UE RLM Accuracy via Downlink Reference Signal Feedback
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Solution Overview
Problem
In LTE and 5G systems, the Listen Before Talk (LBT) mechanism can disrupt the normal operation of radio link monitoring (RLM) processes due to uncertainties in channel availability, leading to inaccurate RLM results and unnecessary reconnections, which increase power consumption and system resource overheads.
Innovation Solution
A method where user equipment (UE) reports detection results and timer/counter status of downlink reference signals to the base station, using bitmap or one-bit information, to receive feedback on signal sending status, allowing for more accurate RLM results and dynamic updating of timer/counter parameters to avoid unnecessary reconnections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the LBT channel contention access mechanism is used on unlicensed frequency bands, then coexistence with other devices is ensured, but it cannot be guaranteed that CSI-RS and SS/PBCH block are sent on preset time-frequency resources, causing RLM process to fail
Solution Approach 1:
The base station feeds back indication information to the UE about whether the downlink reference signal was sent. This feedback mechanism allows the UE to distinguish between link failures caused by LBT and actual radio link degradation, resolving the contradiction by providing reliable RLM results despite LBT interruptions.
Solution Approach 2:
Indication information acts as an intermediary between the base station and UE, conveying the sending status of downlink reference signals. This intermediary mechanism enables the UE to accurately interpret RLM results even when LBT prevents scheduled transmissions, maintaining reliability while preserving LBT-based coexistence.
2Reliability
If UE performs random access reconnection when RSRP/RSRQ is lower than threshold, then link recovery is attempted, but unnecessary reconnections occur due to inaccurate RLM results, increasing power consumption and system resource overheads
Solution Approach 1:
The base station provides feedback indication information to the UE about downlink reference signal transmission status. This feedback enables the UE to distinguish between actual link failures requiring reconnection and temporary failures due to LBT, thereby avoiding unnecessary random access procedures and reducing power consumption while maintaining reliable link recovery when truly needed.
3Measurement precision
If UE continuously monitors downlink reference signal for RLM, then link status is tracked, but inaccurate RLM results are obtained when reference signals are not sent due to LBT, leading to incorrect link failure determination
Solution Approach 1:
The base station feeds back indication information to the UE specifying whether the downlink reference signal was sent. This feedback compensates for the information loss about signal transmission status, enabling the UE to accurately determine whether poor RLM results are due to actual link degradation or LBT-induced signal omission, thereby improving measurement precision.
Solution Approach 2:
Indication information serves as an intermediary that conveys the sending status of downlink reference signals from the base station to the UE. This intermediary mechanism restores the lost information about transmission status, allowing the UE to accurately interpret RLM measurements and distinguish between genuine link failures and LBT-related signal omissions.
Data Source
AI summary
Embodiments of this application provide a control information transmission method. The method includes: User equipment UE sends report information to a base station, where the report information includes a detection result of one or more downlink reference signals of the UE or a status of a timer/counter corresponding to the one or more downlink reference signals; the UE receives feedback information from the base station, where the feedback information includes sending status information of the one or more downlink reference signals.