Here’s one to keep a close eye on: “Ustream,” the online service that streams live video from any of the webcams in your life.
For instance: Sara, who runs our over-the-top 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 livestream 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 and 42 Megahertz. It’s noisy, for another.
That’s why Ustream was a forehead-smack moment for me: Oh, 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 equals 300.) Estimate how many homes are simultaneously online (10% of 300 equals 30.)
For extra drama, imagine how many devices per home are video-capable — at least six by 2015, by some estimates.
Next, estimate how many of those homes (and screens) are live-streaming (say, 30% of 30 equals nine). 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, channel widths aren’t 6 MHz all day long, as 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 and 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 go. I’m looking at you, MCTV.
Stumped by gibberish? Visit Leslie Ellis at translation-please. com or multichannel.com/blog.
