  Motivated by the rapid development of energy harvesting technology and
content-aware communication in access networks, this paper considers the push
mechanism design in small-cell base stations (SBSs) powered by renewable
energy. A user request can be satisfied by either push or unicast from the SBS.
If the SBS cannot handle the request, the user is blocked by the SBS and is
served by the macro-cell BS (MBS) instead, which typically consumes more
energy. We aim to minimize the ratio of user requests blocked by the SBS. With
finite battery capacity, Markov decision process based problem is formulated,
and the optimal policy is found by dynamic programming (DP). Two
threshold-based policies are proposed: the push-only threshold-based (POTB)
policy and the energy-efficient threshold-based (EETB) policy, and the
closed-form blocking probabilities with infinite battery capacity are derived.
Numerical results show that the proposed policies outperform the conventional
non-push policy if the content popularity changes slowly or the content request
generating rate is high, and can achieve the performance of the greedy optimal
threshold-based (GOTB) policy. In addition, the performance gap between the
threshold-based policies and the DP optimal policy is small when the energy
arrival rate is low or the request generating rate is high.
