Handover Reliability in Wireless Networks
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Solution Overview
Problem
Current handover mechanisms in wireless communication systems, particularly in non-terrestrial networks and high-speed train scenarios, face challenges in reliability due to weak link conditions and frequent handover requirements, necessitating improved methods for scheduled and triggered handovers.
Innovation Solution
The implementation of a method that includes a handover timer with associated execution conditions for scheduled and two-stage triggered handovers, featuring abort conditions and group signaling, to enhance handover reliability by optimizing timer configurations based on user equipment location and trajectory, and distributing load in sending RRC reconfiguration messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional handover mechanisms are used in non-terrestrial networks and high-speed train scenarios, then handover frequency increases to meet mobility requirements, but handover reliability deteriorates due to weak link conditions
Solution Approach 1:
The patent implements scheduled handover where the UE is pre-configured with target cell information and handover parameters before actually needing to handover. This allows the UE to prepare handover resources in advance, reducing execution time and improving reliability during frequent handovers in mobile scenarios like high-speed trains and non-terrestrial networks
2Reliability
If handover timer is set to ensure reliable execution, then handover reliability improves, but handover delay increases
Solution Approach 1:
The patent introduces dynamic timer adjustment where the handover timer value is not fixed but adapted based on current radio conditions, UE mobility state, and link quality. This allows the system to use shorter timers when conditions are good (reducing delay) while maintaining reliability through conditional handover execution
Solution Approach 2:
The system changes handover parameters including timer values, power thresholds, and execution conditions based on real-time channel state information. By adjusting these parameters dynamically, the system optimizes the trade-off between handover reliability and delay for different operational scenarios
3Measurement precision
If individual RRC reconfiguration messages are sent to each UE for handover, then handover precision improves, but network load increases
Solution Approach 1:
The patent implements group-based handover where multiple UEs are configured with the same handover parameters and target cell information through a single group RRC reconfiguration message. This merging approach significantly reduces network signaling load while maintaining precise handover control through UE-specific condition evaluation
4Reliability
If handover conditions are made strict to ensure reliability, then handover failure rate decreases, but handover execution speed decreases
Solution Approach 1:
The patent segments handover conditions into multiple independent criteria (signal quality thresholds, timer expiration, event triggers). The handover executes when sufficient conditions are met rather than requiring all conditions to be satisfied, balancing reliability and execution speed through selective condition evaluation
Data Source
AI summary
A method for user equipment (UE) service handover from the serving cell to a target cell includes information regarding a handover timer and an associated handover execution condition. For scheduled handover to be performed upon expiration of the handover timer, the associated handover execution condition comprises one or more abort conditions for aborting the scheduled handover. For two-stage triggered handover to be performed upon receipt of a subsequent triggering message, the handover timer is a handover validity timer and the associated handover execution condition comprises receipt of the handover triggering message prior to expiration of the handover validity timer.