Page 1080 - 5G Basics - Core Network Aspects

2 Transport aspects

Appendix VI

Example applications of discontinuous operation
(This appendix does not form an integral part of this Recommendation.)

VI.1 Discontinuous operation with vectoring disabled
In deployment scenarios where there is no expected self-FEXT, such as in the case of a single-line DPU or a
DPU connected to drop wires with no common cable sheath, the vectoring function may become inactive
or be disabled. Should vectoring become inactive or disabled, only one bit loading table and one set of
gains needs to be maintained by each transceiver in the DPU per direction of transmission. In every logical
frame the transmitter may send data symbols only during symbol periods when data is available for
transmission and send only quiet symbols during all remaining symbol periods in the logical frame where
no data is available. One way to achieve this is to set TTR = TBUDGET, which effectively disables the
discontinuous operations interval.
Figure VI.1 shows an example timing diagram of autonomous discontinuous operation over a single line
when DRA/VCE has vectoring disabled. Figure VI.1(a) gives an example for the downstream direction and
Figure VI.1(b) gives a similar example for the upstream, where in each case the FTU sends a contiguous
block of data for duration of TTR = TBUDGET symbol periods followed by a block of quiet symbols for the
remainder of the logical frame.
Each of the examples given in this appendix uses the valid frame value of MF = 23 symbol periods with
Mds = 14 symbol periods and Mus = 8 symbol periods. The examples mainly demonstrate the configurations
of TTR, TBUDGET and TA per the rules defined in clause 10.7.
Each of the examples show the configuration of TBUDGET, TTR and TA communicated to the receiver in the
RMC for each line in the vectored group. Shown in square brackets are the values of TIQ, B' and B. The
value of TIQ is set by the DRA/VCE block(s) in the DPU and communicated to the FTU-O indicating that if
there is no data available for a data symbol position spanned by TBUDGET interval in the DOI, it may be
filled with a quiet symbol if TIQ=0 or an idle symbol if TIQ=1.

s;
s;
F
TDD frame (M = 23 symbol T F = M × T seconds) TDD sync frame (M = 23 symbol T F = M × T seconds)
S
F
S
F
F
Downstream M = 14 M = 8 Downstream M = 14 M = 8
ds
us
ds
us
Line n d d d d rmc d d d d d d d d d Upstream d d d rmc d d d d d Upstream rmc ...
TTR = TBUDGET = 13; TA = 0; TTR = TBUDGET = 6; TA = 0;
ds
ds
DRMC = 4 [TIQ = 0, B' = B = 0] ds ds [TIQ = 0, B' = B = 0] ds ds
ds
t = 0 t = T F t = 2T F
DS logical frame (T ) containing DS sync symbol DS logical frame without DS sync symbol
F
rmc rmc symbol d data symbol = q quiet symbol sync symbol
G.9701(14)_FVI.1a
TTR = duration of the normal operation interval TA = number of quiet symbols immediately after TTR
TBUDGET+TA–1 = index of the last symbol position in a logical frame eligible for carrying a data symbol
(a) Downstream autonomous discontinuous operation
s;
TDD sync frame (M = 23symbol s; T F = M × T seconds) TDD sync frame (M = 23 symbol T F = M × T seconds)
F
F
S
F
F
S
M = 14 Upstream M = 8 M = 14 Upstream M = 8 M = 14 M = 8
ds
us
ds
us
ds
us
Line n Downstream rmc d d d d Downstream d rmc d d Downstream rmc d ...
TTR = TBUDGET = 7; TA = 0; TTR = TBUDGET = 3; TA = 0;
us
us
us
us
us
us
DRMC = 3 [B' = B = 0] [B' = B = 0]
us
t = 0 t = T F t = 2T F
Upstream logical frame (T ) containing sync symbol Upstream logical frame (T ) without sync symbol
F
F
rmc rmc symbol d data symbol = q quiet symbol sync symbol
G.9701(14)_FVI.1b
TTR = duration of the normal operation interval TA = number of quiet symbols immediately after TTR
TBUDGET+TA–1 = index of the last symbol position in a logical frame eligible for carrying a data symbol
( ) Upstream autonomous discontinuous operationb
Figure VI.1 – Discontinuous operation without vectoring (autonomous discontinuous operation)
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