Terminal Radio Link Failure Detection During Handover
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Solution Overview
Problem
Existing mobility technologies in LTE and NR systems face challenges in detecting radio link failures during handover, leading to inefficient re-establishment of connections and potential service interruptions.
Innovation Solution
A terminal apparatus and method that utilize timers and indications from MAC and PHY entities to detect radio link failures, suspending radio bearers and resetting the MAC entity when specific conditions are met, enabling efficient mobility control and re-establishment of connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing mobility technology is used for handover, then connection re-establishment can be performed, but radio link failure detection is not possible during handover leading to service interruptions
Solution Approach 1:
The patent starts a timer (T310) before handover completion to proactively monitor radio link status. This preliminary action enables detection of radio link failures that occur during handover, allowing the system to take corrective measures before service interruption becomes severe.
Solution Approach 2:
The patent implements a feedback mechanism where the terminal apparatus continuously monitors radio link status during handover and reports to the network. The timer expiration and random access problem indications provide feedback signals that trigger appropriate actions, enabling dynamic adjustment of handover procedures based on real-time conditions.
2Measurement precision
If timer is started for radio link failure detection during handover, then detection accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent segments the handover process into distinct phases with specific timer management rules. Timer T310 is started at a specific point (when reconfiguration with sync is received) and stopped under specific conditions (random access success, handover completion). This segmentation allows precise detection without requiring complex continuous monitoring throughout the entire handover process.
Solution Approach 2:
The patent changes the state of timer T310 (started, stopped, expired) based on specific events during handover. This parameter-based control simplifies the detection logic compared to continuous monitoring, as the system only needs to respond to discrete timer state changes and event triggers.
3Reliability
If random access problem indication is monitored continuously, then radio link failure detection is improved, but energy consumption increases
Solution Approach 1:
The patent uses periodic monitoring through timer T310 instead of continuous monitoring. The timer checks radio link status at regular intervals defined by its period, which is sufficient to detect failures while allowing the terminal to enter low-power states between checks. This periodic action significantly reduces energy consumption compared to continuous monitoring.
Data Source
AI summary
A terminal apparatus includes: a receiver that receives an RRC message from a base station apparatus; and a processing unit that performs processing of RRC. The processing unit causes, when first information is in the RRC message, a first timer to start in a running state, and considers, at least when a random access problem indication is received from a MAC entity of the group and the first timer is not running, or when a random access problem indication is received from a MAC entity of the group and the first timer is running under a specific condition, a radio link failure for the group to be detected. When the radio link failure for the group is detected and that the first timer is running under the specific condition, the processing unit suspends transmission of all radio bearers in the group, and resets the MAC entity of the group.