SC-QAM parameters apply to DOCSIS 3.0 and earlier networks. They are available for graphing from the SC-QAM sub-tab of the Parameters tab on the Alarm Central, Analyze Network View, and Analyze Modem View screens.

On the sub-tab, these parameters are grouped according to where they are measured (downstream or upstream), but the following list is organized alphabetically.

Attenuation

Upstream RF data parameter (in dB).

This is the loss of upstream signal strength as it travels across the cable plant, measured as the difference in dBmV between the upstream transmit power reported by a cable modem and the upstream Rx Power for the modem as reported by the CMTS.

Capacity

Downstream and upstream utilization parameter (in Mbps).

This is the maximum data rate the channel can carry.

CCER

Downstream and upstream RF data parameter, measured on a per-modem, per-channel basis as a percentage (%).

This is the percentage of codewords received on the channel that had recoverable errors.

CCER+CER

Downstream and upstream RF data parameter, measured on a per-modem, per-channel basis as a percentage (%).

This is the percentage of codewords received on the channel that had either correctable or uncorrectable errors.

CER

Downstream and upstream RF data parameter, measured on a per-modem, per-channel basis as a percentage (%).

This is the percentage of codewords received on the channel that had unrecoverable errors.

CMTS Channel CCER

Upstream RF data parameter, measured from CMTS on a per-channel basis as a percentage (%).

This is the percentage of codewords received on the channel that had recoverable errors.

CMTS Channel CCER+CER

Upstream RF data parameter, measured from CMTS on a per-channel basis as a percentage (%).

This is the percentage of codewords received on the channel that had either correctable or uncorrectable errors.

CMTS Channel CER

Upstream RF data parameter, measured from CMTS on a per-channel basis as a percentage (%).

This is the percentage of codewords received on the channel that had unrecoverable errors.

CMTS Channel SNR

Upstream RF data parameter, measured from CMTS on a per-channel basis (in dB).

This is the SNR of the transmissions as measured and reported by the CMTS.

CMTS Channel MER

Upstream RF data parameter, measured from CMTS on a per-channel basis (in dB).

This is the Modulation Error Ratio, or an SNR measure that includes estimated error when performing QAM demodulation.

CMTS Corrected

Upstream data parameter, measured on a per channel basis as a number.

This is the number of codewords received by the CMTS from all modems in the last five seconds that had errors and were corrected using FEC.

CMTS Uncorrectables

Upstream data parameter, measured on a per channel basis as a number.

This is the number of codewords received by the CMTS from all modems in the last five seconds that had uncorrectable errors.

CMTS Unerrored

Upstream data parameter, measured on a per channel basis as a number.

This is the number of codewords received by the CMTS from all modems in the last five seconds that had zero errors.

Composite Eq [NMTER]

Upstream RF data parameter, measured on a per-modem, per-channel basis (in dB).

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.

Corrected

Downstream and upstream data parameter, measured on a per channel basis as a number.

This is the number of codewords received either by the modem or CMTS in the last 5 seconds that had errors and were corrected using FEC.

Deviation of Echo Response

This is a measure of how far a cable modem's Echo Response deviates from its historical average. Used in the calculation of the likelihood for an In-Home Issue.

Device Count

Downstream and upstream data parameter, measured on a per-channel basis as a number.

This is the number of devices on the channel.

Echo Response [POSTMTTER]

Upstream RF data parameter, measured on a per-modem, per-channel basis (in dB).

This is the ratio of the post-main tap energy to the energy in all taps. It measures the total amount of equalization being applied by the positive delay portion of the equalizer to the upstream signal that is transmitted by the cable modem, relative to the main tap level. This is a useful parameter to assess microreflection impairment contribution.

Group Response [PREMTTER]

Upstream RF data parameter, measured on a per-modem, per-channel basis (in dB).

This is the ratio of the pre-main tap energy to the energy in all taps. It measures the total amount of equalization being applied by the negative delay portion of the equalizer to the upstream signal that is transmitted by the cable modem, relative to the main tap level. This is a useful parameter, along with PPTSR, to determine the group delay level in the upstream path.

MER

Modulation error ratio. A downstream RF data parameter, measured on a per-modem, per-channel basis (in dB).

This is an SNR measure that includes estimated error when performing QAM demodulation. It can be triggered when the downstream MER drops below the configured threshold.

Minislot Utilization

Upstream utilization data parameter, measured on a per-channel basis as a percentage (%).

This is the number of minislots the CMTS allocated to modems for transmission on a channel, as a percentage of the total it could have allocated.

Rate

Downstream and upstream utilization parameter measured on a per-channel basis (in Mbps).

This is the actual traffic rate the channel carried during the defined interval.

Rx Power

Downstream and upstream RF power parameter, measured on a per-modem, per-channel basis (in dBmV).

This is the total composite RF power of a single QAM channel, measured at the receiver input of the cable modem, as reported by the cable modem. Triggered when Receive Power is above or below the defined threshold range. If the received power level is too low or too high, communication between the cable modem and CMTS may be slow or may stop completely.

SNR

Signal-to-noise ratio. A downstream and upstream noise parameter, measured on a per-modem, per-channel basis (in dB).

For upstream channels, SNR is the ratio of the transmissions from a cable modem as measured and reported by the CMTS. For downstream channels, SNR is the ratio of the transmissions from the CMTS measured at a cable modem.

SNR Deviation

A downstream and upstream noise parameter, measured on a per-modem, per-channel basis as a sigma (σ) value.

This is a measure of how far the SNR for a cable modem deviates from its historical average. The average is computed using an exponential filtering algorithm.

Spectral Response

A downstream and upstream RF data parameter, measured on a per-modem, per-channel basis (in dB).

This provides an indication of the total amount of correction being applied by the equalization filter on the cable modem receiver. This parameter does not return an absolutely accurate value, but it gives a rough indication of micro-reflections received on this interface.

Ideally, the signal must not be reflected from the receiver to the transmitter. If this happens, the reflected signal may interfere with the desired transmitted signal, and result in errors in the signal, as detected by the receiver. Therefore, the level of micro-reflections must be as low as possible. The unit dBc refers to the power ratio of a signal relative to the carrier frequency, where the carrier is the frequency that carries the desired transmitted signal. In other words, it is based on a ratio of the power of the microreflections, divided by the Power of the Carrier Signal. The CMTSs and CMs report this as a measure of the microreflections below the carrier, so a relatively large positive number is desirable. If this number is too small, it indicates that the undesired microreflections are not far below the carrier in strength. This condition may lead to degraded performance for the user, since the signal may be getting interference from the reflections. The DOCSIS MIB warns that absolute accuracy of this item is not expected and CommScope recommends considering this when evaluating this metric.

T3 Errors

An upstream timeout parameter, measured on a per-modem, per-channel basis as a number.

This is the number of T3 timeouts reported by the cable modem for each discrete upstream channel during the selected period. A T3 timeout indicates a timeout occurred while waiting for a ranging response.

T4 Errors

An upstream timeout parameter, measured on a per-modem, per-channel basis as a number.

This is the number of T4 timeouts reported by the cable modem for each discrete upstream channel during the selected period. A T4 timeout indicates a timeout occurred while waiting for a periodic ranging opportunity.

Tx Power

An upstream RF power parameter, measured on a per-modem, per-channel basis (in dBmV).

This is the total composite RF power of a single QAM channel set by the transmitter at the output of the cable modem, as reported by the cable modem.

Uncorrectables

Downstream and upstream data parameter, measured on a per channel basis as a number.

This is the number of codewords received either by the modem or CMTS in the last 5 seconds that had uncorrectable errors.

Unerrored

Downstream and upstream data parameter, measured on a per channel basis as a number.

This is the number of codewords received either by the modem or CMTS in the last 5 seconds that had zero errors.

Utilization

A downstream and upstream utilization parameter, measured on a per-channel basis as a percentage (%).

This is the percentage of a channel's capacity that is being used. Very high utilization, typically 80% or more, may result in performance degradation for the subscriber.