AMF EBI Pre-Allocation for 5GS–EPS Handover Signaling
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Solution Overview
Problem
The existing 3GPP TS 23.502 specification for inter-RAT handover between 5GS and EPS is inconsistent and inefficient, requiring additional signaling steps for EBI allocation during PDU session establishment, which is not feasible at stage 3 protocol level and increases signaling burden.
Innovation Solution
The AMF pre-assigns one or more EBIs and associates a default ARP during registration, including this information in the Nsmf_PDUSession_CreateSMContext request to the SMF, and updates the SMF on EBI usage or modification through extended service operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional signaling steps are added for EBI allocation during PDU session establishment, then EBI allocation can be performed, but signaling overhead increases and the procedure becomes more complex
Solution Approach 1:
The AMF pre-allocates EBIs and associates default ARP values during UE registration before PDU session establishment. This preliminary action eliminates the need for additional EBI allocation signaling during session setup, as the EBIs are already assigned and ready for use in the Nsmf_PDUSession_CreateSMContext request.
2Adaptability or versatility
If EBI allocation is performed during PDU session establishment, then mobility between 5GS and EPS is supported, but the procedure becomes inconsistent at stage 3 protocol level
Solution Approach 1:
The AMF performs EBI allocation and ARP association during the registration phase (stage 2), before PDU session establishment. This timing ensures that the allocation is performed at the appropriate protocol level with full visibility of UE context, maintaining specification consistency while enabling inter-RAT handover capability.
Solution Approach 2:
The AMF acts as an intermediary that pre-assigns EBIs and manages the association with default ARP values. By centralizing this function in the AMF during registration, the system achieves consistent stage 2 specification while enabling stage 3 interworking through the inclusion of pre-allocated EBI information in session creation requests.
3Manufacturing precision
If EBI allocation is deferred to PDU session establishment, then session-specific EBI assignment is possible, but signaling overhead increases for frequent mobility cases
Solution Approach 1:
The AMF pre-allocates EBIs and associates them with default ARP values during UE registration, before PDU session establishment. This eliminates the need for repeated EBI allocation signaling during each session setup, particularly benefiting frequent mobility cases where the same UE repeatedly establishes sessions.
Solution Approach 2:
The pre-allocation of EBIs during registration establishes a continuous state where EBIs are already assigned and ready for use. This continuous availability of EBI information throughout the session establishment process eliminates the need for additional allocation signaling, reducing overhead while maintaining assignment accuracy.
Data Source
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AI summary
An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive (1202), by a first function, a request for establishing a data connection supporting interworking between a first radio access technology system and a second radio access technology system; allocate (1204), by a first function, at least one identifier identifying traffic within the data connection in the second radio access technology system; and cause (1208), by the first function, the at least one identifier to be sent to a second function.