Over the course of the summer, while co-teaching a class about how cable technology works, one question came up, every time: “If all-IP (Internet protocol) is where we’re going, where are we right now?”
As television milestones go, all- IP is arguably as significant as the shift to color from black and white in the early ’50s, the advent of satellite distribution in 1975 or when analog ceded to digital in the mid-’90s.
Each phase sparked major growth. Color TVs bumped sales of TVs in general. Satellite distribution opened the door to national scale, which begat the hundreds of TV channels available to us now. Digital made room for high-definition, then broadband services. Broadband is innately IP, so making room for more of it is what this transition is all about.
Which brings us back to the question: If all-IP is where we’re going, where are we now? If you asked an engineering colleague this question, you’d likely get one of two answers: “QAM,” or “MPEG transport.”
The first (QAM) is technically wrong, as direct comparisons go, but nonetheless right because we’ve all used it for so long. It just stuck. The other (MPEG transport) is confusing because it also describes digital video compression.
Let’s look at the “P” part of “IP.” Protocol. Protocols are sets of rules that defi ne how data is transmitted and received, so two or more machines can talk to each other.
What size are the packets? How are errors handled — with forward error correction (FEC), or by resending? What’s the data to do when a piece of the transmission path goes kaflooey?
In that case, the correct answer for where we’re coming from is “MPEG transport.” MPEG, for Moving Pictures Experts Group, is the body that gave us MPEG-2 and MPEG-4 compression. Part of that compression standard defi nes transit. Hence, “MPEG transport.” It’s the protocol underlying every fi elded digital set-top, cable modem, gateway and voice adapter out there. And lots of consumer devices.
Still, people often refer to where we are now as “QAM,” for quadrature amplitude modulation. Modulation, in general, defi nes how signals get imprinted onto a communications carrier to get from here to there. Protocols defi ne how the end points talk to each other. So, even when things are “all-IP,” they’ll still (in cable) move using QAM.
It was at The Cable Show in 2003 when Bill Gates and Brian Roberts talked about whether and when cable would go from all-digital to all-IP. That conversation prompted headlines like, “What the Heck Was Bill Gates Talking About?”
And here we are, a decade later. All-IP is still a matter of “when,” not “if.” It’s still the destination. And it’s still going to take a really long time to get there.