The building blocks for a distributed access architecture (DAA) are shipping from Cisco. More than 60 customers in 25 countries spanning 4 continents have received key DAA components, such as Remote PHY nodes, Remote PHY shelves, cBR-8 digital cards and Smart PHY automation software. DAA holds much promise to simplify cable operations and improve overall network reliability and makes it easier to manage and configure the cable network and the services that are delivered by the network. As part of DAA, employing Remote PHY devices (RPDs) in nodes are a key element to enable 10G digital optics, Ethernet and IP used for delivering services to nodes.

Another network element that is key to DAA success is a rack mounted RPD shelf. Rack mounted RPDs are designed to connect analog nodes to digital Converged Cable Access Platform (CCAP) cores. Installed in the hub or headend, they are connected to CCAP cores via 10G digital optical connections routed through Layer2/3 Ethernet switch routers. The output of each rack mount RPD is traditional RF analog broadband, which is connected to analog fiber optics that transmit to and from legacy analog nodes in the access network. Rack mounted RPDs allow digital fiber optics and Ethernet to replace cumbersome RF hub-based coaxial distribution cables and amplifiers that were used to feed analog optical transmitters.

There are two use cases for RPD shelves. The first use case is to enable one CCAP core to serve multiple small and/or distant hubs via digital fiber (i.e. hub site consolidation). The benefits are appreciable savings in both CCAP equipment and operations costs, because RPD shelves enable CCAP processing in fewer locations, using longer distance digital optics between one CCAP core and multiple remote hubs, each with one or more RPD shelf.

However, there is a second, equally valuable benefit of RPD shelves. Consider a network in which a large portion, but not all, of the hub nodes will be upgraded to an N+0 (node + 0), DAA architecture.  For this portion of the network, it doesn’t make economic sense to rebuild and convert existing analog nodes to digital (RPD) nodes. The cable operator is faced with operating and managing a portion of the network with conventional edge QAMs, combining networks and analog optics, while the majority of the network employs digital optics, Ethernet and IP routing to do the same things. Instead of making operations simpler, operations is faced with supporting both the legacy network and the new digital network, having to support two very different operating procedures simultaneously in the same hub.

By using Remote PHY shelves to provide all connectivity to analog nodes, this problem is solved. A single, unified mode of operations is created for the hub, across both the analog and digital portions of the network. Specifically, RF combining networks and amplifiers in the hub can be completely eliminated, replaced by Ethernet switches and digital optics. Video services can be converged with data through the CCAP core if desired. Analog RF outputs from CCAP platforms can be eliminated, and CCAP platforms can be operated as CCAP cores, resulting in a higher service group density per platform. Future node splits can be done in digital, even if the node being split is analog. Simply put, Remote PHY shelves enable a hybrid analog/digital network to be managed as a single DAA network.

Software and hardware interoperability continue to be essential for enabling a DAA. The Open Remote PHY Device (OpenRPD) initiative was established to stimulate the adoption of a DAA by providing reference software for OpenRPD members, encouraging future OpenRPD devices to be based on interoperable software standards and enabling them to develop OpenRPD devices more quickly than by developing code from scratch. Cisco continues to be a key member of the initiative, openly developing and contributing significant portions of RPD software code to the initiative. To verify that hardware and software interoperability work as advertised, CableLabs® has established thorough CCAP core and RPD interoperability testing. Cable operators looking to migrate to a DAA can look for CableLabs’ stamp of interoperable approval and be confident that the devices they choose will work in a multivendor network. As an active participant in interoperability testing, Cisco is committed to interoperability.

The Distributed Access Architecture is a dramatic evolutionary change in the cable network. It is a step toward cloud-native CCAP and the evolution of cable networks to a Converged Interconnect Network (CIN). With our comprehensive hardware and software portfolio for DAA, including the cBR-8 platform, Remote PHY digital nodes and Smart Digital Nodes, Remote PHY shelves that can be configured for redundant operation, and SmartPHY software, Cisco can help cable operators radically simplify the configuration and management of DAA networks.

Visit the Cisco booth at ANGA COM – Hall 7, #E20 – to learn more about how Cisco is helping cable operators thrive in the new age. I hope to see you there! You can also visit our cable access solutions site to learn more about how Cisco is leading the disruption in the industry with our technology innovations.


Sean Welch

Vice President and General Manager

Service Provider - Cable