PDCP COUNT Reset for Multicast Session Reliability
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Solution Overview
Problem
The existing multicast and broadcast services in mobile scenarios face challenges with PDCP COUNT wrap-around issues, leading to data loss and complexity in handover processes, as the PDCP COUNT derived from core network sequence numbers does not reset properly, causing potential data loss and increased complexity in network management.
Innovation Solution
Implementing a mechanism where the core network resets and reinitializes the PDCP COUNT before it reaches the maximum value, by deactivating and reactivating the multicast session, ensuring seamless handover and minimizing data loss through synchronized sequence number management across gNBs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PDCP COUNT is derived from the core network sequence number and not allowed to wrap around, then data loss is avoided during normal operation, but the system becomes unable to handle long-running multicast sessions without manual intervention or complex workarounds
Solution Approach 1:
The patent applies preliminary action by having the gNB proactively detect when the PDCP COUNT is approaching its maximum value and trigger a session reactivation before wrap-around occurs. This advance detection and preparation allows the system to reset the COUNT value smoothly without data loss, enabling long-running multicast sessions to continue indefinitely.
Solution Approach 2:
The patent changes the state of the multicast session by deactivating and reactivating it, which resets the PDCP COUNT parameter. This parameter change allows the system to maintain reliability for long-duration sessions by periodically refreshing the COUNT value through session reactivation, transforming a finite system into one that can operate indefinitely.
2Reliability
If the gNB releases and adds a new MRB when the PDCP COUNT is near maximum, then the COUNT can be reset, but this causes delay and extra complexity in gNB operations
Solution Approach 1:
The patent applies self-service by enabling the gNB to autonomously detect the approaching PDCP COUNT maximum and automatically trigger session reactivation without external intervention. This self-managed mechanism reduces operational complexity by embedding the wrap-around prevention logic directly in the gNB, eliminating the need for manual MRB management or complex external coordination.
3Reliability
If the core network releases and adds multicast session before PDCP COUNT wraps around, then wrap-around is avoided, but this requires implementation complexity in the core network
Solution Approach 1:
The patent inverts the traditional approach by moving the wrap-around prevention responsibility from the core network to the gNB. Instead of the core network monitoring and managing PDCP COUNT values, the gNB performs local detection and triggers session reactivation autonomously. This inversion simplifies core network implementation while maintaining reliability.
4Reliability
If data forwarding and PDCP status reports are used during lossless handover, then data loss is minimized, but the handover process becomes more complex
Solution Approach 1:
The patent extracts the handover complexity from the lossless handover mechanism by using session reactivation as a separate, independent process. Instead of complicating the handover procedure with data forwarding and status reports, the system uses the reactivated session to provide fresh data, simplifying the handover process while maintaining data integrity.
Data Source
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AI summary
There are provided measures for improvement of multicast and broadcast services in mobile scenarios. Such measures exemplarily comprise, at a user plane function entity in a mobile network, resetting sequence numbers corresponding to one or several multicast and broadcast service flows out of all multicast and broadcast service flows of a multicast and broadcast service session, and transmitting information indicative of said resetting.