Engineering plan and build

Digital switchover is the biggest single broadcasting infrastructure project ever undertaken in the UK. It affects every part of the terrestrial television delivery chain, from programme distribution by the broadcasters through to reception at a receiver, and in particular, it affects the transmission equipment at every television transmitter site in the UK.

Such a significant and complex programme of work requires careful management to ensure that the right technical solution is delivered at the right time in order to meet the announced switchover date.

Digital UK is co-ordinating, monitoring and reporting on the activity of all the parties involved in delivering digital switchover. Where appropriate, Digital UK creates management processes and provides a neutral cross-industry forum for reaching agreement on common solutions and approaches. In this way, Digital UK’s role is similar to that of the Managing Contractor on a building site.

The switchover engineering work has been broken down into clearly distinct activities, each one of which is subject to its own set of procedures and agreement. By doing this, the project becomes a relatively small number of distinct tasks, albeit each one is repeated many times. This also reduces the distinction between a large high power transmitter site and a small low power relay site; although the scale of engineering is significantly different between the two, the processes that each site has to pass through are identical. In this way, what at first glance appears to be an unmanageably vast project becomes more easily understood and managed.

Spectrum planning and international coordination

The use of spectrum is regulated by international agreement. Within the UK, the framework for spectrum use is set by the regulator, Ofcom.

Spectrum planning is the process by which channels and powers are chosen for each transmitter site in order to deliver the required coverage, within the licence framework set out by Ofcom (and BERR for BBC Mux 1 and Mux BBC A). For switchover, this is done through cross-industry groups on a region-by-region basis. Television signals do not respect international boundaries and so the plans must be compatible with, and agreed by, the countries which neighbour the United Kingdom. This process is called International Co-ordination, and the agreements reached are a form of international treaty.

Spectrum planning for digital switchover began in 2006, and is a continuing process as frequency plans are locked down region by region. On occasion it is necessary to revise previously agreed plans to accommodate changes in Ofcom requirements, or to accommodate the developing plans of neighbouring countries.

Site specification and regional system design

Although digital television is delivered by a single transmitter network, no one organisation has overall responsibility for the design and construction of the network. Indeed, the many players have different commercial objectives and there is a complex web of contractual relationships between them.

To address this complexity an industry forum was established in 2006, under the umbrella of Digital UK, to manage the process by which the analogue Broadcasters, Multiplex Operators and Arqiva reach agreement on and sign off a common technical solution for each transmitter site.

The process takes place on a region-by-region basis, and follows on from the spectrum planning work. As is the case with spectrum planning, the detailed technical design is subject to ongoing refinement right up until the point that a particular transmitter is actually constructed.

The digital switchover (DSO) roll-out plan

Once the transmitters are built and the switchover date arrives, the transmitter network has to be migrated to all-digital operation. The migration takes place in accordance with the DSO roll-out plan – the detailed step-by-step spectrum and implementation plan for making the change.

The key principles of the plan were agreed in 2006, but it is continually revised to accommodate changes to the spectrum plan and regional system design, and to incorporate learning from previous switchover events. Each release of the plan is developed and agreed by broadcasters, multiplex operators, spectrum planners, Ofcom and Digital UK.

The DSO roll-out plan currently stands at version 17.