ZyXEL Communications Cable Modem, User Manual

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Chapter 1 VLC Overview
VLC1324G User’s Guide
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VDSL2 to ADSL2+ Fallback
The VLC can automatically use ADSL2+ for connections where VDSL2 training fails. This
allows a longer connection distance.
Spectral Mask
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. The VLC transmitter signal complies with the Power Spectrum Density (PSD) mask
specified in ITU-T G.993.2 and supports masks EU32_D32, EU36_D48, and EU40_D48.
Latency Mode
The VLC supports the latency path function specified in ITU-T G.993.2 and you can manually
configure the payload transfer delay for interleaved transmissions.
Rate Adaption
Rate adaption lets the VLC 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.
The rate adaptation conforms to ITU-T G.993.2 and G.997.1 and is manually configurable and
can adjust automatically based on the line quality as determined by the Signal-to-Noise Ratio
(SNR).
Trellis Coding
The VLCuses Trellis coding (as specified in ITU-T G.993.2) to help reduce the noise in VDSL
transmissions.
Impulse Noise Protection (INP)
Short impulses from external sources may cause bursts of errors which could impact
multimedia (ex. voice, video, or picture) quality. The VLC’s VDSL2 supports Impulse Noise
Protection (INP) as defined ITU-T G.993.2. The VLC’s impulse noise protection provides the
ability to correct errors regardless of the number of errors in an errored DMT (Discrete Multi-
Tone) symbol. You can configure the minimum impulse noise protection to provide up to 16
DMT symbols protection.
Loop Diagnostic
The VLC supports the loop diagnostic function specified in ITU-T G.993.2. The test
parameters include quiet line noise, signal-to-noise ratio, loop attenuation, signal attenuation,
signal-to-noise ratio margin, attainable net data rate, and far-end actual aggregate transmit
power. After completing the loop diagnostic function, the VLC displays the test results and
automatically returns to the normal state to be ready for initialization.
System Monitoring
• System status (link status, rates, statistics counters)
• Configurable temperature and voltage monitoring thresholds and alarm reports.