ZyXEL Communications VES1724-56 User Manual page 98

Chapter 9 VDSL Setup
VDSL2 Profiles
Eight VDSL2 frequency profiles (8a, 8b, 8c, 8d, 12a, 12b, 17a, and 30a) are defined in G.993.2.
They are based on each annex specifying spectral characters (Annexes A, B and C). Each profile
covers certain settings and parameters, such as maximum aggregate transmit power. The higher-
frequency profiles (17a and 30a) are mostly used to deliver high speed at shorter distances.
Note: At the time of writing, the Switch supports the Annex A with 8a, 8b, 8c, 8d, 12a,
12b, 17a, and 30a. The following table summarizes the VDSL2 profiles supported
by the Switch.
Table 27 VDSL2 Profiles on this Switch
FREQUENCY
PARAMETER
PLAN
Annex A Maximum aggregate
downstream transmit power
(dBm)
Index of highest supported
downstream data-bearing sub-
carrier (upper band edge
frequency in MHz (informative))
Index of highest supported
upstream data-bearing sub-
carrier (upper band edge
frequency in MHz (informative))
Configured Versus Actual Rate
You configure the maximum rate of an individual VDSL port by modifying its profile (see the
Line Profile Setup
screen). However, the actual rate varies depending on factors such as transmission range and
interference.
Impulse Noise Protection (INP)
Short impulses from external sources may cause bursts of errors which could impact the
multimedia (ex. voice, video, or picture) quality. VDSL2 supports Impulse Noise Protection (INP)
which provides the ability to correct errors regardless of the number of errors in an error DMT
(Discrete Multi-Tone) symbol.
UPBO
In a network with varying telephone wiring lengths, the PSD on each line is different. This causes
crosstalk between the lines. Enable UPBO (Upstream Power Back Off) to allow the device to adjust
the transmit PSD of all lines based on a reference line length. This mitigates the upstream crosstalk
on shorter loops to longer loops. It allows the switch to provide better service in a network
environment with telephone wiring of varying lengths.
An example is shown below. Line 1 and Line 2 are in the same cable binder. Crosstalk occurs when
the signal flows and is near to CPE (A)'s location. Besides, higher Line 1 PSD causes higher
98
PARAMETER VALUE FOR PROFILE
8A 8B
+17.5 +20.5
1971 1971
(8.5) (8.5)
1205 1205
(5.2) (5.2)
screen) or assigning the port to a different profile (see the
8C 8D 12A
+11.5 +14.5 +14.5
1971 1971 1971
(8.5) (8.5) (8.5)
1205 1205 2782
(5.2) (5.2) (12)
12B 17A 30A
+14.5 +14.5 +14.5
1971 N/A N/A
(8.5)
2782 N/A N/A
(12)
VDSL
VDSL Line Setup
VES1724-56 User's Guide