Inter-AMF Handover Optimization via Xn Interface
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Solution Overview
Problem
Frequent mobility events in private 5G networks lead to challenges in UE handovers between gNBs served by different AMFs, due to increased signaling requirements in N2 handovers compared to Xn handovers, which are not optimized for the higher mobility rates in private networks.
Innovation Solution
Implementing an Xn handover for inter-AMF mobility events, enhancing the N14 interface to support Downlink RAN Configuration Transfer messages and UE context transfer, and modifying the N2 interface to include identifiers for source gNB or AMF in path switch requests, while enhancing AMF discovery and selection functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If N2 handover is used for inter-AMF mobility events, then handover between gNBs served by different AMFs is supported, but signaling overhead between core network and NG-RAN nodes increases
Solution Approach 1:
The patent merges the inter-AMF handover procedure with the intra-AMF Xn handover procedure by enabling direct Xn interface communication between source gNB and target gNB even when served by different AMFs. This combines the flexibility of Xn handover with the inter-AMF mobility support, eliminating the need for separate N2 signaling paths and reducing overall signaling overhead.
Solution Approach 2:
The patent introduces the Xn interface as an intermediary channel between source gNB and target gNB that bypasses the core network AMFs for the actual handover execution. While AMFs remain involved in UE context transfer, the critical handover signaling occurs directly between gNBs through Xn, reducing core network signaling load.
2Quantity of substance
If Xn handover is used for intra-AMF mobility events, then signaling overhead is reduced, but handover between gNBs served by different AMFs is not optimized
Solution Approach 1:
The patent makes the Xn handover mechanism universal by enabling it to handle both intra-AMF and inter-AMF mobility events. The Xn interface is enhanced to carry inter-AMF handover signaling, allowing a single handover procedure to serve multiple functions regardless of whether source and target gNBs are served by the same AMF or different AMFs.
Solution Approach 2:
The patent introduces dynamic AMF discovery and selection mechanisms that allow the Xn handover procedure to adapt to inter-AMF scenarios. The source gNB dynamically discovers the target AMF identity through the target gNB and facilitates UE context transfer accordingly, making the handover procedure flexible and adaptable to different AMF configurations.
3Reliability
If frequent mobility events occur in private 5G networks, then network coverage and connectivity are maintained, but handover efficiency decreases due to increased signaling requirements
Solution Approach 1:
The patent implements preliminary Xn connection setup between gNBs before handover events occur. By pre-establishing Xn interfaces and configuring neighboring gNB relationships in advance, the actual handover execution during mobility events can proceed rapidly without requiring time-consuming N2 signaling setup, thus maintaining connectivity while improving handover efficiency.
Solution Approach 2:
The patent enables continuous Xn signaling between source gNB and target gNB during inter-AMF handover events, maintaining the handover process flow without interruption. The Xn interface remains active throughout the handover sequence, allowing seamless UE context transfer and path switching without breaking the signaling continuity that would otherwise require repeated N2 setup procedures.
Data Source
AI summary
A target Access and Mobility Management Function (AMF) switches the path for network traffic to a User Equipment (UE) in an inter-AMF mobility event. The target AMF obtains a path switch request from a target next generation Node B (gNB). The path switch request includes a UE identifier and a source AMF identifier. The target AMF compares the source AMF identifier with a target AMF identifier, and responsive to a determination that the source AMF identifier is different than the target AMF identifier, the target AMF provides a UE context transfer request to the source AMF. The target AMF obtains the UE context from the source AMF and processes the path switch request to update a core network path for a session of the UE. The target AMF also provides a path switch response to the target gNB.