Abstract 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.

中文翻译：

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超密集无线异构网络中的能效技术：概述与展望

摘要 在无线异构网络 (HetNets) 中，通过小型蜂窝进行空间密集化和大规模 MIMO 天线阵列的应用是实现高数据吞吐量、更广覆盖和提高能源效率 (EE) 的关键因素。然而，设想超密集部署小型蜂窝会加剧网络管理并增加 HetNet 的能耗。为此，本文首先确定了使能源消耗成为无线通信网络中具有挑战性的问题之一的特性。此外，我们对无线 HetNet 中使用的 EE 技术进行了分类，并讨论了每种技术下的各种启用策略。基于这些类别，概述了过去在 HetNets 中对 EE 技术进行的工作，并参考了他们的主要贡献和主要发现。这项工作还提供了用于衡量能源消耗率和性能权衡的 EE 指标。最后，论文最后讨论了超密集 HetNets 中 EE 领域的有希望的未来研究方向。