‘Spectrum crunch’ is a term that is often heard in discussions about the dramatic growth of wireless data traffic and the scarcity of radio frequency spectrum. Countries such as Australia, Denmark and the USA have indicated that they will each need an additional 500MHz of spectrum for mobile broadband services in the next decade. Industry observers have suggested that white-space spectrum might help achieve those ambitious targets.
White space in the TV spectrum band (between 470MHz and 790MHz in Europe) refers to unused spectrum at a specific geographical location, which could be used for alternative wireless communication services at that location. It is particularly attractive because it lies in the sub-1GHz UHF spectrum band, which is in higher demand than frequency bands above 1GHz. This spectrum has better propagation characteristics and therefore requires fewer sites to achieve coverage.
However, it is uncertain how much white space is available, and how long it will remain available. It is worth noting that much less white space exists in urban areas than rural areas. Although few regulators have made public statements regarding the amount of white space available, a benchmark comes via Ofcom in the UK, which has estimated that 80% of locations in the UK have more than 40MHz of white-space spectrum available, and over 100MHz is available in some locations.
The following market developments may affect the amount of white space that is available in the future:
- Changes in television broadcast plans: As broadcasters migrate DVB-T services to DVB-T2 (a standard for delivering high-definition (HD) programming) and move from multi-frequency networks (MFNs) to single frequency networks (SFNs), the amount of white space between digital television transmission will diminish. Most countries have historically used MFNs but a few countries are moving to SFNs – for example, in parts of Australia, Italy, the Netherlands and the UK. The change to SFNs and DVB-T2 is motivated by a desire to increase efficiency as well as to fit more TV channels into fewer frequencies.
- Proposed second digital dividends: Any proposal to assign spectrum to traditional MNOs for typical cellular services threatens the potential quantity of available white space. Some countries in Europe such as Finland, France and the UK are considering a potential second digital dividend. In the USA, the FCC is considering ‘incentive auctions’ as a way of developing a voluntary market mechanism to repurpose UHF broadcast spectrum for mobile use.
- Provision of spectrum for public safety networks: Mobile broadband networks for the emergency services in parts of Europe and the USA require new spectrum. The threat of terrorist activity has prompted a call for the provision of spectrum that would be dedicated, at least in part, to the emergency services and ‘first responder’ communication. White space has been suggested as a potential source of spectrum for this application. Although it is unclear whether white space is suitable for the types of
mission-critical, highly responsive networks that the emergency services require, the possibility that it could be used in this way should not be ignored.
White space offers a significant amount of untapped spectrum in an attractive band, but its uncertain availability is a matter of serious concern. As a result, and despite generous press coverage, established wireless network stakeholders are ambivalent about the usefulness of white-space spectrum in addressing the spectrum crunch problem. This has important tangential effects, including the lethargic development of standards and regulations.
In time, technologies for accessing white space (geolocation databases and cognitive radio technology) could give white-space devices the flexibility to move beyond TV broadcast spectrum – so when the crunch comes, smart devices may be able to migrate into other underutilised bands. The future of white space use may depend on whether devices can be made smart enough, quickly enough.
For Analysys Mason’s detailed analysis of the prospects for white-space technology, services and applications, see our Report The future of white-space spectrum and opportunities in the value chain.