ZyXEL Communications P841C, User Manual, Page: 25 / 41

P841C Central-Side VDSL Modem
VDSL-Related Commands 4-5
Table 4-5 VDSL Status Counters
FIELD DESCRIPTION
VDSL Parameters: All these fields except for DISC are displayed in hexadecimal format.
LINK STAT This field displays the link status. The link is up if this field displays 0xac or 0xae; otherwise the link
is down.
DISC This is a VDSL Disconnect counter.
Modem Code This field displays information about the modem code.
VDSL Line Quality Status
US This is the VDSL UpStream rate. 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 is the VDSL raw speed and Fc is the carrier frequency.
DS This is the VDSL DownStream rate.
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 This is the Minimum Square Error. The minimum mean-square error (also known as MMSE)
performance measure is a popular metric for optimal signal processing.
RS_ERR This is the count of bit errors detected and corrected by Reed-Solomon code. Reed-Solomon
codes are block-based error correcting codes and are used to correct errors in many systems.
LT and NT Power Parameters
TXPWR This field displays transmission power information in hexadecimal format.
POCO Port Output Control registers provide the control bit information.
POWER This is the power measured in dBm (decibel milliwatts). It is the product of TXPWR and POCO.
PSD This is the Power Spectrum Density (power divided by bandwidth).
4.1.9 VDSL Clear Command
vdsl clear
This command clears the VDSL status counters.
4.1.10 VDSL Debug Command
vdsl debug [on|off]
This command turns the VDSL auto flag on or off or just shows the current VDSL auto flag status (without “on”
or “off”). When this flag is on, the P841C displays each stage (state) of the VDSL link initialization process.
When the VDSL link is up, no messages are displayed until the VDSL line is disconnected.