ZyXEL Communications VES-1124 -, Руководство пользователя

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VES-1124 User’s Guide
Basic Setting 6-13
Table 6-5 Port Setup
LABEL DESCRIPTION
Cancel Click Cancel to begin configuring this screen afresh.
6.9 VDSL Parameters
The following sections describe the VDSL parameters you configure in the VDSL Common Setup and the VDSL
Profile Setup screens.
6.9.1 Frequency Band Plans
Each VDSL mode operates in a different frequency band allocation, resulting in different upstream and downstream
speeds.
•
10BaseS giving upstream rates from 1.56 Mbps to 18.75 Mbps and downstream rates of 4.17 Mbps to
16.67 Mbps.
•
ANSI/ETSI Plan 998 Mode giving upstream rates from 1.56 Mbps to 6.25 Mbps and downstream rates of
4.17 Mbps to 16.67 Mbps.
•
ETSI Plan 997 Mode giving upstream rates from 1.56 Mbps to 6.25 Mbps and downstream rates of 4.17
Mbps to 12.50Mbps.
Configured Versus Actual Rate
You configure the maximum rate of an individual VDSL port by modifying its profile (see the VDSL Profile
Setup screen) or assigning the port to a different profile (see the Port Setup screen). However, the actual rate
varies depending on factor such as transmission range and interference.
6.9.2 PSD and PBO
PSD (Power Spectral Density) defines the distribution of a VDSL line’s power in the frequency domain. A PSD
mask is a template that specifies the maximum allowable PSD for a line.
In a network with varying telephone wiring lengths, the PSD on each line is different. This causes crosstalk
between the lines. Enable PBO (Power Back Off) to base the transmit PSD of all lines on a reference line length so
that the PSD at the receiving end is the same.
6.9.3 Rate Adaption
Rate adaption is the ability of a device to adjust from the configured transmission rate to the attainable transmission
rate automatically depending on the line quality. The VDSL transmission rate then stays at the new rate or adjusts if
line quality improves or deteriorates.