  We propose a new way to share licensed spectrum bandwidth capacity in mobile
networks between operators, service providers and consumers using
blockchain-based smart contracts. We discuss the foundational building blocks
in the contract as well as various extensions to support more advanced features
such as bulk purchases, future reservations, and various auction mechanisms.
Furthermore, we demonstrate how the system can be implemented with an
open-source, permissioned Enterprise blockchain, Hyperledger Sawtooth. We show
that our smart contract implementation can improve blockchain transaction
performance, by approximately four orders of magnitude compared to serial
transactions and one order of magnitude compared to parallell transactions,
using PKI-driven bulk purchases of mobile access grants, paving the way for
fully automated, efficient, and fine-grained roaming agreements.
