RAN Handover Control via Core Network Synchronization

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Solution Overview

Problem

Current 3GPP specifications for radio access network (RAN) selection do not adequately address situations where core network and UE status are not synchronized, leading to potential failures in completing necessary signaling procedures, such as location area updates and TMSI reallocation, when a UE is moved to a different RAN.

Innovation Solution

The core network instructs the current RAN to keep the UE connected for a configured time or until specific conditions are met, using messages and timers to prevent immediate movement to another RAN, ensuring synchronization and completion of critical procedures before handover.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the RAN moves the UE to another RAN based on static priority instructions, then the UE can be moved to a more suitable RAN, but the movement may occur before critical signaling procedures are completed

Engineering Contradiction:

ImproveRAN movement efficiencyVSAvoidsignaling completion reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The core network node sends a first message to the RAN node before the UE movement is executed, indicating that the UE should be kept in current access. This preliminary action ensures that critical signaling procedures are completed or synchronized before the UE is moved to another RAN, preventing signaling failures while maintaining efficient movement when appropriate.

Inventive Principle:

Principle #10Preliminary action

2Loss of time

If the UE is moved immediately to E-UTRAN after CSFB, then the return to LTE is faster, but location area update and TMSI reallocation procedures may fail

Engineering Contradiction:

Improvetime to return to LTEVSAvoidprocedure completion reliability

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The core network node provides indication information to the RAN node before UE movement, allowing the RAN to keep the UE in current access temporarily. This enables the UE to complete location area updates and TMSI reallocation procedures before being moved to E-UTRAN, ensuring procedure reliability while minimizing delay through controlled timing.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the RAN keeps the UE connected for a configured time, then signaling procedures can be completed, but the UE movement is delayed

Engineering Contradiction:

Improvesynchronization reliabilityVSAvoidUE movement delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The RAN node dynamically adjusts the UE movement timing based on received indication information from the core network. The configured time period is not fixed but adapted according to network conditions and signaling requirements, allowing optimal balance between completing synchronization procedures and minimizing UE movement delay.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9749906B2Controlling a movement of a mobile terminal between radio access networks

Publication Date: 2017.08.29 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Methods and apparatus for controlling a radio access handover with respect to a user equipment, UE, in a radio access domain from a first radio access network, RAN, to a second RAN are described. A radio access node of the first RAN receives a first message (M10) information to keep a radio connection to the UE. In reaction to the first message, a movement of the UE to the second RAN is inhibited, during a certain time period.