  In this paper, a novel approach for providing incentives for caching in small
cell networks (SCNs) is proposed based on the economics framework of contract
theory. In this model, a mobile network operator (MNO) designs contracts that
will be offered to a number of content providers (CPs) to motivate them to
cache their content at the MNO's small base stations (SBSs). A practical model
in which information about the traffic generated by the CPs' users is not known
to the MNO is considered. Under such asymmetric information, the incentive
contract between the MNO and each CP is properly designed so as to determine
the amount of allocated storage to the CP and the charged price by the MNO. The
contracts are derived by the MNO in a way to maximize the global benefit of the
CPs and prevent them from using their private information to manipulate the
outcome of the caching process. For this interdependent contract model, the
closed-form expressions of the price and the allocated storage space to each CP
are derived. This proposed mechanism is shown to satisfy the sufficient and
necessary conditions for the feasibility of a contract. Moreover, it is shown
that the proposed pricing model is budget balanced, enabling the MNO to cover
all the caching expenses via the prices charged to the CPs. Simulation results
show that none of the CPs will have an incentive to choose a contract designed
for CPs with different traffic loads.
