Blockchains for Spectrum Management in Wireless Networks: A Survey

Regulatory radio spectrum management is evolving from traditional static frequency allocation and assignment schemes towards dynamic spectrum management and access schemes. This evolution is necessitated by a number of factors including underutilization of licensed spectrum bands, changing market and technological developments and increased demand for spectrum for emerging applications in multimedia communications, internet-of-things and fifth generation (5G) wireless networks. In simple terms dynamic spectrum management involves allowing unlicensed users known as secondary users (SUs) to access the licensed spectrum of a licensed user also known as primary user (PU). This is primarily achieved using spectrum sharing schemes that leverage spectrum database and cognitive radio techniques. However, the use of spectrum database and cognitive radio techniques faces reliability, security and privacy concerns for spectrum sharing. There is also a need to support other requirements of dynamic spectrum management such as secondary spectrum trading market and dynamic spectrum access coordination. In this work, we review the use of blockchains for enabling spectrum sharing and other aspects of dynamic spectrum management. The review covers the use of blockchain to record spectrum management information such as spectrum sensing results and spectrum auction transactions in a secure manner. The article also covers the use of smart contracts to support complex service-levelagreements (SLAs) between network operators which is key to supporting a self-organized secondary spectrum sharing market and enforcement of regulatory policies. A taxonomy of the intersection between blockchain and various concepts of dynamic spectrum management is also provided