User Plane Optimization in a 5G Radio Access Network

Abstract

5G as a future network is expected to be commercially deployed in 2020 and beyond. At the present time facilitated by industry need, the deployment option is to introduce 5G base stations alongside the existing 4G base stations in order to expedite 5G deployment. This deployment option is what presently is referred to as the Non-Standalone Architecture (NSA). To fully unlock the 5G potential such as enhanced end-user experience, service agility, Ultra Reliable Low Latency Communications (URLLC), improved network capabilities, critical Internet of Things (IoT) and industrial automation use cases, it becomes imperative to deploy a full 5G architecture with its own New Radio (NR) access and 5G Core Network (5GCN).
The goal of the thesis is to design a 5G standalone architecture that leverages on the principle of Control and User Plane Separation (CUPS) to be introduced in the 5G Radio Access Network (RAN). Such separation enables scaling of each plane’s resources and also allows for a flexible deployment of the architecture as chosen by the Mobile Network Operator (MNO). To this effect the New Radio-New Radio (NR-NR) architecture is introduced which makes use of two 5G base stations such that a user can connect simultaneously to the two base stations in what is called Dual Connectivity (DC). One base station, which is referred as the Next Generation NodeB (gNB-CP), specifically handles all the Control Plane (CP) signalling in the RAN and the second base station, called gNB-UP, is dedicated specifically to handle User Plane (UP) traffic. To investigate how the new architecture handles control signalling and optimizes the UP as a result of decoupling the UP functions from CP signalling, IP Multimedia Subsystem (IMS)-based voice telephony, that is voice call made over a 5G network specifically called Voice over New Radio (VoNR), is chosen as an application and two distinct use cases are considered. The first use case is to investigate through signalling messages how the proposed architecture handles control signalling for setting up a VoNR call. The second use case is to investigate through signalling messages and data flow path how user mobility and handover procedures are handled during an ongoing VoNR call. Finally, a comparative study was conducted with the NSA.
From the results obtained and from the comparative study conducted, it is shown that the NR-NR architecture decouples the UP functions from CP signalling. For handover procedures in the NR-NR architecture involving a VoNR call, the gNB-CP initiates and handles all control signalling while maintaining the VoNR call, which allows for the direct forwarding of a voice call from the serving gNB-UP to the target gNB-UP. This handover procedure eliminates any interruption of the ongoing voice call. Finally, we foresee there is a possibility of increased signalling load in the NR-NR architecture proposed because proper co-ordination is needed between a gNB-CP and a gNB-UP to ensure optimal network functionality when compared to the NR architecture which uses a single 5G base station.