## 4 5G Slicing Energy Evaluation  
Following the description of the Katana slicing framework [9], a set of experiments were carried out to evaluate the impact of slicing technologies [10] regarding the energy domain. Katana was previously evaluated in terms of performance in [11; 12] and achieved end-to-end latency down to ~10 ms. Related studies [13; 14; 15; 16] have defined the minimal requirement for end-to-end URLLC slicing to be at 20 ms [17; 18]; therefore, the presented work significantly improves expected latency performance. For the needs of these experiments, a 5G system configured in Standalone Mode (SA) was used, with a set of 5 UEs. The hardware selected was the Amarisoft 5 GC and NR, and the UEs were the HuaweiP40 Pro. In regard to the cloud setup for the hosted virtualized services, the \"Ussuri\" version of an Openstack system was deployed in a Dell R730 xd--Intel(R) Xeon(R) CPU X3450 @ 2.67 GHz. Firstly, in the 5G backend setup, the Slice Manager performed the required operations to ensure slice enforcement, by modifying specific parameters through an Element Management System (EMS) module. More specifically, the network slicing in the RAN layer was achieved through numerology manipulation, which minimized transmission windows. In order to attain the desired latency through transmission window minimization, the following RAN parameters were modified by the Slice Manager: the scheduling request Period (srPeriod--sr) and the slot period (slot) of the gNB. The slicing manager RAN modifications were applied based on the operator's service KPI request. In the next step, the average energy consumption for various slices was measured. This set depicts the overall energy efficiency of the 5G slicing, and how latency and various bitrates affect the overall energy consumption of the UE. In Figure 4, a set of experimental results is presented in terms of energy consumption (mA) regarding different packet sizes and the minimum and maximum latency configurations, as they are deduced from the previous experiments, i.e., minimum (sr = 1, slot = 2.5) and maximum (sr = 40, slot = 5). The corresponding latency achieved by these 2 configurations is 10 ms minimum and 40 ms maximum. This set of experiments was performed over the different eMBB slices (100, 200, 250, 300 Mbps), in order to fully investigate the effect of different packet sizes on different data paths. As can be deduced, the main factor contributing to higher energy consumption is small packet size, which is expected, as the device performs significantly more transmissions to attain the same level of bitrate to attain the slice bitrate requirement. Furthermore, the most important conclusion of these experiments is that lower latency requires more energy, as can be clearly seen from Figure 4. The configuration for minimum latency (sr = 1, slot = 2.5) consumes more energy in all different packet-size cases. Therefore, the trade-off between energy consumption and latency exists in the 5G domain. However, for the investigated eMBB and uRLLC slices, the additional energy consumption ranges between 1.5% and 3% in order to achieve up to ~30 ms lower latency. Consequently, it should be noted that 5G low latency communications are energy efficient, as minimal additional energy consumption can significantly reduce communication latency, a critical factor for emergency communications. Another minor conclusion drawn is that a higher  
Figure 4: Energy consumption results for various packet sizes for the minimum and maximum latency eMBB slices. bitrate also consumes more energy in all cases, which is a logical deduction: as the channel transmits more data, it, thus, uses more energy. Most of the slicing mechanisms currently available depend heavily on NFV/SDN capabilities, plus network virtualization and QoS/traffic prioritization. Katana, for the needs of the proposed platform, enforces policies both on the core and the RAN domain of the infrastructure.