The recent adoption of virtualized technologies in Next Generation Radio Access Network (NG-RAN) has driven a significant impact on energy consumption by subsequently decreasing the number of active base stations. The base station (gNodeB) of 5G is segregated into cost-efficient Central Units (CU) hosted on virtual platforms and cheaper & smaller Distributed Units (DU) present at the cell sites. Multiple CUs are pooled together in a single powerful central cloud, known as CU pool. The logical connection between DU and CU can be dynamically adjusted and can potentially affect the energy consumption of the CU pool. The deployment of NG-RAN imposes strict latency requirements on the fronthaul link that connects DUs to CU. To relax these strict latency requirements, various alternate architectures such as Flexible RAN Functional Splits have been proposed by 3GPP. In this paper, we first evaluate the energy consumption of DU and CU for various functional split options using OpenAirInterface (OAI), a real-time open source software radio solution. We find that lower layer splits have high energy consumption at CU as compared to higher layer split options. We also observe the variation in energy consumption due to traffic heterogeneity. Motivated by the above study, we formulate an optimization model, Apt-RAN, that optimizes the energy consumption of the CU pool and the number of handovers, considering different functional splits. To address the computational complexity of solving the optimization model, a lightweight polynomial time heuristic algorithm is proposed. Simulation results demonstrate that our proposed model outperforms existing state-of-art schemes.

中文翻译：

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Apt-RAN：一种基于灵活拆分的 5G RAN，可最大限度地减少能耗和切换

最近在下一代无线电接入网络 (NG-RAN) 中采用虚拟化技术，通过随后减少活动基站的数量，对能源消耗产生了重大影响。5G 的基站 (gNodeB) 分为托管在虚拟平台上的经济高效的中央单元 (CU) 和位于蜂窝站点的更便宜和更小的分布式单元 (DU)。多个 CU 汇集在一个强大的中央云中，称为 CU 池。DU 和 CU 之间的逻辑连接可以动态调整，并且可能会影响 CU 池的能耗。NG-RAN 的部署对将 DU 连接到 CU 的前传链路提出了严格的延迟要求。为了放宽这些严格的延迟要求，3GPP 已经提出了各种替代架构，例如灵活的 RAN 功能拆分。在本文中，我们首先使用实时开源软件无线电解决方案 OpenAirInterface (OAI) 评估各种功能拆分选项下 DU 和 CU 的能耗。我们发现，与较高层拆分选项相比，较低层拆分在 CU 处具有较高的能耗。我们还观察到由于交通异质性导致的能源消耗变化。受上述研究的启发，我们制定了优化模型 Apt-RAN，该模型优化了 CU 池的能耗和切换次数，同时考虑了不同的功能拆分。为了解决求解优化模型的计算复杂性，提出了一种轻量级多项式时间启发式算法。