A Study of Spectrum Sharing in Dynamic Spectrum Access (DSA) systems

Abstract

Secure and agile wireless technologies enable spectrum assignment through Dynamic Spectrum Access (DSA), a technique for improving the efficiency of spectrum usage. DSA has attracted much attention, with many national administrations keen to promote its development and uptake, but little research has been undertaken to date to simulate, analyse and demonstrate the potential economic benefit of investment in shared networks in general, and DSA in particular, by Mobile Network Operators (MNOs).
This study addresses two distinct areas of shared spectrum and DSA economics: the simulation and optimisation of potential shared spectrum usage opportunities, and the modelling of economic benefits with an associated cost-benefit analysis. Both of these aspects need to be considered in order that stakeholders can decide whether to invest or not. This research study focuses on an assessment of the potential economic benefits from an MNO’s perspective.
The optimisation of spectrum use is considered from a bit rate perspective, and the study illustrates that stakeholders should seek to increase C-Band carrier aggregation bandwidths from the present 300 MHz to 800 MHz. Monte Carlo simulations have been undertaken relating to the 3.8 – 4.2 GHz band in a target market, Exclusion Zones (EZs – where a shared network cannot be deployed without creating excessive interference to incumbent users) plotted, and the excluded population estimated. When enabling spectrum sharing, with or without DSA, the study has found that there is a need to maximise the allowable Secondary User (SU) bandwidths in order to optimise the spectrum sharing opportunity. It has also shown that, due to the sensitivity of results to variations in Primary User (PU) antenna characteristics, extant PU antenna data should be used when assessing the impact of EZs on the spectrum sharing opportunity.
It is shown that one of the biggest positive impacts on the size of potential economic benefit to MNOs can be expected if network investment is also shared, requiring the dynamic form of shared spectrum that is DSA. A more positive Net Present Value (NPV) is also likely to result from seeding the subscriber base with DSA-capable devices and by speeding up the rollout of DSA network infrastructure. If there is a correlation between the location of DSA-capable devices and the areas of highest traffic demand, such that DSA infrastructure
deployment can be effectively targeted, it is also shown that this will be beneficial to the cost-benefit analysis.
Additional work is needed before it becomes clear if there is a viable opportunity for MNOs to deploy DSA-type shared networks. A number of suggestions for further work that may assist MNOs to reach a definitive conclusion are made, including the need to consider the value that may be lost through the overhead associated with introducing DSA protocols, the pros and cons of different inter-operator coordination approaches to a shared DSA network, or the opportunities at higher frequency bands.

Date of Award	23 Jan 2024
Original language	English
Awarding Institution	University of Bristol
Supervisor	Mark A Beach (Supervisor) & Simon M D Armour (Supervisor)