HFC Archives

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:

14 11, 2011

Press Release

Mia Colabrese2011-11-14T07:00:04-05:00November 14th, 2011|

Press Release The Volpe Firm offering solutions, services and products for the broadband telecommunications industry The Volpe Firm gets Seal of Approval from Clients Alpharetta, GA November 14, 2011: The Volpe Firm offers solutions, services and products for the broadband communications industry with a focus in DOCSIS, data, video, and VoIP communications. We provide everything from specialized DOCSIS 3.0 seminars and or tailored DOCSIS training to high level hardware architecture engineering design and system troubleshooting. The Volpe Firm, with 30 years of combined telecommunications experience, specializes in DOCSIS,

22 02, 2009

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

Mia Colabrese2021-08-17T22:35:57-04:00February 22nd, 2009|

DOCSIS Cable Modem Data Burst Defined 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 REQUEST relays the cable modem's Service IDentifier and the number of bytes of information the modem has to transmit in its buffer. The CMTS prioritizes all incoming

9 02, 2009

DOCSIS and Cable Modems – How it works :: Cable Modem Registration

Mia Colabrese2021-08-17T09:54:53-04:00February 9th, 2009|

Through DOCSIS tutorial seminars, I have found the most effective way to bring someone up to speed on DOCSIS communications is by teaching the cable modem registration process. During the registration process, we will cover the RF physical layer, theDOCSIS Media Access Layer (MAC) and the Internet Protocol (IP) layer. Yes, the cable modem exercises the first three layers of the Open Systems Interconnection Reference Model (OSI Reference Model or OSI Model)...

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.

27 01, 2009

DOCSIS and Cable Modems – How it works :: Introduction

Mia Colabrese2021-08-26T08:28:17-04:00January 27th, 2009|

Over the past several years of training people on troubleshooting DOCSIS® networks and explaining how DOCSIS cable modems and CMTSs work, I have been asked numerous times - "Why don't you write a book on this?" You see, there is no definitive book, guide or manual that explains the Data-over-Cable Service Interface Specification (DOCSIS) other than the several hundred page specification...