BD-SAS: Enabling Dynamic Spectrum Sharing in Low-Trust Environment

The spectrum access system (SAS) designated by the FCC follows a centralized server-client model where a spectrum user registers with one SAS service provider for spectrum allocation and other spectrum management functions. This model, however, is vulnerable to adversarial influence on individual SAS servers, causing concerns over system reliability and trustworthiness, especially when the ecosystem embraces a growing base of SAS service providers and heterogeneous user requirements. In this paper, we propose a blockchain-based decentralized SAS architecture called BD-SAS to provide SAS services securely and efficiently, without assuming trust in individual SAS servers. BD-SAS is backward compatible with the existing SAS infrastructure and supports the automatic execution of key spectrum management functions. A global blockchain network (G-Chain) is used for spectrum regulatory tasks while localized blockchain networks (L-Chains) are instantiated in individual spectrum zones for automating spectrum access assignment and other spectrum management activities. To further achieve security against an adaptive adversary, BD-SAS integrates a SAS server reshuffle scheme to resist adaptive corruptions on individual SAS servers. We implemented a BD-SAS prototype with practical blockchain platforms. Evaluation results demonstrate the feasibility and responsiveness of our system, wherein a spectrum access assignment can be finalized at the level of seconds.