DOCSIS PNM: In-channel Frequency Response (ICFR)

Introduction

Rick Yuzzi introduces Carlos Bustamante, Vice President of Strategic Technologies. They discuss the previous broadcast and how they will redo it.

In-Channel Frequency Response

Carlos Bustamante explains in-channel frequency response (ICFR) and its importance in signal transmission.

CMTS and Modems

• The CMTS is the orchestrator of all modems.

• The CMTS sees all signals from the modem and looks for a nice flat haystack.

• If the signal is heavily distorted, the CMTS asks the modem to transmit the inverse of what it received.

RF Network as a Black Box

• The RF network is treated as a black box because we don't know what happens there.

• Inverse signals are sent to ensure that resulting messages received by the CMTS are near flat.

In-Channel Frequency Response Chart

Rick Yuzzi shows slides demonstrating an in-channel frequency response chart and how it can be out of whack.

Spectral View

• A spectral view shows what the CMTS receives from a particular part of the spectrum.

• PreEqualization on a per upstream basis allows for improvements to be made if necessary.

In-channel Frequency Response Chart

• An in-channel frequency response chart is specifically in a PNM tool.

• This chart shows how heavily distorted signals can be handled by the CMTS.

ICFR Metric and Graphical Representation

In this section, Carlos and Rick discuss the ICFR metric and graphical representation. They explain how the CMTS sends a communication message to the modem to make adjustments for the next transmission back to the headend. The inverted signal from the last slide traversed the entire RF network, encountering all these impairments that once it gets to the CMTS, because it did send the inverse, what happens is that you're seeing in essentially a flat signal, which is what the CMTS is expecting.

Modem Adjustments

• The modem makes equalizer adjustments and sends essentially what is the inverse of the last message that the CMTS received.

• The in-channel frequency or response graph represents all of the work that was done by modem on its next transmission back to headend.

• PreEqualization compensates for near-home or in-home issues.

ICFR Thresholds

• Typically want to stay below 3 Db peak-to-valley in your ICFR reading.

• Anything typically above 3 Dd indicates near-home or in-home issues.

• PNM tools will identify modems with green, yellow, or red flags on a map outside of threshold.

Proactive Network Maintenance Platform

In this section, Carlos explains how proactive network maintenance platforms can be used to monitor ICFR metrics. He shows an example of a table view where each modem has been labeled based on severity level.

Severity Levels

• A critical modem would have an ICFR reading above 3 DB peak-to-valley.

• In the example shown, the modem has an ICFR reading of 11 Db, which is off the charts.

Conclusion and Next Steps

In this section, Carlos and Rick summarize their discussion on ICFR metrics and graphical representation. They also mention that they will be discussing group delay in the next episode.

Summary

• The ICFR metric and graphical representation can be used to monitor modem adjustments.

• While PreEqualization compensates for near-home or in-home issues, it does not fix them.

• Proactive network maintenance platforms can be used to monitor ICFR metrics based on severity levels.

Next Steps

• In the next episode, Carlos and Rick will discuss group delay.

PNM Tool and Correlation Groups

In this section, the speakers discuss how to identify problems within a PNM tool and how to identify problems that are affecting multiple homes, which are called correlation groups.

Identifying Problems with PNM Tool

• You can use a PNM tool to identify problems.

• The tool helps you pinpoint issues in specific areas.

Correlation Groups

• Correlation groups refer to problems that affect multiple homes.

• The speakers will discuss vTDRs in more detail later on.

Questions and Subscription

In this section, the speakers encourage viewers to ask questions during future sessions and subscribe to their YouTube channel for updates.

Asking Questions

• Viewers are encouraged to ask questions during future sessions.

Subscribing to YouTube Channel

• Viewers should subscribe to the YouTube channel.

• By ringing the bell next to "Subscribe," viewers will be notified of new videos or live streams.

Conclusion

In this section, the speakers conclude the session.

Conclusion

• The speakers thank viewers for watching.

• Carlos thanks everyone.