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CableLabs' DOCSIS 2.0 Turbocharges Broadband

What started out as a little tweak to Data Over Cable Service Interface Specification networks may create a big opening for enterprise and advanced data services. And thanks to Cable Laboratories Inc., the industry has a single technology standard, now accepted worldwide, that may help accelerate the evolution of cable data products.

As a result of CableLabs' shepherding, DOCSIS 2.0 adds advanced physical layer technology that cuts signal interference and speeds up the data channel throughput, particularly in the upstream. That makes it possible not only for increased upstream-heavy consumer applications, but also symmetric services deemed crucial to gain enterprise customers.

"Obviously, moving forward, cable operators will be delivering more symmetric services either in terms of high-bandwidth data access or telephony," Michael Harris, president of analyst firm Kinetic Strategies Inc., said. "The capacity available with DOCSIS 2.0 will be beneficial to operators as they start offering symmetric services, and the noise resiliency could help to improve reliability of any lifeline telephony services as well. So it is a win-win."

The multiple promise of DOCSIS 2.0 has earned CableLabs this year's Multichannel News
Innovator Award for technology.

Bundle building

The specification started out at CableLabs in early 2000. It was prompted by talk among members about creating symmetric data-rate service, improving bandwidth and solving chronic noise problems in the upstream channel on DOCSIS cable plants.

While more than 50 engineers from MSOs and vendors contributed, DOCSIS 2.0's core technology was derived primarily from two sources: Broadcom Corp. — which originated the advanced frequency agile time division multiple access (A-TDMA) upgrade based on DOCSIS 1.1's TDMA scheme — and Terayon Communication Systems Corp., which developed the synchronous code division multiple access (S-CDMA) scheme, as well as a strategy for both schemes to coexist alongside the existing DOCSIS platform.

"I think now that everyone has seen the whole bundle together, it's pretty widely acknowledged that all of the tools in this DOCSIS 2.0 toolkit are quite valuable, depending on the kinds of ingress and non-perfection in the plant that you face," AT&T Broadband chief technology officer and head of the DOCSIS Certification Board David Fellows said.

Progress in '01

Indeed, CableLabs sought differing opinions and competing proposals from rival technology providers, and it was the consortium's task to sort it all out.

At its annual summer conference in 2001, CableLabs managed to pull together the basic points of the DOCSIS 2.0 specification, including the A-TDMA and S-CDMA modes. Adding both schemes was intended to give the specification the widest possible application.

"When you look at this type of technology what comes to the industry is every given cable plant, every given cable operator might have different conditions," said Rouzbeh Yassini, executive consultant to CableLabs. "Depending on what type of noise you have in the system and depending on what type of condition you have, one of these will always work better than the other one. It's a question of what are the needs of your cable plant."

Noise is essentially interference from signals occupying the same spectrum as the cable data plant's upstream channel. That can come from devices ranging from hair dryers to citizens' band radios and ham ratio signals.

"In some cases you have 40 decibels of greater margin than you do in the 1.0 and 1.1 world," Fellows noted. "That's just an astounding number."

In either mode, DOCSIS 2.0's noise reduction features will provide a boost to MSOs.

With interference down, MSOs can fit more signals into the upstream, thus boosting plant capacity.

"On a day-to-day basis we are looking at different angles we can take to squeeze more out of our plant and our network investment," said Michael Hale, director of data engineering at Cox Communication Inc. "Noise reduction and a lot of the compression is very key for us to continue to leverage what we already have."

More importantly, DOCSIS 2.0 greatly expands the upstream channel, from just 10 megabits per second delivered on DOCSIS 1.1 platforms to 30 mbps. For Cox that added bandwidth comes at a time when residential data-usage patterns are starting to shift, putting more strain on the upstream.

"When we pull our telemetry from our network, the trend is more symmetrical than it is asymmetrical, which is kind of a paradigm shift for some people," Hale said. "They think 'Oh, cable — the upstream is limited, therefore the aggregate trends are going to be very asymmetrical,' which is not the case. That's a fact that is driving us to look at and pursue more symmetrical technologies such as DOCSIS 2.0 to support what the actual trend is."

Enterprise opening

That added bandwidth also opens the door to enterprise markets, where symmetric throughput is a standard ante for voice and data services.

"It is the upstream bandwidth improvement which will allow for more balanced usage of the bandwidth," said Mike Horton, senior vice president of marketing and communications for Arris Group PLC. "That, on top of the QoS implementation of DOCSIS 1.1 will allow improved market focus strategy especially in terms of small to medium business — which I think is going to be the next great market for cable."

In October, the specification hit another milestone when it moved from interoperability to certification testing at CableLabs. Now under way, the certification wave includes five modems and two cable modem termination units seeking the DOCSIS 2.0 stamp. DOCSIS 1.1 modems from Broadcom, Terayon, Motorola Inc. and Scientific-Atlanta Inc. carry the necessary silicon to upgrade to DOCSIS 2.0. That the technology has gone from drawing board to product in a little more than two years is a testament to the industry backing for the project, Yassini said.

"Without the members, without the vendors and without the work of the CableLabs teams, it never would have happened. It was not a one-person achievement; it was a team achievement," he said.

And that team achievement can be credited to CableLabs.

"You wouldn't have gotten the dual mode." Fellows noted. "Without CableLabs, we wouldn't have gotten these two together and we wouldn't have gotten the best of both worlds. We, the cable operators, and of course our customers, are the ultimate beneficiaries."