Digital Dividend - A Gap Between Digital Terrestrial Television and Miserable Failure

The first analog television broadcasts were made before World War II. Since late 1950s we have color television. Starting from 1980s there were many attempts to improve or extend analog television. All these experiments failed. The first real possibility for a significant advance in terrestrial television broadcasting came in 1990s when MPEG compression was successfully introduced into broadcast applications. And with first practical COFDM modulators the last major problem for digital broadcasting was solved.

The first attempts for digital terrestrial broadcasting were initiated because in some areas there was no free spectrum for new TV channels. Digital broadcasting allows us to use spectrum more efficiently since many TV channels and other services can share the same bandwidth which for analog television is used to broadcast only one TV channel. There is quite a lot of radio-frequency spectrum allocated for broadcast television. In Europe there are two frequency bands dedicated for this service: 174 MHz to 230 MHz in VHF band and 470 MHz to 862 MHz in UHF band. In 1961 there was a conference in Stockholm where individual frequency channels were assigned to each country. To avoid interference strict rules and procedures were defined and each country could only use those frequencies that are agreed by other countries. This had a practical consequence that on major transmitting sites only about 4 channels were available in UHF band and 1 in VHF band.

Many countries have come to the situation where expansion of terrestrial television was not possible because there were no free channels available. Digital terrestrial broadcasting was seen as a solution to this problem. First experiments were successful and many countries wanted to have some rules to extend the Stockholm 61 agreement. These rules were put into an agreement called Chester 97 named after the place where in 1997 a conference was held. This agreement defined additional rules for digital terrestrial broadcasting. But this agreement was only a temporary solution because with digital broadcasting it is possible to use spectrum more efficiently and it would be possible to make a brand new plan which will take into account different protection ratios between digital signals.

The "final" solution for new frequency plan for digital broadcasting was finalized at the Regional Radio Conference held in Geneva in 2006 (RRC-06). One of the outputs of this conference was a new digital frequency plan for digital broadcasting (GE06D). This plan replaces the old Stockholm plan (ST61) for analog television and provides a framework for detailed national planning. Because of digital broadcasting, different protection ratios and better tools to analyze possible interference it was possible to make a plan for 7 layers on UHF. Multiplying each layer with the number of TV channels in one multiplex we get quite a significant increase in total number of potentially available TV channels. At least in theory, this new plan should satisfy future broadcasting needs for at least for the next 20 years.

With DVB-T, MPEG-4 and statistical multiplexing you can easily accommodate 10 SDTV channels with decent quality in one multiplex. For HDTV this figure is about 3 to 5 channels, and with DVB-T2 you get an additional gain of up to 50% of capacity. But since the frequencies are now available and TV broadcasting is expanding, new TV services will come in soon future. Terrestrial broadcasting is still an important platform for TV distribution in many countries. This means that the capacity currently available for terrestrial broadcasting will be used also for HD services and many TV channels now available in SD will in the future migrate to HD. This means that the total number of TV channels available on the terrestrial platform will be slightly lower as it would be if only SDTV would be used. However, taking into account all the layers that were planned there would be no problem.

Unfortunately the reality differs from the theory. Immediately after the conference the European Commission got hit by an idea that, since the digital broadcasting is more spectrum-efficient, there should be some part of the spectrum which should be released after the digital switch-over. This part of the spectrum was called the "digital dividend". Of course, this idea was supported (and probably initiated) by the mobile industry. The appetite for some additional frequency spectrum for mobile services is enormous. But there is a problem. This consideration was not taken into account during the preparation of the new frequency plan or at the conference. There is no spectrum that will be released after digital switch-over. The same frequency bands in VHF and UHF that were available for analog television were now planned for digital television. With some compromises many countries were able to tightly squeeze 7 layers of coverage on the UHF band. This means that, at least in general, there is no gap, no possibility to add anything else into the UHF frequency band allocated to terrestrial television. Even changes to the existing plan would be very difficult.

So the Commission instructed technical bodies to investigate technical possibility to find a part of the UHF spectrum, currently allocated to terrestrial television, for possibility of implementing new services. These activities came to the proposal for using TV channels 61 to 69 (frequencies from 790 MHz to 862 MHz) for mobile services on a non-mandatory basis. This means that each country can decide whether it will use this band for broadcasting or for mobile services. In theory this sounds like a good compromise, but in practice this is a very bad solution with limited or no usability and a lot of problems.

All the countries participating at the RRC-06 put a lot of hard word and efforts to make a new digital plan. This plan is using all the available channels in the UHF band, from 21 to 69. This means that countries got their frequency rights also on channels from 61 to 69. Implementing mobile services would mean moving broadcasting out of this band. But moving where? There is no available spectrum for this since the whole UHF band for television was tightly planned for digital broadcasting. Implementing mobile services means simply to forget about broadcasting in this band. This, of course, means less capacity for broadcasting.

There are many aspects of the digital dividend approach.

• The Stockholm 61 analog plan lasted for 45 years. All European countries put a lot of effort to make a new digital frequency plan. The Geneva 06 plan is a result of many years of hard work, negotiations and compromises. Immediately after the conference EC started the activities to destroy it.
• The demand for broadcasting spectrum will grow. HDTV on the terrestrial platform is reality. Now there is more capacity for broadcasting as it was with analog television but not so much as it was initially assumed. Broadcasting is evolving and spectrum capacity for new services yet to be developed will be needed.
• There is probably no country that would give up 72 MHz (9 TV channels) of broadcasting spectrum unless there is a very good and profitable reason. Currently the anticipated mobile services don't seem to be such reason.
• The GE06 plan for digital broadcasting is built on the principle of equitable access to the spectrum. Releasing the digital dividend band will create inequitable access to the broadcasting spectrum since some countries will loose up to 20% of the rights in channels above 60.
• Implementing new mobile services in this band is useless if this approach is not accepted with all countries. If one country decides to keep broadcasting in this band it will affect at least all neighboring countries.
• Significant technical incompatibility between broadcasting and mobile services. There is huge difference in network topology and field strengths. Planned mobile services in the digital dividend band will cause interference to DVB-T reception. This may result in the inefficient use of spectrum.
• Mobile services are never free. The mobile operator is always making profit. The existing models of providing mobile broadband are purely commercial. On the other hand, terrestrial broadcasting is free and is available to everybody. There is no country that has no free-to-air terrestrial broadcasting. Public service broadcasters strive to deliver high quality content to all segments of the population. They use money to make quality content and provide public services, and not the other way around. Digital terrestrial television shall remain a competitive platform. An attractive number of commercial and public services is always in the public interest.

A term 'dividend' denotes the monetary reward (payback) for your investment that you expect, and sometimes get, at the end of a business cycle. The digital dividend is similar - it is the payback for the investment in the digitization of television broadcasting. The investment in digital broadcasting is made partly by the broadcasters that have to change their transmitters but mostly by the viewers that have to change their receivers. So the broadcasters and viewers will pay for a change of technology that will free some spectrum for commercial mobile services. Who invests and who gets the dividend?