DOCSIS 3.1 comes top at Cable Congress 2013 – by Philip Hunter

Cable operators are set to accelerate deployment of the latest DOCSIS 3.1 data over cable standard, in some cases to move quickly to an all-IP strategy, it emerged from the recent Cable Congress held in London.

This is the first new version of DOCSIS since 3.0 arrived in 2006 with channel bonding to boost headline data rates, and 3.1 achieves a similar trick by introducing OFDM (Orthogonal Frequency Division Multiplexing). Apart from bringing forward migration to all video over IP, welcomed by many operators as a route to reduce transmission costs and improved scalability at the network edge as well as easing deployment of cloud based delivery to multiscreen devices, DOCSIS 3.1 enables broadband speeds to keep pace with telcos without having to upgrade the infrastructure. This ability to extract more life from existing cable plant is seen as the key differentiator of DOCSIS 3.1 by many in the cable industry, rather than increasing bit rates since that can always be achieved by techniques such as node splitting that involve pushing fiber closer to the home. While telcos have to push fiber deeper to increase bit rates via VDSL2 technology, cable operators sense that they can compete successfully on price by avoiding having to do the same.

DOCSIS 3.1 does away with the 6MHz and 8MHz wide channel spacing used so far, replacing them with smaller 20KHz-to-50KHz-wide subcarriers that can then be bonded together inside a spectrum block up to 200MHz wide. OFDM is used to spread the symbols carrying data across this whole spectrum, with multiple carriers ensuring that overall high data rates are obtained.

DOCSIS 3.1: The Countdown Begins…

CABLE CONGRESS 2013 – LONDON. Although talk about DOCSIS 3.1 began only late last year, circumstances will require initial deployments to be made as soon as 2015/16.

According to Ralph Brown, CTO Cablelabs, 1 Gbps downstream premium offers are likely to be available in the US as soon as 2016 and “we would be foolish not to start DOCSIS 3.1 before then.”

He added that the roadmap now envisages specs being issued this year and the first products coming onto the market in 2014 ahead of initial deployments in the following one to two years.

John Chapman, CTO CABU, Cisco Systems, meanwhile said that the specs are currently being developed by experts from Canada, Germany, the UK, France, Israel and US, meeting regularly in Denver.

He emphasised that DOCSIS was developed by the cable industry and 3.1 “can be anything we need it to be.”

3.1 will indeed be able to spectrum share with 3.0, allowing for the blending of new and existing services.

A lot of existing 3.0 software will still be used for 3.1 and only necessary changes will be made, with 3.1 being able to compete effectively with FTTH.

Once up and running, DOCSIS 3.1 will allow for downloads and uploads of up to 10 Gbps and 1 Gbps respectively.

By Chris Dziadul, Broadband TV News – Cable Congress Official Online Partner

Interview with John Chapman

John Chapman, Engineering Fellow and CTO of Cisco System’s Cable Access Business Unit, is a pioneer in broadband communications, having helped to define and write the original DOCSIS (Data Over Cable Service Specification) spec — which spawned the cable modem marketplace, and, consequently, the broadband explosion we’re living in right now. He’s currently leading the development of the DOCSIS 3.1 specification, which promises substantial throughput and speed gains for residential broadband consumers. In this Q&A, he characterizes the highlights of DOCSIS 3.1, why it matters, and current events.

Q. What does DOCSIS 3.1 mean to cable-delivered broadband, as opposed to fiber?

Chapman: Service providers are often under scrutiny in terms of their competitiveness, against fiber-to-the-premise architectures. DOCSIS 3.1 will go a long way in assuaging those misperceptions. It can make that hybrid fiber-coax plant perform as well as fiber, at a fraction of the price of a fiber upgrade. DOCSIS 3.1 is all about getting more bang for the buck – it’s a higher performing, lower cost technology.

Q. What is the biggest changing coming, in DOCSIS 3.1?

Chapman: It’s difficult to identify just one – there are many. In an over-arching sense, it’s a technology and product refresh for cable-delivered IP services. By that I mean it advances the progression to full-spectrum technology, which gives service providers the ability to stripe IP services across the entire cable spectrum, over time. And, it enables more bits per Hertz, on the wire – always good.

Q. Published reports indicate that DOCSIS 3.1 has the potential to create 50% bandwidth increases, in the downstream and upstream signal direction. What does that mean for capacity and speed?

Chapman: It means data rates as high as 10 Gbps in the downstream (home-facing) signal direction, and as high as 2 Gbps in the upstream (network facing) direction.  The capacity angle is quite interesting, especially for the upstream path. DOCSIS 3.1 offers a way to widen that spectral range, to as high as 200 MHz. That’s a quadrupling. Now, it’s a matter of figuring out when, why and how one would do that. But generally speaking, DOCSIS 3.1 is a far-reaching value proposition.

Q. When people talk about DOCSIS 3.1, the term “OFDM” usually is somewhere nearby. What is OFDM?

Chapman: It’s a really cool technology that will allow us to shape the spectrum to fit the downstream, rather than the other way around. It’s cool because it’s infinitely configurable – tens of thousands of tiny, 25 kHz-wide carriers. Mobile carriers already use OFDM, but it’s new to cable providers. They traditionally use Quadrature Amplitude Modulation, or QAM. Our role as a vendor is to find a backwards-compatible way to augment a provider’s modulation portfolio with OFDM, without disaffecting the installed base of QAM.

Q. What’s the current status of DOCSIS 3.1?

Chapman: Well, we just sequestered ourselves in Denver for a most of a week – It’s a really high-energy group. I’d say we’re seeing the light at the end of the tunnel, in terms of having a completed 3.1 specification. Then we can all start building product. I think it’s safe to say that most vendors anticipate product in the marketplace in the 2015 timeframe.

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