British Telecom will change the bulk of its broadband network to use multicast routers as from next year – this will mean that full IPTV services, using quality of service protocols, could then be launched for the first time on the BT network.
BT has always said that it didn't see the point of building out its network with multicast routers, which would have meant replacing its entire network, because of the strength of Freeview in the UK, the free-to-air DVB-T broadcast network. This is why it has no IPTV linear TV service, and instead relies on internet delivered VoD, offering mostly movies and catch up on its BT Vision service. BT Vision devices also have DVB-T tuners so they can receive Freeview on the same device.
But at the Connected TV Summit in London last week Steve White, head of information systems and technology for IPTV at BT, said that the BT network was being upgraded to multicast to allow full IPTV. When asked why, White said: "It's too expensive renting DVB-T multiplex space to deliver Sky Sports to BT Vision customers, so we want to send it multicast."
A multicast network uses a Type D internet addressing system whereby content is sent from one point in a network to another, and any branch along the way can opt to also access that address, or not. It is the basis of the Internet Group Management Protocol and is the basis of modern IPTV systems and saves a huge amount of bandwidth, because each TV channel only has to be sent around a city fiber network once, not as multiple unicast copies. Most public broadband networks across Europe do not cater for multicast, except where they have been specifically upgraded for IPTV.
Last year BT and other UK broadcasters were given the rights to a fair market price for re-broadcasting a number of BSkyB channels, and these were immediately added to BT Vision. But White says that sending over the internet without full quality of service protection as an adaptive stream would not have been good enough, so BT rented a TV channel on one of the UK DVB-T multiplexes which drive Freeview.
Now the telecommunications giant sees a way to get back the millions it costs to rent a channel and instead run the service over its own network. Such a public multicast service could lead to more channels being launched in that way, and White confirmed, "BT Wholesale will certainly resell the multicast capability."
That would mean an almost unlimited number of IPTV TV channels could be launched through BT, all of them with a signal good enough to show on a connected TV screen, indistinguishable from broadcast TV quality, up to HD and beyond. Believers in adaptive streaming may think this is unnecessary, but the difference in quality and reliability is likely to be noticed.
BT has already launched its own CDN called Wholesale Content Connect, and can use this to either to protect its own network from video stream workloads, but also to offer as a service for video partners, to put video assets out at the edge of its network so that when HD video is streamed, it is only over very short distances, not much more than from your local phone exchange. The combination of the two, the multicast routers and the CDN, will make BTs network very video friendly.
One application might work well for YouView partners that are supporting the new set-top box due next year. They could use the BT multicast network to deliver whole TV channels which need high definition and use the CDN to distribute VoD streams.
Copyright © 2011, Faultline
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