Hybrid Architecture for Spectrum Access Systems With Permissioned Blockchain

Dynamic spectrum sharing is a cornerstone of Beyond 5G (B5G) networks, yet current Spectrum Access System (SAS) coordination relies on bilateral trust and complex mesh integrations that scale quadratically (O(N2)). This paper presents a hybrid architecture that integrates a permissioned blockchain into SAS coordination, transforming the topology into a linear (O(N)) shared-state model. By explicitly decoupling temporal domains, the architecture preserves low-latency REST APIs for operational spectrum requests while migrating regulatory synchronization to a distributed auditable ledger. Validated through a functional prototype, our results demonstrate that while the blockchain layer introduces higher latency than REST baselines, the performance trade-offs are fully compatible with asynchronous synchronization requirements. Furthermore, the event-driven ledger model improves bandwidth efficiency by approximately 55 times compared to traditional redundant full-dump exchanges. More importantly, the proposed architecture establishes a foundational governance layer that enables passive auditability and forensic readiness, transitioning spectrum management from a legacy trust-based model to a verifiable, proof-based cryptographic environment.