Sidelink Contention Window Updates Using HARQ Feedback
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Solution Overview
Problem
Sidelink communication in unlicensed spectrum lacks support for features like CBG-based PDSCH transmission, HARQ, and TTI bundling, and lacks a defined contention window size (CWS) update process, which are essential for efficient channel access and data transmission.
Innovation Solution
Implement methods for updating the contention window size (CWS) based on hybrid automatic repeat request (HARQ) feedback and transmission/retransmission grants, tailored for unicast, groupcast, and broadcast modes, considering channel access priority classes (CAPCs) and feedback mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If contention window size is fixed in sidelink unlicensed band, then device complexity is reduced, but channel access efficiency deteriorates due to inability to adapt to varying transmission conditions
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed contention window size to a dynamic CWS that changes based on transmission conditions. The base station adjusts CWS values according to HARQ feedback and transmission success rates, allowing the system to adapt to varying channel conditions and optimize channel access efficiency in unlicensed spectrum.
Solution Approach 2:
The patent implements feedback mechanisms where the base station receives HARQ feedback from UEs and uses this information to adjust the contention window size. This closed-loop feedback system enables the base station to optimize CWS based on actual transmission performance, improving channel access efficiency while managing complexity through standardized feedback protocols.
2Reliability
If CBG-based PDSCH transmission and HARQ are implemented, then transmission reliability is improved, but device complexity increases due to additional processing requirements
Solution Approach 1:
The patent applies segmentation by dividing the PDSCH transmission into code block groups (CBGs) instead of transmitting entire transport blocks. This segmentation allows for more granular error correction and selective retransmission of only the failed CBGs, improving transmission reliability while managing processing complexity through structured division of data units.
Solution Approach 2:
The patent implements HARQ feedback mechanisms that provide reliability information back to the base station. The base station uses this feedback to determine whether retransmission is needed and adjusts transmission parameters accordingly, improving transmission reliability through systematic feedback-based error correction.
3Productivity
If TTI bundling is implemented, then channel access efficiency is improved, but device complexity increases due to additional time management requirements
Solution Approach 1:
The patent applies merging by combining multiple transmission time intervals (TTIs) into bundled transmissions. This allows the base station to allocate and manage multiple TTIs as a single unit, improving channel access efficiency in unlicensed spectrum by reducing the overhead of individual time management operations while maintaining coordinated transmission control.
Data Source
AI summary
Systems, methods, and circuitries are provided for a UE performing sidelink (SL) communication in unlicensed spectrum to update contention window size (CWS). In one example, a method includes, during a sidelink (SL) channel occupancy time (COT), transmitting one or more physical sidelink shared channels (PSSCHs) transmissions to one or more respective receiving (RX) UEs according. Each PSSCH includes one or more transport blocks (TBs) and is associated with a channel access priority class (CAPC). The UE updates the CWS for the CAPC based on feedback received with respect to the one or more PSSCHs associated with the CAPC and transmits subsequent PSSCH associated with the CAPC based on the updated CWS.