5G MBS Handover Using PDU Session Fallback and QoS Sync
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Solution Overview
Problem
In 5G networks, user equipment (UE) moving from a base station supporting multicast broadcast service (MBS) to one that does not support MBS requires a wasteful transition to unicast mode, leading to resource inefficiencies due to unpredictable handovers and potential long delays.
Innovation Solution
The method involves triggering PDU session establishment on the target base station after handover, synchronizing QoS flows with the activated MBS session, and maintaining MBS continuity by avoiding immediate association with the PDU session, allowing asynchronous unicast handovers when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE associates MBS session with PDU session immediately upon activation to support handover, then service continuity is maintained, but PDU session resources are wasted due to premature establishment
Solution Approach 1:
The patent applies preliminary action by establishing the PDU session before the MBS session is activated. The network pre-configures the PDU session with the target base station, so that when handover occurs, the session is already ready and can be immediately associated with the MBS service, avoiding both service interruption and resource waste from delayed establishment
Solution Approach 2:
The patent implements dynamic session management where the association between MBS session and PDU session is not fixed but adaptable. The system dynamically determines whether to maintain multicast mode or switch to unicast mode based on target base station capabilities, and the PDU session can be established, modified, or released based on actual handover needs rather than being statically pre-configured
2Loss of energy
If the UE delays PDU session establishment until after handover to avoid resource waste, then resource efficiency improves, but service continuity may be compromised due to handover timing uncertainty
Solution Approach 1:
The network performs preliminary actions by pre-establishing the PDU session with the target base station before the actual handover occurs. This allows the session to be ready in advance, ensuring that when the UE completes handover, the PDU session is already configured and can immediately support MBS data transmission, thus maintaining service continuity without delaying resource allocation
Solution Approach 2:
The system uses feedback mechanisms where the network monitors UE location, handover status, and target base station capabilities to dynamically adjust PDU session establishment timing. The network receives feedback about handover completion and MBS session activation status, and based on this feedback, it determines the optimal moment to establish or modify the PDU session, balancing resource efficiency with service continuity
3Adaptability or versatility
If the system establishes PDU session immediately upon MBS activation to support any future handover, then handover readiness is ensured, but system resources are consumed unnecessarily for handovers that may not occur for long periods
Solution Approach 1:
The patent implements dynamic session management where the PDU session establishment is not a static immediate action but an adaptive process. The system dynamically evaluates handover likelihood based on UE mobility patterns, target base station MBS support capabilities, and current network conditions. The PDU session is established or modified only when actually needed for handover, rather than being proactively created for all potential future handovers, thus optimizing resource usage while maintaining handover readiness when required
Data Source
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AI summary
Provided in the embodiments of the present disclosure are a method for realizing the handover of a multicast and broadcast service, and a related device. The method is applied to a user equipment. A source base station accessed by the user equipment before handover supports an MBS, and the user equipment has established, but not activated, an MBS session at the source base station before handover. The method comprises: receiving a handover completion indication sent by a target base station, wherein the handover completion indication is used for indicating that a user equipment has been handed over to the target base station; if it is determined that the target base station does not support an MBS, triggering the establishment of a PDU session on a target base station side, so that an SMF subscribes to an MB-UDM, wherein an S-NSSAI of the PDU session is the same as an S-NSSAI of an MBS session, and a DNN of the PDU session is the same as a DNN of the MBS session; and when the MBS session is activated, executing a triggered modification process of the PDU session, so that the SMF acquires quality-of-service flow information corresponding to the activated MBS session, so as to establish, on the PDU session, a quality-of-service flow corresponding to the activated MBS session, there being one or more pieces of quality-of-service flow information comprised.