Cognitive radio/Secondary spectrum use – the graceful path to Mobile Broadband in TV bands ?

Consumer interests shift and so does the media industry – the real-time TV viewers are an aging species and the numbers are going down every year. On-air broadcasting is more an more becoming an economically sound solution only in rural areas as cable-TV  and IP-TV have taken over over in urban areas.  For the younger generation – those under 30,  clearly a good IP connection is more important than many TV-channels. Mobile broadband is addictive and will continue to increase. Mobile-TV is already dead since the same services can be provided over Mobile Broadband connections.  It is clear that at some point in the not so distant future, there is a cross-over point when a vast majority of the general public is more interested in mobile broadband than nationwide on-air TV-broadcasting. This may happen in 5 years, 10 years or later, but it will no doubt happen – and eventually the new generation of politicians will realize this. The technical consequence is that it will at that point become very hard to motivate to use 2-300 MHz of prime spectrum for mobile use to serve a  few percent of the population receiving TV “over the air”  in urban areas.

Analyzing this and the consequences for the technical developments  was a interesting discussion topic a the COST TERRA meeting in Lisbon, Jan 19-21,2011. Voices from the regulatory environment pointed out that at an international (WRC) level this may never happen due to the highly varying requirements in different countries and, even if there is a political consensus, the time lag is still 8 years (2 successive WRCs) before international coordination can be achieved.  

So the prospects for mobile broadband in current TV bands look grim, or do they ? Personally I am not that pessimistic.  I think we need to make the debate less polarized. Its not about getting rid of UHF-broadcasting right away, but rather seeing a graceful transition. If there can be an agreement in principle, that TV-broadcasting eventually will only have a limited existence  in VHF/UHF frequencies (e.g. rural areas) , we have solved a lot. We need, however, not necessarily to have a definite time table.   Cognitive Radio  or rather secondary TV White Space use offers a rather elegant solution along some time table like

  1. Short range high capacity pico/femto cell use in urban areas om secondary basis (today)
  2. Broadcasting vacates spectrum that becomes exclusive spectrum for mobile broadband in urban areas (“2nd digital dividend”, possibly reducing services to “Must carry” channels). Rural area broadcasting on primary basis, mobile service on secondary basis.
  3. Broadcasting completely shut down in UHF spectrum (far future)

This allows also for a gradual, graceful deployment of equipment. Note that the transition from secondary use to dedicated spectrum use can happen without new infrastructure investments and the “White Space” equipment can easily operated in exclusive spectrum mode.

Jens Zander

About Jens Zander

Professor Jens Zander is professor in Radio Communication Systems at the Royal Institute of Technology, Stockholm, Sweden. He has been among the few in Swedens Ny Teknik magazine's annual list of influential people in ICT that have been given the epithet “Mobile Guru”. He is one of the leading researchers in mobile communication and is the Scientific director of the industry/academia collaboration center Wireless@KTH. His research group focuses on three main areas – the efficient and scalable use of the radio frequency spectrum, economic aspects of mobile systems and application and energy efficiency in future wireless infrastructures.
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