Technology focus > Next-generation cable architecture
Digital TV Europe July/August 2010
Mapping the future
As demand for narrowcast video services grows, cable operators both in the US and Europe face a number of critical technology choices. Stuart Thomson looks at some of the key developments.
the industry towards its vision of the next- generation cable architecture. The focus of its current activity is the CMAP, or Converged Multiservice Access Platform, which grew out of Comcast’s need for a dense headend platform in order to allocate ever-greater amounts of bandwidth for video applications – a need driven in the US by the deployment of switched digital video (SDV) services, HD and online video. The wider project, of which CMAP is a part, is know as the Next-Generation Access Architecture (NGAA).
US cable giant Comcast is
CMAP is actually a product specification. It is not an attempt to create a new standard for the delivery of IP over cable – the CMAP platform is designed to be fully DOCSIS- compliant. The product specification there- fore is for a much denser and more flexible combination of Edge QAM device and cable modem termination system (CMTS) that will work with existing DOCSIS interfaces but will deliver vastly more QAMs per port than existing gear. Comcast has decided to specify a device with a certain number of ports per rack-unit,
currently pulling
leaving it open to vendors to decide on the precise RU configuration.
Because it is not a ‘standard’ as such,
CableLabs (and EuroCableLabs) do not really need to get involved (although they are fol- lowing the project closely). They just need to qualify the products as they would with any CMTS device.
Impact for operators
One of the key objectives for cable operators including Comcast is to reduce the amount of space required for CMTS racks (as well as the amount of cabling required) and to reduce energy consumption.
The key cost savings are expected to come from saving space and energy – the cost of the equipment itself is likely to remain rela- tively high, and it is questionable whether it will prove to be cheaper than the (in any case progressively declining) cost of conventional CMTS and Edge QAM gear. But energy and space are emerging as key concerns for serv- ice providers as they address the need to build facilities to serve ever-increasing band- width demand.
As Ramin Farassat, vice-president of prod- uct marketing at RGB Networks, says CMAP is in a sense an attempt to define what the next-generation CMTS will look like. As such, it comes in variant forms that carry echoes of recent attempts to push a more modular data-over-cable infrastructure. Charles Cheevers, chief technology officer, Europe at broadband cable specialist Arris, says that CMAP is a “natural evolution of the headend architecture of cable networks” as a growing proportion of traffic becomes uni- cast. “The first thing about CMAP is that it’s a technology that converges and puts out more capacity on less hardware with greater density,” says Cheevers.
The modular variant of CMAP can be seen in some ways as an alternative to the modu- lar CMTS (M-CMTS) standard, a technology that failed to gain the traction many predict- ed for it. “M-CMTS was not really good enough,” says Gil Katz, senior director of cable solutions at Harmonic. The essential flaw in the standard, he says, is that it did not go far enough by separating RF technology elements entirely from the IP platform – the CMTS – thus permitting new entrants with purely IP expertise including the likes of
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