ZyXEL Communications IES4005M, Руководство пользователя

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Chapter 24 VDSL
IES4005M User’s Guide
166
A sample of optional band PSD masks and associated frequency bands used in the Device is shown
next.
The “eu” number in the limit PSD mask is a tone index. A tone spacing, 4.3125 KHz, is used for
VDSL2 profile from 8a up to 17a. So “eu32” means the optional band ending at around 138 kHz.
VDSL2 Profiles
The following table lists the supported Annex A VDSL2 profiles defined by the VDSL standard. Refer
to the ITU G.993.2 specifications for more information on other profiles. The VDSL2 profiles
available in an individual VDSL2 line card varies.
Configured Versus Actual Rate
You configure the maximum rate of an individual DSL port by modifying its profile or assigning a
different profile to the port. However, the actual rate varies depending on factors such as
transmission range and interference.
Impulse Noise Protection (INP)
Sudden spikes in the line’s noise level (external noise) can cause errors and result in lost packets.
Set the impulse noise protection minimum to have a buffer to protect the DSL physical layer against
impulse noise. This buffering causes a delay that reduces transfer speeds. It is recommended you
use a non-zero setting for real-time traffic that has no error correction (such as video-
conferencing). The number of DMT (Discrete Multi-Tone) symbols specifies the time in which errors
can be completely corrected. A higher symbol value provides higher error correction capability, but
it causes overhead and higher delay which may increase error rates in received multimedia data.
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.
Table 112
Optional band PSD mask
LIMIT PSD MASK OPTIONAL BAND FREQUENCY
nus0_d32 = No optional band
eu32_d32 = 25-138 kHz
eu36_d48 = 25-155.25 kHz
. . .
Table 113
Supported VDSL2 profiles (annex A)
PROFILE 8A 8B 8C 8D 12A 12B 17A 30A
Bandwidth (MHz) 8.5 8.5 8.5 8.5 8.5 8.5 17.66 30
Tone 1972 1972 1972 1972 1972 1972 4096 4096
Tone Spacing (kHz) 4.3125 4.3125 4.3125 4.3125 4.3125 4.3125 4.3125 4.3125
Line Power (dBm) +17.5 +20.5 +11.5 +14.5 +14.5 +14.5 +14.5 +14.5