Radio Link Monitoring Thresholds for Multi-Coverage Wireless Systems
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Solution Overview
Problem
Current Radio Link Monitoring (RLM) methods for wireless communication systems with multiple coverage levels are inefficient due to the use of fixed thresholds for determining in-sync and out-of-sync status, leading to improper triggering of Radio Link Failure (RLF) and performance degradation in NB-IoT systems.
Innovation Solution
The method involves determining RLM thresholds based on all configured NPDCCH parameters, with the base station providing specific in-sync and out-of-sync thresholds for each coverage level, allowing the user equipment to adjust its status accordingly, and considering additional offsets for enhanced coverage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fixed RLM thresholds are used for all coverage levels, then the system is simple to implement, but RLM performance degrades in multi-coverage-level systems
Solution Approach 1:
The patent implements dynamic RLM thresholds that adapt to different coverage levels. The base station configures multiple sets of RLM thresholds (Qout and Qin) corresponding to different coverage enhancement levels, and the UE dynamically selects and applies the appropriate threshold set based on its current coverage level, thereby resolving the contradiction between implementation simplicity and RLM performance in multi-coverage systems
Solution Approach 2:
The patent changes the RLM threshold parameters according to coverage levels. Different Qout and Qin threshold values are configured for different coverage enhancement levels, allowing the system to maintain optimal RLM performance across varying coverage conditions while keeping the implementation mechanism relatively simple through parameter configuration
2Measurement precision
If separate RLM thresholds are configured for each coverage level, then RLM accuracy improves, but system complexity increases
Solution Approach 1:
The patent segments the RLM threshold configuration into multiple sets, each corresponding to a specific coverage enhancement level. The base station configures separate Qout and Qin thresholds for different coverage levels, and the UE selects the appropriate segment based on its coverage level, thereby achieving accurate RLM determination without requiring a completely new complex system
Solution Approach 2:
The base station performs preliminary configuration of multiple RLM threshold sets before the UE begins monitoring. By pre-configuring the thresholds for different coverage levels and indicating which set to use, the system achieves high RLM accuracy while minimizing runtime complexity through advance preparation
3Ease of operation
If conventional RLM methods are used, then the procedure is simple to implement, but RLF triggering becomes improper in multi-coverage systems
Solution Approach 1:
The patent modifies the RLM procedure by changing the threshold parameters based on coverage levels. The UE determines its coverage enhancement level and applies the corresponding Qout and Qin thresholds from the configured sets, ensuring proper RLF trigger accuracy while maintaining the overall simplicity of the monitoring procedure through parameter-based adaptation
Data Source
AI summary
A method, apparatus, and computer program product where a user equipment, in a wireless communications system, measures downlink radio quality based on available downlink signals. The user equipment compares the measured downlink radio quality with RLM thresholds. Based on that comparison, the user equipment determines its in-sync or out-of-sync status. Prior to the measuring, the user equipment can determine the RLM thresholds based on hypothetical NPDCCH channels; can receive in-sync and out-of-sync thresholds from the base station; can receive an additional offset for in-sync and out-of-sync thresholds under enhanced coverages and can determine the RLM thresholds for normal converge on the hypothetical NPDCCH channels; or can receive an offset between in-sync and out-of-sync thresholds from a base station and determine the RLM out-of-sync threshold based on the hypothetical NPDCCH channels and the RLM in-of-sync threshold based on the out-of-sync threshold and the offset provided by the base station.