RAN Multicast Group Joining for Dynamic Unicast-Multicast Switching
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Solution Overview
Problem
Existing wireless communication systems face inefficiencies in managing multicast and broadcast services, leading to inefficient use of radio resources and degradation of user experience due to the lack of dynamic switching between multicast and unicast modes, particularly for UEs in RRC_CONNECTED state.
Innovation Solution
A Central Unit (CU)-User Plane (UP) of a RAN node performs Multicast Listener Discovery (MLD) and/or Internet Group Management Protocol (IGMP) Join procedures to efficiently manage multicast and broadcast services, allowing dynamic switching between unicast and multicast modes based on the number of connected UEs and resource availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multicast/broadcast service delivery is changed dynamically between multicast and unicast modes, then resource utilization is improved and service continuity is maintained, but system complexity increases due to the need for coordination functions and switching mechanisms
Solution Approach 1:
The RAN node is divided into two functional units: CU-CP (Control Plane) and CU-UP (User Plane). The CU-CP handles control functions including deciding when to switch between multicast and unicast modes, while the CU-UP handles user data transmission. This segmentation allows complex switching decisions to be made by the control plane without burdening the user plane, resolving the contradiction between dynamic switching capability and system complexity.
Solution Approach 2:
The CU-CP acts as an intermediary between the network controller and the CU-UP. It receives control decisions from the network controller regarding multicast/unicast switching and translates them into appropriate actions for the CU-UP. This intermediary layer simplifies the overall system architecture by centralizing control logic while maintaining operational flexibility.
2Reliability
If multicast channel is used continuously for broadcast services, then service availability is improved, but radio resources are used inefficiently when few UEs receive the service
Solution Approach 1:
The system dynamically switches between multicast and unicast modes based on the number of UEs receiving the service and current resource conditions. When multiple UEs are receiving, multicast mode is used to efficiently share resources. When few UEs are receiving, the system switches to unicast mode to avoid wasting radio resources on broadcast transmissions with minimal audience, thus resolving the contradiction between service availability and resource efficiency.
Solution Approach 2:
The system changes the transmission mode parameter (multicast vs. unicast) based on the number of active UEs and resource availability conditions. This parameter change allows the system to adapt to varying traffic conditions, using multicast when beneficial for resource efficiency and unicast when it better serves resource utilization, thereby resolving the contradiction between maintaining service availability and optimizing radio resource efficiency.
3Device complexity
If multicast service is provided without dynamic switching capability, then system complexity is reduced, but user experience degrades due to lack of service continuity during mode changes
Solution Approach 1:
By segmenting the RAN node into CU-CP and CU-UP with clearly defined responsibilities, the system can implement complex service continuity management in the CU-CP without making the overall system unmanageably complex. The CU-CP handles the complexity of coordinated switching between multicast and unicast modes to ensure seamless service continuity, while the CU-UP focuses on efficient data transmission.
Solution Approach 2:
The system implements feedback mechanisms where the CU-CP monitors the status of ongoing multicast/unicast services and makes real-time decisions about mode switching. This feedback-driven approach ensures that transitions between modes are smooth and maintain service continuity, preventing user experience degradation while managing system complexity through intelligent control.
Data Source
AI summary
A method and apparatus for multicast and broadcast service in a wireless communication system is provided. A CU-UP of a RAN node receives, from a CU-CP of the RAN node, a first message to join a multicast group for a MB service. A CU-UP of a RAN node performs the MLD and/or IGMP Join procedure for the MB service indicated by the identity for the MB service along with an MB-UPF based on the LL MC address. A CU-UP of a RAN node transmits, to the CU-CP of the RAN node, a second message including a Join Complete Indication informing that joining the multicast group for the MB service is completed.