Distributed Access Architecture Is Now Widely Distributed (2021)

By Dr. Robert Howald, Frank Eichenlaub & Adi Bonen, Comcast; Tobias Peck, EnerSys

A large-scale production Distributed Access Architecture (DAA) footprint in terms of both homes connected and the number of digital nodes is being built by Comcast right now. Comcast began deploying DAA in 2018, focusing on the mature, multi-vendor Remote-PHY (RPHY) standard. The company continues to aggressively deploy DAA across all regions. A core premise of RPHY is that because it is a CableLabs standard, devices from different manufacturers of CMTS and Digital node are interoperable.

Comcast has succeeded in delivering on this promise with Digital Nodes from three technology partners connected to its virtual CMTS (vCMTS) platform.

Many of today’s DAA deployments are in areas with an N+0 (node plus zero amplifiers) architecture, which is sometimes referred to as “Fiber Deep.” There is also an existing footprint of N+0 based on traditional analog fiber nodes. In both cases, there are no actives between the fiber node and customer homes. This creates the perfect opportunity to make A/B comparisons between the best-in-class analog HFC and DAA technology. Without RF amplifiers “watering down” any differences between the two networks, such as might exist in N+x deployments, we can attain a clear and unvarnished, side-by-side view of yesterday’s and today’s cable access technologies in production scale.

In this paper we will compare observations and numerical results obtained from operating these two N+0 variants. We will:

1) Describe lessons learned building both architectures, and adjustments made along the journey

2) Describe the transitional operational challenges and best practices

3) Quantify key performance metrics

  • EOL MER (End of Line Modulation Error Ratio)
  • Capacity
  • Network power consumption – a critical area of focus for 1.2GHz DAA over N+0 in particular

This paper will address the journey, results, and future expectations of the industry’s largest known initiative to take DAA from concept to reality.

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