When cable operators saw huge demands in linear video,  Video-on-Demand (VoD) and high-speed data services, and faced with an aging  analog infrastructure, they moved to a Converged Cable Access Platform (CCAP)  to increase capacity and throughput. CCAP combines headend functions into a  single architecture by combing Edge Quadrature Amplitude Modulation (EQAM) and  Cable Modem Termination System (CMTS).

A brief history in  CCAP

Back in June 2011, CableLabs created CCAP by blending two competing platforms, a Comcast-backed Converged Multiservice Access Platform (CMAP) and a Time Warner Cable  Converged Edge Services Access Router (CESAR) platform. The following year CCAP  products were introduced, and deployed the year after.

Fast forward to today, cable operators are looking to  implement software-based access platforms, migrate away from commonly deployed  centralized, purpose-built CCAP equipment, and virtualize CCAP (vCCAP) -- and  thus begin the shift to a Distributed Access Architecture (DAA). Developed by  CableLabs, vCCAP is the latest cable technologies that combines functions  including the CMTS and EQAM.

What is DAA?

As its name implies, DAA is an architecture where functional  components of a legacy Centralized Access Architecture (CAA) are migrated to  different locations of the end-to-end network. In a CAA network MAC and PHY  layer functions of the CMTS, EQAM, or CCAP all resided and were distributed  within a centralized headend or hub location, using standard Hybrid Fiber Coax  (HFC).

Traditional Cable Access Network

Traditional HFC can only support CAA, this is a limitation  of analog optics. However, digital optical node technology can support both CAA  and DAA architectures. In a DAA network MAC and PHY layer functions of the  CMTS, EQAM, or CCAP may be in a node, cabinet, or MDU location.

Currently there are two approaches to DAA:

  1. Remote PHY (R-PHY), only the PHY is moved to the  digital optical node, and the DOCSIS MAC remains at the hub-site
  2. Remote MAC/PHY (R-MAC/PHY), both the MAC and PHY  are moved to digital optical node

Only one other deployed variation of DAA exists: C-DOCSIS.  To enable high-speed data, and cover modifications made in Asia, CableLabs  published annexes to the DOCSIS 3.0 family of specifications naming them  C-DOCSIS. While the concept is similar to DAA, C-DOCSIS is data only, and does  not support digital video broadcast (DVB).

vCCAP chart

With the impact  DOCSIS 3.1 will have on fiber, virtualizing  DAA functions helps drive more capacity, and resolve cable operators’ space and  power constraints in the headend and hub.

Virtualizing and distributing MAC and PHY functions enables  digital combining, eliminates analog optics with cost effective 10G Ethernet  transport, and converts analog fiber nodes to digital optic IP-enabled devices.  DAA makes it easier to push fiber deeper into the edge of the network, and along with the ability to support  denser wavelengths for each fiber, digital optics greatly improves  Carrier-to-Noise-Ratio (CNR), which will enable higher orders of QAM on the  coax and higher performance DOCSIS technologies.

Virtualization via software is a better solution than proprietary hardware.

So, get ready, as this virtual world is about to  get real, very real! Ask us how Ciena helps build the next generation fiber distribution network.