Clearing legacy services from the Digital Dividend band, making way for mobile network use, is a key policy consideration. In addition, the characteristics of the 700MHz and 800MHz frequencies may create more complex cross-border negotiation, and involve more countries, than with higher-frequency bands. Here we describe some of the issues that may arise on the road towards Digital Dividend allocation for mobile.
Before mobile can be deployed in the 700MHz or 800MHz band, existing services using the band must be moved. Clearing the band can present a significant barrier to regulators and governments. The most common occupants of this spectrum are digital television, CDMA networks, fixed government uses and wireless microphones.
Analogue television has been the main historical use of the UHF band at 470–862MHz (ITU Region 1) or 470–806MHz (ITU Regions 2 and 3). However, the fact that broadcasters do not need the same amount of spectrum after the digital switch-over is becoming universally accepted. It is well understood that, despite giving up the small portion of the Digital Dividend to mobile broadband, broadcasters will still have the opportunity to provide a much wider array of services, including HDTV and other products.
Nevertheless, difficulties in the digital switch-over can delay the release of Digital Dividend spectrum for mobile. But these can be greatly resolved by clear, realistic and consistent guidelines from government, covering:
While in Region 1 the Digital Dividend allocation stands at 790–862MHz, parts of Africa and the Middle East have allocations for CDMA 800 that sit in the middle of the band. This has caused African and Middle Eastern administrations to look into the best option for the Digital Dividend. Elsewhere in the world, CDMA 800 allocations can co-exist with mobile broadband, as they sit above the lower Digital Dividend band at 698–806MHz.
Region 1 administrations are looking at options to solve the CDMA 800 issue, and this was a major reason for the eventual decision to settle on a post-2015 allocation of the 698–790MHz band in Region 1 at WRC-12. Many administrations in Africa and the Middle East hold CDMA 800 operations which are fairly small. In this case, it will be economically advantageous to retune and reuse the 790–862MHz band for LTE according to the CEPT band plan as soon as possible. If this strategy is adopted, consultation with all stakeholders is vital to ensuring a smooth transition.
However, there are some areas where there are significant numbers of CDMA 800 subscribers. The decision at WRC-12 to allow, on a national basis, the use of 698–790MHz in Region 1 was partly driven by the need to continue to support CDMA 800 services at 850MHz for the time being. As such systems migrate to LTE, these administrations will be able to take up 790–862MHz as well as the lower allocation. The WRC-12 decision presents new possibilities for Region 1 administrations looking to deploy mobile in the Digital Dividend spectrum.
Fixed Links for Government users
A few markets have allocated fixed links for government services within the band. These have needed to be migrated, and the costs covered. In some cases, in Region 1, this issue caused administrations to support the decision at WRC-12 to allow markets use the lower band at 698–806MHz.
As the entertainment and news industry has pointed out — channels used by wireless microphones in the US and certain European markets sit within the Digital Dividend spectrum. Migration has been the option taken. In the UK, microphones originally sat at the top of the Digital Dividend spectrum in channel 69, but were migrated to channel 38.
Concerns over the impact of a Digital Dividend band allocation to mobile on other users been a barrier in some markets.
The very good propagation characteristics of Digital Dividend spectrum can lead to concerns about cross-border interference. This can result in a far-wider group of countries brought in to negotiate spectrum usage than would be true at 2.1GHz. Egypt, for example, must negotiate with countries as far apart as Italy and Yemen, while some of the smaller countries in Europe face multiple negotiations as well. Cross-border issues may be compounded in regions where progress towards digital television is radically different.
Models for mitigating interference have been worked out all over the world for the Digital Dividend. In Europe, these have varied from the Franco-Italian model for mitigating broadcast and mobile interference, to the CEPT-RCC framework agreement, mitigating mobile and Aeronautical Radar Navigation Systems (ARNS) interference. This agreement has seen exclusion zones in Eastern Europe around ARNS systems significantly reduced, and has paved the way to a wide allocation of Digital Dividend spectrum for mobile broadband throughout the region.
Within Russia, the political will to boost broadband penetration led to calls from the president and prime minister that the military should be more efficient with its spectrum use, freeing up spectrum to be allocated for broadband where possible. Russia made incredible progress on this issue over the three years since the programme started, which allowed it to become, in July 2012, one of a group of early leaders in allocating the Digital Dividend.
Interference with cable modems was cited by that industry as a potential problem. However, this proved to be a marginal issue in markets where LTE has been deployed and not a threat to the allocation of the Digital Dividend. Extensive work has been undertaken to understand how to mitigate the risk and to address problems if they arise during LTE deployment.