July 7, 2008

DOCSIS - Where Do We Go From Here?

By Bruce Bahlmann

This year's lineup of engineering workshops presented at SCTE Cable-Tec Expo included presentations by two of the industry's sharpest technology minds: ARRIS Chief Strategy Officer Tom Cloonan and Cisco Systems Cisco Fellow and Chief Architect, Cable Business Unit, John Chapman.

Back from 2016

The way content will be delivered in the future presents challenges to MSOs trying to maintain profit margins while keeping up with per-subscriber bandwidth use, which is increasing 1.5 times every year. Assuming such growth, Cloonan took a futuristic look at what content demand will mean to existing HFC networks in 2016 and then worked backward to suggest strategic ways to incrementally get there.

Instead of proposing such things as 1 GHz upgrades, passive optical networking (PON) or some other new technology, ARRIS CSO Cloonan advocated deeper fiber (via node splits), switched digital video (SDV) and video compression (e.g., MPEG-4) as ways for MSOs to claw back the bandwidth already available in the HFC plant.

At the heart of the paper's proposed convergence of all services (including Wi-Fi/WiMax, wireless backhaul) over DOCSIS is the subtle implication of the use of universal edge QAM modulators (U-EQAMs) and newer CMTS technologies under development, namely integrated, modular and partitioned CMTSs. The take-away is that HFC networks combined with DOCSIS (U-EQAM and CMTS) still have a lot of legs left when they're coupled with deeper fiber, switching and analog reclaim.

Put it on paper

As multi-service networks become increasingly complex, the big picture can become difficult to grasp without writing something down on paper.

Cisco Fellow Chapman presented a paper that enables anyone involved in any aspect of network design or deployment to easily represent and understand complex systems. Network Design Language (NDL), while broadly applicable to any networking scenario, was developed by Chapman during his efforts to sort out cable's network interconnectivity.

Chapman described the basic approach of NDL through the use of three NDL components (objects, ports, and attributes) and a description of how certain special cases are handled. The paper provided numerous examples to help the reader understand how to leverage NDL to describe various cable-related components.

The take-away is that NDL provides individuals who work with networks a tool they can use to consistently convey networks in a concise, readable (self-documenting) way, which may ultimately be used to provide guidance to future network design exercises.

- Bruce Bahlmann

Read more news and analysis on Communications Technology's Web site at http://www.cable360.net/ct/news/.