Cable Fires Starting Gun on DOCSIS 3.1

Cable Fires Starting Gun on DOCSIS 3.1

ORLANDO, Fla. — CableLabs and MSO executives have disclosed plans for DOCSIS 3.1, the next generation of cable-modem technology that promises to enable data speeds of 10 Gigabits per second or more — and let MSOs stay ahead of the bandwidth curve into the next decade.

The DOCSIS 3.1 spec uses new modulation technology and eliminates the traditional 6-Megahertz channel divisions, to use spectrum more efficiently. However, 3.1 will require backward-compatibility with existing 3.0 cable modems and CMTSs, and will not force MSOs to make any changes on their hybrid fiber-coax plant to deploy initially.

“I can’t emphasize this enough: You don’t have to change your plant to deploy DOCSIS 3.1,” Matt Schmitt, CableLabs director of DOCSIS specifications, said. “It can maximize what you can get out of your existing plant, but make it future-proof.”

Schmitt outlined the plans for the specification at a 90-minute special session jointly presented by the Society of Cable Telecommunications Engineers and CableLabs here last Thursday (Oct. 18).

CableLabs expects to publish the DOCSIS 3.1 spec in 2013, and hopes to enable equipment vendors to deliver their first products in 2014.

“It’s a pretty quick follow-on to 3.0 and is a very substantial change,” SNL Kagan analyst Ian Olgeirson said. “I foresee challenges ahead for the development of the spec and the equipment, and the eventual implementation.”

Some vendors were skeptical that DOCSIS 3.1 products could be introduced within two years. Silicon vendors will likely take 18 to 24 months after the spec is published to release 3.1 chips, according to Mark Palazzo, vice president and general manager of Cisco Systems’ Access Network business unit, meaning equipment would not be available before 2015.

The 3.1 spec will be designed to efficiently provide 10 Gigabits per second of bandwidth downstream and at least 1 Gbps upstream — “probably more,” Schmitt said. “That’s where we believe we’ll need to go with the technology.”

At the same time, CableLabs is aiming for a significant cost reduction in terms of cost per bit delivered with DOCSIS 3.1. “It should be dropping signifi cantly from one generation to the next, and that’s absolutely a key component of what we’re trying to do,” Schmitt said.

DOCSIS 3.1 uses a new forward errorcorrection (FEC) scheme, Low Density Parity Check (LDPC). That will let MSOs move to higher-order modulations, from 256-QAM today to up to 4096-QAM or even beyond, according to Schmitt. The advantage: 4096-QAM is 50% more efficient than 256-QAM.

“You get more bits per second over the same spectrum,” he said.

For example, with DOCSIS 3.1, delivering 5 Gbps of downstream capacity will take 500 Megahertz of spectrum, whereas 3.0 would take 780 MHz.

To gain even more efficiencies, DOCSIS 3.1 also incorporates orthogonal frequency division multiplexing (OFDM) for both upstream and downstream. That will create 20- 50 KHz channels transferred in a block — “mini-channels” essentially bonded together — to break the traditional 6-MHz channelization (or 8 MHz in Europe).

Another benefit of OFDM is that it’s widely adopted, and the cable industry hopes to “ultimately attract a larger ecosystem of chip set vendors into the ecosystem,” Schmitt said.

DOCSIS 3.1 will be required to be backward-compatible with 3.0. On the headend side, a 3.1 CMTS or Converged Cable Access Platform (CCAP) device will have to support at least 24 downstream and eight upstream DOCSIS 3.0 QAMs, Schmitt said.

That hybrid 3.0/3.1 approach will let MSOs start buying DOCSIS 3.1 modems or gateways even if they don’t have headend equipment yet.

Comcast vice president of access architecture Jorge Salinger said he expects the MSO to deploy 3.1-based customer-premises equipment first, then turn on DOCSIS 3.1 in the downstream before finally — if necessary — switching on 3.1 for the upstream.

“We wanted to develop a smooth transition strategy,” he said.


Key features of the proposed DOCSIS 3.1 spec, which CableLabs expects to publish next year: 

Targeted at providing upwards of 10 Gigabits per second downstream and 1 Gbps or more in the upstream; 

Eliminates 6-MHz channel divisions using more efficient OFDM modulation and LDPC forward-error correction; 

Will not require changes to HFC plant or headend for initial deployment; and  Will require backward compatibility with DOCSIS 3.0, with 24 downstream and eight upstream QAM channels.

SOURCE: Multichannel News research


CableLabs and its MSO members have set an aggressive schedule for DOCSIS 3.1, which aims to dramatically boost data speeds to 10 Gbps or more.