  We examine the dimensional limitations of Licensed Shared Access (LSA)
regulatory framework for spectrum sharing and propose a solution for its more
dynamic implementation. We consider an additional dimension for sharing, beyond
those of time, space and frequency, i.e. the sharing of the infrastructure. We
explain why we believe that the emerging regulations and use-case scenarios are
limiting the potential of LSA, and with this in mind make a set of
recommendations to unlock it fully. As a specific case study, we present our
architectural work around Cloud-based Radio Access Network (C-RAN) and LSA to
demonstrate the possibility of a dynamic implementation of multiple incumbents
and multiple LSA licensees engaged in sharing. Our case study highlights
multiple ways for LSA framework to evolve into a global and flexible sharing
model, and prove that LSA and C-RAN are a good match to rethink how we look at
networks targeting a more flexible, efficient and profitable way of operating
them.
