Radio Link Failure Indication for Handover Optimization

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Solution Overview

Problem

In radio communications networks, the ambiguity in determining whether a re-establishment cell is successful or not during a radio link failure (RLF) leads to challenges in Mobility Robustness Optimization, as network nodes cannot accurately assess whether the re-establishment cell is a valid handover candidate, affecting network performance.

Innovation Solution

The solution involves enhancing RLF indications by including a first indication of the cell identity the UE was connected to and a second indication of the result of a comparison between this cell and the re-establishment cell, allowing network nodes to determine whether to consider the re-establishment cell for handover adjustments, thereby clarifying the success or failure of re-establishment attempts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the UE reports the cell ID of the re-establishment cell without indicating success or failure, then the reporting procedure is simple, but the network node cannot determine whether the re-establishment cell is a valid handover candidate

Engineering Contradiction:

Improvereporting procedure simplicityVSAvoidre-establishment outcome information

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

The RLF indication message is segmented to include separate information elements: one for the re-establishment cell ID and another for the re-establishment outcome (success/failure/rejected). This segmentation allows the network node to receive both pieces of information in a structured manner, resolving the ambiguity while maintaining procedural simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An intermediary indication element is introduced in the RLF indication message that mediates between the UE's simple cell ID report and the network's need for outcome information. This intermediary element carries the re-establishment outcome status, enabling the network to make informed decisions without complicating the UE's reporting procedure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If additional information is added to the RLF indication message to clarify re-establishment outcome, then the network can accurately assess re-establishment cell validity, but the message complexity increases

Engineering Contradiction:

Improvere-establishment assessment accuracyVSAvoidRLF indication message structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The RLF indication message structure is enhanced with local quality by adding specific information elements only where needed. The re-establishment outcome indicator is included as an optional or conditional element that appears only when relevant, maintaining message simplicity for common cases while providing enhanced precision when required.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The message structure parameters are changed to include an additional field indicating re-establishment outcome status. This parameter change allows the message to carry both the cell ID and the outcome information without fundamentally altering the message format, thus balancing precision improvement with complexity management.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the network node considers all reported re-establishment cells for handover optimization, then no valid candidates are missed, but incorrect cells may lead to suboptimal handover decisions

Engineering Contradiction:

Improvehandover optimization reliabilityVSAvoidincorrect handover decisions

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The network node performs preliminary filtering of re-establishment cells by checking the outcome indicator before including them in handover optimization. Cells with rejected or failed re-establishment outcomes are pre-filtered out, ensuring that only valid candidates are considered for handover adjustments, thus preventing incorrect optimization decisions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The re-establishment outcome information provides feedback to the network node about which cells are suitable for handover. This feedback mechanism allows the network to reliably identify valid handover candidates and exclude inappropriate ones, improving handover optimization reliability while avoiding harmful incorrect decisions.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10484916B2Network nodes and methods therein for handling communications in a radio communications network

Publication Date: 2019.11.19 GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP LTD

AI summary

A method performed by a network node for handling communications in a radio communications network is provided. The network node is configured to be in the radio communications network. The network node receives a report of a radio link failure (RLF) of a user equipment (UE), which report comprises an identity of a re-establishment cell, configures an RLF indication comprising the received report to further comprise a first indication of the cell identity of the current cell the UE is connected and/or a second indication of a result of a comparison between the cell identity of the cell the UE was connected to upon sending the RLF report and the identity of the re-establishment cell, and sends the RLF indication to another network node. A network node for handling communications in a radio communications network is also provided.