NCTA Tech Papers II: ‘Prisoners’ and ‘Ships’6/11/2012 12:01 AM Eastern
LAST WEEK WE TOOK THE SHORT ROUTE
through the longest-ever NCTA Tech
Paper, a whale of a thing at 182
This week, the bigger trends
noted by engineering scribes,
starting with the colorful analogies:
“the prisoner’s dilemma” and
“the ships passing in the night
problem,” used in different papers
to illustrate that adaptive bit-rate
streaming clients inside PCs, tablets and other
screens playing IP video typically work in isolation.
So that multi-megabit-per-second pipe into the
house might pour a fat stream to the smallest
screen and a skinny stream to the HDTV —
because the two screens don’t know of each
other’s existence under the same roof.
It’s a “prisoner’s dilemma” (handily abbreviated
“PDIL” by Arris authors Carol Ansley, Jim Allen and
Tom Cloonan) because “clients are faced with
electing to optimize (bandwidth) for their own benefit, or they can optimize for the common good of
all clients on the network, including their own.”
In a prison sense, then, eat all the food or share
it; either way, face the consequences.
The “ships passing in the night problem,” described
by Ericsson’s Michael Adams in a lunch
meeting prior to the show and co-written with Chris
Phillips, references a classic networking problem,
akin to Schrodinger’s cat for mathematicians. It
goes like this: Networks work in seven independent
layers, known as the “OSI stack.” (People tend to
identify themselves by which “stack” their work
represents — “I’m a Layer 3 guy,” and so on.)
So, by design, what’s transpiring on, say, Layer
2, cannot fathom what’s happening up on Layer
3 or 4, and so on, up through Layer 7. Like ships
passing in darkness.
Weirdest pronounceable acronym: “CAPWAP,”
for “Control and Provisioning of Wireless Access
Points,” about MSOs and Wi-Fi backhaul. (Authors:
Cisco’s Rajiv Asati, Rajesh Pazhyannur and Sangeeta
If you saw NDS’s “Surfaces” exhibit at the
Cable Show and wondered how to turn that mancave
wall into a giant TV screen without projectors,
check out “Surfaces: A New Way of Looking at TV,”
by Kevin Murray and James Walker.
And, go figure, MPEG-4/AVC/H.264 digital video
compression turns 10 this year (seems like yesterday).
Its successor: “H.265” and/or “HEVC,” for
High Efficiency Video Coding.” Just as MPEG-4 did
for MPEG-2, H.265 offers 50% coding efficiencies
over H.264, explain Motorola’s Robert Howald and
Sean McCarthy in “Bits, Big Screens and Biology.”
What this means, practically: An HDTV
stream compressed to 16 Mbps using MPEG-2
squishes down to 4 Mbps using H.265. Which
seems a good thing for the commercial plausibility
of 4K video. The efficiency gains come
from “context-adaptive binary arithmetic-entropy
coding,” or “CABAC.” (Uh-huh.)
Those are the highlights. For a deeper dive, get
the collection at http://www.springtechforum.com/store.
Stumped by gibberish? Visit Leslie Ellis at translationplease.com or multichannel.com/blog.