NR-U Radio Link Monitoring Adaptation for Missed TXOPs

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Solution Overview

Problem

In New Radio Unlicensed (NR-U) systems, the inability of a NR NodeB to acquire a channel and transmit Downlink Reference Signals (DL-RS) during a Transmission Opportunity (TXOP) leads to erroneous Radio Link Monitoring (RLM) and Radio Resource Management (RRM) measurements, causing false or missed detection of measurement events, even when the link quality is good.

Innovation Solution

The introduction of a Missed RS TXOP Indicator is provided to higher layers to adapt measurement functions, and RLM measurements are performed based on in-sync or out-of-sync indications combined with estimated radio link quality and missed RLM-RS TXOPs, allowing for accurate detection of radio link failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the gNB transmits DL-RS during TXOP in NR-U, then RLM and RRM measurements can be performed, but the gNB may not be able to acquire the channel and transmit DL-RS due to LBT failure

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidchannel access blockage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a missed RS TXOP indicator that is provided in advance to higher layers before measurement functions are executed. This indicator allows the system to pre-identify and account for blocked TXOPs, enabling higher layers to adapt measurement functions accordingly and avoid erroneous measurements from the outset

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary indicator (missed RS TXOP indicator) that mediates between the physical layer transmission status and higher layer measurement functions. This intermediary signal allows higher layers to understand when DL-RS transmissions were blocked without directly observing the channel access process, enabling appropriate measurement adaptations

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the UE measures DL-RS during a blocked TXOP, then measurement can be performed, but the measurement is calculated in error since DL-RS is not transmitted

Engineering Contradiction:

Improvemeasurement throughputVSAvoidmeasurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The missed RS TXOP indicator is provided to higher layers in advance, allowing them to identify blocked TXOPs before attempting measurements. This prevents the UE from performing measurements on blocked DL-RS transmissions, thereby avoiding erroneous measurement results while maintaining measurement continuity through adaptation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts and separates the identification of blocked TXOPs from the measurement process itself. By providing a dedicated missed RS TXOP indicator, the system isolates the blockage detection function, allowing measurement functions to be adapted or skipped for specific blocked instances without affecting overall measurement operations

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If the UE declares out-of-sync based on erroneous RLM measurements, then link quality monitoring is performed, but false out-of-sync declarations occur even when link quality is good

Engineering Contradiction:

Improvelink monitoring reliabilityVSAvoidfalse link status information

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent implements a feedback mechanism where the missed RS TXOP indicator is fed back to higher layers, which then adapt measurement functions and out-of-sync declaration logic accordingly. This feedback loop prevents false out-of-sync declarations by providing context about blocked TXOPs that would otherwise be misinterpreted as link quality degradation

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The missed RS TXOP indicator serves as an intermediary that mediates between raw measurement data and link status decisions. It provides higher layers with additional information needed to correctly interpret measurement results, preventing false out-of-sync declarations while maintaining sensitive detection of actual link problems

Inventive Principle:

Principle #24Intermediary (Mediator)

4Adaptability or versatility

If the UE performs RRM measurements without accounting for blocked TXOPs, then measurement events are detected, but false or missed detection of measurement events occurs

Engineering Contradiction:

Improvemeasurement event detectionVSAvoidmeasurement event accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The missed RS TXOP indicator is provided to higher layers in advance, allowing them to adapt RRM measurement functions before measurement events are evaluated. This enables the system to account for blocked TXOPs in measurement event detection logic, preventing false or missed detections while maintaining event detection capability

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20240357390A1Radio link monitoring and radio resource management measurement procedures for NR-u

Publication Date: 2024.10.24 INTERDIGITAL PATENT HOLDINGS INC

AI summary

Radio resource management measurements for new radio unlicensed are performed that are based on a measurement model where a missed received signal transmission opportunity indicator is provided to higher layers to adapt the measurement functions performed by the radio resource control when a missed received signal transmission opportunity is detected. Radio link monitoring for new radio unlicensed is performed based on in-sync or out-of-sync indications that are based on the estimated radio link quality in combination with missed radio link monitoring reference signal transmission opportunities.