Abstract—The growing environmental awareness coupled with the rising costs of energy have sparked a keen interest in the deployment of energy-efficient communication technologies over the infrastructure of cellular networks. Base stations (BSs) are responsible for the largest portion of power consumption and energy usage in cellular networks. Thus, sleep/wake-up scheduling strategies for BSs can significantly improve the energyefficiency (EE) of cellular networks. In this paper, we propose a Fuzzy Q-Learning (FQL) based energy-efficient sleep/wake-up mechanism for BSs in a heterogeneous network (HetNet). The goal is to save energy, without compromising the offered Quality of Service (QoS), by switching off the redundant BSs according to the local traffic profile and depending on the required area coverage and cell EE. The energy savings achieved under our proposed sleep scheduling strategy may lead to inevitable coverage holes as fewer BSs are active. To this end, we propose to enhance the sleep/wake-up mechanism with device-to-device (D2D) communications to compensate for the coverage loss in areas where BSs are switched off. Simulation results validate that the proposed framework provides significant improvements in power consumption and the EE while satisfying the minimum coverage and QoS requirements.
