Tag Archives: Media Access Layer

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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DOCSIS 3.0 Tutorial – Downstream Channel Bonding

July 18, 2010   Brady   2 Comments

Downstream Channel Bonding is perhaps the ball bearings of DOCSIS 3.0, enabling subscriber data speeds in excess of 160 Mbps (4 times that of previous DOCSIS versions). While conceptually simple, the principle of combining multiple downstream DOCSIS channels together to carry the same user data must have tight constraints in order to preserve the integrity of the data and have the data arrive at the correct subscriber’s device and in sequence. This article will cover both the physical layer aspects and DOCSIS protocol aspects that enable channel bonding.

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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 :: 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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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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