LTM Fallback Configuration for RLF and HO Failure Handling
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Solution Overview
Problem
Existing technologies face challenges in efficiently handling Radio Link Failure (RLF) and LTM Handover (HO) failures in User Equipment (UE), leading to costly RRC re-establishment and data transfer interruptions.
Innovation Solution
A method is introduced to prepare a fallback configuration for UE by identifying L1/L2 Triggered Mobility (LTM) candidate cells, predicting HO or RLF failures, and preparing a fallback LTM or Conditional Handover (CHO) configuration. This configuration allows the UE to autonomously perform a cell switch without explicit network commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RRC re-establishment is performed in case of LTM HO failure, then the UE can recover from failure, but the network cost and data transfer interruption increase
Solution Approach 1:
The network pre-configures fallback configurations for candidate cells before handover execution. When LTM HO failure occurs, the UE can immediately activate the pre-prepared fallback configuration without needing to perform expensive RRC re-establishment procedures, thus reducing recovery time and maintaining data transfer continuity
Solution Approach 2:
The fallback configuration acts as an intermediary solution between normal LTM HO operation and expensive RRC re-establishment. It provides a middle-ground recovery mechanism that allows the UE to switch to a candidate cell using pre-configured parameters, avoiding the need for full RRC re-establishment while still recovering from HO failure
2Loss of energy
If multiple LTM candidate cells are configured without resource reservation, then the network resources are optimized, but the UE cannot autonomously select candidate cells when needed
Solution Approach 1:
The patent applies different resource reservation strategies to different candidate cells based on their individual characteristics and failure predictions. Instead of uniformly reserving resources for all candidate cells, the network selectively prepares fallback configurations only for cells that are predicted to be suitable targets, optimizing resource usage while maintaining autonomous selection capability where needed
3Speed
If RACH preamble is reserved at target cell configuration preparation, then the UE can perform RACH immediately, but the resource reservation cannot account for beam changes
Solution Approach 1:
The fallback configuration includes dynamic parameters that allow the UE to adapt to beam changes at the candidate cell. Instead of reserving a fixed RACH preamble that assumes a specific beam, the configuration enables the UE to select or adjust the RACH preamble based on the actual beam conditions when the UE arrives at the candidate cell, thus maintaining both speed and adaptability
Data Source
AI summary
A fallback configuration is prepared for one of a Radio Link Failure (RLF) or a handover (HO) failure of a User Equipment (UE). Layer 1 (L1)/Layer 2 (L2) Triggered Mobility (LTM) candidate cells are identified for fallback. An HO failure or an RLF is predicted for LTM target cells and at least one of a fallback LTM configuration or a fallback Conditional Handover (CHO) configuration is prepared for a target cell selected from the one or more LTM candidate cells. The UE is provided with the at least one of the prepared fallback LTM configuration or the fallback CHO configuration for the target cell. Control information is sent to the UE to initiate a cell switch by the UE from a serving cell to the target cell based on the at least one of the prepared fallback LTM configuration or the fallback CHO configuration for the target cell.