LBT Failure Reporting in 5G Unlicensed Base Stations
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Solution Overview
Problem
In a next-generation mobile communication system, there is a challenge in distinguishing between a service shadow area and an SSB transmission failure due to an LBT failure, which affects the accuracy of minimization of drive tests (MDT) and other reporting mechanisms.
Innovation Solution
A method where a terminal performs listen-before-talk (LBT) for uplink transmission, detects LBT failures, and if the number of detected failures meets a preconfigured threshold, determines a radio link failure (RLF). The terminal then reports this failure, including the cause as an LBT failure, through specific RRC messages. Additionally, the base station reports to a TCE server that an SSB has not been broadcast due to an LBT failure, allowing discrimination between coverage holes and LBT failure areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LBT procedures are implemented to share unlicensed frequency bands, then spectrum utilization efficiency is improved, but transmission reliability deteriorates due to LBT failures
Solution Approach 1:
The patent implements feedback mechanisms where the terminal detects LBT failures and reports them to the base station through RRC messages. The base station receives failure information including the number of LBT failures and determines whether to declare radio link failure based on this feedback, enabling adaptive response to channel conditions.
Solution Approach 2:
The patent introduces configurable parameters including a preconfigured number threshold for LBT failures, timer values for monitoring periods, and report configurations. These parameters can be adjusted to balance between aggressive channel access (improving productivity) and conservative failure declaration (maintaining reliability).
2Productivity
If MDT operations are performed to monitor service quality, then network optimization is improved, but measurement accuracy deteriorates due to inability to distinguish shadow areas from LBT failure areas
Solution Approach 1:
The patent introduces an intermediary reporting mechanism where the terminal acts as a mediator between the physical layer LBT failure detection and the MDT measurement system. The terminal collects LBT failure information from lower layers, processes it through RRC logic, and reports it to the base station, which then uses this information to distinguish LBT failure areas from shadow areas in MDT measurements.
Solution Approach 2:
The patent segments the service area measurement problem by separately tracking LBT failure occurrences and their locations. By dividing the measurement space into regions with and without LBT failures, the system can independently analyze shadow area characteristics without contamination from LBT failure effects, thereby improving measurement precision.
Data Source
AI summary
The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. Disclosed are a method and a device for a terminal to indicate whether LBT has failed or not and declare a detected LBT failure, in report mechanisms such as RLF, SCG failure, establishment failure, and MDT.