Cisco Cisco DOCSIS EuroDOCSIS Transponder for Compact Amplifiers and Nodes Installation Guide
Chapter 3 Operation
This following table provides useful information on how to interpret the information
presented in the table.
Specification
Description
Frequency
The downstream frequency given in Hz
Power
The downstream power given in dBmV
SNR
The downstream signal quality.
Signal Noise Ratio (SNR)
Signal Noise Ratio (SNR)
MER
The downstream signal quality.
Modulation Error Ratio (MER)
Modulation Error Ratio (MER)
Note: The MER value displayed are subject to the
transponder itself and varies from the field test results
tested from the test points of amplifier and nodes.
CER Interval
The intervals of each CER check.
Codeword Error Rate (CER) refresh rate.
Codeword Error Rate (CER) refresh rate.
Pre FEC CER
Codeword error rate (CER) before forward error correction
is applied.
Post FEC BER
Codeword error rate (CER) after forward error correction is
applied.
Interpreting QAM Constellation Data by Visual Inspection
The usefulness of the QAM constellation comes in the ability to recognize common
shapes and configurations within the map. The following table summarizes the
shapes commonly visible in the RF Constellation page. Examples of these shapes are
illustrated in the figures that follow.
Shape
Focus
Impairment
Description
Individual
cells
and
entire QAM
constellation
Normal
Dots are centered in the
individual QAM quadrants.
The QAM constellation has a
uniform square shape.
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