DOCSIS 2.0 Likely to Stay In Interoperability Mode


Though progress on Data Over Cable Service Interface Specification 2.0 has been steady, the spec is probably not yet ready for primetime testing.

Some vendors had been expecting the newest sibling in the DOCSIS family to go live for product certification when the 23rd testing wave begins July 22. But it appears that the specification will stay in the interoperability mode for now, said Cable Television Laboratories Inc. senior executive consultant Rouzbeh Yassini.

"The product maturity is not there for these upcoming waves," Yassini said. "There is no expectation for a certification, because the full interoperability has not yet been proven."

DOCSIS 2.0 is an advanced physical layer addition to modem functions. Using either advanced frequency agile time-division multiple access (A-TDMA) or synchronous code-division multiple access (S-CDMA) modes, the specification can boost upstream bandwidth for cable modems to 30 megabits per second — six times that of DOCSIS 1.0 modems and three times that of DOCSIS 1.1 units.

Not only does that open the door for symmetrical business services, it also offers cable operators greater network efficiency to support additional modems per headend.

DOCSIS 2.0, which was finalized in January, is now in the interoperability phase. That's when CableLabs tries to test every feature of the specification at least once with at least two vendors' devices — and with those devices linked to other equipment — all without changing the core software.

Of the 18 or 20 key elements in the specification, four or five features still have yet to gain interoperability. But Yassini quickly emphasized that there have been no "show-stopper" problems.

"As of today, I'm not aware of a single piece of a broken spec or silicon," he said. "But we need more time as everyone else does to get the maturity up there for interoperability and the product testing to where it needs to go."


Although the specification does require that devices be outfitted for both schemes, much of the focus among vendors initially has been on A-TDMA. Nevertheless, Yassini said, progress has also been made on the S-CDMA front.

"We have now multiple silicon vendors, without naming any, that have S-CDMA and built in either as the gateway or as the silicon or they have the board that has it," Yassini said. "So there is at least good momentum in there, and we like that. We have actually seen silicon being delivered to people that have that level of functionality built in. So we don't see it as an issue whatsoever."

S-CDMA was developed by Terayon Communication Systems Inc. That modem maker is banking much of its future cable gear success on DOCSIS 2.0.

Using silicon from its Imedia Semiconductor Corp. subsidiary, Terayon said its 2.0 CMTS unit and modems are the first to incorporate both S-CDMA and A-TDMA.

Other vendors are working on incorporating both modes into their CMTS units and modems, so the fact certification has not begun could allow them to catch up. But that doesn't hurt Terayon's chances of gaining a jump on its competitors, according to director of product marketing Elisa Camahort.

"As long as there is a perception out there that it is a proprietary Terayon thing it doesn't help us," she noted. "We are helped by it being driven by CableLabs; we are helped by it being a multi-vendor effort. I can still go out there and make the point that even when it is a multi-vendor environment, we have certain skills and advantages and technological expertise."


Fellow gearmaker Motorola Inc., meanwhile, is starting with A-TDMA. It has created a blade insert for its existing 1.1 CMTS units that adds A-TDMA functions, and plans are to add S-CDMA down the road, said Broadband Communications Sector senior director of marketing Kevin Keefe.

Neither mode is more difficult to incorporate, but operators will choose based on their plant conditions.

"Generally, what we see is folks with better plants tend to gravitate toward the A-TDMA approach — it gives them a lot more of what they are looking for," Keefe said. "[For] some of the really noisy plants, the S-CDMA is basically more robust in noisy situations. So that is why you will see some of the folks with older, noisier plants gravitate toward the S-CDMA."

Although the first version of the blade will not contain the S-CDMA element necessary for full DOCSIS 2.0 compliance, Keefe said Motorola does not expect operators will hesitate about buying it once it hits the market in early 2003.

"Frankly, I haven't heard any of that," Keefe said. "I've heard more folks looking to 'how do we get from current generation to an A-TDMA-capable version,' as opposed to looking long-term to the S-CDMA."

The primary focus among cable executives now is DOCSIS 1.1, he added. Once they have mined the 1.1 spec, "then they will start to layer in 2.0 where it makes sense," he said.