Genie: An optimal green policy for energy saving and traffic offloading in heterogeneous cellular networks

To enhance the utilization of base stations (BSs) and face the challenge of the upcoming mobile data tsunami, energy saving and traffic offloading are two important issues to address in green cellular networks. In this paper, we design an optimal green policy, called Genie, to strike a balance between energy saving and traffic offloading in the heterogeneous cellular network, so that the system can either activate hotspot cells for traffic offloading or to deactivate the hotspot cells for energy saving. We prove that the optimal green policy is monotone hysteretic, and our system can thus be realized by simple switch-up and switch-down thresholds, while avoiding the ping-pong effect suffered by existing works. We show via simulations that our optimal green policy can significantly reduce total energy cost and perform energy saving and traffic offloading intelligently under all traffic conditions.