  The next frontier for the Internet leading by innovations in mobile
computing, in particular, 5G, together with blockchains' transparency,
immutability, provenance, and authenticity, indicates the potentials of running
a new generation of applications on the mobile internet. A 5G-enabled
blockchain system is structured as a hierarchy and needs to deal with different
challenges such as maintaining blockchain ledger at different spatial domains
and various levels of the networks, efficient processing of cross-domain
transactions, establishing consensus among heterogeneous nodes, and supporting
delay-tolerant mobile transactions. In this paper, we present Saguaro, a
hierarchical permissioned blockchain designed specifically for Internet-scale
mobile networks. Saguaro benefits from the hierarchical structure of mobile
network infrastructure to address the aforementioned challenges. Our extensive
experimental results demonstrate the high potential of Saguaro being the first
5G-enabled permissioned blockchain system in the community.
