UE Reachability Notification in Mobile Communications
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Solution Overview
Problem
In mobile communications, there is an uncertainty about when user equipment (UE) becomes reachable again after sending a NOTIFICATION RESPONSE message, leading to delays in downlink data transfer as the Session Management Function (SMF) is not notified of the UE's availability, causing inefficiencies in 3GPP access network connectivity.
Innovation Solution
The UE implements methods to indicate its reachability over 3GPP access after network availability, either by initiating a connection establishment procedure or sending a message over non-3GPP access, using timers or specific information elements to manage notification responses and connection states, allowing for timely data transfer resumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the UE enters 5GMM-REGISTERED.NORMAL-SERVICE state after camping on a cell in registered TA list, then the UE can maintain idle mode without initiating connection establishment, but the AMF remains unaware of UE reachability and DL data transfer is delayed
Solution Approach 1:
The UE performs a preliminary service acceptance action by entering 5GMM-REGISTERED.NORMAL-SERVICE state when camping on a registered TA, which prepares the UE for potential future data transfer while avoiding immediate connection establishment. This preliminary state transition resolves the contradiction by allowing the UE to conserve energy while the network can later page the UE when data arrives, eliminating the need for continuous connection maintenance.
2Loss of information
If the UE does not initiate connection establishment when in NORMAL-SERVICE state, then the UE avoids unnecessary signaling overhead, but the network cannot determine when the UE is reachable for data transfer
Solution Approach 1:
The system implements a feedback mechanism where the AMF maintains awareness of UE reachability through the notification response exchange. When the UE sends a notification response indicating it can be reached via 3GPP access, the AMF stores this reachability information. This feedback loop resolves the contradiction by providing the network with reliable reachability information without requiring continuous connection establishment or excessive signaling from the UE.
3Reliability
If the SMF refrains from requesting DL data transfer when UE is unreachable, then the network avoids failed data delivery attempts, but data transfer is delayed until reachability is confirmed
Solution Approach 1:
The notification response mechanism performs a preliminary action by having the UE proactively indicate its reachability status to the network before actual data transfer occurs. This allows the SMF to maintain an updated view of UE accessibility, enabling faster resumption of data transfer when the UE becomes reachable again, thus resolving the contradiction between avoiding failed deliveries and maintaining transfer efficiency.
Data Source
AI summary
Examples pertaining to user equipment (UE) reachability after notification in mobile communications are described. An apparatus (e.g., UE) receives an indication to initiate a notification procedure from a network over a non-3rd Generation Partnership Project (non-3GPP) access while a 3GPP access with the network is unavailable. In response, the apparatus transmits a notification response message to the network. After the 3GPP access with the network becomes available, the apparatus indicates to the network that the apparatus is reachable over the 3GPP access.