Zyxel VES-1624FT-55A [100/312] Fast mode

Zyxel VES-1624FT-55A [100/312] Fast mode
Chapter 16 xDSL Port Setup
VES-1624FT-55A User’s Guide
100
16.3.1 Fast Mode
Fast mode means no interleaving takes place and transmission is faster (a “fast channel”). This
would be suitable if you have a good line where little error correction is necessary.
16.4 VDSL Parameters
The following sections describe the VDSL parameters you configure in the following screens:
xDSL Port Setup (see Section 16.9 on page 105).
xDSL Port Profile (see Section 17.1 on page 117).
16.4.1 PSD
PSD (Power Spectral Density) defines the distribution of a VDSL line’s power in the
frequency domain. A PSD mask specifies the maximum allowable PSD for a line.
16.4.2 Limit PSD Mask
To reduce the impact of interference and attenuation, ITU-T 993.2 specifies a limit PSD mask
that limits the VDSL2 transmitters PSD at both downstream and upstream.
16.4.3 RFI (Radio Frequency Interference)
RFI is induced noise on the lines by surrounding radio frequency electromagnetic radiation
from sources such as AM and HAM radio stations. Since VDSL uses a much larger frequency
range that overlaps with other radio frequency systems, signals from VDSL lines and other
radio systems interfere with each other. To avoid performance degradation due to RFI, set the
switch to not transmit VDSL signals in the RFI band defined by the regulatory bodies (ETSI
and ANSI). You can also configure your own RFI bands on the system.
16.4.4 Frequency Band Plan
Each VDSL mode operates in a different frequency band allocation, resulting in different
upstream and downstream speeds. Your Device automatically changes the band plan based on
the loop condition and loop length.
A band plan example is shown next. Band plans include an optional band (between 25 kHz
and 276 kHz) controlled by "limit PSD mask".
The optional band is used for upstream transmission which is to be negotiated during line
initiation. The optional band frequency (for example, the positions of x and y in the following
figure) varies depending on the limit PSD mask you use.

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