Joint optimization of content caching and push in renewable energy powered small cells

In this paper, we explore the content information to design the joint caching and push mechanism in the small-cell base stations (SBSs) powered by renewable energy. The problem is formulated as a Markov decision process by exploring the features of content popularity and renewal and by taking into consideration the energy consumption for both content fetch from core network and push to the users. The objective is to minimize the number of requests which cannot be met by the SBSs. We adopt the policy iteration algorithm to obtain the optimal caching and push policy. According to the numerical results, the performance gain with large SBS cache size is marginal due to the limited energy. We also find that the optimal policy reveals noticeable performance gain compared with the greedy fetch policy and the non-push policy. In addition, simulations shows the tradeoff between the number of cached contents in the SBS and the available energy for content push.