30 July 2024
Dynamic assignment is the ultimate future way of managing radio spectrum. In this article, we argue that Europe must start adopting this approach in pioneer bands, otherwise it risks being left behind in the same way as it has in the cloud computing market. Adopting dynamic assignment technologies in the upper 6GHz band and future 6G pioneer bands provides an opportunity for Europe to catch-up.
What is dynamic spectrum access?
Traditionally a radio frequency channel has been assigned to a specific user in a specific location. Dynamic spectrum access (DSA) allows the user (and sometimes the use) to vary with time.
The most advanced implementation of DSA to-date is the CBRS frequency range (3.55-3.7GHz) in the USA where spectrum assignments can shift between highest priority users (including the military), other licensed priority users and unlicensed (lowest priority) users. Spectrum channels used for 4G and 5G base stations by either mobile operators or private network operators are released and returned for use by the US military when aircraft carriers and supporting naval vessels approach coastal areas.
This enables greater value to be derived from the spectrum – if it was statically assigned to the military (as was historically the case), it would be unused for much of the time, generating no value.
DSA is enabled by spectrum access systems (databases programmed with the priorities of different users in different geographic areas, as well as the constraints required to prevent harmful interference). Sensing technologies can also play a role – for example, CBRS uses environmental sensors to detect when the US Navy is using spectrum and migrate second priority users to alternative frequencies.
Why is dynamic spectrum access important?
In future, spectrum will increasingly be assigned dynamically. As network equipment can increasingly operate over wider frequency ranges, there is more scope for assignments to change to reflect changes in demand, allowing more spectrum bands to be shared between different services.
The potential benefits of DSA are illustrated by the upper 6GHz band. This is currently allocated to a range of uses (including satellite and fixed links), but there is demand for this spectrum for both public mobile (high power outdoor) and Wi-Fi (low power indoor/outdoor, licence-exempt) use. As illustrated below, DSA may allow the spectrum to be shared between all these services. In future, dynamic assignment might occur on an hourly basis; for example, in cities more spectrum could be assigned to mobile use during commuting hours, and to Wi-Fi at other times when people are in their homes/offices.
Figure 1: Illustration of DSA’s benefits in a city centre
Figure 2: Possible stages of evolution of dynamic spectrum assignment
Why does Europe need to embrace dynamic assignment?
DSA has been implemented in the USA in two key bands – the CBRS band and the 6GHz band, where it is used to licence higher-power uses, ensuring that any transmissions do not interfere with existing users or each other. The DSA systems providers are mostly US companies/organisations, including Federated Wireless, Google, CommScope, Wireless Broadband Alliance.
Europe to-date has a limited history of DSA. The use of TV White Spaces (TVWS) was explored but the power limits (to protect television broadcasts in adjacent areas) and the need for new equipment specifically for this band (i.e. limited economies of scale) meant it was not commercially viable.
This set-back should not discourage European regulators from introducing DSA. It is vital that European competence and expertise is built up in the supporting technologies. Otherwise, it risks being left behind, as it has in the cloud services market. Europe needs its own service providers, and it needs to act now, before DSA really takes off, if it is going to benefit.
How can Europe ensure it is at the forefront of developments?
Whilst the USA is ahead, it is not too late for Europe to catch-up. It should start by introducing DSA in:
- Upper 6GHz: enabling sharing between mobile, Wi-Fi (home and enterprise) and existing uses (e.g. satellite and fixed links). Given the uncertainty over how much spectrum mobile and Wi-Fi will need in the future, a dynamic approach avoids the need for a ‘once and for all’ decision to be made today.
- 3.8-4.2GHz: enabling assignments for private 5G networks alongside the existing uses (incl. satellite). In time, it could also enable higher-power use on existing mobile base stations.
- Existing mobile allocations: spectrum licensed to mobile operators could be made available for localised use in areas where it is not being used. The feasibility and benefits of this are currently being researched by Queen Mary University, Telet, Federated Wireless and Aetha as part the UK Department of Science, Innovation and Technology’s (DSIT) ‘spectrum sandbox’ programme.
European regulators and governments may have concerns about the complexities and costs associated with DSA at this relatively early stage of its evolution. However, it is important that European companies obtain the knowledge, experience and learnings from this new approach to ensure that once DSA goes “mainstream”, as it inevitably will, Europe is at the forefront.
