Enabling O-RAN Closed-Loop Control over Wi-Fi-Based Untrusted Non-3GPP Access Networks

This thesis bridges the gap by integrating the N3IWF as an O-RAN- compliant E2 Node, focusing on Wi-Fi as the target non-3GPP radio technology, representing the most common untrusted access scenario in current 5G deployments. A co-located agent implements the E2 Application Protocol and exposes two RAN Functions (KPM and RC) to the Near-RT RIC. Through E2SM-KPM, Wi-Fi station-level metrics are mapped onto 3GPP-aligned measurement definitions, enabling xApps to monitor non-3GPP and 3GPP access nodes with uniform logic. Through E2SM-RC, the Near-RT RIC can issue control actions to the gateway; specifically, an N2-based handover mechanism between N3IWF instances is implemented, with a Handover xApp closing the control loop. The N2 handover between N3IWF instances represents a significant challenge: unlike classical 3GPP mobility, there is no radio-level RRM layer, no Xn interface between access nodes, and data-plane continuity depends on IPsec tunnels rather than radio bearers. The proposed solution synchronizes the full IKE/IPsec Security Association state between gateways through the N2 handover signalling, leverages the MOBIKE protocol for tunnel re-binding after the Wi-Fi switch, and introduces an early path switch at the UPF combined with target-side buffering to mitigate packet loss during the transition. Experimental evaluation on a four-node physical testbed demonstrates a mean handover latency of 815 ms, primarily limited by the physical WiFi re-association process. Target-side buffering reduces peak UDP downlink packet loss from 54% to 0.4% at 60 Mbps. The results also confirm that IPsec state synchronization is necessary for stable operation under repeated handovers: disabling it approximately doubles the latency (from ∼815 ms to ∼1 961 ms) and causes progressive AMF failures. Overall, the work shows that O-RAN closed-loop control can be extended to non-3GPP access nodes, bringing Wi-Fi gateways under the same management framework used for 3GPP RAN elements.