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Digital TV Europe July/August 2010


Technology focus > Next-generation cable architecture


Juniper and Alcatel Lucent to enter the mar- ket. “What we pushed was a modular approach where the CMTS is really just an IP router in-and-out with no RF,” says Katz. He distinguishes this ‘packet shelf’ from the RF ‘access shelf’ – a platform akin to the existing Edge QAM device – that delivers RF both up and downstream. This separation enables the service provider to keep core CMTS functions, including HTTP servers, Quality of Service monitoring and sub- scriber management, in a single location and put an Edge QAM-like device out in the net- work. This is in contrast to M-CMTS deploy- ments, where an RF return path all the way to the headend has been necessary. For Katz, the combination of an all-IP headend and IP infrastructure between headend and hub, with distributed access shelf devices positioned in each hub, is a “great architecture for Europe” that would allow more vendors to enter the mar- ket. “Those companies do not want to deal with RF but DOCSIS is just another protocol that they can run on their routers so there are more vendors that can com- pete in the CMTS space,” he says. Taking IP all the way to the node would offer further benefits to operators, he says, by making it much simpler for them to segment each node – a key future require- ment for many European operators that still operate nodes serving 1,200- 1,500 homes.


Next-generation CMTS


Brad Ferris, head of portfolio management, TV solutions area at Ericsson, another Edge QAM supplier and supporter of modular solutions, says that CMAP is squarely addressed at addressing the challenge of an increasing number of narrowcast channels. He says that the packet shelf and the access shelf are derivatives of the CMTS and the Edge QAM. At present, integrated CMTS have the lion’s share of the market by far, with M-CMTS having relatively limited take- up to date. “The integrated approach has advantages and disadvantages. From the access shelf perspective we think we can cooperate with people on the packet shelf side,” says Ferris.


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RGB’s Farassat says that CMAP is in a sense an attempt to define what the next- generation CMTS will look like. He agrees with Katz that the modular variant is a “big- ger idea” than M-CMTS. Farassat says that RGB is building an access shelf that does all upstream and downstream RF transmission both for data and IP-based video as well as traditional QAM-based video delivery. The CMAP access shelf will be able to deliver “hundreds of QAMs”, while a packet or IP shelf, separated from the RF elements, will take care of IP Quality of Service, subscriber management and all the things that routers do well, according to Farassat. “Each compa- ny can focus on their core capabilities,” he says. “We are opening things up to any strong router vendor on the market.” Cisco Systems, a major infrastructure sup- plier to Comcast, has expertise both in RF and IP of course. Daniel Etman, product manager at Cisco’s cable business unit, says that Cisco is already “85% compli- ant” with CMAP. He believes that some aspects of the product specification will feed into CableLabs standards, though not things like form factor. “It’s up to CableLabs and the MSOs to make that decision,” he says. “I think if you look at the spec, the key point is that it’s bringing more density and versa- tility in a smaller form factor.” The more advanced version of the spec, which requires the splitting of the RF elements from IP completely, will likely require CableLabs involvement. “That’s not nec- essarily the direction Cisco is going,” he says. “We base our products on indus- try requirements.”


One obstacle to a radical depar- ture in terms of the cable architecture is that opera- tors are organisa- tionally still


divided into video


and data groups with different procure- ment responsibilities, says Etman. “Operators need to change their internal approach to procurement,” he says.


Etman also points out that CMAP does not specify the size of the device – only the maximum size (16RU). “If you look at Europe, 16RU is often quite large, especially


looking at the densities you can offer with next-generation capabilities,” he says. According to Harmonic’s Katz, other oper- ators in the US and Europe have been follow- ing CMAP discussions closely.


Platforms with limited capabilities should be available next year, with fully functional systems up and running by 2012, according to Katz. Key to the platform’s wider success, he says, will be its ability to “scale down”. Katz (like other Edge QAM vendors) does not believe that the ‘integrated CMAP’ model will win many adherents other than existing CMTS vendors that have little choice in the matter because they do not supply Edge QAMs. CableLabs has not so far been formally involved in CMAP, but RGB’s Farassat says it is likely to become so at the later stages to cover questions such as how the platform will handle encryption and testing. Whether variations in the platform will be necessary to handle the requirements of international operators remains a moot point. It is possible, at least in the view of some of the vendors, that an integrated model might be suitable for operators with smaller headends.


Integrated v modular


North American concerns are clearly driving the initiative, and key to the thinking behind it is the need to support a large installed base of legacy set-tops. “The numbers are big enough to make sure that any initiatives going forward have to support those devices,” says Cheevers. “That’s not the same for Europe or Asia.” European imple- mentations of CMAP would need to accom- modate a number of variations in require- ments. For example, in the US, each CMAP device is likely to have the capability to sup- port multiple local ad insertion zones, a requirement that doesn’t really exist in Europe where, as well as high interest in switched digital-video to recapture band- width. In Europe, on the other hand, there may be high-demand for more narrowcast channels as operators migrate to IP services.


Cheevers believes that European requirements may converge to some extent with North American ones as operators


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