Page 808 - 5G Basics - Core Network Aspects

2 Transport aspects

The FTU-O shall transmit quiet symbols for the last (Mds – (TTRds + TAds + B'ds)) downstream symbol positions
of the logical frame, except if this position is a sync symbol position.
The FTU-R shall transmit quiet symbols for the last (Mus – (TTRus + TAus + B'us)) upstream symbol positions of
the logical frame, except if this position is a sync symbol position.
NOTE – Power savings may be achieved in the discontinuous operation interval by transmission of quiet symbols in
symbol periods where there is no end user data. Further power savings may be achieved by appropriately aligning the
data symbols in each of the lines in the vectored group so as to reduce the size of the crosstalk cancellation matrix by
using one or more MxM matrices instead of the one full NxN matrix where M<N. The configuration of the idle and the
quiet symbol periods across the lines in the vectored group is controlled by the VCE/DRA.
During the NOI, the line uses a certain transmit PSD. This PSD setting may be different from those used
during the DOI.
Both FTU-O and FTU-R shall support a separate baseline bit-loading table for each of the intervals (a bit-
loading table for NOI and a bit-loading table for the DOI). The NOI baseline bit-loading tables in both
upstream and downstream are established during initialization (see clauses 12.3.4.2.7 and 12.3.4.2.8); the
DOI baseline bit-loading tables are determined after transition into showtime (see clause 12.3.5). The
baseline bit-loading tables for both NOI and DOI are updated via eoc-based OLR procedures (SRA and TIGA),
as defined in clauses 13.2.1.1 and 13.2.2.1, respectively. The active bit-loading tables for both NOI and DOI
are updated through the RMC by the FRA commands defined in Table 9-10 (for the downstream) and
Table 9-11 (for the upstream).

Figure 10-29 – General illustration of discontinuous operation in the DOI for downstream logical frames

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