Cellular architectures not great for TV: study
Terrestrial broadcast still the winner for now
A study by the KTH Royal Institute of Technology in Sweden has found that cell-based distribution of broadcast TV content can be a glutton for spectrum.
Around the world, mobile network owners have their eyes on spectrum being vacated by the move to digital TV, and the received wisdom is that video is going to keep driving huge traffic growth. However, the Arxiv-published study on “CellTV”, as the authors call it, finds that spectrum efficiencies only emerge if viewer habits also change.
Modelling users in Sweden in both urban and rural areas, the study seeks to model both the feasibility and potential benefits of replacing all VHF/UHF television broadcasts with IP-based cellular systems (which goes beyond the current digital TV proposals that merely shrink TV's spectrum requirements and open up frequencies for mobile carriers).
What their modelling suggests is twofold: first, that cellular network efficiency varies greatly between rural and urban areas; and second, that the cellular model is much more efficient for unicast rather than broadcast content.
In the broadcast case, the study finds, “it is doubtful whether the expected spectrum savings can motivate the necessary investments in upgrading cellular sites and developing advanced TV receiver required for the success of CellTV distribution.”
While this works well for video-on-demand service models, it's far less useful for “event” programming such as high-profile sports broadcasts, where lots of users can be expected to be turning into the same content.
Among the study's core assumptions are:
- That a cell-based system is proposed as a full replacement for current conventional TV broadcast;
- That the new system needs to replicate the current geographical coverage of television broadcast; and
- Since this is considering “CellTV” as a replacement for conventional broadcast, it has to support bit-rates able to deliver TV-like quality (rather than low bit-rate mobile video transmissions).
As noted over at Technology Review's Arxiv blog, it's unlikely that the spectrum saving offered by a move to an “all-cellular” model would justify the cost of replacing broadcast TV infrastructure, so “we’re going to have conventional terrestrial TV broadcasts for the foreseeable future.” ®
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