Tag Archives: RF

DOCSIS 3.0 | Impaired Service

December 21, 2011   Brady   2 Comments
DOCSIS 3.0 Impaired Service

“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.

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Cable Modems Stuck? | init(r1), init(r2)…

September 21, 2011   Brady   5 Comments
Cable Modems Stuck in init(r1) init(r2)

Many of us have been there before – one or more cable modems stuck in one of numerous “init()” conditions – how do we interpret these messages and what do we do? A recent reader wrote in and had just this problem.  DOCSIS cable modems going offline and getting stuck in “R1″ or “R2″  condition, also known

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DOCSIS 3.0 Tutorial – The EQAM

July 01, 2010   Brady   1 Comment

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.

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DOCSIS 3.0 Tutorial – CMTS Architecture

June 21, 2010   Brady   5 Comments

Before we dive into bits, bytes and protocol, first we will discus some hardware. During the evolution of DOCSIS 3.0 there were a number of interesting interim steps along the way, shall we say building blocks, to arrive at a full blown D3.0 CMTSs. This left us with two fundamentally different system architectures in production by CMTS vendors, Integrated and Modular CMTSs. It is important to understand these “architectures” from a purchasing, operational and deployment standpoint as they have different requirements in some cases, some are better than others depending on the system layout.

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

February 09, 2009   Brady   30 Comments
DOCSIS Network Cable Modem Registration Illustration

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)…

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