Multicast Broadcast Service Continuity in RRC Inactive Mobility
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Solution Overview
Problem
Current New Radio (NR) standards lack support for broadcast/multicast features, leading to service continuity issues during mobility, particularly for UEs in RRC_INACTIVE state, resulting in data loss and interruptions when moving to a new cell/node.
Innovation Solution
The proposed solution enables RRC_INACTIVE UEs to report data loss and allows for cooperative handling between the current and new network nodes, minimizing data loss by maintaining PDCP sequence numbers and using efficient signaling to ensure seamless service continuity during mobility, with options for retransmitting missing packets and configuring RLC modes for reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If UEs in RRC_INACTIVE state move to a new cell/node during multicast service, then mobility is enabled, but data loss and service interruption occur
Solution Approach 1:
The source gNB performs preliminary actions by determining the last PDCP sequence number before the UE enters RRC_INACTIVE state and includes this information in the RRC release message. This preliminary setup enables the target gNB to quickly synchronize and resume data transmission without causing data loss when the UE moves to a new cell.
Solution Approach 2:
The UE provides feedback by reporting the first PDCP sequence number of missing MBS data to the network after resuming from RRC_INACTIVE state. This feedback mechanism enables the network to identify and retransmit missing data packets, ensuring complete data delivery and maintaining service reliability during mobility.
2Reliability
If cooperative handling between source and target network nodes is implemented, then data loss is minimized, but signaling overhead increases
Solution Approach 1:
The patent extracts only the essential information needed for service continuity - specifically the last PDCP sequence number - and includes it in the RRC release message from source to target gNB. This selective extraction minimizes signaling overhead while providing sufficient information for the target gNB to resume data transmission without requiring extensive cooperative signaling between network nodes.
3Reliability
If PDCP sequence numbers are maintained during mobility, then data loss is reduced, but system complexity increases
Solution Approach 1:
The UE performs self-service by autonomously determining and reporting the first PDCP sequence number of missing MBS data to the network after resuming from RRC_INACTIVE state. This self-service approach enables the UE to identify its own data loss without requiring complex network-side tracking mechanisms, thereby reducing overall system complexity while maintaining data loss prevention.
Data Source
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AI summary
The present application generally relates to wireless communication technology. More particularly, the present application relates to a method and apparatus for providing service continuity for Multicast and Broadcast Service (MBS). The present application also relates to computer program product adapted for the same purpose. According to one embodiment of the present application, a method in a first RAN node for providing service continuity for Multicast and Broadcast Service (MBS) comprises: receiving (510) from a UE a request for retransmitting one or more missing Packet Data Units (PDUs) in MBS data associated with an MBS session previously transmitted from a second RAN node to the UE; and handling (520) retransmission of the missing PDUs based on the request.