A Queueing Model for Threshold-Based Scaling of UPF Instances in 5G Core

The fifth-generation networks User Plane Function (UPF) provides necessary procedures to connect end-devices and data networks. A Protocol Data Unit (PDU) session between specific user equipment (UE) and the UPF is established before data transmission in 5G networks. The UPF software can be packed into either a virtual machine (VM) or a container image and instantiated in service providers' cloud infrastructure. Each UPF instance may handle several concurrent PDU sessions from various users. Operators should control the number of UPF instances to save resource consumption in the provision of Quality of Service (QoS). This paper presents a queueing model for a scenario where a threshold-based algorithm controls the number of UPF instances depending on users' traffic. We derive a method to compute the steady-state probabilities and performance measures efficiently. We investigate the performance of the UPF scaling algorithm in various scenarios with the assumption of specific hardware. Numerical results show that scaling UPF instances can lead to the good utilization of the system resource.