Cost-Oriented Cooperative Caching Scheme in Energy-Harvesting-Powered Ultra-Dense Networks

Caching contents at wireless edge nodes has been regarded as a promising solution for improving quality of experience (QoE) and reducing energy consumption. Integrating caching to energy-harvesting-powered (EH-powered) ultra-dense small cell networks (UD-SCNs) is an efficient way to alleviate the burdens of backhaul links and further save on-grid energy. In this paper, we propose a cooperative caching scheme which can balance two caching actions, caching the most popular contents and caching diverse contents, in EH-powered UD-SCNs. The former helps reducing transmission delay while the latter contributes to saving on-grid energy. We regard delay and energy as two types of cost and introduce a weighted cost function. Then, the caching problem is transformed to be a cost minimization problem, and a genetic algorithm (GA) is designed to solve the problem in an effective way. Numerical results demonstrate that compared with the existing cooperative caching schemes, the proposed cooperative caching scheme succeeds in balancing transmission delay reduction against on-grid energy saving.