Blockchain-Empowered Secure Spectrum Sharing for 5G Heterogeneous Networks

In the future 5G paradigm, billions of machinetype devices will be deployed to enable wide-area and ubiquitous data sensing, collection, and transmission. Considering the traffic characteristics of machine-to-machine (M2M) communications and the spectrum shortage dilemma, a cost-efficient solution is to share the underutilized spectrum allocated to human-to-human (H2H) users with M2M devices in an opportunistic manner. However, the implementation of large-scale spectrum sharing in 5G heterogeneous networks confronts many challenges, including lack of incentive mechanism, privacy leakage, security threats, and so on. This motivates us to develop a privacy-preserved, incentive-compatible, and spectrum-efficient framework based on blockchain, which is implemented in two stages. First, H2H users sign a contract with the base station for spectrum sharing, and receive dedicated payments based on their contributions. Next, the shared spectrum is allocated to M2M devices to maximize the total throughput. We elaborate the operation details of secure spectrum sharing, incentive mechanism design, and efficient spectrum allocation. A case study is presented to demonstrate the security and efficiency of the proposed framework. Finally, we outline several open issues and conclude this article.