The Tool That Sees Around Corners


Innovation can happen in the strangest places. Latest example: a tool built from a tangent of the DOCSIS cable-modem specification, which lets cable operators find, map and fix network problems — before they affect consumers.

Up until now, technicians could see “green-yellow-red” notifications about network impairments, but not their precise location. (Squirrels and rats don’t typically tweet their whereabouts when chewing through wires.)

The source of the invention are the “pre-equalization” techniques within the DOCSIS specification (versions 1.1 and above), which anticipate and correct distortions between cable modems and the headend.

Turns out those same distortion “signatures” can be mined to triangulate where a problem is. On a map. Which makes this a tool that can see around corners.

Or, in tech terms, it means that every fielded cable modem becomes a network analyzer, a tool that goes for about $10K otherwise.

I saw the invention in action last week, when an engineering pal at Comcast (we’ll call him Larry, because that’s his name) showed me, on my New York-situated laptop screen, that the cable modems in my Denver office were working just fine. All green.

He then switched the screen to show the diagnostics from his house — an older home, with older wiring. Uh-oh: yellow lights. Why? Larry’s modem’s upstream transmit levels were huffing and puffing, trying to push the data through the aged wires.

That tool designed for customer-care people — plus one tailored to line techs and another that shows network health, by region — are all built on top of a foundational tool Comcast calls the “network scout.” (Internally, it also goes by “flux capacitor.”)

Next, Larry showed me a “ripple,” shorthand for a microreflection caused by an impedance mismatch. (Those happen when connectors aren’t connected right, or when coax gets kinked or squished.)

And then — poof! — he overlaid the ripple data onto a network map, showing major plant components (nodes, amplifiers). From there, he overlaid a street map, with the precise location of the fault.

The scout tool stems from a CableLabs effort called “Proactive Network Maintenance,” which was “productized” by Comcast. (Cox Communications, Charter Communications and others built or are building versions, too.)

Anything that can see around corners is spooky, in my book. Fixing problems before they occur? Spooky-cool.


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