  Many of the key enabling technologies of the fifth-generation (5G), such as
network slicing, spectrum sharing, and federated learning, rely on a
centralized authority. This may lead to pitfalls in terms of security or single
point of failure. Distributed ledger technology, specifically blockchain, is
currently employed by different applications related to the Internet of Things
(IoT) and 5G to address the drawbacks of centralized systems. For this reason,
mobile blockchain networks (MBNs) have recently attracted a great deal of
attention. To add a transaction to the blockchain in MBNs, mobile or IoT users
must perform various tasks like encryption, decryption, and mining. These tasks
require energy and processing power, which impose limitations on mobile and IoT
users' performance because they are usually battery powered and have a low
processing power. One possible solution is to perform the tasks virtually on
commodity servers provided by mobile edge computing (MEC) or cloud computing.
To do so, all tasks needed to add a transaction to the blockchain can be
treated as virtual blockchain functions that can be executed on commodity
servers. We introduce a blockchain virtualization framework called blockchain
function virtualization (BFV), through which all blockchain functions can be
performed virtually by MEC or cloud computing. Furthermore, we describe
applications of the BFV framework and resource allocation challenges brought by
the BFV framework in mobile networks. In addition, to illustrate the advantages
of BFV, we define an optimization problem to simultaneously minimize the energy
consumption cost and maximize miners' rewards. Finally, simulation results show
the performance of the proposed framework in terms of total energy consumption,
transaction confirmation rate, and miners' average profit.
