The issue group Modems tab shows PreEQ statistics for modems in the issue group. Click the arrow next to the Issue name to expand the issue and display the Modems tab.
The Issues Modems tab shows the following information for all modems in the group. To see information for a single modem, use the PreEQ Stats tab.
- MAC Address
- MAC addresses for modems in this group.
- MTC
- Main Tap Compression, measured in decibels. This is the ratio of energy in all taps to energy in the main tap. Main tap compression at the modem translates to a lower RF power level delivered to the CMTS. An MTC of 2 dB means the CMTS receives 2 dB less input power. An MTC ratio greater than 2 dB may suggest that equalization compensation can no longer be successfully achieved. MTC is a good indicator of the available margin for continued reliance on equalization compensation. Main tap compression at the CMTS is not expected under normal operating conditions. Any level of main tap compression at the CMTS should raise an alarm.
- MTR (dB)
- Main Tap Ratio. This is the ratio of energy in the main tap to energy in all other taps combined. This metric is useful to determine the distortion level in the upstream path. It is approximately the same as the non-main tap to total energy ratio (Comp Eq), except at extremely high distortion levels. In most cases MTR can be used instead of Comp Eq.
- Comp Eq (dB)
- Composite Equalization. This is the total amount of equalization being applied to the upstream signal that is transmitted by the cable modem, relative to the main tap level. This metric is also useful to determine the distortion level in the upstream path. It can be used as an initial assessment tool to determine which modems should receive additional, frequent attention. Severity level icons used are the same as those defined for the Alarms view Issues tab (see related information, below).
- Group Rsp (dB)
- Group Response. This is the ratio of the pre-main tap energy to the energy in all taps. This is a useful parameter, along with PPTSR, to determine the group delay level in the upstream path.
- Echo Rsp (dB)
- Echo Response. This is the ratio of the post-main tap energy to the energy in all taps. This is a useful parameter to assess micro-reflection impairment contribution.
- PPESR (dB)
- Pre-Post Energy Symmetry Ratio. This is the ratio of post-main tap to pre-main tap energy. Along with Group Response, this parameter is useful to indicate the presence of group delay in the upstream path.
- PPTSR (dB)
- Pre-Post Tap Symmetry Ratio. This is an estimate of the PPESR ratio using only the tap immediately before and after the main tap.