Cell-to-eNB Handover with Candidate Lists
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Solution Overview
Problem
Handover failures in wireless communication systems result in disruption of service for user equipment (UE) as they often require re-establishing context information with a new base station, leading to unnecessary complications and service disruptions.
Innovation Solution
Implementing a cell-to-eNB handover technique where context information is transferred directly between base stations, allowing the UE to seamlessly switch to any cell of the target base station without additional overhead, using a list of candidate cells provided by the source base station or determined through system information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs handover from a serving cell to a target cell in a traditional cell-to-cell manner, then the handover process requires context information transfer from source base station to target base station, but this results in service disruption and handover failure when the target cell cannot be successfully accessed
Solution Approach 1:
The patent segments the handover target into multiple candidate cells within the target base station. Instead of attempting handover to a single target cell, the UE is provided with a list of candidate cells and can attempt handover to any of them. This segmentation allows the handover process to be divided into multiple attempts across different cells, increasing reliability while maintaining manageable complexity through structured candidate cell lists.
Solution Approach 2:
The source base station performs preliminary actions by providing the UE with a list of candidate target cells before the handover execution. This preliminary provision of candidate cell information enables the UE to have multiple pre-selected options ready, allowing immediate switching if the primary handover attempt fails, thereby improving reliability without adding complex real-time decision-making during handover execution.
2Ease of operation
If the UE enters idle state after handover failure to re-establish connection, then the UE can recover service, but this causes service disruption and delays
Solution Approach 1:
The source base station provides the UE with a list of candidate target cells before handover execution. This preliminary provision of alternative cell options enables the UE to immediately attempt handover to another candidate cell if the first attempt fails, avoiding the time-consuming process of entering idle state and re-establishing connection from scratch.
Solution Approach 2:
The system implements feedback mechanisms where the UE monitors handover success and can provide feedback about handover outcomes. This feedback loop allows the UE to understand when handover has succeeded or failed and to appropriately switch between attempting alternative candidate cells or entering idle state, optimizing the balance between service recovery simplicity and minimizing disruption time.
3Reliability
If the source base station provides multiple candidate cells to the UE for handover, then the UE has more options for successful handover, but this increases signaling overhead and system complexity
Solution Approach 1:
The system provides a limited list of candidate cells (e.g., 1-3 cells) rather than all possible target cells. This partial provision of candidate options strikes a balance between giving the UE enough choices to ensure handover success and limiting the signaling overhead to manageable levels. The candidate cell list includes sufficient options to handle typical handover failures without overwhelming the system with excessive signaling.
Solution Approach 2:
The candidate cell list is tailored to local conditions and requirements. The source base station selectively provides candidate cells based on local network topology, UE position, and service requirements. This localized customization ensures that the candidate cell list contains relevant options for each specific handover scenario, improving reliability without uniformly increasing signaling overhead across all situations.
Data Source
AI summary
Techniques for performing handover of a user equipment (UE) in a cell-to-base station manner are described. The UE may receive a handover command to perform handover from a source base station to a target base station. The source base station may send context information for the UE to the target base station, and the context information may be available to all cells of the target base station. The UE may attempt handover from a serving cell of the source base station to a first cell of the target base station. The UE may attempt handover to a second cell of the target base station if the handover to the first cell fails. The UE may (i) receive the first and second cells from the source base station or (ii) receive only the first cell from the source base station and determine the second cell based on broadcast system information.