Tag Archives: CATV

Fresh Tech | Leakage Detection with Brains!

November 22, 2011   Brady   3 Comments
CPAT Flex Ingress Detection solution

I admit that while I help my clients better understand the sources and negative impacts of RF ingress on DOCSIS in a cable plant, I have never found leakage/ingress detection itself particularly high-tech. That was until Daniel Babeux of VGI Solutions gave me a demo of their CPAT Flex Platform. The live demo was straightforward which made it so convincing and intriguing. It consisted of a truck-mount magnetic antenna that connected into a little green box (the brains behind the operation), and a piece of coax cable seemingly chewed upon by a squirrel. The latter connected back into the CATV plant. The awesome part of the demonstration was seeing the location of the antenna appear on Google maps at the Georgia Convention Center in Atlanta, GA. Next when the damaged coax was replaced, the leakage point on the map disappeared along with magnitude of the leakage entering the plant.

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Fresh Tech | Awesome Spectrum Analyzer at a Cool Price!

November 21, 2011   Brady   No comments
Televe's CATV Spectrum Analyzer

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:

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Fresh Tech from Cable-Tec Expo 2011

November 19, 2011   Brady   No comments
Rohde & Schwarz Cable Load Generator

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:

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DOCSIS 3.0 Tutorial – Upstream Channel Bonding

August 22, 2010   Brady   5 Comments
DSAM DOCSIS 3.0 Throughput Test

The focus of this article will be on the mechanics of upstream channel bonding and how it works more from a DOCSIS protocol perspective. Much more detailed information can be found in the DOCSIS 3.0 MULPIv3.0 document located in the Library, but this will provide a high level overview for the layman who is curious about the basics. First lets understand that it is the cable modem that is doing the channel bonding, remember in the upstream the cable modem transmits data to the CMTS. Per DOCSIS 3.0, the CM can bond from one to four channels in the upstream as coordinated by the CMTS. The CM is always under control by the CMTS.

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Speeding Upstream – Part II

October 07, 2009   Brady   5 Comments

This article will focus more specifically on DOCSIS 3.0 issues that will occur as you are deploying DOCSIS 3.0 or post -deployment.

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DOCSIS and Cable Modems – How it works :: Tutorial Wrap Up

April 20, 2009   Brady   10 Comments
DOCSIS tutorial wrap up

If you have followed the “DOCSIS and Cable Modems – How it works” tutorials this far, congratulations! You now have a basic foundation of how DOCSIS networks operate and the ability to pick up the DOCSIS specification and read and comprehend it – this is hard to do for the novice. If you are just finding this blog for the first time, then I recommend that you go to the DOCSIS Tutorial Series and start at the beginning before proceeding.

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DOCSIS and Cable Modems – How it works :: Quality of Service

March 09, 2009   Brady   2 Comments
Quality of Service

DOCSIS 1.0 enabled data over coax with a “best effort” service using a data request-grant methodology. DOCSIS 1.1 and subsequent specifications added guaranteed Quality of Service (QoS) by providing Unsolicited Grant Synchronization (UGS) which means that a cable modem does not have to send a data request in order to receive a bandwidth grant from the CMTS. The new UGS service is an enabling technology which has allowed cable operators to successfully deploy the highly revenue generating Voice-over-IP (VoIP) services. In the following sections I will illustrate the differences between best-effort (request-grant) and QoS (UGS) services.

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DOCSIS and Cable Modems – How it works :: Station Maintenance

March 03, 2009   Brady   33 Comments
DOCSIS Station Maintenance

While the UCD provides the language of the DOCSIS network, the Station Maintenance messaging is the proverbial “heartbeat” of the DOCSIS network. A station maintenance session consists of a Range Request sent from a cable and a Range Response sent by the CMTS. The CMTS analyzes the signal quality of the Range Request message and sends back any necessary RF adjustments in the Range Response message. This “handshake” between every cable modem and the CMTS must occur once every 30 seconds as dictated by the DOCSIS specification.

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DOCSIS and Cable Modems – How it works :: UCD

February 28, 2009   Brady   11 Comments
DOCSIS Upstream Channel Descriptor - UCD

Just as a picture is worth a thousand words, so is a complete Upstream Channel Descriptor (UCD) as seen by a cable modem. This message, sent every two seconds by the the CMTS, contains an enourmous amount of valuable information that every cable modem on a DOCSIS network needs to know in order to communicate. Often undervalued, the UCD is a virtual Hitchiker’s Guide to the DOCSIS network! So without any further ado, let me show you an example of a full UCD message and then explain its contents further

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DOCSIS and Cable Modems – How it works :: Anatomy of a Burst

February 22, 2009   Brady   8 Comments
DOCSIS Anatomy of a Burst

Previously I have discussed that cable modems share the upstream channel by using Time Division Multiple Access (TDMA).  This means that when a cable modem is not transmitting data its RF transmitter is turned off.  In order to transmit data it must transmit a burst of data which contains a REQUEST to the CMTS.  The

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