DOCSIS 3.1 Promises Major Leap in Speed, Flexibility

DOCSIS Matures A special session at Cable-Tec Expo to introduce DOCSIS 3.1 began with a pep talk about the greatness of cable. One wonders, however, if the new DOCSIS specification  is driven by competitors such as Google (NASDAQ: GOOG), which is signing up customers on its new fiber plant with a data offering of 1 Gbps.

Thoughts of those competitors were far away on launch day - at least publicly. “Cable has always been just ahead of where it needs to be to enable consumers to do what they want on the network,” said Dan Rice, vice president, access network technologies for CableLabs.

DOCSIS 3.1 promises efficient support of at least 10 Gbps in the downstream and 1 Gbps in the upstream. The spec is being written by the SCTE in a Special Working Group within the organization's Standards Program. Matt Schmitt, director of DOCSIS specifications for CableLabs, laid out the key goals of DOCSIS 3.1 as follows:

  • Greatly increased speeds

  • A significant reduction in cost-per-bit moving forward

  • Flexibility for use by operators with different amounts of spectrum and different plant conditions

  • The ability to operate on existing HFC networks

  • A logical migration strategy from DOCSIS 3.0 to DOCSIS 3.1, with full backward compatability

In terms of the technology to enable the higher capacities, DOCSIS 3.1 will utilize advanced forward error correction (FEC) to help overcome noise, operate across larger bands of spectrum and adopt orthogonal frequency division multiplexing (OFDM) modulation in both the upstream and downstream.

Schmitt described OFDM as “lots of little channels of 20-50 kHz translated together in a block.” Each subcarrier can be individually adjusted, releasing operators from 6 MHz or 8 MHz channel restrictions. He said: “Subcarriers don’t have to be always on. If you had 50 MHz of spectrum, you could turn on 50 MHz of subcarriers. Another year later, if you’ve got more capacity demands, just turn on more subcarriers.”

OFDM scales to large bandwidths more cost effectively than MAC layer bonding of many single carrier QAM channels. Schmitt added that economies of scale may cut costs. “OFDM is actually very widely adopted. We’re hoping to tap into the economies of scale and attract a larger ecosystem of people and new chipset and system vendors to the cable market.”

Jeff Finkelstein, senior director, network architecture for Cox Communications, clarified the choice: “We could continue with DOCSIS bonding at the MAC layer or go with OFDM and bond at physical layer.”

A key is not making operators and vendors reinvent the DOCSIS wheel. “A lot of the effort we’re expending is working out the migration strategy,” said Howard Pfeffer, senior vice president of broadband engineering and technology for Time Warner Cable (NYSE: TWC). “DOCSIS 3.1 preserves the DOCSIS service plane - the rich scheduling, security, filtering for protecting the network, IP source verification, IPDR for accounting - all these back-ends."

Jorge Salinger, vice president of access architecture for Comcast (NASDAQ: CMCSA), echoed Pfeffer’s assessment. “From the very get-go, we developed a migration strategy,” said. “We did that thoughtfully because we know from experience if we don’t, we’ll hit break points. This specification is developed in a way that we don’t hit breakpoints.”

Salinger expects the migration to happen in this order: CPE first, then downstream, then upstream, with CCAP platforms designed to scale to capacity.

What about CCAP?

Schmitt said the emergent CCAP architectures will be able to support upgrades to DOCSIS 3.1, adding, “We don’t want to force people who have just bought these nice new (CCAP) chassis to rip them out and replace."

Salinger said new 3.1 modems will operate with either existing CMTSs or CCAP equipment, and the 3.1 modems will be backward compatible with DOCSIS 3.0.

Asked how operators can reserve more spectrum for DOCSIS 3.1, Salinger said bandwidth has been reclaimed from analog. Also, moving to more IP video will free up more spectrum. And DOCSIS 3.1 will use spectrum that is not currently in use.

Schmitt pointed out that “technically, at least to start deploying 3.1 CPE, you don’t have to reserve anything; it can operate with whatever DOCSIS channels are there."

And Finkelstein said it’s less about reserving spectrum and more about “the art of spectrum planning.”

DOCSIS 3.1 specification development is currently underway with collaboration among CableLabs members and a large vendor working group. The goal is to have DOCSIS 3.1 products available as early as 2014.

Linda Hardesty is a freelance writer. Contact her at

Get the Broadband Technology Report Newsletters Delivered to Your Inbox

Subscribe to email newsletters today at no cost and receive the latest information on:

  • Video Technology
  • Network Technology
  • Technology Alerts
  • BTR LATAM (Latin America)

SCTE-Cable Tec Expo 2016 Video Show Dailies

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 3

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 3

In our Video Show Daily for Day 3 of exhibits at SCTE Cable-Tec Expo in Philadelphia, BTR Editorial Director Stephen Hardy covers trends in distrib...

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 2

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 2

In our Video Show Daily for the second day of exhibits at SCTE Cable-Tec Expo in Philadelphia, BTR Editorial Director Stephen Hardy highlights furt...

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 1

BTR's SCTE-Cable Tec Expo Video Show Daily, Day 1

BTR Editorial Director Stephen Hardy reviews the hot technologies and announcements from the first day of exhibits at SCTE Cable-Tec Expo 2016 in P...

Diamond Technology Reviews - 2016 High Scores

2016 Diamond Technology Reviews Slideshow

2016 Diamond Technology Reviews Slideshow

Diamond Technology Reviews 2016

Diamond Technology Reviews 2016

BTR's Diamond Technology Reviews, now in its twelfth year, is a technology recognition program wherein vendors serving the broadband cable ...

Related Articles

Charter Communications

Charter Taps ARRIS for WorldBox 2.0

October 12, 2016

<!-- /* Font Definitions */ @font-face {font-family:&...


Cisco Powers OTT Sports Apps

October 12, 2016

FloSports, a subscription-based OTT sports media company, has tapped Cis...


2016 SCTE Cable-Tec Expo Wrap Up

Whether you couldn't make it to Cable-Tec this year or want to see if you missed anything while you were there, you'll want to join BTR editors Stephen Hardy and Ron Hendrickson as they reveal their picks for the...

October 12, 2016
Sponsored by

Counting the cost: Efficiently transitioning from HFC to FTTH

HFC networks are uniquely positioned to provide compelling and competitive services, and are also uniquely positioned to transition to symmetrical FTTH as commercial requirements demand.  This webinar will d...

Date:September 22, 2016
Sponsored by

Maintaining High Quality of Experience in an Adaptive Bitrate System

This webinar will look at the many points in an ABR system where the video is touched.  From ingest (satellite, file, and IP), to egress, each point should be qualified for compliance to help maintain a high...

Date:August 25, 2016
Sponsored by

White Papers & Special Reports

Cable VoIP 2.0: Voice Moves to the Cloud

October 2016

Cable providers led the charge on the VoIP evolution and won customers and market share. Now voice networks are evolving again. The cloud voice platform has ...

Understanding Ultra High Definition Television

October 2016

Over the last 10 years, high definition television (HDTV) has been replacing standard definition television as the expected viewing format for television pro...

Are You Ready for DOCSIS 3.1? The Future of Cable Technology and How to Prepare Your Network

October 2016

DOCSIS 3.1 promises 10x capacity throughput and a range of technical benefits for cable providers and users alike. Are you ready? Discover the technical adva...

BTR Blogs

BTR Managing Editor Ron Hendrickson

FCC Rethinks Set-Top Plan

September 10, 2016

By Ron Hendrickson - The FCC has reworked the "unlock the set-top b...


In Memoriam: Richard Covell

August 18, 2016

By Rob Stuehrk, Publisher - We at Broadband Technology Report were sadde...

BTR Managing Editor Ron Hendrickson

Court Overturns FCC Municipal Broadband Order

August 11, 2016

By Ron Hendrickson - You win some, and you lose some, and the FCC just l...

Featured Hangouts

4K 4 U: How to Prepare for UltraHD Video

4K 4 U: How to Prepare for UltraHD Video

4K/UltraHD video is coming - consumers are buying the TV sets, and more content is becoming available. Watch this inf...

DOCSIS 3.1: A Look Ahead

DOCSIS 3.1: A Look Ahead

Watch a 30-minute video chat of experts from a variety of related disciplines discuss how close deployments really ar...

Featured Hangout

4K 4 U: How to Prepare for UltraHD Video

4K/UltraHD video is coming - consumers are buying the TV sets, and more content is becoming available. Watch this informative Hangout on demand by clicking the link above.

Sponsored by Verimatrix.