By Colin Howlett, Douglas Johnson & Kai Meisen, Vecima Networks
The shift from centralized access to distributed access architectures (DAA) represents a fundamental change in the operation of hybrid fiber-coax (HFC) networks. Operators are moving to DAA for a plethora of reasons including:
- Radio frequency (RF) signal improvements by generating signals at the node
- Evolve outside plant fiber network to an all-digital network to serve other Ethernet-based needs (wireless, Metro Ethernet)
- Hub space and power savings
While the DOCSIS portion of the HFC network is the primary focus of this DAA transition, operators cannot simply replace other key services with a full DOCSIS system. Traditional set-top boxes (STB) still require video to be delivered as MPEG Transport Streams (MPEG-TS) over J.83 QAM channels and many operators require out-of-band (OOB) signaling such as [SCTE 55-1] and [SCTE 55-2] to control those STBs, provide channel maps, program guide data, conditional access authorizations, and remote firmware upgrades.
When DAA standards were first being created back in 2014-2015, there was an implicit assumption that QAM video would be controlled and processed by a single Converged Cable Access Platform (CCAP) Core. Evolution of the overall DAA ecosystem to embrace other technologies such as virtualization and an interoperable multi-vendor environment has greatly expanded the possibilities for operators and a primary CCAP Core for QAM video delivery is just one of several architectures that may be used.
This paper outlines the challenges in delivering QAM video using DAA and compares the architectural options available to vendors and operators with specific examples of real-world operator feedback as part of early DAA deployments.