Three-Tier Hierarchical Model of Dynamic Spectrum Sharing Based on Hybrid Authorization Using Geolocation Database and Cognitive Radio

Dynamic spectrum sharing~(DSS) has been envisioned as a promising approach to address the imminent shortage of spectrum resources caused by the exploding growth of wireless traffic. Contrast to the existing DSS approaches which are either based on individual authorization using a geolocation database, such as Licensed Shared Access and Spectrum Access System, or general authorization using spectrum sensing techniques, such as Collective Use of Spectrum, in this paper, we propose a three-tier hierarchical model of DSS based on hybrid authorization, in which primary licensees~(PLs) and secondary licensees~(SLs) register with a geolocation database to guarantee predictable quality-of-service, and tertiary licensees~(TLs) opportunistically access the small spectrum holes in time and space to further improve the spectrum usage. We provide a mathematical analysis of the optimal access strategy for each type of licensees in the proposed hierarchical model, such that the weighted sum throughput of SLs and TLs is maximized while the PL throughput is guaranteed. Simulation results show that the proposed hierarchical approach can highly increase the system performance, compared to the current database-driven approaches.