Dynamic Contention Window Size Control for Unlicensed Band Uplink
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Solution Overview
Problem
Wireless access systems supporting unlicensed bands face challenges in efficiently transmitting uplink data and managing radio resources, particularly when uplink data transmission fails due to Listen Before Talk (LBT) failures, and there is a need for effective control of the Contention Window Size (CWS) to optimize channel utilization.
Innovation Solution
A method and apparatus for adjusting the Contention Window Size (CWS) in user equipment (UE) to optimize uplink data transmission in unlicensed bands, involving the reception of CWS adjust information from an eNB, adjusting the CWS based on this information, and performing Listen Before Talk (LBT) to ensure efficient radio resource utilization, even in cases of uplink data transmission failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uplink data transmission is performed in unlicensed band without CWS adjustment, then transmission speed is maintained, but transmission reliability deteriorates due to LBT failures
Solution Approach 1:
The contention window size is dynamically adjusted based on LBT failure detection and channel conditions. When LBT failures are detected, the CWS is increased to reduce contention and improve reliability. When channel conditions improve, the CWS is decreased to minimize transmission delays. This dynamic adaptation resolves the contradiction between reliability and time loss.
Solution Approach 2:
The system implements feedback mechanisms where LBT failure events are monitored and used to adjust the CWS parameter. The base station receives LBT failure information from UEs and sends CWS adjustment commands back, creating a closed-loop control system that continuously optimizes transmission reliability while minimizing delays.
2Reliability
If CWS is increased to improve LBT success rate, then transmission reliability is improved, but channel utilization efficiency deteriorates
Solution Approach 1:
The CWS parameter is dynamically adjusted rather than fixed, allowing the system to increase CWS temporarily during high contention periods to improve LBT success rate, then decrease it when channel conditions improve to restore channel utilization efficiency. This dynamic behavior resolves the contradiction between reliability and productivity.
Solution Approach 2:
The system changes the CWS parameter value based on detected channel conditions and LBT failure rates. By adjusting this key parameter, the system can optimize the balance between LBT success rate and channel utilization efficiency according to current traffic conditions and interference levels.
3Adaptability or versatility
If LBT process is performed with fixed CWS, then device complexity is reduced, but adaptability to channel conditions deteriorates
Solution Approach 1:
The UE autonomously performs LBT procedures and the base station autonomously adjusts CWS based on received LBT failure reports. This self-service approach allows the system to adapt to channel conditions without complex centralized control, improving adaptability while keeping device complexity manageable through standardized procedures.
Data Source
AI summary
The present invention relates to a radio access system that supports an unlicensed band, and provides methods for controlling a contention window size (CWS) for performing uplink LBT, methods for effectively utilizing a radio resource even when an uplink data transmission fails, and apparatuses supporting the same. As an embodiment of the present invention, a method for controlling a contention window size (CWS) for transmitting uplink data in a radio access system supporting an unlicensed band by a user equipment, may comprise the steps of: receiving, from an evolved node B, a radio signal including CSW control information indicating information required for controlling a CWS; controlling the CWS on the basis of the CWS control information; performing a listen before talk (LBT) process using the controlled CWS; and transmitting uplink data when a result of the LBT process shows that an unlicensed band is in an idle state.