Article - Issue 31, June 2007

Digital Switchover

Dr William Webb FREng and Simon Crine

Download the article (179 KB)

There are many policy and technical challenges that accompany the switchover from analogue to the digital broadcast spectrum currently underway. Dr William Webb FREng from Ofcom, and Simon Crine from Digital UK put forward the issues surrounding the digital transformation of the UK’s television system.

The Policy Debate By DR William Webb FREng

New antenna panels were recently hoisted to the top of Arqiva’s 235-metre Selkirk mast in preparation for Digital Switchover (DSO) starting in 2008. The mast serves about 100,000 people in the Scottish borders from Berwick-on-Tweed to Hawick and also feeds a dozen relay stations

New antenna panels were recently hoisted to the top of Arqiva’s 235-metre Selkirk mast in preparation for Digital Switchover (DSO) starting in 2008. The mast serves about 100,000 people in the Scottish borders from Berwick-on-Tweed to Hawick and also feeds a dozen relay stations

Broadcasting Regulation

Broadcasting is regulated in a somewhat different manner from other uses of radio spectrum. Until the formation of Ofcom in 2003, broadcasting had its own set of regulatory bodies and this continues to be the case in many countries. There are two key drivers for this:

  • Broadcasting is often seen as having economic externalities in that the benefits to society may be greater than the benefits experienced by an individual.

  • For non-subscription models there are very limited linkages between broadcaster and viewer, unlike, for example, cellular where there is a contract and regular payments. This makes equipment replacement more problematic.

These drivers have historically resulted in a number of policy and regulatory decisions such as the concept of the BBC as a public service broadcaster, providing material of value to society in exchange for a licence fee. There has also been the imposition of a range of regulations on broadcasters covering issues such as the number of hours of news, children’s programming, regional production and more.

Broadcasters accept these in return for access to scarce broadcasting spectrum, often for free. In addition there are obligations to achieve high levels of population coverage – in the UK this represents around 98.5% of households – and to show consideration to viewers who are obliged to replace their equipment. In the case of digital switchover, broadcasters have been required to run parallel transmission in both formats for a considerable time.

The Switchover Decision

If broadcasting was run on an entirely commercial basis, like the cellular radio spectrum, then the decision to switch from analogue to digital broadcasting would have been simple. Digital broadcasting allows around four to six times as many programmes as analogue to be transmitted in the same spectrum. This enables an increased mix of programmes for viewers and the freeing of spectrum for other purposes. Were broadcasters subject to market forces alone it is likely that they would have made the digital transition come time ago, just as the cellular operators have migrated from First Generation to Third Generation in the radio spectrum (see Ingenia 30,‘Wireless Communications Reach Maturity’). If broadcasters were subject solely to market forces it is likely that they would have made the digital transition some time ago. In the regulated world of UK broadcasting however, the decision for switchover was made not by commercial entities but ultimately by relevant Secretaries of State. This degree of intervention was felt necessary to ensure viewers were protected, that appropriate controls were maintained over broadcast content and to achieve coordination across a number of broadcasters who might otherwise not have acted in concert. The decision was discussed in a range of policy documents culminating in Regulatory and environmental impact assessment: The timing of digital switchover, published by the DCMS and DTI, in September 2005. These suggested that the key benefits from switchover were:

  • “To the UK economy and consumers from the scope for new services through greater spectrum efficiency.” This is achieved by liberating spectrum as a result of the more efficient digital broadcasts and then using this spectrum for other valuable application, discussed further below.

  • “To consumers from extending and improving the digital terrestrial network to substantially match the existing analogue terrestrial television coverage and thus extending choice of free to air television services.” By turning off analogue transmission, higher powers can be used for digital transmission without risk of interference, allowing more to receive digital with a greater choice of channels.

  • “To public service broadcasters from efficiencies and long-term cost savings on terrestrial transmission.” Currently the broadcasters are transmitting both analogue and digital TV with resultant high equipment and power costs. Turning off analogue transmissions will allow them to make cost savings.

The decision was taken to turn off analogue broadcasting on a rolling basis throughout the UK between 2008 and 2012. As this occurs the power levels on digital signals can be increased to improve the coverage and around 112 MHz – nearly a third – of the spectrum will be liberated for other purposes.

The use of liberated spectrum

There is an almost infinite range of possible uses for radio spectrum but, given the propagation characteristics and value of the TV spectrum and the availability of spectrum elsewhere for other applications, the likeliest potential uses seem to be more broadcasting (either more ’standard definition’ (SD) channels, some high definition (HD) channels, broadcasting targeted at mobiles (’mobile TV’) or local broadcasting), personal communications such as 3G, programme making such as wireless cameras, or licence exempt usage such as those used by WiFi devices.

The spectrum could accommodate a mix of these, although some combinations such as broadcasting and personal communications do not sit well alongside each other, potentially requiring special measures to avoid interference. Attempting to determine the optimal allocation of liberated spectrum amongst such a wide range of uses and possible further innovations in digital technology, is a near-impossible task.

Market or policy driven

In determining how to divide up the liberated spectrum, the UK faces a major choice between using market approaches or making policy decisions. With the market approach, the UK would take the view that market mechanisms, most likely to be auctions, could be used to determine who valued the spectrum the most, and hence who was likely to generate the greatest value. The spectrum would be auctioned in as flexible a manner as possible and the market would decide on future use.

With the policy approach, the UK would take the view that there were reasons why using the market might not lead to optimal results – ‘market failures’ in the terms of economists. It would intervene to make a regulatory decision in order to meet certain policy goals, such as a view that broadcasting of key channels in HD was an important social ‘good’.

In 2004 Ofcom published its over-arching spectrum strategy document – the Spectrum Framework Review. In this it was clearly argued that spectrum should not be used as a tool for policy making. This is because spectrum is an input to a ‘production’ process. Other inputs might include manpower, land, vehicles, electricity, etc.

If a particular outcome, such as broadcasting coverage of the whole country, is required, then it is better to intervene at the output stage. In this example, this might be via explicit subsidy to achieve a certain coverage. Interventions at the input stage tend to result in organisations making more use of the ‘free’ input than they might otherwise in order to reduce their costs of other inputs. For example, they might use spectrum less efficiently than optimally to reduce costs of additional transmitters. While this maximises their profitability, it results overall in an inefficient use of resources for the country.

All this is taking place against a backdrop of increasing choice of broadcast material, through satellite, cable and Internet Protocol Television (IP-TV) systems, and with more broadcasting content available on the internet. Convergence is occurring between telecommunications and broadcasting, for example with podcasts downloaded over cellular and watched on mobile phones or iPods. Switching to digital, liberalising spectrum and then making use of market forces will probably add additional fervour to the debate as to the future regulating of broadcasting.

Further reference

Ofcom’s Digital Dividend Review, published in December 2006, is a consultation document that sets out the proposed approach to the award of the digital dividend spectrum – 470-862 MHz. See:

BIOGRAPHY – Dr William Webb FREng

William joined Ofcom as Head of Research and Development and Senior Technologist in 2003. He worked previously for a range of communications consultancies in the UK and spent three years providing strategic management across Motorola’s entire communications portfolio. William has published ten books, is a Visiting Professor at Surrey University and a Trustee and Fellow of the IET.

The technological challenges of digital switchover

By Simon Crine of Digital UK

Digital switchover is the biggest change to broadcasting in the UK since colour television was introduced 40 years ago. It will change the way people receive TV, how they watch, what they watch and the television equipment they buy. It’s an enormous engineering and communications challenge, demanding significant investment but with the potential to yield enormous public benefits, including the universal availability of free digital TV via an aerial and the creation of increased capacity for the broadcasting spectrum.

The UK is already a world leader in digital television, thanks largely to strong demand for digital channels and services. By the end of 2006 the three main digital platforms – terrestrial, satellite and cable – accounted for 18.5 million households. Digital satellite was in more than eight million homes and digital terrestrial television (DTT), commonly known as Freeview, in more than seven million households. Digital cable had more than three million subscribers, mainly in urban areas.

The birth of freeview

For switchover, the key technical objective is to modernise the terrestrial television network – the aerial-based system which has been in use since 1936. Between 2008 and 2012, analogue terrestrial television services will be replaced with a digital equivalent providing many additional channels, such as BBC Three, ITV2, Film Four plus digital radio services and red button interactive features.

It is possible to provide all these extra services using the same terrestrial network because digital broadcasting is much more efficient than analogue. It uses less broadcast spectrum to deliver many more TV services.

When the ITV Digital service collapsed in 2002, the DTT platform operating licence was awarded to Freeview, a BBC-led consortium. Instead of offering extra channels for a subscription, the service provided a line up of free channels to consumers who bought a set top box and connected it to their existing television. Since its launch, 14 million Freeview boxes or integrated TV sets (with the box built in) have been sold in the UK, making it one of the fastest selling new technologies of all time.

But unlike analogue broadcasts, Freeview is not currently universally available. One in four households cannot receive the signal and the digital channels – including those paid for by everyone through the BBC licence fee. There is a postcode checker at which informs people whether or not their property is within current coverage.

Logistical challenges

Extending DTT to everyone is a public goal, but one constrained by the lack of available broadcast frequencies; the current analogue transmitter network plus the current low power DTT network use all the available spectrum.

The only way to make Freeview universally available is to switch off the analogue services and convert the entire terrestrial transmission network to digital, but this presents a number of major challenges:

  • The modernisation of 1,154 TV transmitters in just seven years.

  • Preparing every household and workplace for digital only broadcasts.

  • Working with retailers, suppliers and installers to ensure sufficient equipment and support is available for consumers.

Transmitter modernisation

In developing the switchover plan, the UK’s entire transmission infrastructure has been reviewed to determine its suitability for the all-digital future. One key achievement was the development of a digital spectrum plan for Europe in Geneva in June 2006. This agreement provides for more transmissions in each country than was the case with the analogue plan and, as a consequence, the transmission footprint of many transmitters will not be the same on every channel to avoid interference.

On the ground, the engineering task is enormous; the largest ever broadcasting project of its kind in the UK, requiring 600 man-years of effort. Each of the 1,154 terrestrial transmitter sites, owned and operated by the transmission companies National Grid Wireless (NGW) and Arqiva, must be upgraded to carry either three or six high power digital ‘multiplexes’ (groups of channels).

In many cases the existing analogue antenna system must be replaced by one or more new transmitting antennae and their associated feeder systems. This in turn has implications for the supporting structure which involves replacement of the 320- metre mast at two sites, and significant strengthening work at a further 20 sites.

The new transmitting equipment needs to be accommodated and, even though the new modern solid-state transmitters are generally smaller than the analogue masts they replace, extensive building work is required at the high power sites to accommodate them. Even the low-power ‘relay’ sites present a problem; space is already so tight in the cubicles that around 450 need to be replaced to accommodate the new equipment.

Antenna switching

Much of the work on replacing antenna systems is weather dependent and can only be scheduled to take place between April and September each year. Even so, 13 main transmitters and 288 relay transmitters will be re-engineered each year, with the antenna work being completed up to two years ahead of the transmitter, power and building work. Work has already started at a number of sites in the first switchover regions and will continue over the next six years, culminating in the creation of a high power digital network which boosts availability of digital television via an aerial to 98.5% of households, the same proportion as can receive analogue television today. The first major milestone was the completion in September 2006 of the antenna replacement work at Selkirk in the Scottish Borders, the first main transmitter to switch over in Q4 2008.


Everyone will need to have the necessary receiving equipment by the time of switchover to avoid losing access to television. A number of factors may lead to reception problems. Old installations may not be directed at the optimum transmitter for the area; high winds can move aerials out of alignment; DIY installations are a particular issue – self-installed aerials, often in lofts, are frequently of the wrong band, pointing away from the transmitter, or incorrectly polarised; defective cabling or set-top aerials within multi-occupied dwellings commonly produce sub-standard analogue pictures. In all such cases, people frequently become accustomed to viewing degraded analogue pictures and yet may even claim they have good reception.

When viewing digital television via an aerial, defective aerial arrangements may lead to image pixellation or loss of picture altogether. Ofcom estimates that around 10% of UK homes may need remedial work to aerials, but this does not take account of set-top aerials receiving very poor analogue signals, significant numbers of which may require upgrading.

TV options

Once the signal has reached an aerial, householders must also ensure their television set is able to receive a digital signal. All three main digital platforms (satellite, cable and DTT) have been established by converting existing TV sets with ‘set top box’ adaptors.

For the DTT platform, there is a growing range of affordable new TV sets with built-in DTT tuners (iDTVs) and these are being sold in increasing numbers. Recent research among electrical retailers suggests that more than 80% of televisions with screens of over 26 inches have digital receivers built in.

Video recorders and other devices reliant on a built-in analogue tuner can still be used for playback and basic recording, but in a fully digital system will not allow simultaneous viewing of one programme and recording of a different one.

The best solution for most consumers is a digital television recorder (DTR) which records onto a built-in hard disk. Satellite, cable and Freeview all offer such products, offering better picture quality than a VCR as well as features such as the ability to pause and rewind live TV.

The communications challenge

The switchover programme will only be successful if everyone in the UK understands what is happening and what they need to do. If households and businesses are not prepared, people will be left looking at blank screens when the analogue signal is switched off. So, in parallel with our work to co-ordinate the technical aspects of switchover, Digital UK is also embarking on one of the longest and most wide-ranging public information campaigns this country has ever seen.

While most people love TV and rely on it as a source of information and entertainment, they rarely think about how the signal is received or whether their aerial has been installed correctly. Our awareness-raising work operates at a number of different levels. We undertake communications activity nationally and in each region for three years leading to local switchover. We also have a website that addresses a variety of stakeholders including retailers, service suppliers, as well as end users.

Now, just over one year on from the Secretary of State’s announcement of the timetable for digital switchover, we are seeing real momentum building towards switchover. Our research shows more than seven out of ten people are aware of switchover and sales of digital television equipment are now outselling analogue for the first time.

Digital vanguard

The Cumbrian town of Whitehaven will lead the switchover programme, bringing its 60,000 residents the full range of digital TV options in October 2007. Success in Whitehaven and elsewhere will depend on hard work, detailed planning and our ability to bring together the resources and expertise of broadcasters, industry, government, volunteers and regulators.

Just as forty years ago, when television was freed from a black and white world, together we can liberate this crucial medium from the limitations of analogue. In doing so, we can guarantee that every household in the UK shares in the benefits of digital broadcasting and pave the way for television’s continuing evolution.

Further reference

Information on digital TV and switchover can be found on each of the following websites:

Helpline 08456 50 50 50

BIOGRAPHY – Simon Crine

Simon Crine is Director of Corporate Affairs at Digital UK, the not-for-profit company established by UK broadcasters to coordinate digital television switchover. Previously he was Ofcom Director for England, with special responsibility for representing Ofcom to stakeholders in the English Regions.

[Top of the page]