UE Multicast Reception in RRC Inactive State

Solution Overview

Problem

Existing multicast and broadcast services (MBS) in 3GPP standards face inefficiencies and network congestion due to the need for user equipment (UE) to maintain a radio resource control (RRC) connected state for Hybrid Automatic Repeat Request (HARQ) and reporting, which is power inefficient and increases congestion.

Innovation Solution

Methods for user equipment (UE) and access network nodes to maintain point-to-multipoint (PTM) transmission configurations while in an RRC inactive state, allowing UE to receive multicast transmissions efficiently by keeping RLC configurations and determining when to enter RRC connected or inactive states based on stored multicast configuration information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If UE maintains RRC connected state for multicast reception, then reliability of multicast service is improved, but power consumption increases and network congestion worsens

Engineering Contradiction:

Improvereliability of multicast serviceVSAvoidpower consumption of UE

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements dynamic state transitions between RRC connected and inactive states based on multicast service requirements. The network can configure UE to transition to inactive state while maintaining multicast reception capability through stored configuration parameters, allowing the system to adapt between reliability and power efficiency based on service conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the operational parameters of UE by storing RLC configuration parameters and multicast reception parameters in inactive state. This allows the UE to maintain essential multicast reception capabilities without the overhead of full RRC connection, reducing power consumption while preserving service reliability

Inventive Principle:

Principle #35Parameter changes

2Reliability

If UE maintains RRC connected state for multicast reception, then reliability of multicast service is improved, but network congestion increases

Engineering Contradiction:

Improvereliability of multicast serviceVSAvoidnetwork congestion

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent implements dynamic state transitions between RRC connected and inactive states based on multicast service requirements. The network can configure UE to transition to inactive state while maintaining multicast reception capability through stored configuration parameters, allowing the system to adapt between reliability and power efficiency based on service conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent extracts the essential multicast reception parameters (RLC configuration, multicast reception parameters) from the full RRC connection context. By storing only the necessary parameters in inactive state, the system maintains multicast service reliability while removing the overhead that causes network congestion

Inventive Principle:

Principle #2Taking out (Extraction)

3Use of energy by moving object

If UE enters RRC inactive state for power saving, then power consumption is reduced, but ability to receive multicast transmission deteriorates

Engineering Contradiction:

Improvepower consumption of UEVSAvoidability to receive multicast transmission

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies preliminary action by storing essential RLC configuration parameters and multicast reception parameters in the inactive state before the UE fully transitions to power-saving mode. This pre-storation of critical parameters ensures that when the UE needs to receive multicast transmissions, it can do so immediately without full connection establishment, maintaining service reliability while enabling power saving

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the operational parameters of UE by storing RLC configuration parameters and multicast reception parameters in inactive state. This allows the UE to maintain essential multicast reception capabilities without the overhead of full RRC connection, reducing power consumption while preserving service reliability

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20260107293A1Method for user equipment, method for access network node, user equipment, and access network node

Publication Date: 2026.04.16 NEC CORP

AI summary

A method for a user equipment, UE, (3) is disclosed. The method includes: receiving, from an access network node (5), a message for causing the UE (3) to move to a radio resource control, RRC, inactive state, the message including information indicating that the UE (3) can keep configuration for a point-to-multipoint, PTM, transmission of a multicast while the UE (3) is in the RRC inactive state; and keeping the configuration for the PTM transmission while the UE (3) is in the RRC inactive state, based on the information.