Spectrum scarcity and the auction-based allocation of newly released spectrum, means that commercial operators should investigate innovative ways of accessing this valuable resource. One option could be through new opportunities for government bodies to share their spectrum with commercial users.
Government users may be able to lease or sell their spectrum to commercial users following proposed Government reforms based on Professor Martin Cave’s Independent Audit of Spectrum Holdings. Once implemented, these have the potential to significantly alter supply and demand for spectrum in the UK.
What are the implications of such reforms? Public sector users must carefully manage access rights in order to protect existing uses, and commercial users looking for additional bandwidth must consider whether their consumers will be affected by the constraints of sharing.
Government departments’ spectrum usage rights
Public sector use accounts for around 66% of the spectrum below 15GHz, and it is used for a wide range of applications (defence and aeronautical radar, tactical radio systems, early warning systems, public safety communications), which all have fundamental ‘safety-of-life’ implications. These requirements will continue to be of vital importance.
As such, developing arrangements for commercial use of government spectrum must guarantee to protect these requirements. Furthermore, negotiating arrangements is not straightforward because government spectrum is typically jointly allocated to various different government users (e.g. MoD and public safety), with differing coverage and protection requirements.
In realising Cave’s recommendations – where commercial users negotiate access to public access spectrum directly with the public sector spectrum holder – there are a number of hurdles to overcome.
- Government departments need to formalise their existing sharing arrangements, which requires co-ordination between multiple government users (e.g. defence, public safety, aeronautical, transport).
- Individuals from the affected government departments need to be brought together to determine which, if any, bands offer potential for trading or sharing with commercial users, and the basis of sharing, be it on a basis of sharing time, frequency or geography.
- Once potential commercial organisations have expressed an interest in sharing spectrum, the government user(s) will need an understanding of the business model for the new commercial use to enable the commercial and technical agreements to be reached.
Issues that need to be considered within a commercial sharing agreement include terms of trade (duration, bandwidth, geographic areas), international obligations, protection arrangements for primary users, interference management and licensing arrangements.
Once commercial arrangements are in place, the technical options for sharing need to be considered. These options include calculating the field strength to monitor propagation losses and creating ‘exclusion zones’. A number of options to develop technical criteria for sharing are outlined in Figure 1 below.
Figure 1: Technical sharing options [Source: Analysys Mason]
Given the economics of wireless coverage, particularly in rural areas, spectrum sharing could offer a potentially more cost-effective means for providers to gain spectrum for coverage in specific areas, rather than sourcing spectrum from Ofcom.
However, for this to be feasible, operators need to understand the basis for co-ordination with the public sector shared use, as outlined in this article, and the most feasible option to meet sharing requirements while also meeting the commercial coverage and service objectives defined by their business plans and roll-out strategies.