Efficient Location Privacy for Moving Clients in Database-Driven Dynamic Spectrum Access

Dynamic spectrum access (DSA) is envisioned as a promising framework for addressing the spectrum shortage caused by the rapid growth of connected wireless devices. In contrast to the legacy fixed spectrum allocation policies, DSA allows license-exempt users to access the licensed spectrum bands when not in use by their respective owners. More specifically, in the database-driven DSA model, mobile users issue location-based queries to a white-space database, in order to identify idle channels in their area. To preserve location privacy, existing solutions suggest the use of private information retrieval (PIR) protocols when querying the database. Nevertheless, these methods are not communication efficient and fail to take into account user mobility. In this paper, we address these shortcomings and propose an efficient privacy-preserving protocol based on the Hilbert space filling curve. We provide optimizations for mobile users that require privacy on-the-fly and users that have full a priori knowledge of their trajectory. Through experimentation with two real life datasets, we show that, compared to the current state-of-the-art protocol, our methods reduce the query response time at the mobile clients by a large factor.