  Motivated by the recent development of energy harvesting communications, and
the trend of multimedia contents caching and push at the access edge and user
terminals, this paper considers how to design an effective push mechanism of
energy harvesting powered small-cell base stations (SBSs) in heterogeneous
networks. The problem is formulated as a Markov decision process by optimizing
the push policy based on the battery energy, user request and content
popularity state to maximize the service capability of SBSs. We extensively
analyze the problem and propose an effective policy iteration algorithm to find
the optimal policy. According to the numerical results, we find that the
optimal policy reveals a state dependent threshold based structure. Besides,
more than 50% performance gain is achieved by the optimal push policy compared
with the non-push policy.
