Troubleshooting DOCSIS Archives

7 01, 2021

NanoVNA Calibration to 75 Ohm for CATV

brady2022-07-04T19:38:55-04:00January 7th, 2021|

NanoVNA Calibration for CATV 75 Ohm This article focuses on calibration of the NanoVNA to a 75 ohm environment. There's a lot of talk about the NanoVNA with calibration, the NanoVNA come's standard with 50 ohm SMA connectors on it, but for CATV broadband networks we must calibrate to a 75 ohm standard and not the 50 ohm cal standards that come with the NanoVNA. There are a lot of discussions on the forms about calibrating and that's the proper way of calibrating nano VNAs for a 75

24 09, 2012

DOCSIS Return | Dirty Fiber Optic Connectors

Mia Colabrese2012-09-24T03:14:16-04:00September 24th, 2012|

An often overlooked, but easy to resolve RF impairment are loose and/or dirty fiber optic connectors. This issue often manifests itself as an increased noise floor when viewed on a spectrum analyzer. The key to determining the difference between regular ingress and fiber connector noise is that the noise created by a loose or dirty fiber connector does not stop at the diplex filter roll-off frequency (typically 42 MHz in North America and 65 MHz Europe). The image below shows a perfect example of this type of impairment:

17 09, 2012

DOCSIS Codeword Errors | What you should know

Mia Colabrese2024-04-19T10:18:35-04:00September 17th, 2012|

Calculating... Calculating... DOCSIS Codeword Errors - You will likely see them DOCSIS correctable codeword errors and uncorrectable codeword errors are available as a metric in most cable operator monitoring tools and Operations Support Systems (OSS). The monitoring tools and OSS generally provide data and dashboards for users to monitor overall network health and then identify a problem when it occurs. Metrics like codeword errors are extracted directly from DOCSIS CMTSs using Simple Network Management Protocol (SNMP) or Internet Protocol Detail Records (IPDR), the later being preferred due to

5 07, 2012

Subscribers get lower data rates than provisioned?

Mia Colabrese2020-06-09T09:36:58-04:00July 5th, 2012|

Why do my DOCSIS subscribers and their Cable Modems get lower speeds than what my DOCSIS config file says they should get? This is a common question that I am asked and it has more than one answer. All too often the RF plant is the first to blame for low DOCSIS cable modem speeds, but in many cases the root cause of the problem can be traced back to the cable modem configuration file and/or the lack of appropriate speed test applications in the headend. Also, some

15 05, 2012

SCTE DOCSIS 3.0 Presentation Blacksburg, VA

Mia Colabrese2012-05-15T09:30:18-04:00May 15th, 2012|

DOCSIS 3.0 Troubleshooting, SCTE Blacksburg, VA View more presentations from The Volpe Firm, Inc.

1 03, 2012

Impact of Impulse Noise on Adaptive Pre-Equalization Part II

Mia Colabrese2021-08-18T09:36:31-04:00March 1st, 2012|

In part I of this article I discussed adaptive pre-equalization in DOCSIS cable modems and how it can compensate for many upstream impairments such as frequency response, group delay and micro-reflections. I also left off with a cliff-hanger, which is also the title of the article; impulse noise has an impact on adaptive pre-equalization, but how and what is it? I'll cover both what impulse noise is and why and how it impacts adaptive pre-equalization.

29 02, 2012

Impact of Impulse Noise on Adaptive Pre-Equalization

Mia Colabrese2021-11-24T09:26:04-05:00February 29th, 2012|

For those of you who have attended my seminars you are familiar with adaptive pre-equalization in cable modems (if not I'll explain it in detail momentarily). Also, if you have done any amount of RF plant troubleshooting you are certainly familiar with Impulse noise (again, I'll cover this too). But if you are like me, I never knew that the two topics were co-related.

26 01, 2012

Advanced Troubleshooting in a DOCSIS 3.0 Plant

Mia Colabrese2020-07-02T17:55:04-04:00January 26th, 2012|

If you missed the SCTE Cable-Tec 2011, I am making available my presentation and white paper on Advanced Troubleshooting in a DOCSIS 3.0 Plant. Each speaker had only 20 minutes to cover topics that could easily last hours, so the presentations are understandably brief. Below you will find my presentation in "Slideshare" for online viewing as well as a fully downloadable PowerPoint version. The PowerPoint version also has reader notes attached at the bottom of each slide which you may find useful. In addition, the animations work a little better in the downloadable version.

21 12, 2011

DOCSIS 3.0 Impaired Service

Mia Colabrese2021-08-17T16:00:00-04:00December 21st, 2011|

"Impaired Service" in which case one or more bonded upstream channels are impacted by upstream RF impairments while other bonded channels are not. Since subscriber data is striped (that is broken into pieces and spread across each upstream channel and then re-assembled by the CMTS), some of the data will be lost or have errors while other data will not. Subscribers will most likely notice an impaired condition as upstream data rates slow down due to TCP/IP transmissions and/or VoIP, gaming, teleconferencing and other real-time applications will be noticeably impacted.

7 12, 2011

DOCSIS 3.0 Partial Service

Mia Colabrese2021-08-17T10:25:49-04:00December 7th, 2011|

Partial Service is a new term encountered in the DOCSIS 3.0 MULPI specification and realized in field deployments of DOCSIS 3.0 cable modems using upstream bonding. This was a topic that I touched on in this years SCTE Cable-Tec Expo, but will explore in greater detail in this article. Partial service can be considered a feature because the cable modem will stay online even when one or more upstream transmit channels goes offline.