Cable’s Multi-Gigabit Era Takes a Big Step Forward

CableLabs Releases DOCSIS 3.1 Product Specs

Cable’s path toward multi-Gigabit speeds made a big, albeit expected, leap forward last Wednesday (Oct. 30) when CableLabs published the product specs for DOCSIS 3.1, a new Internet-protocol platform that will enable cable operators to scale their hybrid fiber/coax networks to speeds of 10 Gigabits per second downstream and between 1 Gbps to 2 Gbps upstream.

The release was anticipated, as CableLabs announced at the SCTE Cable-Tec Expo in Atlanta earlier this month that the D3.1 specs would be out before the end of October.

The initial batch of D3.1 interoperability specs define DOCSIS 3.1’s physical layer and MULPI (MAC and Upper Layer Protocol) specifications. Cable- Labs expects to complete the DOCSIS 3.1 networking- management specs sometime in 2014, according to Matt Schmitt, CableLabs’ director of DOCSIS.

The product specs, which provide the blueprint necessary for silicon, cable-modem and cable-modem termination system (CMTS) vendors to start building D3.1 gear, have been on a fast track ever since CableLabs publicly disclosed plans for the specs about a year ago. CableLabs estimates that it completed the development of the DOCSIS 3.1 specs 40% faster than previous DOCSIS projects.

According to the spec’s minimum requirements, the first DOCSIS 3.1 modems will be hybrids that support both DOCSIS 3.1 and DOCSIS 3.0 spectrum, capable of supporting downstream speeds of up to 4 Gbps to 5 Gbps. The DOCSIS 3.0 side will carry a baseline requirement of bonding 24 downstream QAM channels and 8 upstream QAM channels, alongside a DOCSIS 3.1 minimum that calls for the ability to tie in two channels, or blocks, of orthogonal frequency-division multiplexing (OFDM) at 192MHz-wide each, and two 96MHz-wide OFDM channels for the upstream.

MSOs and vendors have not announced any specific product launch or deployment dates, but the initial DOCSIS 3.1 products should emerge by late 2014, enabling operators to start deployments sometime in 2015. CableLabs said it is prepared to facilitate interoperability testing of D3.1-facing products and to help gear makers prepare for certification and qualification testing “as soon as prototypes are available.”

DOCSIS 3.1 will implement techniques and technologies that will increase bandwidth efficiency by pumping more bits per hertz down the wire than DOCSIS 3.0 can do today.

Overall, DOCSIS 3.1 is expected to be about 50% more efficient than DOCSIS 3.0, partly through the use of OFDM, a technique that will enable operators to pack tiny subcarriers into wide blocks of bandwidth and utilize higher levels of modulation. DOCSIS 3.1 will also support low-density paritycheck (LDPC), a Forward Error Correction (FEC) scheme that uses less bandwidth than the current Reed-Solomon approach.


The release last week of DOCSIS 3.1 specs means the first products built to the standard could hit the market by late next year.

This Day in DOCSIS 3.1 History

A timeline of key moments in the spec’s development:

May 14, 2012: In discussing its plans for next-gen cable access products, Cisco Systems execs reveal that CableLabs is working on a next-gen DOCSIS spec, referring to it as “DOCSIS 3.x” and “DOCSIS 3.1.”

Oct. 18, 2012: CableLabs and cable-operator executives reveal plans and technical details for DOCSIS 3.1 at the SCTE Cable-Tec Expo in Orlando, Fla., announcing that the initial product specs would be complete by the end of 2013 and would aim to scale up to 10 Gbps downstream.

June 10: Speaking at The Cable Show in Washington, D.C., Comcast executive vice president and chief technology officer Tony Werner predicts DOCSIS 3.1 trials could get underway as early as 2014, with commercially-ready products becoming available by late 2014 or 2015.

Oct. 21: CableLabs says it expects to issue the product specs for DOCSIS 3.1 before the end of the month, beating its anticipated deadline by two months.

Oct. 30: CableLabs issues the hardware specs for DOCSIS 3.1.

On the horizon: CableLabs is expected to release the networking management specs for DOCSIS 3.1 sometime in 2014.

— Jeff Baumgartner