QAM Archives

15 07, 2021

DOCSIS Primary Channel Impaired Downstream Troubleshooting

Mia Colabrese2023-02-17T18:41:43-05:00July 15th, 2021|

In this episode Brady and John discuss what happens to an impaired DOCSIS Primary channel & ANGA COM highlights. When an impaired DOCSIS Primary channel occurs, do to one ore more impairment, how does it impact other DOCSIS channels? Primary being a type of "management" SC-QAM channel. Does it make a difference? We also cover the top content from the ANGA COM show. Didn't have time to watch all of the ANGA COM show material. No problem. Brady and John will make sure your up to speed

20 04, 2016

RF Measurements in the Cable Plant

Mia Colabrese2021-08-16T20:15:37-04:00April 20th, 2016|

RF Measurements in the Cable Plant - Learn more about RF Episode 20 Hosted by Brady Volpe of the Volpe Firm and Nimble This. Guest John Downey, CMTS Technical Leader at Cisco Systems and special guest, Ron Hranac Technical Leader at Cisco Systems. Today’s show we will cover a number of topics including RF measurements and fundamentals. The discussion starts with basic building blocks of the sine wave and evolves to how QAM (quadrature amplitude modulation) signals are comprised of sine waves with varying amplitude and phase shifts, which means even though we call

18 12, 2015

Doubling Down on DOCSIS 3.1

Mia Colabrese2022-01-20T11:36:56-05:00December 18th, 2015|

Doubling Down on DOCSIS 3.1 DOCSIS 3.1 and PNM were hot topics at Cable Tec Expo in New Orleans and in most major publications and articles for 2015. Comcast is the largest driver of DOCSIS 3.1, but my recommendations are that whether you are a tier 1, tier 2 or even tier 3 cable operator DOCSIS 3.1 should be on your roadmap. Consumer behavior and technical innovations are leading factors behind this statement and I elaborate below. Consumer Behavior and the State of Internet Traffic Growth In May

22 01, 2014

DOCSIS 3.1: Modulation Options and Impacts – Part Two

Mia Colabrese2023-02-17T13:02:40-05:00January 22nd, 2014|

What’s Next for DOCSIS 3.1 Modulation Options and Impacts DOCSIS 3.1 modulation - Many wonder how today’s networks will support high order modulations such as 4096-QAM. There are two technologies in the DOCSIS 3.1 standard that will enable this without requiring changes to existing outside plant. The first is Orthogonal Frequency Division Multiplexing (OFDM). This is a complex word for taking many small QAM channels, like 25 kHz instead of 6 MHz, and placing them very close together. OFDM also has dynamic properties. If you have a block

2 05, 2012

Why is QAM Getting Me Down?

Mia Colabrese2021-08-18T09:11:04-04:00May 2nd, 2012|

64-QAM lower than Analog video on the downstream? 64-QAM lower than 16-QAM on the upstream? Why is a 6.4 MHz channel lower than a 3.2 MHz DOCSIS channel? Someone said there is math for all of this, but man QAM is getting me down! These questions come up in every lecture I give on DOCSIS. Why do QAM measurements show up at different levels on a spectrum analyzer than analog measurements. What's more, why do QAM signals of different bandwidth have different levels? Some of the questions have

22 11, 2011

Fresh Tech | DOCSIS Protocol Analyzer – Can’t stop a good idea!

Mia Colabrese2021-08-18T10:13:29-04:00November 22nd, 2011|

When I first heard rumor that a knew company had a DOCSIS protocol analyzer floating around I had to see it! With full disclosure, many of you know that after 10 years in RF and fiber-optic transport equipment, I spent a few years designing, marketing and selling DOCSIS protocol analyzers. More specifically I focused on making them available to cable operators because I knew they could detect really difficult to isolate problems. Averna know owns the technology from my Sigtek days, so it is nice to see a new competitor in the space. What's more is that its nice to see this competitor at SCTE Cable-Tec Expo who is interested in cable operator's issues.

21 11, 2011

Fresh Tech | Awesome Spectrum Analyzer at a Cool Price!

Mia Colabrese2011-11-21T15:54:40-05:00November 21st, 2011|

What first caught my eye by Televes H45 Spectrum Analyzer was the HDMI port feeding a flatscreen television. How cool is that? I also noticed the small unit was displaying a QAM "haystack" along with its power, MER, BER, and the demodulated picture just beside the measurements. The picture was on a high resolution display, not the low quality displays I've seen in the past, so tiling or macro-blocking would be apparent to the user. See the picture below:

19 11, 2011

Fresh Tech from Cable-Tec Expo 2011

Mia Colabrese2020-06-09T09:59:13-04:00November 19th, 2011|

At this year's Cable-Tec Expo, Rohde & Schwarz (www.rohde-schwarz.com) introduced a 1U Cable Load Generator (CLG) capable of simulating cable TV networks with full channel loading. This baby is not just limited to North America, but can do channel plans for the World over! Here are the highlights:

18 07, 2010

DOCSIS 3.0 Tutorial – Downstream Channel Bonding

Mia Colabrese2021-08-17T16:09:16-04:00July 18th, 2010|

Downstream Channel Bonding is perhaps the ball bearings of DOCSIS 3.0, enabling subscriber data speeds in excess of 160 Mbps (4 times that of previous DOCSIS versions). While conceptually simple, the principle of combining multiple downstream DOCSIS channels together to carry the same user data must have tight constraints in order to preserve the integrity of the data and have the data arrive at the correct subscriber's device and in sequence. This article will cover both the physical layer aspects and DOCSIS protocol aspects that enable channel bonding.

7 07, 2010

DOCSIS 3.0 Tutorial – Basic Protocol 1

Mia Colabrese2021-08-18T09:58:46-04:00July 7th, 2010|

Now that we have established the two primary architectures available in DOCSIS 3.0, I-CMTS and M-CMTS (thought hybrids do exist), and the hardware components of these architectures, it is time to delve into the protocol of the DOCSIS specifications that make up DOCSIS 3.0. There are five primary specifications that I will be drawing upon from here on out listed below and located in my document library and also on the CableLabs website.