ZyXEL Communications VES-1000 Series, User Manual, Page: 103 / 227

VES-1000 Series Ethernet Switch
Diagnostic 13-3
Table 13-2 DSL Line Diagnostic
LABEL DESCRIPTION
Constellation Constellation shows the modulation method and speed. The constellations are QAM 4,
QAM 8, QAM 16, QAM 64, QAM 256 where QAM (Quadrature Amplitude Modulation)
defines how many bits there are per symbol; for example QAM 4 means 2 bits per
symbol (2
2
), QAM 8, 3 bits (2
3
) per symbol and so on.
Int (Interpolation) defines how fast the symbols go through the line. It is equal to
25.0MHz / baud rate, so for example, Int 8 = 25.0 / 8 Mbaud.
Rate This is the VDSL raw speed.
Fc This is the carrier frequency
SNR The higher the SNR (Signal-to-Noise Ratio) number, the better. SNR (Signal-to-Noise
Ratio is the ratio of the amplitude of the desired signal to the amplitude of noise signals
at a given point in time.
MSE Minimum Square Error. The minimum mean-square error (also known as MMSE)
performance measure is a popular metric for optimal signal processing.
RSERR This is the Reed-Solomon error count. Reed-Solomon codes are block-based error
correcting codes that are used to correct errors in many systems.
PSD This is the Power Spectrum Density.
DISC This is a VDSL Disconnect counter.
VDSL Port Select the port you want to diagnose from the drop-down list box here.
VDSL Status Click this button to view the VDSL status. The large text box above then displays the
progress and results.
Local Loop Back Use these loop back tests to determine if there's a problem with the line card’s VDSL
chipset. Click this button to do a local loopback test.
Remote Loop Back Click this button to do a remote (from the switch to the VDSL modem) loop back test to
determine if there’s a problem with the line card or the connection to the subscriber’s
VDSL modem. You can only do this when the VDSL line is connected.
13.4 Logout Screen
Click Logout in the navigation panel to open this screen and exit the web configurator.
Figure 13-3 Logout