Energy efficiency techniques in ultra-dense wireless heterogeneous networks: An overview and outlook

In wireless heterogeneous networks (HetNets), the spatial densification through small cells and the application of massive MIMO antenna arrays are key enablers for high data throughput, wider coverage, and improved energy efficiency (EE). However, ultra-dense deployment of small cells is envisioned to exacerbate network management and increase energy consumption in HetNets. To this end, this paper first identifies the peculiarities that make energy consumption one of the challenging problems in wireless communication networks. Further to this, we categorize the EE techniques used in wireless HetNets and discuss various enabling strategies under each technique. Based on these categories, an overview of past works carried out on EE techniques in HetNets is provided with reference to their major contributions and key findings. This work also presents EE metrics used to gauge energy consumption rate and performance trade-off. Finally, the paper concludes by discussing promising future research directions in the area of EE in Ultra-dense HetNets. (C) 2020 Karabuk University. Publishing services by Elsevier B.V.