  Neutral Host Small Cell Providers (SCP) represent a key element of the 5G
vision of ultra-dense mobile networks. However, current business models mostly
focus on multi-year agreements for large venues, such as stadiums and hotel
chains. These business agreements are regulated through binding Service Level
Agreements (SLAs), which tend to be too cumbersome and costly for smaller scale
SCPs. As a result, the neutral host model does not scale up to its full
potential. In this paper, we propose a framework to enable the participation of
small- to medium-sized players in the cellular market as providers offering
network resources to Mobile Network Operators (MNOs). To this purpose, we
review the current and emerging spectrum and technology opportunities that SCPs
can use for neutral host deployments. We also propose the use of
blockchain-enabled smart contracts as a simple and cost-efficient alternative
to traditional SLAs for small-scale SCPs. To demonstrate this, we describe a
proof of concept implementation of an Ethereum-based smart contract platform
for best-effort service between an SCP and an MNO. Our simulations on potential
smart contract-based deployments in city centre Dublin show that the received
signal strength in the considered area will increase by an average of $10$
percent.
