LBT Failure Counter Handling for UE Uplink Recovery

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Solution Overview

Problem

In wireless communication systems operating on unlicensed spectrum, consistent LBT failures lead to issues with RACH counters and SR counters not being incremented, resulting in deadlock situations and failure to trigger RLF or SR transmission due to optional UE capabilities and network configurations not supporting consistent LBT failure recovery procedures.

Innovation Solution

Implement UE behaviors where RACH and SR counter handling depends on UE capabilities and network configurations for consistent LBT failure recovery, incrementing counters only when LBT failures occur without support or configuration, and indicating LBT success to the MAC layer for non-recoverable failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If consistent LBT failure recovery procedure is implemented, then reliability of channel access is improved, but device complexity increases due to additional MAC entity configuration and counter handling logic

Engineering Contradiction:

Improvechannel access reliabilityVSAvoidMAC entity configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the parameter of counter handling behavior based on LBT failure conditions. When consistent LBT failure is detected, the transmission counter is prevented from incrementing, which changes the state management parameter to avoid deadlock situations and enable proper recovery procedure activation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements feedback mechanism where the MAC entity monitors LBT failure indications and adjusts counter handling accordingly. The system feeds back the LBT failure status to control whether the transmission counter increments or remains static, enabling adaptive recovery behavior.

Inventive Principle:

Principle #23Feedback

2Productivity

If transmission counter is incremented on LBT failure, then productivity is improved by enabling retransmission attempts, but reliability deteriorates when UE capabilities or network configurations do not support consistent LBT failure recovery

Engineering Contradiction:

Improveretransmission capabilityVSAvoidchannel access success rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent makes the counter handling dynamic based on UE capability and network configuration. The system adapts its behavior by determining whether consistent LBT failure recovery is supported, and accordingly decides whether to increment the transmission counter or indicate LBT success to the MAC layer, optimizing both productivity and reliability.

Inventive Principle:

Principle #15Dynamics

3Reliability

If LBT success is indicated without transmission when consistent LBT failure recovery is supported, then reliability is improved by preventing counter increment on unsupported failures, but loss of time increases due to additional determination and indication steps

Engineering Contradiction:

Improvecounter handling accuracyVSAvoidprocessing time for LBT failure determination

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent performs preliminary determination of UE capability and network configuration support for consistent LBT failure recovery before actually handling the LBT failure. This preliminary action establishes the handling mode in advance, allowing faster and more accurate counter management when LBT failures occur.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12557138B2Incrementing a transmission counter in response to LBT failure

Publication Date: 2026.02.17 LENOVO (SINGAPORE) PTE LTD

AI summary

Apparatuses, methods, and systems are disclosed for counter handling in case of LBT failure. One apparatus includes a transceiver and a processor that performs a Listen-Before-Talk (“LBT”) procedure for a transmission and detects LBT failure for the transmission. The processor determines whether a medium access control (“MAC”) entity of the apparatus is configured with a consistent LBT failure recovery procedure. The processor increments a transmission counter without transmission of an uplink transmission in response to an indication of the LBT failure and in response to MAC entity not being configured with the consistent LBT failure recovery procedure.