Technology focus > Next-generation cable architecture


Digital TV Europe July/August 2010


seek to compete with DTH players by offer- ing bandwidth-hungry expanded HD tiers. As was the case in the debate over modu- lar versus integrated CMTS to accompany the move to DOCSIS 3.0, suppliers of CMTS gear without Edge QAM products, including US cable industry stalwart Motorola, believe that integrated models will be adopted first, for a variety of reasons. Motorola has for some time been working on its own next-generation product, the Video Edge Services Platform (VESP), which it has more recently said is relatively closely aligned with Comcast’s requirements. “We


expand rapidly.


Arris will also initially produce an integrat- ed product and Cheevers argues that the modular version could be problematic for operators with smaller hub sites. Arris will migrate its C4 CMTS to become an integrat- ed CMAP platform. “We have been success- ful in the CMTS space with integrated devices and we still see that the integrated version is the right way to launch,” says Cheevers. He argues that the advantages of having devices from multiple vendors in the same facility, which has been made possible by the development of fully standardised


“Each company can focus on their core


capabilities. We are opening things up to any strong router vendor on the market.”


Ramin Farassat, RGB Networks


are in the process of defining our implemen- tation of a CMAP-compliant platform [based on] VESP but one that will also meet the requirements of European operators,” says Mike Gannon, EMEA business develop- ment, Motorola. Gannon says Motorola believes in an integrated platform combin- ing IP switching and routing with headend functionality including subscriber manage- ment. However, he says that the company’s roadmap is “not finalised” and argues that the density (i.e. number of QAMs delivered per port) being called for by Comcast might not be applicable to all operators’ headends. Regarding ‘integrated’ versus ‘modular’ implementations, Gannon says Motorola believes that the requirement for RF redun- dancy will grow as platforms deliver ever greater numbers of QAM channels, mean- ing that ‘integrated’ is the way to go. “There is a lot more to delivering video over DOC- SIS than just pure IP routing,” he says. “It’s an area where experience is invaluable.” However, he says that such a platform may not necessarily be applicable for smaller headends, and points out that European requirements are different because opera- tors are under different pressures. Switched- digital video, for example, by and large remains a technology that appeals specifical- ly to US operators, which have seen band- width-hungry MPEG-2-based HD tiers


interfaces, can cause problems for an opera- tor, which then has a number of different vendors to call for support.


Cheevers makes the salient point that service providers are unlikely to switch off legacy equipment and migrate to an entirely new architecture overnight. “There is a chal- lenge of getting CMAPs into smaller head- ends,” he says. Moreover, the transition to ‘all-IP’ is fraught with practical problems. “Serving groups for video and DOCSIS do not necessarily have a one-to-one correla- tion,” says Cheevers. One possible solution could be for operators to subdivide video service groups into separate groups for data. Because CMAP will have to be deployed alongside existing legacy equipment, at least in the first phase of deployment, it is unlike- ly that service providers will be able to har- vest the full benefit that should be possible in terms of reduced operating expenses.


DVB-C2


While cable technologists in the US have focused on the Comcast project, less has been heard recently about a European initia- tive to solve some of the challenges faced by


RGB has developed dense video processing platforms such as the VMG-6 and VMG-14.


Visit us at www.digitaltveurope.net 24


operators by dramatically increasing the bandwidth available over their networks – the DVB-C2 project. DVB-C2, the next gen- eration of the European DVB for cable stan- dard deploys a range of techniques – notably the use of COFDM rather than single-carrier QAM modulation and 16 up to 4096 QAM modulation schemes rather than the DVB-C range of 16 to 256 QAM – to deliver 30% higher spectrum efficiency and possibly 60% improvements in bandwidth over the existing DVB-C standard. Unlike CMAP, a product definition creat- ed to meet a need by a specific operator, the DVB-C2 standard is an initiative driven pri- marily by technologists that is in search of operator support. As such the standard may have a diminished chance of success – something that would, in the view of Harmonic’s Katz at least, be a pity. DVB-C2 addresses the legacy of analogue video that forced operators to carve up their available spectrum into 6MHz or 8MHz slices in order to deliver analogue video channels – an entirely wasteful procedure in the digital world. “It’s all about narrowcast services moving forwards,” says Katz. “Cutting the spectrum up makes it less efficient and makes resource management much more complicated – you need multiple tuners [in equipment] to get different frequencies at the same time, which makes management of the boxes more complicated.” Ericsson’s head of system management, solutions area TV, Paul Stallard, argues that all vendors are currently in much the same position – waiting to find out what the sili- con suppliers will do. “We were involved at an early stage in C2 and it was something we supported,” says Stallard. “I think we are in the same position as a lot of other vendors on our side. It will really depend on the availabil- ity of chipsets and the pricing of those chipsets in terms of when C2 becomes a market reality.”


While DVB-C2 would overcome this lega- cy problem, it would require operators to


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