Multicast UE State Transition Management in 5G RRC Inactive
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Solution Overview
Problem
Current wireless communication systems face challenges in managing state transitions, service continuity, and packet data convergence protocol (PDCP) synchronization for multicast user equipment (UE) in wireless networks, particularly when UEs transition to a radio resource control (RRC) inactive state or select MCCH-less cells.
Innovation Solution
The method involves performing cell selection and detection of cell changes during RRC state transitions, determining the availability of point-to-multipoint (PTM) configurations on selected cells, and initiating an RRC connection resume procedure to maintain multicast sessions and PDCP synchronization across cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the UE transitions to RRC inactive state to save energy and reduce complexity, then power consumption and device complexity are reduced, but service continuity and PDCP synchronization may be disrupted
Solution Approach 1:
The network performs preliminary actions by providing PDCP synchronization information and configuration parameters to the UE before the UE transitions to RRC inactive state. This includes providing PDCP COUNT values, PTM configuration information, and cell reselection priorities in advance, enabling the UE to maintain multicast service continuity without full RRC connection establishment upon returning to active state
Solution Approach 2:
The patent introduces an intermediary mechanism where the network stores and manages PDCP synchronization context information for the UE during its inactive state. This intermediary storage allows the network to quickly restore PDCP synchronization without requiring complete re-establishment of the radio connection, thus maintaining service continuity while the UE remains in low-power state
2Reliability
If the UE performs cell selection and reselection to maintain connectivity, then service availability is improved, but PDCP synchronization and multicast session continuity may be lost
Solution Approach 1:
The network provides feedback to the UE about PDCP synchronization status and cell reselection priorities through system information blocks and dedicated signaling. The UE uses this feedback information to perform cell reselection while maintaining awareness of PDCP synchronization requirements, and the network provides further feedback to confirm synchronization restoration after cell reselection
Solution Approach 2:
The network provides preliminary cell reselection information including PDCP synchronization status, PTM configuration validity, and neighbor cell priorities before the UE performs cell reselection. This allows the UE to select target cells that maintain PDCP synchronization and multicast service continuity without requiring re-establishment of the radio connection
3Reliability
If the UE maintains RRC connected state to ensure multicast service continuity, then service reliability is improved, but power consumption and network resource usage increase
Solution Approach 1:
The patent applies local quality by providing differentiated treatment for different UEs based on their multicast service requirements. UEs with active multicast sessions receive specific PDCP synchronization information and configuration parameters that enable them to transition to RRC inactive state while maintaining service continuity, whereas other UEs follow standard procedures. This localized optimization reduces power consumption for multicast-capable UEs without compromising service reliability
4Reliability
If the network provides detailed PTM configuration information to maintain multicast sessions, then service continuity is improved, but signaling overhead and network complexity increase
Solution Approach 1:
The patent applies universality by using existing RRC signaling structures and information elements to convey PDCP synchronization and PTM configuration information, rather than introducing entirely new signaling protocols. The same RRC Release message structure used for standard connection release is extended to include multicast-specific parameters, reducing network complexity while maintaining enhanced service continuity capabilities
Data Source
AI summary
The disclosure relates to a fifth generation (5G) or sixth generation (6G) communication system for supporting a higher data transmission rate. A method and a system for manage state transitions of a multicast broadcast service (MBS) user equipment (UE), manage a service continuity of the multicast UE, and manage packet data convergence protocol (PDCP) synchronizations of the multicast UE in a wireless network are provided. A radio resource control (RRC) connection resume procedure is initiated when point-to-multipoint (PTM) configurations are not available in a cell after cell selection and/or cell reselection, and the UE has at least one activated session in the RRC_INACTIVE state. The RRC connection resume procedure is also initiated when the cell after cell selection and/or cell reselection is an MBS control channel (MCCH)-less cell and the UE has at least one activated session (for example, indicated to monitor G-RNTI) in the RRC_INACTIVE state. Further, multicast MRBs are handled during motility by providing a mechanism for multicast reception across cells in the radio access network (RAN) notification area (RNA), where PDCP synchronizations are indicated or not indicated in the multicast session.