UE Emergency Service Failure Handling via NAS Layer Notification
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Solution Overview
Problem
Current 3GPP specifications do not comprehensively outline the procedures for user equipment (UE) behavior during lower layer failures, particularly in emergency service failures, leading to unclear protocols for initiating emergency calls and network registration.
Innovation Solution
The proposed solution involves the UE's non-access-stratum (NAS) layer informing upper layers of the 5GMM protocol stack about lower layer failures, initiating remedial mechanisms, such as local de-registration and re-attempting initial registrations with the network or alternative networks like IP-CAN, to ensure emergency service connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current 3GPP specification procedures are followed for lower layer failure during emergency PDU session initiation, then the UE can maintain standard protocol compliance, but the UE behavior becomes unclear and emergency service access reliability deteriorates
Solution Approach 1:
The patent applies preliminary action by defining specific UE behaviors to be executed when lower layer failures occur during emergency PDU session initiation. The specification pre-establishes the procedure: when a lower layer failure is detected, the UE should abort the current emergency PDU session initiation, perform local de-registration, and initiate a new emergency PDU session. This predetermined response mechanism eliminates ambiguity in UE behavior during failure scenarios, directly improving both reliability and operational clarity.
2Adaptability or versatility
If the UE aborts the registration procedure and performs PLMN selection upon lower layer failure, then the UE can attempt to access alternative networks, but the time required for emergency service access increases
Solution Approach 1:
The patent applies partial action by implementing a tiered response strategy. Instead of immediately performing full PLMN selection upon any lower layer failure, the UE first attempts local de-registration and re-initiation of the emergency PDU session on the current network. Only if this partial remediation fails does the UE proceed to the more time-consuming PLMN selection process. This graduated approach minimizes time loss while maintaining adaptability to recover from failures.
3Reliability
If the UE increments the registration attempt counter and starts timer T3502 upon lower layer failure, then the UE can track failure attempts, but the complexity of failure management procedures increases
Solution Approach 1:
The patent applies self-service by implementing automatic failure management through the existing 3GPP counter and timer mechanisms. The UE autonomously increments the registration attempt counter and starts timer T3502 without requiring external network intervention or complex manual tracking procedures. This self-managing approach accurately tracks failure attempts while keeping the implementation relatively simple by leveraging already-defined protocol elements.
Data Source
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AI summary
Solutions pertaining to user equipment, UE, behavior for UE behavior for emergency services failure due to lower layer failure are proposed. An apparatus implemented in a UE determines that a lower layer failure occurred during a mobility and periodic registration update, MRU, procedure or a service request, SR, procedure being performed for initiating an emergency protocol data unit, PDU, session with a network for establishing an emergency call (320). In response to the determining, the apparatus performs one or more operations comprising a UE non-access stratum, NAS, layer in a 5th Generation Mobility Management, 5GMM, protocol stack informing one or more upper layers of the 5GMM protocol stack of a failure of the MRU or SR procedure for accessing the network such that an upper layer of the 5GMM protocol stack initiates a mechanism for remedying the failure, or performing a local de-registration and attempting to initiate an initial registration for emergency services with the network (320).