Sidelink CW Adjustment for LBT Without HARQ Feedback
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Solution Overview
Problem
Existing sidelink communication in unlicensed bands requires improvements in listen before talk (LBT) operations, particularly in adjusting the contention window (CW) size for effective channel access.
Innovation Solution
A method and apparatus for adjusting the CW size based on reference parameters such as distance, RSRP, CBR, and resource availability, rather than relying solely on HARQ feedback, with signaling from a base station to configure CW tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CW size is adjusted based on HARQ feedback for first data, then channel access efficiency is improved, but reliability deteriorates when HARQ feedback is not received
Solution Approach 1:
The patent uses HARQ feedback as the basis for adjusting CW size, where the transmitting UE modifies the CW size based on whether ACK or NACK is received from the receiving UE. This feedback mechanism enables the system to adapt channel access behavior based on actual transmission success, improving both efficiency and reliability.
Solution Approach 2:
The patent applies preliminary action by adjusting the CW size before the next LBT operation based on the outcome of the previous transmission. The transmitting UE proactively modifies the contention window parameters in advance of the next channel access attempt, ensuring optimal settings are ready for the subsequent transmission without waiting for additional feedback cycles.
2Device complexity
If LBT operation is performed with fixed CW size, then device complexity is reduced, but productivity deteriorates due to suboptimal channel access
Solution Approach 1:
The patent implements dynamics by making the CW size adjustable rather than fixed. The transmitting UE dynamically modifies the CW size based on HARQ feedback outcomes and transmission conditions. This dynamic adaptation allows the system to optimize channel access efficiency for different scenarios while maintaining manageable complexity through standardized adjustment rules.
3Reliability
If CW size is increased to improve reliability, then channel access efficiency deteriorates due to longer backoff periods
Solution Approach 1:
The patent applies parameter changes by modifying the CW size parameter based on transmission outcomes and channel conditions. The transmitting UE adjusts the CW size up or down depending on whether transmissions are successful or fail, allowing the system to optimize the balance between reliability and access efficiency for each specific transmission scenario.
Data Source
AI summary
Disclosed are a method and device for adjusting CW size in sidelink communication in an unlicensed spectrum. A method performed by a transmission UE comprises the steps of: performing a first LBT operation on the basis of a CW having a first CW size; transmitting first data to a reception UE when the first LBT operation is successful; adjusting the first CW size on the basis of reference parameters instead of HARQ feedback for the first data; performing a second LBT operation on the basis of the CW having the adjusted CW size; and transmitting second data to the reception UE when the second LBT operation is successful.