LTE Unlicensed CWS Adjustment via Segmented HARQ Feedback
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Solution Overview
Problem
In the LTE unlicensed spectrum, determining the Non-Acknowledgement (NACK) ratio based on Hybrid Automatic Repeat reQuest (HARQ) feedback of Code Block Groups (CBGs) for adjusting the Contention Window Size (CWS) is challenging due to the complexity of channel access priorities and channel conditions.
Innovation Solution
A method and apparatus for adjusting the CWS by receiving HARQ feedback information, determining target data units with NACK information, and calculating the NACK ratio within a reference duration to accurately adjust the CWS based on the calculated ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HARQ feedback information for multiple data units (CBGs and TBs) is aggregated to calculate NACK ratio, then the accuracy of channel condition assessment is improved, but the calculation complexity increases
Solution Approach 1:
The patent segments the HARQ feedback information processing by separately handling CBG-level NACK ratios and TB-level NACK ratios. The terminal device calculates NACK ratio based on CBG feedback information and separately calculates NACK ratio based on TB feedback information, then selects one for CWS adjustment. This segmentation reduces the complexity of aggregating all individual CBG feedbacks while maintaining accurate channel condition assessment.
Solution Approach 2:
The patent introduces an intermediary approach by using TB-level NACK ratio as a mediator when CBG feedback information is not available or when TB-level assessment is sufficient. This intermediary layer simplifies the calculation by aggregating feedback at the TB level rather than requiring detailed CBG-level analysis, thus reducing computational complexity while maintaining assessment accuracy.
2Adaptability or versatility
If CWS is adjusted frequently based on real-time NACK ratio, then the adaptability to channel conditions is improved, but the system stability deteriorates
Solution Approach 1:
The patent implements dynamic CWS adjustment by continuously monitoring NACK ratio and adjusting CWS based on threshold comparisons. The system dynamically adapts CWS values (e.g., switching between minimum CWS and maximum CWS) based on real-time channel condition assessments, allowing the system to respond to changing channel conditions while maintaining stability through structured adjustment rules.
Solution Approach 2:
The patent employs feedback mechanisms where the terminal device continuously monitors HARQ feedback information, calculates NACK ratio, and uses this feedback to adjust CWS. The adjusted CWS then feeds back into the channel access process, creating a closed-loop system that adapts to channel conditions. This feedback-driven approach ensures both adaptability to changing conditions and system stability through controlled adjustment cycles.
Data Source
AI summary
A method for adjusting a contention window size (CWS), applicable to a data transmission terminal, includes: receiving Hybrid Automatic Repeat reQuest (HARQ) feedback information for first data units and/or second data units from a data reception terminal within a reference duration, the HARQ feedback information including acknowledgement (ACK) information or non-acknowledgement (NACK) information, one second data unit including one or more first data units; determining target first data units or target second data units, for which the HARQ feedback information is counted as the NACK information; calculating a NACK ratio within the reference duration based on the determined target first data units and/or target second data units; and adjusting the CWS based on the NACK ratio.