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Executive summary

As part of its Digital Dividend Review^(-1-), Ofcom has identified that local television is a likely use of the interleaved spectrum (termed ‘interleaved’ because these frequencies are amongst the national digital television services). This report examines the technical issues associated with the introduction of local terrestrial television services and makes a comparison of alternative approaches. There are two distinct options for local television: carriage in a national multiplex from selected transmitters, or broadcast from dedicated local television transmitters that are either co-sited with national services or are completely separate.

The main issues arising from the introduction of local services concern coverage and interoperability with national DTT services. Of the latter category, the main consideration is how Local TV Service Information (data that is broadcast invisibly alongside programme services that receivers require to operate properly) can be integrated with the arrangement for national services.

The report finds that both options are feasible from a technical perspective, although each involves some degree of compromise.

Local TV services inserted into one or more ‘national’ multiplexes^(-2-) would achieve extensive coverage, but are difficult or impossible to target at specific communities. Service Information would be carried consistently in the national multiplexes to ensure consistent operation of viewers’ receivers. However, channel listing, Electronic Programme Guide content and programme information would have to be severely constrained if more than one local service is broadcast per multiplex in each of the national broadcasters’ regions. There are currently 29 such regions across the UK, of which only 25 are in use, so this would severely limit the number of services that could be carried with full Service Information unless capacity on several multiplexes becomes available.

Using a separate transmitter for Local TV offers flexibility to target specific communities, but UK-wide coverage would be less extensive than if carried in a national multiplex. Two studies have been carried out for Ofcom that indicate that there are sufficient frequencies for local services to be broadcast from at least 40-80 transmitters, and this number could be increased by optimisation of the frequency plan. However, there may also be reception and/or interference issues if Local TV transmitters are not co-sited with national multiplexes. The advantage, however, of this approach is that the EPG and channel information can carry full details of the local service and its programmes regardless of how the local services are arranged geographically. The Local TV operator would be under a greater responsibility to carry Service Information in a consistent and reliable manner.

Footnotes:

1.- The Digital Dividend Review which consults on Ofcom’s proposed approach to the award of spectrum made available through the UK’s digital switchover may be found at http://www.ofcom.org.uk/consult/condocs/ddr/.

2.- National multiplexes are the three public service multiplexes and three commercial multiplexes already planned for digital switchover. It is possible that new national or regional multiplexes could broadcast in the future if spectrum such as the spectrum cleared by digital switchover (the ‘Digital Dividend’) is used for this purpose.

The full document is available below

• Technical options for terrestrial local television services [pdf]
  Full Print Version

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