Technology focus > Next-generation cable architecture


Digital TV Europe July/August 2010


Cable gateways: controlling the home


Next-generation consumer premises equip- ment differs significantly from network ele- ments of the next-generation cable architec- ture in that operators have widely different views about what they want. Some believe in the integrated gateway model, with a high- end device combining the functions of media gateway and set-top box, while others believe that most of the video processing, decryption and GUI functions should be performed by other devices (set-top, smart-phone, PC,


Katz: investing in gateways could mean cable operators being left behind by the pace of development.


games console) or done in the network. The growing popularity of adaptive streaming technology could also work well in conjunc- tion with media gateways. One potential dilemma that cable opera-


tors face is whether to invest in a sophisticat- ed integrated gateway that they subsidise and supply to their customers, only potential- ly to find themselves left behind by product innovation in the wider consumer electronics market a year or so down the road. “Will the


deploy new customer premises equipment – something that those operators with large legacy digital TV subscriber bases would obviously be loath to do. This problem, together with the fact that operator interest has so far largely been confined to Germany (led by Kabel Deutschland) means that sili- con suppliers will continue to be cautious about investing in chipsets. This is the cru- cial problem facing the standard. Introducing DVB-C2 alongside existing DVB-C systems means simulcasting, remov- ing the advantage in bandwidth savings that DVB-C2 was supposed to confer in the first place. This will lead to delays as silicon sup- pliers hold out to see if the market will take off. But even in Germany, where interest is currently greatest, another couple of years will see existing digital rollouts expand, cre- ating exactly the kind of legacy base that


cable operator pay US$500 [€387] per box and then find that two years later it lacks some requirements?” says Gil Katz, senior director of cable solutions at Harmonic. Nevertheless, cable operators in general


seem for now at least to think that the inte- grated services gateway is a an idea whose time has come. “The advantage is you do not have to change a lot of existing infrastruc- ture,” says Brad Ferris, head of portfolio man- agement, TV solutions area at Ericsson. “The existing MPEG-2 RF QAM set-tops can operate just as they do now and you can start to layer on IP services without replacing them.” Arris meanwhile is developing both inte-


grated hybrid gateways and transport gate- ways. Transport gateways combine DOCSIS and QAM tuners and the device can extract the video and translate it to IP before sending it out over the home network to other devices. The hybrid gateway is a media hub for the home that includes video processing elements – it is essentially a full video set-top that can “talk” to other IP set-tops and devices. Such devices have to support multi- ple middleware and client software. Charles Cheevers, chief technology officer, Europe, at Arris, says that the company is developing products that will support all the main mid- dleware solutions in the market as well as its own MOXI middleware.


operators in more mature markets already have to content with. “Migration is the great challenge to C2,” says Motorola’s Gannon. “Existing set-tops will not have access to [services]. You either need a C2 overlay net- work or to replace existing set-tops.”


Wider market


There is also a question of whether the wider market, even within Europe, requires invest- ment in such a technology to be a priority. Ericsson’s Stallard points out that the related DVB-S2 standard arrived at a time when satellite pay-TV operators were looking to deploy HD. “It was perfect timing,” he says. There were no legacy boxes in the market to speak of. “Cable is in a different situation because [C2] came along after many of them


had already made the HD transition.” Nevertheless, Arris’s Cheevers believes that interest is growing, even if it is from a small base. Cheevers believes that physical layer technologies for cable will have to advance. Addressing one of the key hurdles – the lack of consumer equipment – he points out that set-top providers have an opportunity to leverage the work already done on the closely related DVB-T2 stan- dard, now being deployed for the launch of digital-terrestrial HDTV channels in the UK and Italy. “There is a huge cross-over,” says Cheevers, who adds that companies active in the T2 space will have the ability to make C2 set-tops very quickly. “The question mark is over the commercial viability of carrying that extra overhead in the silicon.” Set-top boxes would have to be rigorously tested and whether vendors could develop a single-chip C2 solution that could be sold across the World is open to question. However, one solution, says Cheevers, is to develop equip- ment based on a limited subset of the “full” DVB-C2 standard. The technology works by dividing each 8MHz carrier into multiple OFDM sub-carriers, with multiple possible modulation rates of up to 4096QAM. On top of that multiple DVB-C2 tuners can com- bine carriers to increase the available band- width. “The number of permutations is huge,” says Cheevers. Supporting all the ele- ments of the standard could involve a signif- icant investment, but working within a smaller sub-set of parameters could help operators and vendors to manage the cost of deployment, according to Cheevers. For example, initial deployments could be based on a more limited number of modulation schemes, starting say with 256QAM. However, the development of integrated sili- con for the set-top box remains key. The developments in parallel of these technology initiatives point to some of the key challenges cable network operators face as they look to accommodate the shift from broadcast to narrowcast and converged serv- ices. There are many technology areas that operators could focus their investment prior- ities on (not least driving fibre deeper into their access networks). However, the head- end and consumer premises equipment choices they make will be crucial in deter- mining their ability to support the kind of new services that their customers will increasingly demand. ●


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