Proactive XnAP/NGAP Handover Selection via AMF Support Verification

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Solution Overview

Problem

The reactive approach to handovers in 5G RAN, which initially attempts Xn handover and only switches to NGAP upon failure, leads to increased handover time, potential call drops, additional signaling, and negatively impacts Xn signaling KPIs due to lack of proactive support verification for AMF between gNBs.

Innovation Solution

Modifying the Xn setup request/response procedure to include all supported GUAMIs, allowing gNBs to proactively determine if the target gNB supports the AMF serving the UE, and initiating Xn or NGAP handover accordingly, with updates to NG-RAN Configuration procedures for changes in supported GUAMIs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If reactive approach is used to initiate handover only after Xn handover failure, then handover preparation simplicity is maintained, but handover time increases and call drop risk increases

Engineering Contradiction:

Improvehandover preparation simplicityVSAvoidhandover time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by having the target gNB prepare and store the list of supported GUAMIs during the Xn setup phase before handover occurs. This allows the source gNB to proactively check AMF support status before initiating handover, avoiding the need to wait for Xn handover failure and subsequently triggering NGAP handover, thereby reducing overall handover time while maintaining preparation simplicity.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If reactive approach is used to switch to NGAP handover after Xn failure, then procedure simplicity is maintained, but call drop risk increases due to delay

Engineering Contradiction:

Improvehandover procedure simplicityVSAvoidcall drop risk

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies preliminary action by having the target gNB pre-configure and store the list of supported GUAMIs during Xn setup. This enables the source gNB to check AMF support status before initiating handover, allowing proactive selection of the appropriate handover type (Xn or NGAP) and avoiding delays that lead to call drops, thereby improving reliability without significantly complicating the procedure.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies feedback by having the target gNB provide information about supported GUAMIs back to the source gNB during the Xn setup phase. This feedback mechanism enables the source gNB to make informed decisions about handover type selection based on actual AMF support status, reducing call drop risk while maintaining procedure simplicity through automated decision-making.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If reactive approach is used with additional Xn signaling for handover failure handling, then handover flexibility is maintained, but signaling overhead increases

Engineering Contradiction:

Improvehandover flexibilityVSAvoidsignaling overhead

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent applies preliminary action by having the target gNB prepare and store the list of supported GUAMIs during the Xn setup phase. This eliminates the need for additional signaling during handover failure handling, as the source gNB already has the information needed to determine the appropriate handover type. The solution maintains handover flexibility while reducing signaling overhead by avoiding redundant check and retry cycles.

Inventive Principle:

Principle #10Preliminary action

4Speed

If Xn handover is attempted without AMF support verification, then handover speed is maintained, but Xn signaling KPIs are impacted negatively

Engineering Contradiction:

Improvehandover speedVSAvoidXn signaling KPIs

Core Design Contradiction:

SpeedVSProductivity

Solution Approach 1:

The patent applies preliminary action by having the target gNB pre-configure and store the list of supported GUAMIs during the Xn setup phase. This allows the source gNB to quickly check AMF support status before initiating handover, enabling proactive selection of the optimal handover type. This approach maintains handover speed by avoiding unnecessary delays while improving Xn signaling KPIs by ensuring Xn handover is only attempted when AMF support is confirmed, reducing failure rates and retransmissions.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20230379779A1PROACTIVE APPROACH TO SELECT XnAP/NGAP-BASED HANDOVER

Publication Date: 2023.11.23 MAVENIR US INC

AI summary

In a method of operating a Radio Access Network (RAN) to optimize a handover between two gNBs, in addition to exchanging the respective AMF region IDs between the two gNBs, all supported GUAMIs of each gNB shall be exchanged as part of the Xn setup procedure, thereby enabling each gNB to know the supported GUAMIs of the peer gNB. Before initiating the Xn handover, source gNB shall check whether the target gNB supports the AMF which currently serves the UE. If supported, the source gNB shall proceed with the Xn-based handover. If the AMF is not supported by the target gNB, the source gNB shall initiate the NGAP handover. In addition, whenever there is any change in supported GUAMIs (addition/deletion/modification), each gNB shall initiate a New Generation Radio Access Network (NG-RAN) Configuration Update procedure towards the peer gNB with the changed list of GUAMIs.