RF Archives

21 12, 2011

DOCSIS 3.0 Impaired Service

Mia Colabrese2021-08-17T16:00:00-04:00December 21st, 2011|

"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.

21 09, 2011

Cable Modems init(r1) init(r2) Why are they stuck?

Mia Colabrese2021-08-20T09:21:27-04:00September 21st, 2011|

Cable Modems init(r1) init(r2), DOCSIS Cable Modems going offline? DOCSIS Cable Modems init(r1) init(r2) are stuck or offline! Many of us have been there before - one or more DOCSIS cable modems init(r1) init(r2) 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, or Cable Modems init(r1) init(r2), because these are the status conditions displayed on the DOCSIS CMTS

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.

21 06, 2010

DOCSIS 3.0 Tutorial – CMTS Architecture

Mia Colabrese2021-08-18T10:10:11-04:00June 21st, 2010|

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.

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)...

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, [...]

29 01, 2009

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

Mia Colabrese2021-08-17T09:58:12-04:00January 29th, 2009|

Most of us are quite comfortable with changing the dial on our FM radios. Don't like what's on Soft 95.1 FM, then change the frequency (Kenneth) to 102.5 FM for some classic rock. What you have actually done is changed the RF (radio frequency) tuner in your car stereo from a lower frequency of 95.1 MHz to a higher frequency of 102.5 MHz where there was a different station playing. The fact that two different stations were playing...