QoS Flow Mapping for 5G Handover Call Continuity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In 5G networks, mobile devices experience call failures during handovers between 4G and 5G due to missing mapping of EPS bearer indicators (EBI) and QoS-Flow-Identifier (QFI) parts of QoS Flow-Descriptions, leading to deletion of EPS bearers and subsequent call drops.
Innovation Solution
A method is implemented where the Session Management Function (SMF) ensures that the user equipment (UE) receives QoS-Flow-Identifier (QFI) to EBI mapping when in a 4G RAT, by sending an update bearer request message with QoS information during inter-RAT handovers, preventing the deletion of EPS bearers and maintaining connection continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the UE deletes QoS flow description during handover to 5G, then the handover process is simplified, but the call continuity is lost and call failures occur
Solution Approach 1:
The network side performs preliminary actions by sending the QoS flow description information to the UE before the handover is completed. The SMF includes QoS information in the PDU session establishment accept message, ensuring the UE has the necessary mapping information before deleting the old QoS flow description during handover, thus preventing call failures.
Solution Approach 2:
The system implements feedback by having the UE report its QoS flow description state to the network, and the network responding by providing updated QoS information. This feedback loop ensures the UE maintains correct QoS mapping information across handovers between 4G and 5G networks.
2Reliability
If the UE maintains QoS flow description mapping information, then call continuity is preserved, but the information management complexity increases
Solution Approach 1:
The UE autonomously manages its QoS flow description by locally storing the QoS information received from the network and using it to maintain proper mapping relationships. The UE self-updates its QoS flow description based on network-provided information without requiring complex network-side coordination for each handover event.
Solution Approach 2:
The QoS flow description mechanism is designed to be universal across different radio access technologies (4G and 5G). The same QoS information structure and management principles apply whether the UE is connected to LTE or NR, simplifying the overall system design while maintaining call continuity across RAT boundaries.
3Measurement precision
If the network sends QoS update messages frequently, then the QoS mapping accuracy is maintained, but the signaling overhead increases
Solution Approach 1:
Instead of sending complete QoS updates in every handover scenario, the system uses partial updates only when necessary. The network sends QoS flow description information selectively based on the handover type and UE state, avoiding unnecessary signaling while maintaining sufficient accuracy for call continuity.
Solution Approach 2:
The system changes the QoS information parameters dynamically based on the network situation. The SMF adjusts what QoS information is included in update messages depending on whether the handover is intra-RAT or inter-RAT, and whether the UE is in 4G or 5G, optimizing the balance between accuracy and signaling overhead.
Data Source
AI summary
Disclosed are systems, apparatuses, methods, and computer-readable media to address bearer loss during inter-radio access technology (RAT) handovers. A method includes sending a create bearer request for establishing a service for the mobile device using a first connection; receiving a create bearer response message to setup a second connection for the mobile device to continue the service; and, in response to the create bearer response message, sending an update bearer request message to provide the mobile device with the QoS information associated with the second connection, the QoS information allowing the mobile device to verify an existing QoS flow to continue the service after the handover. In some cases, a user equipment (UE) may delete a mapping between a QoS information when a previous message does not include an evolved packet core (EPC) bearer indicator (EBI) that identifies QoS policies.