Sleep Mode Control for Low Power Nodes in Heterogeneous Networks

Heterogeneous networks are an attractive method to make cellular networks cope with the increasing popularity of Mobile Broadband. Heterogeneous networks are formed from a mix of traditional macro cells and many small cells that are realized with Low transmit Power Nodes (LPNs). A massive use of LPNs provides significant improvement in system capacity and end user experience, but also brings additional overall energy consumption to the network. In this paper we investigate and compare three dynamic algorithms to control a deep LPN sleep mode, in which most components in the LPN are shut down. A LPN is shut down when the traffic demand is low; the main challenge is to make a timely reactivation in order to maximize the energy saving while minimizing any negative effect on the end user experience. Our results show that all three variants of the dynamic LPN sleep mode provide substantial energy savings at low traffic demand. When introducing an elaborate activation criterion that considers both the traffic load and the user proximity, the energy efficiency of the network can also be improved at high traffic demand.