Upstream Bonding, Multicast And CMAP

DOCSIS 3.0 deployments are poised to begin moving into multicasting and up-channel bonding during the next year, despite the continued lack of more than a handful of cable-modem termination systems (CMTS) certified for the technology by the industry’s CableLabs.

Only three fully DOCSIS 3.0-certified CMTS systems are on the market plus three more that are only partially certified – a number that hasn’t changed for two years.           

But even that issue may become moot. Comcast says it now is planning a migration from CMTS to a converged multiservice access platform (CMAP) in the 2012-13 time frame. Much of the industry is expected follow Comcast’s lead, making the CMTS an endangered species.

Speaking at a recent Denver symposium on the cable industry’s next-generation broadband strategies, Comcast Senior Director of Network Architecture Chris Bastian and Comcast Distinguished Engineer Saifur Rahman outlined plans for a rollout that will be gradual. “There’s going to be a period of coexistence (with both CMTS and CMAP in use) for some period of time,” Bastian said. Rahman added that Comcast has started a focus team at CableLabs with the goal of establishing CMAP standards to integrate into DOCSIS 3.0.

Of a more immediate nature, Bastian revealed that Comcast either just has or soon will unveil what it calls “extreme upstream,” using channel bonding.

“We’re getting to the point that the engineering and marketing groups are ready to pull the trigger” on upstream bonding, he said, with only a sign-off from Comcast business units still needed.

He declined to disclose just how fast the offering will be, but said in lab tests the MSO had achieved speed bursts of more than 100 Mb/s using four channels. That compares with 10 Mb/s for Comcast’s fastest current offering. The introduction will make Comcast one of the first MSOs, and the first in the United States, to offer up-channel bonding.

Cox And DOCSIS 3.0

Meanwhile, at Cox, an unexpected problem has emerged in DOCSIS 3.0 deployment. Cox is planning DOCSIS 3.0-based wireline telephony services using embedded multimedia terminal adapters (eMTAs), an offering scheduled to roll out in May. The problem is with “some” DOCSIS 2.0 modems, said David Knight, Cox’s director/Data & Telephony Engineering. The issue is that “certain 2.0 chipsets” won’t work in bands higher than 800 MHz.    

The plan originally had been to use eight DOCSIS carriers, centered on 860 MHz for the DOCSIS 3.0 offering, but that would have meant replacing the older DOCSIS 2.0 modems, a move he said would involve a huge number of truck rolls and that would have cost “hundreds of thousands of dollars.”  As a result, Cox has come up with the somewhat novel idea of centering just four of the channels around 860 MHz, and then leaving the other four to function in bands lower than 600 MHz. That means Cox needs DOCSIS 3.0 modems that can handle both frequencies.

Matt Schmitt, CableLabs’ director/DOCSIS Specifications, predicts that large-scale migration from unicast to multicast technology by the industry is imminent — the result of the planned addition of a pair of key sections to the DOCSIS 3.0 unicast specs: Multicast Quality of Service (QoS) and three types of group service flows, a feature that “controls how much of the pipe gets consumed,” particularly by data flows that come with no QoS parameters (think Netflix IP Video versus IP video from the MSO itself). However, in the end, the way data-flow standards are implemented may be dictated by politicians rather than by the industry.