Multicast Bearer Handover Across RRC Inactive and Connected States
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Solution Overview
Problem
In the 3GPP Release 17 specifications, multicast reception in a user equipment (UE) is limited to the RRC connected state, which can lead to interruptions and loss of multicast data when transitioning to the RRC inactive state, compromising the continuity of multicast reception.
Innovation Solution
The UE maintains a first multicast radio bearer (MRB) during the RRC inactive state and receives a point-to-multipoint (PTM) configuration for a second MRB upon transitioning to the RRC connected state, ensuring continuous multicast reception by maintaining or discarding the first MRB based on specific conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multicast reception is limited to RRC connected state as per 3GPP Release 17 specifications, then device complexity is reduced and ease of operation is maintained, but multicast data continuity is lost during state transitions
Solution Approach 1:
The network configures the first MRB for multicast reception before the UE transitions to RRC inactive state. This preliminary configuration allows the UE to maintain multicast reception capability without establishing a full RRC connection, thereby ensuring continuity while avoiding the complexity of frequent state transitions.
Solution Approach 2:
The patent implements dynamic bearer management where the UE maintains the first MRB during RRC inactive state and can transition to a second MRB upon receiving PTM configuration in RRC connected state. This dynamic adaptation allows the system to optimize between reliability and complexity based on current operational conditions.
2Reliability
If the UE transitions from RRC inactive state to RRC connected state, then multicast reception reliability can be improved, but service interruption occurs during the transition process
Solution Approach 1:
The first MRB is configured to maintain multicast reception continuity during the transition from RRC inactive to connected state. By keeping the bearer active and using it for reception throughout the transition period, the patent eliminates service interruptions while still allowing the UE to benefit from improved reliability in connected state.
Solution Approach 2:
The first MRB acts as an intermediary bearer that bridges the gap between RRC inactive and connected states. It allows multicast reception to continue seamlessly during the transition, serving as a temporary bridge until the second MRB is established in the connected state.
3Reliability
If the UE maintains the first MRB after transitioning to RRC connected state, then multicast data continuity is preserved, but resource efficiency decreases due to redundant bearers
Solution Approach 1:
Upon transitioning to RRC connected state and receiving PTM configuration for the second MRB, the UE discards the first MRB to eliminate redundancy. This ensures that only one active bearer exists at any time, optimizing radio resource efficiency while maintaining session continuity through the transition process.
Solution Approach 2:
The patent changes the operational parameters of the MRB based on the RRC state. In inactive state, the first MRB is maintained with specific parameters optimized for that state. Upon transitioning to connected state, the parameters change as the second MRB is configured, automatically adjusting resource usage to match current operational requirements.
Data Source
AI summary
A communication method performed by a user equipment in a mobile communication system providing a multicast/broadcast service (MBS) includes receiving a multicast session in a radio resource control (RRC) inactive state from a network by using a first multicast radio bearer (MRB) for the RRC inactive state, maintaining the first MRB until a predetermined condition is satisfied even after transitioning from the RRC inactive state to an RRC connected state, and receiving point-to-multipoint (PTM) configuration in the RRC connected state from the network, the PTM configuration including a configuration of a second MRB for receiving the multicast session in the RRC connected state. The predetermined condition includes receiving, by the user equipment, the PTM configuration from the network.