AMF UE Context Transfer for 5G Mobility
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Solution Overview
Problem
In 5G systems, during Initial Registration or Mobility Registration Update, when a UE switches from one Access and Mobility Function (AMF) to another with a different access type, the current specifications do not allow for the selective transfer of UE context, leading to potential disruptions of PDU Sessions and mobility management issues, especially when the UE lacks a valid 5G-GUTI for the new AMF.
Innovation Solution
The introduction of a UE context transfer mechanism where the new AMF requests the old AMF to transfer only the Subscription Permanent Identifier (SUPI) for integrity protection, allowing the old AMF to determine if the N2 interface can be relocated, and if not, rejecting the context transfer request to prevent session disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the old AMF transfers the entire UE context to the new AMF during inter-access type registration, then the new AMF can retrieve complete mobility management information, but the PDU Sessions established over the first access type will be disrupted
Solution Approach 1:
The UE context is segmented into different components: the N1 N2 interface information (which is transferred) and the PDU session information (which is not transferred when access type changes). This segmentation allows the new AMF to obtain necessary mobility management data without inheriting context that would cause session disruption on the original access type.
Solution Approach 2:
The patent applies local quality by making the context transfer selective rather than uniform. When access type changes, only specific UE context parameters related to mobility management are transferred, while PDU session context is excluded. This localized approach ensures that session continuity is maintained on the original access type while enabling proper mobility management on the new access type.
2Loss of information
If the new AMF requests full UE context transfer from the old AMF, then mobility management information is complete, but the complexity of context management increases and errors may occur
Solution Approach 1:
The context transfer mechanism is made dynamic by introducing conditions based on access type. The old AMF evaluates whether the access type has changed and adjusts the transfer scope accordingly. When access type changes, only N1 N2 interface information is transferred; when access type remains the same, full context transfer can occur. This dynamic approach reduces unnecessary complexity while ensuring information completeness.
Solution Approach 2:
The patent implements feedback by having the old AMF evaluate the registration request and determine the appropriate transfer scope based on the access type comparison. This feedback mechanism allows the system to automatically adjust the context transfer behavior, reducing complexity through intelligent decision-making rather than requiring complex pre-configured transfer rules.
Data Source
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AI summary
An apparatus of an Access and Mobility Function (AMF) comprises one or more baseband processors to process a request from a new AMF for a user equipment (UE) context transfer for a UE registered to the AMF via a first access type, wherein UE context transfer request includes an indication of a second access type for the UE to register with the new AMF, and to determine whether an entire UE context should be returned to the new AMF based on the second access type. The apparatus can include a memory to store the request.