VDSL2 Versus DOCSIS Smackdown

Light Reading is reporting that Cox is offering 50 Mbps DOCSIS cable modem service in Arizona on Cisco gear to counter Qwest’s 40 Mbps VDSL2 service offering.  Prices are $89.99 per month for Cox’s DOCSIS-based offering and $109.99 per month for Qwest’s VDSL2-based offering.  The informal poll on FTTxtra indicated that the majority of participants were willing to spend as much as $100 per month on broadband access service, so the prices Cox and Qwest are charging make sense as initial conditions.

The bulk of HFC electronics are deployed in OutSide Plant (OSP) cabinets serving a neighborhood or portions of a large neighborhood, and with DOCSIS, all of this substantial investment is retained by the MSO.  These node cabinets are fed with fiber and serve many homes with telephone, DOCSIS cable modem, and television services over coax.  A typical HFC node cabinet (this is the actual one serving my neighborhood) is shown below.

HFC Cabinet

The picture below shows the power, telephone, and cable connections into my house.  The grey box is the HFC coax NID, which is span powered from the cabinet above.  The HFC NID has a coax connection to a three-way splitter installed above the NID and a two-wire telephone connection to the brown box on the top right.

Telcos often deploy VDSL/VDSL2 services in FTTN (at the node) or FTTC (at the curb) architectures.  The length of some copper local loops served from a FTTN node (typically up to 5000 feet or so, depends on the telco) tend to be a bit long for VDSL2, but sometimes FTTN is a telco’s only feasible option for installing VDSL2.

FTTN VDSL2 nodes are installed in locations with access to the copper local loop, usually through what is called a Feeder Distribution Interface or FDI, shown below.  The DSL electronics accessing the loops at this FDI are housed in the beige boxes located behind the FDI.  The FDI houses no electronics, just cables and cross-connects.  A typical concentration level at an FDI is one upstream copper pair (feeder pair) for two downstream (distribution) copper pairs, so on average, before any electronics are installed at the node, only perhaps half of the local loops delivered to subscribers are already in use.

DSL Feeder Distribution Interface (FDI)

If you want to see what an HFC network can do with broadband, do not miss the video at the end of the article on DOCSIS 3.0 showing a speed test on a Comcast DOCSIS 3.0 network.

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1. Joe Johnson says:

   May 2, 2010 at 1:39 pm

   Interesting blog. I’m in the process of starting a CLEC and found a lot of the information on your site to be insightful. Thanks.