reverse path

A Wider Upstream Path: 2018?

DENVER–A surefire way to fire up cable technologists used to involve smiling broadly while asking: “When will you need to widen the upstream path?”

For decades, the answer, usually harrumphed, was this: “Never!”

Why: It’s a pretty big hassle. Very plant-intensive, possibly to the point of having to revisit or replace gear at the tap level. (Taps are expressed in number of ports — 4-port, 8-port — and exist to adjoin fatter cable, like feeder cables, to the thinner, coaxial cable that drops into homes. So there’s tons of them.)

Later, queries about a wider upstream softened into variations of “not in my lifetime.” Why: The upstream is a very skinny portion of the total available capacity of a cable system. “Very skinny” meaning five percent or less, occupying a slender spectral spot from 5-42 MHz.

Then broadband happened. Right now, the growth of downstream (home-facing) broadband consumption still far outpaces the growth of upstream (network facing) bandwidth usage. But! Think about how many things come with a built-in video camera. Your phone, for instance, or any of the webcams monitoring any of the things in your life.

Video is big. Sending it upstream, live, chews up bandwidth.

Think, too, about the fact that more Wi-Fi traffic is happening right now than mobile or wired, combined. Offloading some of that onto the wired network in the house is a plausible reality.

Which brings us to the latest round of responses to the age-old question of when the industry might consider a wider upstream. Last week, specifically, during a panel of technologists at Light Reading’s annual “Cable Next-Gen Technologies & Strategies” event. Answer, extrapolated from the guts of the panel and not expressed directly: 2018-ish.

“We’re all exploring it,” said Jorge Salinger, VP/Access Architectures for Comcast, to the point of an organized, weekly call amongst involved technologists at several MSOs.

Here’s where the 2018-ish prediction comes from:  DOCSIS 3.1 includes language supporting a “mid-split,” which is tech talk for widening the upstream.

The silicon for DOCSIS 3.1-based gear is expected this year. The cable modems and gateways that use it will follow in 2015. Then interops, then trials — which makes 2016 plausible as “the golden year” for widespread DOCSIS 3.1 deployments.

After that, 3.1-based headend gear (known industrially as “CMTS,” for “Cable Modem Termination System”) catches up. Let’s say that happens in a big way in 2017.

After all of that, and should we continue to see gadgetry in our homes that streams video constantly, it will probably make sense to move the upper boundary of the upstream spectrum, from 42 MHz, to 65 MHz, or higher.

That’s why we’re putting a 2018-ish stamp on it. (Heavy on the -ish.)

This column originally appeared in the Platforms section of Multichannel News.

 

 

 

 

 

Ustream, I Stream, We All Stream … Upstream

Here’s one to keep a close eye on: “Ustream,” the online service that streams video, live, from any of the webcams in your life.

For instance: Sara, who runs our OTT video lab, raises chickens. Sometime next week, she’ll assemble an incubator, to keep the eggs warm and cozy.

A webcam, fed by Wi-Fi, will peer into the incubator. Ustream will live-stream from the “hatch-cam,” to the tablets, phones and PCs of anyone who wants to watch the progression from eggs to little fluffy chicks.

If you’ve read this column for any period of time, you know that I’m forever concerned about cable’s upstream path. It’s skinny, for starters – a scant 5% of total available bandwidth, located between 5-42 MHz. It’s noisy, for another.

That’s why Ustream was a forehead-smack moment for me: Ohhh, it’s not that we’re all going to be live-streaming upstream directly from the cameras inside phones or tablets. It’s that we’re going to be watching the stuff in front of our home/barn/work webcams.

As one MSO technologist noted, in the research for this column: “Cameras that stream are part of the feared “machine-to-machine” world that consumes bandwidth in ways never before seen.”

Gulp.

Naturally, there’s no easy way to model a “breaking point” for the upstream path, in light of Ustream-like traffic and webcam proliferation. As with most things technical, it depends. (No really. It does.)

A few basics do exist. Always start with node size (typically around 500 homes.) Count only homes that subscribe to broadband (say, 60% of 500 = 300.) Estimate how many homes are simultaneously online (10% of 300 = 30.)

For extra drama, imagine how many devices per home are video-capable – at least six per home by 2015, by some estimates.

Next, estimate how many of those homes (and screens) are live-streaming (say, 30% of 30 = 9.) Pick a compression technique (H.264, in Ustream’s case) to ascertain stream size (this is a big area of “it depends.”)

Subtract that number from total available upstream capacity – also a tub of “it depends.” Why: The upstream path was never envisioned or designed to carry “traditional” video. As a result, channels widths aren’t 6 MHz all day long, like they are in the downstream (home-facing) path.

Upstream channel widths typically use one of three sizes: 1.6 MHz, 3.2 MHz, and 6.4 MHz. The width differences accommodate three modulation types for sending traffic upstream.  In a small/medium/large terms, there’s QPSK (“bumpy path – slow down!”), and 16-QAM, for adequate spectrum, and 64-QAM, used in clean, wide, quiet upstream conditions.

The carrying capacity of each differs, in terms of data throughput (how much stuff can be stuffed back up the network.)

So, the math of the upstream path is far from clean,  but it’s probably time to give it a serious ago. I’m looking at you, Massillon Cable….

This column originally appeared in the Platforms section of Multichannel News.

 

 

 

 

 

 

 

On Widening Cable’s Upstream Path: All Eyes on YOU, Massillon Cable!

ORLANDO–Finally! Someone is going to see what it takes to widen cable’s upstream path.

At last week’s Society of Cable Telecommunications Engineers, burrowed into an opening session featuring engineers from mid-sized operators, Massillon Cable GM and technical operations manager Kelly Rehm made this understated but momentous declaration: “One of the projects we’re working on next year is to go to 85 MHz, to improve the return path.”

In the hall, an audible murmur: Did he say what I think he said?

Trust me: If ever you want to raise the energy level in a room full of cable engineers, ask them when they’re going to widen the upstream. Answers like “hopefully not in my lifetime” tend to follow.

It’s nearly a religious debate. Why: Widening the upstream is a big deal, operationally and technically. It’s not for the faint of heart, is the common refrain.

Plus, technologists and bandwidth watchers submit, the need for more upstream capacity isn’t as dire as the need for more room in the downstream, so far.  That 50% CAGR in broadband usage that we keep hearing about is a downstream phenomenon only.

Think about it: Of all the IP-connected devices you use (smart phones, tablets, PCs, connected TVs), most activities that eat up bandwidth are downstream – towards you. Streaming video is a classic example. Until we’re using our digital, IP gadgetry to, say, videoconference through the cable modem (as opposed to Facetiming through the cellular network), or to send live video streams, it’s less of an issue.

Cable upstream basics: Spectrally slender, cable’s upstream path (which also goes by the “return” or “reverse” path) represents a scant 5% of total available bandwidth. Because of where it sits (between 5-42 MHz), it’s riddled with different types of noise – much of it generated inside the home.

Just as you slow down when driving on a road pocked with potholes, transmitting upstream traditionally required modulation sturdiness, more so than boffo speeds.

In Expo conversations about the new DOCSIS 3.1 specification, also unveiled here, MSOs said they’ll phase new, higher-order modulation and forward error correction techniques into the downstream first. Then, if the need arises, they’ll have the tools they need to expand the upstream too.

That’s why Massillon’s decision to experiment with widening the upper boundary of the reverse path, to an 85 MHz “mid-split,” is a big deal. Finally, we’ll see what it really takes to get ready for a wider upstream, if and when needed. Go Massillon!

This column originally appeared in the Platforms section of Multichannel News.

 

 

Move over, Moore — Shannon’s Law Is On

A few weeks ago, an engineering elder called to pose this bit of industrial wisdom: “For the last 20 years, we’ve seen the monetization of Moore’s Law. From here on out, we’ll see the monetization of Shannon’s Law.”

Haven’t heard of Shannon? Welcome to this week’s translation.

First off, one important distinction: There are laws, and then there are “laws.” Think laws of gravity, motion, thermodynamics, and physics here. Not legal law, or laws of unintended consequences, or marketing lingo that sounds peppier with “law” in the title.

In that sense, Moore’s Law isn’t technically a law; Shannon’s Law is a law of physics. It’s a physical law, meaning it’s true, universal, simple, absolute, and stable.

Moore’s Law is more of an economic observation, eponymized by Gordon Moore, co-founder of Intel Corp., who wrote a paper in 1965 stating that the number of transistors (processing power) within chips was doubling about every 18 months. It’s still true.

By contrast, and more relevant every “connected” day, is Shannon’s Law. It’s named for Claude Shannon, who did his work 20 years before Moore, in the 1940s.

Shannon’s Law defines “the theoretical maximum rate at which error-free digits can be transmitted over a bandwidth-limited channel in the presence of noise.” (It comes with an equation but we’ll spare you the math.)

In other words, Shannon figured out a way to calculate how much stuff can be crammed over a broadband network, without problems, even when there is noise, which there always is.

The dramatic rise in broadband usage – upwards of 50% compound annual growth – is true on fixed and mobile networks. In London last week, some social media outlets got bogged down because of all the gadgetry trying to send Olympics pictures and videos. We are gunking up networks.

Which is why it’s important to be able to calculate throughput maximums on data networks. And to be able to ease the situation – by adding spectrum, or mitigating noise.

In cable tech circles, invoking Shannon usually means you’re having a conversation about upstream (home to headend) signaling. It’s why there’s so much talk about advanced modulation, and finding ways to make that slender spectral area carry more stuff.

Will Shannon’s Law get monetized like Moore’s Law did, with a fury of investment and development that lasted a half century? Let’s hope so, for the sake of clear connections and unclogged networks.

This column originally appeared in the Platforms section of Multichannel News.