The potential use of UHF white space technology has been widely discussed during the past 12 months – for example, see Analysys Mason’s report, The future of white-space spectrum and opportunities in the value chain. White spaces are gaps in the spectrum used for digital terrestrial TV (DTT) within UHF Bands IV and V (470–698MHz in the Americas and Asia, and 470–790MHz in Europe, the Middle East and Africa), where frequencies cannot be used for TV transmission in an adjacent region, without interfering. Because of the large coverage areas of TV transmitters, these gaps may be sufficiently large (both in terms of bandwidth and the area they cover) that they can be re-used for other services.
A number of initiatives have emerged proposing that UHF white space could be used for a range of applications. Many consider that white spaces will be suitable for the provision of wireless broadband services, particularly in rural areas. It is noted that existing uses of UHF white space includes programme making and special events (PMSE) and local TV in some countries, and so new white space applications would need to co-exist with existing uses. Other possible uses include machine-to-machine applications and short-range, high-speed data links similar to WiFi technology. Technology to use white space spectrum is being developed at present. These technologies are being designed such that devices will operate in a self-coordinating way, and as a result, regulators including the FCC and Ofcom in the UK have proposed to make licence-exempt those devices that utilise unused white spaces.
A threat to licence-exempt white space: incentive auctions
However, in the USA the FCC has subsequently suggested an innovative auction format, called an incentive auction, as a possible means of changing the use of UHF frequencies and enabling new services to access the bandwidth on a licensed basis. The aim of incentive auctions would be to repackage UHF spectrum and re-allocate it for licensed mobile services (such as 3G and 4G mobile). Intended to be a voluntary mechanism for broadcasters to release UHF spectrum if sufficient demand does not exist to retain those frequencies for DTT, the underlying objective is to encourage existing frequency assignments to be re-licensed through an auction mechanism. Since the proposed incentive auction seeks to balance supply with demand by allowing broadcasters to voluntarily release spectrum, and mobile and/or wireless broadband operators to purchase that spectrum on a licensed basis, it could also potentially reduce the amount of unused white space available for licence exempt use.
The FCC’s proposal could therefore represent a significant drawback in terms of further global development of licence-exempt white space devices. However, the success of the proposal relies upon spectrum being released in such a way as to be useable for mobile services. This would require the FCC to be able to re-plan released spectrum into contiguous regional blocks (paired or unpaired) suitable for mobile use. Given the importance of harmonised spectrum for the mobile industry (to ensure timely and cost-effective development of mobile devices in particular), this process of re-planning is particularly important. However, it would be a complex task, as broadcast spectrum is typically planned regionally, since the network configuration typically used for DTT involves digital multiplexes that are broadcast using multiple frequencies in different areas (i.e. a multi-frequency network or MFN).
How applicable is this approach outside the USA?
It is unclear whether a similar approach will be appropriate for re-setting the balance of UHF spectrum allocations between broadcasting and mobile use in countries other than the USA. In particular, incentive auctions are unlikely to take place in countries where terrestrial TV is the most important TV platform, since UHF frequencies in those countries are in high demand for DTT services – which includes many European countries (see Figure 1), and also in Brazil and Mexico (the two most populous countries in the Americas after the USA).
Figure 1: Status of the DTT platform in European countries [Source: Ofcom, EAO, national regulators]
A further complexity in implementing incentive auctions is that different countries use various different approaches to licensing spectrum for DTT services – in some cases, individual transmitters are licensed, whilst in others a block of frequencies is awarded either to broadcasters, or to a separate transmission provider. The release of specific channels may therefore require all broadcasters who are broadcasting over a particular multiplex (which might be using multiple frequencies, assigned to an independent transmission provider) to agree to release the selected channels, and/or to re-distribute existing programming slots to other multiplexes. This will make the re-planning process considerably more complex. Any changes to UHF allocations will also potentially affect existing secondary users of UHF spectrum, notably PMSE as indicated at the beginning of this article. It is not clear what alternative spectrum options exist for those services.
Without a harmonised approach to releasing UHF spectrum across regions and internationally, there is a danger that the majority of value from spectrum being released will be lost, particularly if the released spectrum is to be used for mobile services, since mobile networks largely rely upon harmonised spectrum to ensure a wide availability of devices at reasonable cost. Further harmonised mobile spectrum in the UHF frequency range is expected to be highly sought after for various uses, including commercial 4G networks but also potentially to address the future spectrum requirements for specialist users such as public safety.
Ultimately, how UHF spectrum is used in future is a complex issue that is likely to require much debate by regulators and industry at national, regional and international levels. Evidence-based analysis of the competing uses for UHF spectrum, their associated values, as well as the cost of achieving any spectrum re-distribution, will be a vital input to this debate.