ZyXEL Communications P8701T Guia do Utilizador descarregar pdf (Página 69)

Chapter 3 Device Info Screens

Basic Home Station VDSL2 P8701T User’s Guide

Upstream These are the statistics for the traffic direction going out from the port to the service

provider.

Line Coding

(Trellis)

This displays whether or not the port is using Trellis coding for traffic. Trellis coding helps to

reduce the noise in ADSL transmissions. Trellis may reduce throughput but it makes the

connection more stable.

SNR Margin

(0.1 dB)

This displays the Signal-to-Noise Ratio margin (in 0.1 dB). A DMT sub-carrier’s SNR is the

ratio between the received signal power and the received noise power. The signal-to-noise

ratio margin is the maximum that the received noise power could increase with the system

still being able to meet its transmission targets.

Attenuation

(0.1 dB)

This displays the line attenuation, measured in tenths of a decibel (0.1 dB). This attenuation

is the difference between the power transmitted at the near-end and the power received at

the far-end. Attenuation is affected by the channel characteristics (wire gauge, quality,

condition and length of the physical line).

Output Power

(0.1 dBm)

This displays the far end actual aggregate transmit power (in dBm). Downstream is how

much port the service provider is using to transmit to the port. Upstream is how much

power the port is using to transmit to the service provider.

Attainable Rate

(Kbps):

These are the highest theoretically possible transfer rates at which the port could send and

receive data.

Rate (Kbps) This displays the data transfer rates at which the port is receiving and sending.

Super Frames This displays the number of ADSL superframes the DSL connection received and

transmitted. Each superframe contains 68 ADSL data frames and a one-frame synch symbol

for a total number of 69 frames.

Super Frame

Errors

This displays the number of errored ADSL superframes the DSL connection received and

transmitted.

RS Words This displays the number of Reed Solomon error correction words for received and

transmitted traffic.

RS Correctable

Errors

This displays the number of errored packets corrected by Reed Solomon error correction for

received and transmitted traffic.

Uncorrectable

Errors

This displays the number of errored packets that Reed Solomon error correction could not

correct for received and transmitted traffic.

HEC Errors Header Error Control (HEC) checks for errors in packet headers.

OCD Errors The number of Out of Cell Delineation errors for received and transmitted traffic. An OCD

error means seven consecutive ATM cells had Header Error Control (HEC) violations.

LCD Errors The number of Loss of Cell Delineation errors for received and transmitted traffic. An LCD

state means an OCD condition persisted for 4 milliseconds.

Total Cells This displays the total number of DSL cells including headers.

Data Cells This displays the number of data payload DSL cells, excluding headers.

Bit Errors This displays the number of errored bits.

Total ES This displays the number of Errored Seconds meaning the number of seconds containing at

least one errored block or at least one defect.

Total SES This displays the number of Severely Errored Seconds meaning the number of seconds

containing 30% or more errored blocks or at least one defect. This is a subset of ES.

Total UAS This displays the number of UnAvailable Seconds.

xDSL BER Test Click this to open a screen where you can perform a ADSL Bit Error Rate (BER) test to

determine the quality of the ADSL connection.

Reset Statistics Click this to clear the screen’s statistics counters.

Table 8 xDSL Statistics Screen (continued)

LABEL DESCRIPTION

1 2 ... 64 65 66 67 68 69 70 71 72 73 74 ... 239 240

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