Conditional Handover RLM Timer Management
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Solution Overview
Problem
In wireless communication networks, especially in 5G systems, existing handover procedures are inefficient due to immediate suspension of radio link monitoring (RLM) timers during handovers, leading to potential radio link failures and increased power consumption, particularly when conditional handover (CHO) configurations are not properly managed.
Innovation Solution
A method and user equipment (UE) implementation that allows conditional handover by receiving RRC reconfiguration messages, determining the presence of CHO configurations, and either continuing or suspending RLM timers and procedures based on these configurations, enabling more controlled handovers and reducing power consumption by allowing UE to manage state transitions based on specific conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If RLM timer is immediately suspended during handover, then handover execution is simplified, but radio link failure risk increases and power consumption increases
Solution Approach 1:
The patent applies preliminary action by continuing the RLM timer and procedure during the handover process instead of immediately suspending them. This allows the UE to proactively monitor the radio link quality on the source cell before the handover is fully complete, enabling early detection of potential radio link failures and providing time to take corrective actions.
Solution Approach 2:
The patent implements feedback by maintaining continuous radio link monitoring through the RLM procedure during handover. The UE provides feedback about the radio link quality to the network, allowing the network to make informed decisions about handover execution and potential fallback actions if link quality deteriorates.
2Reliability
If RLM timer is continued during handover, then radio link failure detection is improved, but system complexity increases
Solution Approach 1:
The patent applies dynamics by making the RLM timer behavior adaptive based on handover configuration type. The system dynamically adjusts whether to continue or suspend the RLM timer depending on whether it's a conditional handover (CHO) or regular handover, optimizing reliability without unnecessarily increasing complexity in all cases.
Solution Approach 2:
The patent changes the operational parameters of the RLM procedure based on the handover type. For conditional handovers, the RLM timer is continued with modified behavior to detect failures while allowing conditional execution, whereas for regular handovers, the traditional suspension approach is maintained.
3Reliability
If conditional handover configuration is provided, then handover reliability is improved, but processing requirements increase
Solution Approach 1:
The patent applies partial action by implementing selective continuation of RLM timer based on handover type. Not all handovers require continued RLM monitoring - only conditional handovers do. This partial application of the more reliable (but more demanding) approach optimizes the balance between reliability and processing requirements.
Data Source
AI summary
A method for executing conditional handover by a UE in a wireless communication network is provided. The method may include receiving an RRC reconfiguration message from a source cell of the wireless communication network. The RRC reconfiguration message may include a handover configuration and determining whether a CHO configuration may be provided in the handover configuration. Further, the method may include performing one of: continuing an RLM timer and an RLM procedure on the source cell, in response to determining that the CHO configuration is provided in the handover configuration; and stopping the RLM timer and suspending the radio link monitoring procedure on the source cell, in response to determining that the CHO configuration is not provided in the handover configuration. The method may then include executing the CHO from the source cell to a candidate target cell in the wireless communication network based on the CHO configuration.