How Video Slinging Fits in the Upstream


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.

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