Sidelink Feedback Handling for Unlicensed Spectrum Reliability
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Solution Overview
Problem
In sidelink communications over unlicensed radio frequency bands, the absence of feedback messages can lead to erroneous declarations of radio link failures due to random collisions and increased LBT failure rates, causing unnecessary sidelink connection rejections and inefficient resource utilization.
Innovation Solution
A method for the transmitting user equipment to determine the absence of feedback messages and adjust the discontinuous reception counter accordingly, based on pre-configured behaviors and channel access types, to differentiate between actual negative acknowledgments and other scenarios, thereby reducing unnecessary counter increments and maintaining accurate connection quality assessments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the transmitting UE increments the discontinuous reception counter upon detecting absence of feedback messages, then the radio link failure detection becomes more sensitive, but false declarations of radio link failures increase due to random collisions and LBT failures in unlicensed spectrum
Solution Approach 1:
The patent changes the parameter of counter increment behavior based on channel access type. When Listen Before Talk type 2 is used, the counter is not incremented upon feedback absence, whereas for other channel access types, the counter may be incremented. This parameter change resolves the contradiction by adapting the detection sensitivity to the specific channel access mechanism being used.
Solution Approach 2:
The patent introduces feedback about the channel access type (LBT type 2 vs. other types) to modify the counter increment behavior. The transmitting UE uses this feedback information to determine whether to increment the discontinuous reception counter, thereby avoiding false radio link failure declarations while maintaining proper failure detection for actual link issues.
2Reliability
If the transmitting UE declares radio link failure based on consecutive DTX counter threshold, then link quality monitoring is maintained, but unnecessary connection releases occur due to false detections in unlicensed spectrum
Solution Approach 1:
The patent modifies the counter increment parameter based on the channel access type. For LBT type 2, the counter does not increment on feedback absence, preventing false threshold crossings and unnecessary connection releases. For other channel access types, the counter may increment normally, maintaining link quality monitoring effectiveness.
Solution Approach 2:
The patent makes the counter increment behavior dynamic rather than static. The behavior adapts based on the channel access type being used, allowing the system to maintain reliable link quality monitoring while avoiding false detections in unlicensed spectrum where LBT type 2 is employed.
3Productivity
If the transmitting UE performs reduced listen before talk procedure within acquired channel occupancy time, then transmission efficiency is improved, but feedback message transmission may be blocked by other transmitters
Solution Approach 1:
The patent makes the feedback absence handling dynamic based on channel access type. When LBT type 2 is used (indicating operation within acquired channel occupancy time), the counter behavior changes to account for potential feedback blocking by other transmitters. This dynamic adjustment maintains transmission efficiency while compensating for reduced feedback reliability.
Solution Approach 2:
The patent converts the potential harm of blocked feedback messages into a beneficial adaptation by modifying the counter increment behavior. Instead of treating all feedback absences as link failures, the system recognizes that in LBT type 2 scenarios, feedback blocking is expected and adjusts the failure detection mechanism accordingly, turning a reliability issue into a manageable parameter.
Data Source
AI summary
A method, apparatus, and computer program for determining, by transmitting user equipment, absence of a feedback message from receiving user equipment, which feedback message is related to a transmission of the transmitting user equipment over a sidelink to the receiving user equipment; determining by the transmitting user equipment whether the feedback message is absent from a sidelink physical feedback channel associated with a listen before talk type 2 channel access or with a shared channel occupancy time; and performing a first action that comprises incrementing a discontinuous reception counter associated with the sidelink in response to determining that the feedback message is absent from the sidelink physical feedback channel associated with the listen before talk type 2 channel access or with the shared channel occupancy time.