Ofcom Spectrum Management Update: Technical Planning for Digital Switchover Around the UK

09 February 2005

Background

On December 28 2004 , new digital licences came into force for all of the commercial public service broadcasters in the UK (Channel 3 (ITV), Channel 4, Channel 5 and Teletext). The new licences include an obligation on these broadcasters to end the transmission of their services in analogue terrestrial form and commit them to a date of December 31 2012 by which they are required to complete the process of digital switchover.

As part of its spectrum management duties as described in the Communications Act 2003, Ofcom has – together with its planning partners (ntl Broadcast, Crown Castle and the BBC) and in discussion with the broadcasters – undertaken an engineering-led analysis to examine how the switch from analogue to digital terrestrial transmission might be achieved by this date. In order to complete switchover by 2012, a complex series of inter-related milestones need to be met throughout the remainder of this decade. Consequently, providing the technical foundations for the overall timetable is a relatively urgent task for this year and has been the focus of planning work in recent months. This note presents the summary findings of a spectrum planning project to examine options for the regional ordering of switchover, including an indicative sequence for individual regions around the UK.

This project has taken forward the switchover plan originally developed in 2002/03 by the Spectrum Planning Group as part of the Digital Television Action Plan. More recently, the planners have initiated co-operation with the SwitchCo Working Group. This group is working to set up SwitchCo, an organisation expected to take responsibility during 2005 for the development, co-ordination and implementation of the range of technical and other activities which will underpin the switchover programme. As such, it will be the primary body charged with the responsibility for ensuring the successful conversion from analogue to digital broadcasting in the UK .

It is worth noting that the project to which this note refers is one aspect of a range of planning activities currently underway, only some of which fall within Ofcom's remit. Ofcom expects this sequencing analysis to be taken forward by SwitchCo, once it takes on its responsibilities, as part of its detailed implementation planning. Although the order in which regions will be switched off is not for Government, as it is based on technical criteria, the Government will confirm the overall timetable for switchover once all of the remaining issues are resolved and the interests of consumers, especially the most vulnerable, are well protected.

The switchover process

At present, digital terrestrial signals reach 73% of all UK households. Due to the already crowded nature of the UHF spectrum, it is not possible to extend DTT coverage significantly beyond this level without first switching off the analogue transmissions. The planning for digital switchover has assumed that three of the frequencies currently used by the nationally available analogue terrestrial services (BBC1, BBC2, ITV1 and Channel 4) will be re-used for the three digital public service multiplexes at switchover. These are expected to be multiplexes 1 and B (controlled by the BBC) and multiplex 2 (controlled by Digital 3&4, an ITV-Channel 4 joint venture).

This frequency conversion process requires careful management to ensure that those analogue viewers using these frequencies at a specific transmission site prior to switchover are fully aware of the changes in advance and have sufficient time to convert to digital before the transition process is completed.

It is expected that this conversion process will be carried out over a period of about four years between 2008-2012 on a region-by-region basis. For reasons to do with transmitter location and overlaps between them, this will be done on the basis of ITV regions (e.g. Westcountry, Scottish, Carlton ) rather than geographic regions. As a result of the sequenced rollout, some regions in the UK would make the switch to digital a number of years before others.

In any given region, in order to allow all the remaining analogue viewers sufficient time to make the switch and ensure that all the transmitters in that region are converted, it is proposed that each region will take about six months to convert. The transition process would begin with one analogue service being replaced by a digital multiplex service (carrying the digital version of that analogue service plus a number of other public service channels). This digital multiplex will be broadcast throughout the region (on all main stations and relays) with sufficient power to replicate the coverage of the analogue broadcasts across the entire region. The other analogue services will continue to be broadcast and the remaining analogue-only viewers will have a number of months to make arrangements for watching television after the switch-off by means either of digital terrestrial, satellite or cable services.

At the end of this transition period the remaining PSB digital multiplexes will move to their new high coverage assignments and the remaining analogue broadcasts in that region will be switched off. At this point the other three commercial multiplexes will also move to new high power frequencies at the sites that they intend to adopt at switchover.

Technical constraints

The regional sequence for switchover has been determined by three technical factors:

  • Interference management. The planners have considered carefully how to order the sequence in which regions switch to minimise the impact that one region converting may have on analogue (or digital) viewers in an adjacent region. The risk of interference between transmission sites in neighbouring regions constrains the degrees of freedom with respect to the ordering of regions and means in practice that the number of alternative sequences which are technically feasible is very limited.
  • Infrastructure constraints. In developing the order, it is also necessary to ensure that the number of transmitters which have to be converted in any one year is approximately the same for each year of the switchover process. This reduces potential problems that could be caused by shortages of relevant resources and reduces risk of delay in the implementation of switchover. Similar considerations has also been given to the need for manufacturers, platform operators and retailers to ensure adequate supply for consumers in each region.
  • International spectrum negotiations. International considerations add a further degree of complexity. Planners have also sought to minimise any risk that the switchover process will be affected by the international negotiations currently underway for a Europe-wide digital switchover plan. These are due for completion in 2006. This risk is best minimised by converting regions most affected by these negotiations last - this principally affects regions in the south and east of England, as well as Northern Ireland and the Channel Islands.

Indicative switchover order

Table 1 below presents the results of the planners' analysis and shows the year in which each television region could switch over while continuing to ensure that switchover is completed by 2012. Due to the complicated technical interdependencies of switchover planning described above (both domestic and international), while this order is not fixed it represents the final recommendation of the planners as to the optimal sequence from an engineering and spectrum management perspective. It remains possible that some refinement may prove essential in the light of the detailed implementation work now being undertaken by the broadcasters and transmission companies together with the SwitchCo Working Group and, in due course, SwitchCo itself. However, it should be emphasised that there are very few practical alternatives to this sequence.

The actual year in which switchover begins and regions subsequently convert remains a matter for Government to determine as part of its overall switchover policy. Ofcom remains committed to the earliest practicable switchover, while recognising the need to take proper account of the interests of viewers and other key parties such as the broadcasters and transmission companies. Ofcom will continue to support Government in the formulation of this policy and to work with the SwitchCo Working Group in preparation for the launch of SwitchCo later this year.

Table 1: indicative switchover order – subject to final Government decision

Indicative date

Region

Indicative date

Region

2008

 

 

Border

Westcountry

HTV Wales

2010

 

Central

Yorkshire

Anglia

2009

Granada

HTV West

Grampian

Scottish TV

2011

 

Meridian

Carlton/LWT

Tyne Tees

Ulster

2012

Channel

Source: Ofcom