Multicast Session Join in RRC Inactive State Using SDT

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Solution Overview

Problem

In 3GPP Release 17, multicast reception in a user equipment (UE) is limited to the RRC connected state, leading to increased load when transitioning to RRC connected state for session join processing in RRC inactive state, which is inefficient and undesirable for load reduction.

Innovation Solution

The UE employs a small data transmission (SDT) technique to perform session join processing while maintaining the RRC inactive state, utilizing random access SDT (RA-SDT) and receiving necessary configurations via system information or multicast control channels to facilitate multicast reception.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If session join processing is performed in RRC connected state, then multicast reception can be achieved, but network and UE load increases due to state transitions

Engineering Contradiction:

Improvemulticast reception capabilityVSAvoidnetwork load

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies preliminary action by enabling the UE to perform session join processing while in RRC inactive state before transitioning to RRC connected state. This is achieved by allowing the UE to send session join requests and receive multicast session information while maintaining the inactive state, thus avoiding unnecessary state transitions and reducing network load while ensuring multicast reception capability

Inventive Principle:

Principle #10Preliminary action

2Productivity

If session join processing is performed in RRC inactive state using SDT technique, then network and UE load is reduced, but requires specific technical support and configuration

Engineering Contradiction:

Improvenetwork load reductionVSAvoidstate operation flexibility

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by making the SDT technique configurable and adaptable. The network can dynamically control whether SDT is permitted for session join processing through configuration parameters transmitted to the UE. This allows the system to adapt between traditional connected-state processing and inactive-state SDT processing based on network conditions and capabilities, achieving load reduction while maintaining flexibility

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20260067980A1Communication method, user equipment, and network node

Publication Date: 2026.03.05 KYOCERA CORP

AI summary

A communication method performed by a user equipment in a mobile communication system for providing a multicast/broadcast service (MBS), the communication method including: receiving information from a base station, the information relating to whether session join processing of joining a multicast session is permitted to be executed using a small data transmission (SDT) technique of performing communication with the base station while maintaining a radio resource control (RRC) inactive state; and executing the session join processing using the SDT technique while maintaining the RRC inactive state, based on the information indicating that the session join processing is permitted to be executed using the SDT technique.