Network transformation – moving towards DAA

Date of publication: 23.07.2018

While Hybrid Fiber Coax (HFC) has been around for over 20 years, most current cable networks rely on Centralized Access Architecture (CAA), where the access network involves a combination of coaxial RF and analog optical solutions, whereas the core network consists of CMTS and EQAM equipment. Existing HFC networks, until recently perceived as a blessing, are now forced to keep pace with growing demand. Most MSOs already have, or will soon have to face the challenge of limited space in their headends and hubs, which rapidly become filled to the brim with racks of Converged Cable Access Platform (CCAP) equipment.

The further development of existing analog infrastructure will result in high operation and maintenance costs, as well as the inability to future-proof the network. Not surprisingly, MSOs are turning their attention towards Fiber Deep and Distributed Access Architecture (DAA) for their infrastructure. They require a robust technology solution that will not only save space and reduce power consumption but also meet rising customer demand and drive new revenue opportunities in the future. Although HFC networks are facing some serious challenges, cable access technology isn’t finished yet. Moreover, its latest developments allow it to compete with any other type of access network.

From Centralized Access Architecture to Distributed Access Architecture

Today’s hybrid fiber coaxial networks can be described as active with no intelligent processing ongoing in the outer plant. This kind
of architecture has served MSOs very well. However, the time has come when the possibility of making a smart network is now
a reality. Contemporary HFC architecture completes all the processing in a central headend, and then it goes out through fiber optic
cables into the node in the plant and then out to subscriber’s homes. The idea behind distributed architecture is to take some of that
processing from the headend and put it out into the plant. According to this approach digital transport uses digital optics instead of using
analog optics. There are several ways that MSOs can achieve that and there are multiple types of processing power that can be put out
into the node. There are all kinds of options as to how much equipment might be located out in the node, but they are all parts of the
DAA. The idea of splitting the functionality in half and putting some of it out into the plant, is the key to saving significant space in the
headends and hubs.

The future – evolutionary paths toward Distributed Access Architecture (DAA)

In order to make DAA a reality we obviously need the right equipment that will allow MSOs to extend fiber to digital fiber nodes.
To make the transition, operators have to get that first plant online, but this requires a different headend piece of equipment. Once
that processing piece is ready to go, then the rest of the migration is fairly simple. While there are several DAA approaches, here are
the two that dominate the conversation these days.

DAA with Remote PHY
moves the DOCSIS PHY layer into the digital fiber node and the optical links between headend and node become digital. The big
advantage of this approach is a much better performance in the plant. What’s more, leaving the complex-MAC layer inside
the headend allows for better control and scale.

DAA with Remote MAC-PHY
places the MAC-PHY access layer functions in the access node. In this approach, apart from the benefits of digital fiber,
MSOs can free up a vast amount of room in the headend.


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