Quadrature Amplitude Modulation Archives

11 11, 2013

DOCSIS Burst Demod – SCTE EXPO 2013 – Fresh Tech

Mia Colabrese2013-11-11T09:00:21-05:00November 11th, 2013|

DOCSIS Burst Demod SCTE EXPO 2013 - Fresh Tech There were some new and exciting things at this years SCTE. There was a good drum line at the opening event but also there were new products and innovative ideas (Cisco and PNM). In test equipment this year at the SCTE EXPO Rohde and Schwarz, JDSU and VeEx all had some new things on display. None of the items are currently shipping (with the exception of R&S who used existing equipment) but it does show that test equipment vendors are

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:

1 07, 2010

DOCSIS 3.0 Tutorial – The EQAM

Mia Colabrese2021-08-17T15:58:05-04:00July 1st, 2010|

In my article on DOCSIS 3.0 M-CMTS architecture, I talked about the distributed nature of the CMTS with an M-CMTS core (the CPU of the system), a DOCSIS Timing Server, and an edge Quadrature Amplitude Modulator (EQAM). I am going to cover the EQAM in detail in this article because in the past couple of years, EQAM (also spelled eQAM) has rapidly become part of our vocabulary but its operation and value often go unappreciated. Further, in order to fully understand DOCSIS 3.0 operation, downstream channel bonding, and possible issue which may arise, a thorough understanding of the eQAM is critical.

12 10, 2009

DOCSIS 3.0 Tutorial – Introduction

Mia Colabrese2021-08-17T16:05:13-04:00October 12th, 2009|

This is the first of a new series of Tutorials focused on the Data Over Cable Service Interface Specifications (DOCSIS) version 3.0. I will make the assumption that you are familiar with the DOCSIS 1.x / 2.0 standards or have already reviewed my DOCSIS Basics Tutorial as I will be using many terms without explanation since they were previously covered. The DOCSIS 3.0 specification is an extension of the DOCSIS 1.x and 2.0 specification which dramatically increases the data throughput by adding a technology known as channel bonding to the DOCSIS downstream and upstream, adding increased security, adding support for IPv6, and substantially improving the back-office management support (MIBs, SNMP, IPDR, etc.) for DOCSIS. Each of these topics will covered in much greater detail in this DOCSIS 3.0 tutorial in multiple posts yet to come.

2 10, 2009

Speeding Upstream – Part I

Mia Colabrese2021-08-18T10:19:55-04:00October 2nd, 2009|

The first part of this article (in CT's March 2009 issue) discussed downstream potential issues, while this one focuses on the potential issues associated with upstream deployments. In particular, this article covers the critical upstream areas that one should be aware of when getting ready to deploy or already deploying DOCSIS 3.0.

5 02, 2009

DOCSIS and Cable Modems – How it works :: Upstream RF

Mia Colabrese2021-08-17T13:29:04-04:00February 5th, 2009|

Cable modems use RF (radio frequency) signals to transport data over hybrid-fiber coax (HFC) networks according to the DOCSIS® specification. This blog will discuss the finer points extracted from the DOCSIS specification related to how cable modems communicate with the headend Cable Modem Termination System (CMTS), allowing two-way transport of Ethernet traffic over a cable TV network. There are currently three major revisions and one sub-revision of the DOCSIS specification; DOCSIS 1.0, 1.1, 2.0 and 3.0. With each major revision came significant changes to the cable modem upstream specification because the upstream has typically been the bottleneck in terms of data through-put rates as will be discussed.

2 02, 2009

DOCSIS and Cable Modems – How it works :: Advanced RF

Mia Colabrese2021-08-17T13:36:52-04:00February 2nd, 2009|

In high speed data communications, the industry has evolved and implemented complex modulation schemes which vary a signals voltage (amplitude), phase, and frequency in order to transmit more data, faster. The following will cover these methods in order to describe how Quadrature Amplitude Modulation (QAM) works in DOCSIS communications. We live in an analog world. Sure, [...]