SMC Networks TigerAccess SMC7816M - Manual (Page 256)

VDSL C
ONFIGURATION
10-4
Upstream power back-off (UPBO) is used to mitigate far-end crosstalk
caused by upstream transmissions from shorter to longer loops. The
bounding power levels specified in this table are used to reshape the
PSD, ensuring that the signals on short to long loops are compatible.
The transceiver will adjust its transmitted signal to conform to the
power limitations set in this table.
If upstream power backoff is enabled, the transceiver will automatically
reduce the PSD at each frequency breakpoint set the by the PSD
breakpoint specified on the Global Configuration screen or the VDSL
Port Configuration screen (see page 10-7).