May 20, 2008

Bandwidth Expansion and More

By Jonathan Tombes

Former Comcast CTO and Executive Fellow Dave Fellows took a friendly dig at industry peer Dan Pike at the start of his technical session on Sunday afternoon by noting that there are two ways to increase bandwidth.

"Either work harder or smarter," Fellows said.

Fiber (the topic of Dan Pike's session on Monday) is the harder way, Fellows said, setting up the members of his panel as the industry's smart team.

The brains on this panel included included Cisco Systems' Xiaomei Liu, whose discussion of a variable bit rate (VBR) network statmux architecture included a this takeaway number: 57.5 percent. That being the measurement of VBR over constant bit rate (CBR) efficiency (i.e., bandwidth utilization improvement) afforded using four DOCSIS bonded channels.

The test found a 50 percent improvement using two bonded channels and 40 percent using a single one. Interesting how those numbers echo those we discussed in an IPTV Thought Experiments article in March.

What's a VBR network statmux? The short answer: It doesn't come in a single box.

Efficiency is implicit within much of the technology surrounding BigBand Networks, but in this case, the company's Chief Architect Doug Jones focused on the scale and interactivity of a national, interactive platform.

The scales actually tip in the other direction, as the MPEG-2 program identifiers (PIDs) that bind individual, enhanced television (ETV) or tru2way (OCAP) formatted applications themselves increase the amount of bandwidth needed for a program.

The momentum behind this move to a national platform is strong, Jones said, being driven as it is by a combination of subscribers, programmers, advertisers and MSOs. Paying the PID bandwidth tax is one challenge; defining interfaces (via a next phase of DVS 629) that enable communication with programmers and advertisers is another.

The two presentations by Cisco's Dave Lively and Motorola's John Ulm diverged, respectively, into a discussion of peer-to-peer protocols (P2P) and content distribution networks (CDNs) as ways to deliver broadband video on the one hand, and a firehose-style projection of all the kinds of technologies that MSOs may consider using over the next dozen years, on the other.

The virtualization capabilities of a CDN, which blur the line between local and centralized storage, also make it an appealing choice for both short and long tail content.

A CDN works well for niche, Lively said, and "it works especially well for really popular content." In the end, he suggested a hybrid CDN/P2P approach.

For his part, Ulm offered a rapid-fire look at "future directions in cable broadband bandwidth capacity" covering more terrain than can be summarized here. He did end with a few noteworthy predictions.

"I see a cable-friendly PON being in the future for cable systems," Ulm said.

He also raised the possibility of a "Next-Gen Coax" system, one capable of operating up to 3-5 GHz with "very wideband channels."

- Jonathan Tombes

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