Terminal Sidelink Sensing with Adaptive Contention Windows
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Solution Overview
Problem
In unlicensed bands, fair channel access is challenging due to the coexistence of equipment from multiple systems, necessitating improved Listen Before Talk (LBT) mechanisms for terminal apparatuses in 5G communication systems.
Innovation Solution
A terminal apparatus determines a contention window size based on a first number of second sidelink transmissions with HARQ-ACK feedback disabled, applying this size to channel sensing and performing first sidelink transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Listen Before Talk (LBT) based on Clear Channel Assessment (CCA) is used for coexistence in unlicensed bands, then fair channel access among multiple systems is improved, but channel access efficiency and productivity deteriorate due to increased sensing time and contention delays
Solution Approach 1:
The patent dynamically adjusts the contention window size parameter based on the number of detected sidelink transmissions. When multiple transmissions are detected, the contention window is enlarged to reduce collision probability; when fewer transmissions are detected, the contention window is reduced to improve access efficiency. This adaptive parameter adjustment resolves the contradiction by optimizing channel access efficiency while maintaining fair coexistence.
2Productivity
If contention window size is reduced to improve channel access efficiency, then productivity is improved, but reliability deteriorates due to increased collision probability among terminal apparatuses
Solution Approach 1:
The patent implements dynamic adjustment of the contention window size based on real-time detection of sidelink transmissions. The contention window is not fixed but adapts its size according to channel conditions and traffic load, allowing the system to optimize between efficiency and reliability based on current environmental factors.
Solution Approach 2:
The patent employs feedback mechanisms where terminal apparatuses detect the number of sidelink transmissions in the channel and use this information to adjust their contention window sizes. This feedback loop enables the system to respond to changing channel conditions, maintaining reliable transmission while optimizing access efficiency.
3Reliability
If contention window size is enlarged to improve transmission reliability, then reliability is improved, but channel access efficiency and productivity worsen due to increased waiting time
Solution Approach 1:
The patent implements dynamic adjustment of the contention window size based on real-time detection of sidelink transmissions. The contention window is not fixed but adapts its size according to channel conditions and traffic load, allowing the system to optimize between efficiency and reliability based on current environmental factors.
4Ease of manufacture
If fixed contention window size is used to simplify device complexity, then ease of manufacture is improved, but adaptability worsens due to inability to adjust to varying channel conditions
Solution Approach 1:
The patent enables terminal apparatuses to autonomously determine and adjust their own contention window sizes based on detected channel conditions and the number of sidelink transmissions. Each device performs self-service adaptation without requiring complex centralized control, achieving adaptability while maintaining relatively simple device implementation.
Data Source
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AI summary
A terminal apparatus including a transmitter configured to perform, for sidelink transmission with HARQ-ACK feedback disabled, channel sensing while maintaining a contention window size last applied, wherein in a case that the number of times that the contention window size is maintained reaches a prescribed number of times, the contention window size is configured to a next larger value.