Adaptive energy-efficient small cell sleeping and zooming in heterogeneous cellular networks

With the rapid growth of the number of cellular network users and their tendency to share various multimedia files, providing better coverage for users and guaranteeing the quality of service (QoS) to serve them by base stations (BSs) are essential. On the other side, with the increase in the number of users and BSs, the power consumption augments in the cellular network. Heterogeneous network (HetNet), which consists of a large number of small cells deployed in the coverage of macrocell, can increase the network capacity. To fulfill the users' demands and meanwhile reduce the power consumption, we present three energy-efficient adaptive sleeping, zooming, and zooming + sleeping schemes for ultra-dense HetNets to increase the minimum energy efficiency (EE) of small cell BSs (SBSs). In the proposed sleeping technique, the SBS with the minimum EE switches to sleep mode until the minimum EE is improved. The proposed zooming technique performs the user association and power control to maximize the EE of each SBS as well as utilize the lowest possible number of SBSs. Finally, SBSs with the minimum EE switches to sleep mode after applying the zooming technique. The proposed joint zooming and sleeping method reduces the total power consumption and SBS utilization ratio about 100% and 25%, respectively, compared to the static user association scheme, in which the users connect to the nearest SBS. Also, it enhances the SE and EE of static user association about 1.5 and 1.4, respectively, which indicate its efficiency.