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DOCSIS 3.1 in '13

1/21/2013 8:30 AM

By now, hopefully, you’ve heard that there’s a new chapter coming in cable modems. It’s the latest iteration in the specification known by technologists as “DOCSIS 3.1” for “Data Over Cable Service Interface Specification.”

DOCSIS 3.1 is a doozy — both in terms of what it will do for broadband capacity and the sheer density of the tech talk that surrounds it.

Let’s face it: “QAM” is a little long in the tooth as impressively nerdy industrial tech-talk goes. Not to worry. With 3.1, you too can impress your friends and colleagues by blurting out 3.1-speak like “Orthogonal Frequency Division Multiplexing with Low Density Parity Check.”

Feature-wise, DOCSIS 3.1 is so crammed with improvements that some of us wondered why it didn’t qualify as “DOCSIS 4.0.” (Answer: To thwart any misperceptions from the investor community about “forklift upgrades.”)

First off : DOCSIS 3.1 matters and was devised because of the billowing consumer demand for broadband usage — a growth rate of 50% or higher since about 2009. Again: In the history of consumable goods, nothing has grown at a sustained rate of 50%, year over year.

DOCSIS 3.1 basics: When complete (2013) and in market (2014?), it will expand the industry’s downstream and upstream carrying capacity for digital, IP traffic by 50%.

“Half as much again” is always a big deal, especially for that spectrally anemic upstream signal path.

Also impressive about DOCSIS 3.1: It could enable connection speeds of 10 Gigabits per second. Note: Don’t inhale too deeply on this one. It’s 10 Gbps if, and only if, all other channels on a system are empty. No analog, no SD or HD video, no voice.

Let’s get back to the tech-talk of 3.1. What makes for these enormous gains in IP capacity and speed is a new (to cable) form of modulation called “OFDM”.

OFDM, when coupled with a new (to cable) form of forward error correction (LDPC), brings the 50% efficiency gains. OFDM is widely used by mobile carriers, because they’re already pretty bandwidth-challenged (ship any video from your phone lately?). It works by chopping the typical 6 MHz digital cable channel into smaller “subcarriers,” in the lingo. That’s good for both transmission and dealing with impairments.

Those are the basics of DOCSIS 3.1 — why it matters, and how to talk about it with aplomb. Watch for it to be a major undercurrent of the 2013 cable-tech scene.

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