Multicast Radio Bearer Switching Across RRC Connected and Inactive States
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Solution Overview
Problem
Existing 3GPP specifications limit multicast reception in 5G NR systems to user equipment in an RRC connected state, restricting the efficiency and flexibility of multicast services, particularly with the introduction of RRC inactive state support in 3GPP Release 18.
Innovation Solution
A communication method and user equipment design that enables multicast session reception in the RRC inactive state by transitioning from an RRC connected state using a first MRB, establishing a second MRB with configuration information from an RRC release message, and suspending the first MRB to maintain continuous multicast service.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If user equipment transitions to RRC inactive state to save resources, then energy consumption is reduced, but multicast reception capability is lost
Solution Approach 1:
The network provides configuration information for the second MRB in advance within the RRC release message before the UE transitions to inactive state. This preliminary configuration enables the UE to quickly establish multicast reception capability upon transitioning, avoiding the need to reconfigure from scratch and ensuring seamless service continuity while in the low-power inactive state
Solution Approach 2:
The patent creates a parallel multicast reception mechanism by establishing a second MRB specifically for inactive state operation. Instead of relying on the first MRB designed for connected state, the system copies the essential multicast reception functionality into a separate bearer structure that can operate independently in the inactive state, ensuring capability preservation while enabling energy savings
2Device complexity
If a single MRB is used for multicast reception, then device complexity is reduced, but service continuity during state transition is interrupted
Solution Approach 1:
The patent segments the multicast bearer functionality into two distinct structures: the first MRB optimized for RRC connected state operations and the second MRB optimized for RRC inactive state operations. This segmentation allows each bearer to be independently configured and activated based on the current RRC state, ensuring seamless service continuity during transitions while keeping each individual bearer structure relatively simple
Solution Approach 2:
The system dynamically switches between the first MRB and second MRB based on the UE's RRC state. The network controls this dynamic behavior by providing appropriate configuration information in RRC release messages, enabling the UE to activate the second MRB when transitioning to inactive state and deactivate it when returning to connected state, thus adapting the bearer structure to current operational requirements
Data Source
AI summary
A communication method performed by a user equipment in a mobile communication system that provides a multicast/broadcast service (MBS) includes receiving a multicast session from a network in a radio resource control (RRC) connected state using a first multicast radio bearer (MRB) for the RRC connected state, receiving, from the network, an RRC release message for causing the user equipment to transition to an RRC inactive state, the RRC release message including configuration information indicating a configuration of a second MRB used for reception of the multicast session in the RRC inactive state, and establishing the second MRB by applying the configuration information before suspending the first MRB in response to the reception of the RRC release message.