Master Cell Group Handover Using Shared UE Context and SN Retention

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Solution Overview

Problem

In wireless communications systems, there is a lack of mechanism for a target master base station to share UE context information, including secondary node information, with the source master base station during a state change, leading to increased latency in data path establishment when a user equipment (UE) switches from an RRC connected state to an RRC inactive state.

Innovation Solution

The source master base station shares UE context information, including secondary node information, with a target master base station, enabling the target base station to determine whether to maintain or release the secondary base station, thereby improving delta signaling and facilitating faster data path establishment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the target master base station does not have access to UE context information including secondary node information, then the system maintains simpler signaling procedures, but latency in data path establishment increases when UE switches from RRC connected state to RRC inactive state

Engineering Contradiction:

Improvelatency in data path establishmentVSAvoidsignaling procedure complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The source master base station performs preliminary actions by sharing UE context information including secondary node information with the target master base station before the UE state change is complete. This advance preparation allows the target base station to have the necessary information ready, reducing the latency during the actual state transition without significantly increasing ongoing signaling complexity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The source master base station acts as an intermediary by transferring UE context information to the target master base station. This intermediary action enables the target base station to obtain necessary context information without the UE itself needing to re-transmit or re-negotiate the information, thereby reducing latency in the data path establishment process.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the target master base station maintains the same secondary base station, then power saving and reliability are improved, but the complexity of context information management increases

Engineering Contradiction:

Improvereliability of wireless communicationsVSAvoidcontext information management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The target master base station receives a copy of the UE context information including secondary node information from the source master base station. This copying mechanism allows the target base station to maintain the same secondary base station configuration without requiring complex real-time negotiation or re-establishment procedures, thereby improving reliability while keeping the complexity manageable through information replication.

Inventive Principle:

Principle #26Copying

3Productivity

If UE context information is shared between master base stations, then faster data path establishment is achieved, but the amount of information that needs to be managed and transmitted increases

Engineering Contradiction:

Improvedata path establishment speedVSAvoidamount of context information

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The source master base station extracts only the essential UE context information including secondary node information that is necessary for the target base station to maintain continuity. By selectingively transmitting only the critical information elements rather than the complete UE context, the patent achieves faster data path establishment while limiting the quantity of information that needs to be managed and transmitted.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS12526706B2Techniques for wireless communications with a master node in a master cell group without a change in a secondary node in a secondary cell group

Publication Date: 2026.01.13 QUALCOMM INC

AI summary

Techniques for wireless communications are described. A communication device, for example, a user equipment (UE) may transmit a request message to a target master base station based on a change in a state of the UE, and receive a response message from the target master base station based on the transmitted request message from the UE. The response message may include secondary node (SN) information and UE context reference shared to the target master base station from a source master base station (also referred to as a primary base station). The SN information corresponding to the same secondary base station associated with the UE while previously connected to the source master base station. The UE context reference may be stored at the same secondary base station.