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4.4 Digital switch-overWithin the national laws on sound broadcasting services that control the standardization of the signal and the application to frequencies and services, one approach for the introduction of digital services into Band II could be the replacement of analogue transmissions with digital transmissions. In many parts of Europe this would mean an instantaneous switch to digital.
For most commercial broadcasters such an instantaneous switch to digital is not feasible, because the listener base will be lost for a long time period, until the digital platform gains widespread receiver penetration. A significant period of simulcasting is almost inevitable to maintain a commercial presence during the transition with its inherent extra costs. If the simulcast signal is in another band for example via T-DAB in Band III, then it becomes easier to switch off or convert the Band II transmitter once the audience has migrated or is able to receive in both bands.
Perhaps, in some situations, it might be possible to create some free spectrum by condensing the existing analogue FM. Condensing in that respect refers to re-organising the spectrum usage in geographical and spectral separation terms. However, this is likely to result in significantly increased levels of FM to FM interference.
In a situation where broadcasters might consider that the introduction of a digital terrestrial broadcasting system in Band II is unnecessary, they could be confronted by others wishing to introduce digital systems either nationally or internationally. In such a scenario it would be necessary to develop planning parameters to allow for co-existence of digital broadcasting systems and FM analogue transmissions in Band II. A set of compatibility criteria would be required for each candidate system to allow the network planning to be undertaken together with cross border coordination.
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