Cable’s 5Gbps Dream Is Harder Than It Looks

April 26th, 2010 by · 3 Comments

The media is reporting that the cable industry is now looking beyond Docsis 3.0 to a new standard that can support as much as 5Gbps, which on the surface would seem to allow their coax to keep up and perhaps even surpass fiber.  But the situation is far more complicated than this.  Actually, cable is already offering this speed, it's just that most of it is already carrying traffic that we call cable TV.  The 64 billion dollar question here is what happens to that cable TV traffic if all the spectrum is dedicated toward broadband.

The short answer is simply IPTV:  the final step in our migration of everything onto an IP platform - TV on demand for everyone, with no more inefficient use of our assets.  If it sounds too good to be true, that's because it's bypassing a few engineering realities.  Cable networks as currently designed are shared assets that do a very good job of sending the same bits to everyone.  A whole neighborhood gets those same programs at exactly the same time across the same spectrum.  Only a small portion of their connectivity actually goes toward broadband, and that is shared too with others on their loop - so if everyone uses their full connection then their actual speeds fall.

Reapportioning the entire available capacity to broadband and putting TV traffic over it via IP rather than in separate channels may be more efficient one day.  But right now the infrastructure is tightly tied to the broadcast model, because it was designed to save money by sharing that bandwidth.  If you simply turn all that TV into IPTV such that video streams vary by household and even each TV in those households, then you may unleash a 5Gbps last mile but the rest of the network would surely collapse.

I don't mean it isn't possible to develop and implement such a standard, and it may be the right way to go in the long term and I applaud the cable industry for finally taking a hard look at its future infrastructure.  I'm just saying that the media needs to realize that this is far more than developing a new standard or a new access technology.  The standard would be by far the easiest step.  What has hit the news lately as cable's 5Gbps potential is none other than the contemplation of a complete and total redesign of their video delivery business.

Once you get past the limitations of copper, it doesn't really matter whether the last bit is via fiber or coax.  Connectivity to the home ceases to be the bottleneck whether it is via a 50Mbps or 1Gbps broadband connection.  It's the rest of the network that gets hard then, and older infrastructures will have to be replaced.

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Categories: Cable · Video

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3 Comments So Far


  • John A. Danko says:

    if an innovative standard is accomplished, then perhaps it is a step towards an a la carte offering…which maybe is why it has and will take some time to see

  • Dave Rusin says:

    ” …would seem to allow their coax to keep up and perhaps even surpass fiber.”

    Physics says this is impossible …

    • Rob Powell says:

      You are talking of theoretical limits, I was speaking of the horse race of actual implementations – and with my tongue in my cheek as well.

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