The PreEQ Issues tab displays a table of grouped issues that affect one or more modems on the fiber node.
For each frequency, modems that have been flagged as crossing the Echo Detection Threshold (NMTER) are compared to one another. Modems that exhibit the same defect signature at the same frequency indicate that the CMTS is correcting both similarly. If the correction values are similar enough, the modems meet an established comparison threshold and are put into the same issue group. If only one modem is exhibiting a specific defect at a frequency, that modem is placed into its own group and labeled as a Unique Issue.
Each issue group has one tap that displays the lowest performance, which is determined by comparing the average magnitude at each tap to the comparison threshold. The lowest performing tap is usually the tap with an average magnitude that exceeds the comparison threshold by the largest margin. If no tap has an average magnitude that exceeds the threshold, then the average magnitude closest to the threshold determines the lowest performing tap.
- Issue
- Issue Group identifier, including any unique issues.
- Frequency (MHz)
- The frequency the defect is identified at.
- Size
- Size of the echo cavity or cavities.