

The PSD reduction (relatively to the L0 link state) of the sync symbols shall not change at the transition to
the L2.2 link state (shall stay the same as in the L2.1 link state whence the transition was performed). Sync
symbols shall be transmitted at the same symbol position as in the L0 link state. The subcarrier set used by
sync symbols during the L2.2 link state shall be the same as in L2.1.
NOTE – During the L2.2 link state, downstream and upstream probe sequences may include one or more zero-
elements set at the VCE's discretion, and can be updated for channel estimation and tracking. Those sync symbols
modulated by zero-elements are essentially quiet symbols and facilitate power saving.
During the L2.2 link state, BDR shall be a multiple of the DTU size (DTU size = NDTU + Q × RFEC) and the timing
of DTUs shall be synchronized with RMC symbol boundaries so that an integer number of complete DTUs is
transmitted per RMC symbol.
13.4.2.2 L2.2 Entry procedure

The procedure defined in this clause shall be used to transition from the L2.1B link state to the L2.2 link
state. Transition to the L2.2 link state shall be initiated by the FTU-O. Upon reception of a LinkState.request
(L2.2) primitive across the γ-O interface (see Table 8-3), the FTU-O shall complete or terminate all OLR
procedures and send an L2.2-Entry-Request eoc command to the FTU-R that indicates the RMC symbol
transmission schedule, the relevant upstream transmission parameters and the constraint for the FTU-R to
determine the downstream transmission parameters during the L2.2 link state (see clause 11.2.2.16).
Upon reception of L2.2-Entry-Request, the FTU-R shall respond to the L2.2-Entry-Request eoc command
within a time consistent with the timeout value specified in Table 11-3 by sending either an L2.2-Entry-
Confirm eoc response with the downstream transmission parameters, if the L2.2-Entry-Request eoc
command is accepted, or an L2.2-Entry-Reject eoc response with an appropriate rejection code, as defined
in Table 11-48.6 (see clause 11.2.2.16).

The FTU-O shall not initiate an L2.2 entry procedure before all running OLR procedures have been
completed (i.e., either rejected or accomplished). After sending an L2.2-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 L2.2 entry
procedure using rejection code "wait". After reception of an L2.2-Entry-Request eoc command, the FTU-R
shall not send any Type 1 and Type 2 OLR requests until the end of the L2.2 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 L2.2-Entry-Confirm eoc response, the FTU-O shall send an RMC L2-TRNS command
indicating at which superframe count the transition from the L2.1B to the L2.2 link state shall occur. This
superframe count shall be jointly coordinated by the FTU-O and VCE according to the L2.1B  L2.2
transition time, as defined in Table 12-1, and the L2.2 RMC transmission schedule (see clause 13.4.2.1).
Starting from this superframe count, the transmission of RMC symbols, in both upstream and downstream,
shall change from the L2.1 schedule to the L2.2 schedule and all other L2.2 transmission parameters
requested by L2.2-Entry-Request 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 the L2.2 schedule and all
other L2.2 transmission parameters are applied, the link is in the L2.2 link state, and the FTU-O shall
respond to the DRA over the γ-O interface (see Table 8-3) with a LinkState.confirm (L2.2) primitive within
the time shown in Table 12-1.

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