October 20, 2015

Cable Operators Weigh Their Options for Virtualizing Key Access Architecture Functions

Cable operators are evaluating several options for virtualizing key equipment and functions in their access architectures.

Eager to expand bandwidth capacity, reduce costs and offer more innovative services to customers, cable operators are evaluating several options for virtualizing key equipment and functions in their access architectures.

This distributed access architecture (DAA) approach, also called Distributed CCAP, calls for shifting some or all of the Converged Cable Access Platform (CCAP) functions from the cable headend to the network node through virtualization. CCAP itself is a next-gen solution that combines the data processing functions of the cable modem termination system (CMTS) and the video processing functions of the edge QAM in a single dense chassis, significantly cutting power, space and costs.

Cable technologists say Distributed CCAP (D-CCAP) will build on CCAP's efficiency benefits by leveraging ‘digital transport’ to simplify the access network and increase its scale by 10 times or more. As a result, they predict it will further alleviate the power, cooling and space challenges that MSOs currently face.

How Soon Is Now for D-CCAP?

Rob Howald, VP of Network Architecture for Comcast, recently said his company's engineers are now considering several DAA approaches, "because of their potential to deliver some important benefits to Comcast that ultimately will allow us to deliver better services to our customers." He described these benefits as greater fiber efficiency through the replacement of analog transport with digital transport; better RF performance through moving RF signal generation closer to the customer; and greater facility scaling through the reduction or elimination of large CCAP or CMTS chases in the headend.  

Comcast executives are not alone. In a recent survey by IHS, 42 percent of cable providers worldwide said they plan to put in place some type of DAA solution by 2017. Similarly, in an online readership poll conducted by Light Reading, 22 percent of participants pointed to DAA as the highest next-gen technology priority for the cable industry right now, putting it a solid second behind the new DOCSIS 3.1 gigabit spec.

Virtualization Becomes a Reality for Cable

The big question, then, is not whether cable operators will go the D-CCAP route, but how they will do so. The three main options are:

  • Remote PHY, which calls for separating the PHY circuitry or chip from the CCAP core and moving it to the network node;
  • Remote MAC-PHY, which calls for moving both the PHY circuitry and the CCAP device's media access controller (MAC) to the network node;
  • Virtual CCAP, which calls for eliminating all the CCAP equipment in the headend and splitting its functions among the headend router, network and cloud.

No industry consensus has emerged yet, with the IHS poll showing cable operators fairly well split among the different options. As a result, CableLabs is busy laying the groundwork for pursuing at least the first two approaches, issuing interface specs for Remote PHY in early July and a technical report for Remote MAC-PHY about a month later.

Photo by Mark Turnauckas via Flickr


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