Translation Please

How Video Slinging Fits in the Upstream

1/30/2012 10:47 AM

Last week’s mail contained this query from reader Steve, who asked, “How would slinging video up cable’s upstream path work, given how little bandwidth there is down there?”

He was referring to last week’s column about Broadcom putting Sling Media’s technology into the silicon that goes inside cable modems and set-top boxes.

When available (Q3 of 2012), when included in those devices (TBD) and if activated by service providers, Sling-on-a-chip becomes a potentially pervasive way to stream subscription video to tablets - outside of the home.

Right now, cable operators are contractually obligated to household boundaries in streaming video to screens not connected via the set-top box. That means tablets, PCs and smart phones.

And that brings us to this observation from the Department of Not So Fast: The clash between technology and rights is perennial. We’re living another chapter now. It shows up in these kinds of caveats: “If rights weren’t an issue, the technology part would work like so.”

So, if rights weren’t an issue, what about that upstream path? Quick refresher: Cable’s upstream (or “reverse”) path sits in a tiny slice of spectrum, between 5 and 42 MHz. Compared to the total capacity, downstream and upstream (assuming 750 MHz total), it’s about 5%.

Other upstream basics: That swath of spectrum was never intended to move video, way back when. For that reason, it doesn’t use the 6-MHz spacing common to the downstream (headend-to-home) direction. Instead, it generally uses three widths: 1.2 MHz, 3.2 MHz and 6.4 MHz.

It also uses a mix of modulation techniques: QPSK, 16-QAM and, in really clean plant conditions, 64-QAM. Generally speaking, the higher-order you go in modulation, the cleaner the plant needs to be in terms of signal-to-noise ratio. Why: The upstream path is a noisy place. It’s important to be able to downshift to a safer zone, when zapped by noise.

Bonus: That channel-bonding feature in DOCSIS 3.0 cable modems works in the upstream path, too. That means there are ways to staple channels together, to make enough room for video.

Plus, it’s not like “slinging” video would involve moving the entire channel lineup upstream. One stream at a time. Add in MPEG-4 compression? Even better, bandwidth-wise.

That’s a long way of saying that cable’s upstream path, however anorexic, is in reasonably good shape to move a stream of video up and out of the home.

Which brings us back to what one can do vs. what one may do. That’s right! Rights.

If you’ve gotten this far, you’ve heard the banter about how Sling hasn’t been successfully legally challenged in court. The back-at-ya programmer scoff on that one? A standalone video-slinging device with low penetration is one thing. On-chip with broad penetration is quite different. (Harumph!)

And so, it’s another example of how the technology parts of TV Everywhere are moving faster than the muck of rights.
________________________________________
Stumped by gibberish? Visit Leslie Ellis at translationplease.com or multichannel.com/blog.