EBU Technical Review

“ What is the spectrum demand for future HDTV, T-DAB and DVB-H services – i.e., the minimum spectrum requirements for public service media, resulting from the digital dividend? ”

This was the challenge recently put to the technical experts of the EBU's Spectrum Management Committee (SMC). It is a question that all broadcasters need to answer.

Our first thoughts in the SMC were that the starting point is not technical: there are some fundamental business aspects to be addressed ... not least being – what services do broadcasters expect to deliver in the future and when? Furthermore, it seemed clear that any estimates should also include an element of commercial broadcasting in order to make up a bouquet that can succeed in the market place when up against cable and satellite services.

The result was 25 television programme streams for fixed or portable reception (DVB-T) and, in addition, a similar number of streams for mobile reception (DVB-H).

In the case of radio, it is necessary to at least match the existing FM capacity – but with all the advantages that digital broadcasting brings – and the figure we chose was 50 radio programmes. You might like to consider if this is appropriate for your own market place – we would like to know.

Before attempting any detailed calculations, it is also worthwhile understanding why the original question was posed. This is easy to answer: we are now facing increasing pressure to relinquish parts of the spectrum traditionally allocated for broadcasting in favour of other services that want to capitalise on the "digital dividend". Clearly, broadcasters should not monopolise the spectrum – just in case it might be needed sometime in the future – at least not without good justification. Nevertheless, it is vital that broadcasters make a sustainable case for their future spectrum requirements before it is too late.

In various European countries the demand for TV and audio programmes is highly likely to be different. It is therefore necessary to make estimates based on the reasonable average demand at an appropriate date in the future. The point in time when the full digital dividend becomes available (2015) seems a good starting point because it is the end of the analogue-to-digital TV transition period for Europe, as established in the Geneva 2006 (GE06) Agreement. The next step is to consider the latest developments in broadcasting technology.

There are important developments taking place that will provide for a significant increase in the capacity of the digital television platform. These relate to improvements in the standards used for coding (compressing) digital signals to squeeze as much as possible into a given amount of spectrum, and also in their physical transmission. If we are to construct a credible case, these factors must be taken into account.

HDTV is already a reality – HD television sets are widely available and prices are falling to levels that are acceptable for the general public. It has been estimated that, by 2010, there will be over 120 High Definition TV Channels in Europe [1] and that, by 2011, over forty million Europeans will have adopted HDTV [2]. In five to six years time, standard definition television will begin to disappear in the most advanced markets as HD becomes a consumer expectation. Consumers will expect HD to be delivered on all platforms including DTT.

Based on such predictions, is seems reasonable to assume that the majority of programme services will be in HD by 2015. Clearly, HD needs greater multiplex capacity than standard DTT, and significantly more spectrum, but it is expected that this can be met by the latest technological advances. This includes: (i) MPEG-4 AVC (or H.264 AVC), the improved video and audio coding compression standard, and (ii) DVB-T2, a new transmission standard that can deliver an increase over the current standard of at least 30% in the capacity of a DTT multiplex for fixed reception.

There are many technical standards for mobile television broadcasting, but the standard with the greatest momentum in Europe today – for terrestrial broadcasting – is DVB-H. Work is also under way on next-generation DVB-H systems (DVB-NGH) but this is still some years away. Whilst DVB-H (which is matched to the existing 7 and 8 MHz television channelling schemes) is the preferred European technology for mobile television, T-DMB (Terrestrial Digital Multimedia Broadcasting) provides another solution for those countries wishing to enhance or build on their existing DAB (1.7 MHz) channelling schemes in the VHF band.

Digital radio broadcasting in Europe can use the DAB family of standards: DAB, DAB+, DMB, DAB-IP are complementary and have been scaled for radio (DAB/DAB+) and mobile television (DMB/DAB-IP) broadcasting. They all rely on the same DAB transmission layer and so can co-exist inside the same multiplex without compatibility problems.

It is currently considered that there will be no single winning standard for digital radio – DAB, DMB and even DVB may have a role to play. Clearly, whatever mainstream system is adopted (DAB or DMB), when assessing the longer term needs it is necessary to allocate sufficient spectrum to broadcasting services to support ongoing technology upgrades. Radio broadcasters will move beyond an audio-only output to produce programme-associated graphics and video content in order to play a key role as providers of multimedia content to digital platforms.

The number of "layers" was commonly used in defining the input requirements and output results of the RRC-06 Conference, although not defined in the GE06 Agreement. For most European countries, one layer represents a set of channels which can be used to provide one full, or partial, nationwide coverage. Most countries in Europe were successful in achieving three T-DAB layers and one DVB-T layer in Band III, and seven to eight DVB-T layers in Bands IV/V.

The results of a recent DigiTAG survey in January 2008 revealed a significant variation in the number of multiplexes/layers to be implemented, owing to the different situations that occur within Europe; for example, geographical size, proximity and number of neighbouring countries, type of reception mode adopted (fixed or portable).

Nevertheless, it is clear from the survey that most countries are committed to providing DVB-T national services and at least one layer of DVB-H. Conversely, for some countries, the use of one or even more multiplexes remains to be decided. This could lead to the conclusion that there is spare capacity which is not required for broadcasting purposes! Broadcasters need to think carefully about this and if their future requirements are not covered, they should take appropriate action by holding negotiations with their national administrations, or there is every possibility that this capacity will be lost to other users.

Currently, further work is needed to refine the detailed calculations but it can be concluded that, based on what is considered to be a reasonable scenario to provide for HDTV, mobile television/multimedia and digital radio, there should be adequate spectrum available for terrestrial digital broadcasting.

NB: This assumes that certain key technological advances are realised within the next five or so years and, critically, that a significant proportion of the digital dividend is retained for broadcasting purposes. In practice, this will vary from country to country. There is no time to be lost if we are to secure the future of terrestrial broadcasting in Europe.

All broadcasters in Europe should now consider their future service requirements and carry out calculations to determine their resulting spectrum requirements.

EBU Technical can help Members in constructing a case for obtaining a sufficient share of the digital dividend – but only when Members' individual service needs, including future developments, are defined.

Armed with this information, it is essential that broadcasters discuss and negotiate with their respective Governments in order to. (i) influence national decisions on spectrum re-allocations and (ii) secure the required capacity they need for their own digital broadcasting purposes.

Nigel Laflin
Head of Spectrum Management, BBC Distribution
Chairman of the EBU Spectrum Management Committee

-----------------------------------------------------------

EBU Members: If you wish to contact Nigel Laflin for further advice on securing your share of the digital dividend, please address an e-mail to "12345nigel.laflin@bbc.co.uk" but ignore the numbers at the start of his name, i.e. write his e-mail name as "nigel.laflin" and not "12345nigel.laflin".

(We are resorting to this trickery to prevent him from getting any more spam e-mails than he probably already gets !!)

European Broadcasting Union L'Ancienne Route 17A CH-1218 Grand-Saconnex Geneva Switzerland

We also get a lot of unwanted spam. So if you would like to contact EBU Technical Review, please address an e-mail to techreview@ebu.ch – but insert an underscore between "tech" and "review", i.e.write it as "tech_review".