NR V2X PSFCH Congestion Control Through Slot-Based CBR Measurement
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Solution Overview
Problem
Conventional NR V2X systems lack effective congestion control methods that can adaptively guarantee the performance of physical sidelink feedback channels (PSFCH) due to inaccurate interference level measurements across different resource domains, particularly when PSCCH/PSSCH transmissions do not require SL HARQ feedback.
Innovation Solution
A method and apparatus for a UE to determine a physical sidelink feedback channel (PSFCH) resource based on a subchannel and slot, obtaining a channel busy ratio (CBR) value through measurements in a specific time interval, allowing for accurate interference level assessment and adaptive congestion control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CBR measurement is performed in PSCCH/PSSCH resource domain, then congestion control for PSCCH/PSSCH is enabled, but accurate interference level measurement for PSFCH cannot be obtained
Solution Approach 1:
The patent divides the resource domain into separate measurement windows: one for PSCCH/PSSCH (first resource domain) and one for PSFCH (second resource domain). By segmenting the measurement process, the system can obtain accurate CBR values for each domain independently, resolving the contradiction between enabling congestion control for PSCCH/PSSCH and obtaining accurate interference levels for PSFCH.
Solution Approach 2:
The patent introduces a time-domain dimension by defining specific measurement time windows before the PSFCH transmission time. Instead of measuring interference at the same time as PSFCH transmission, the system measures in a preceding time interval, adding a temporal dimension to the measurement process and enabling accurate PSFCH interference assessment.
2Reliability
If PSFCH transmission is performed without accurate CBR measurement, then communication simplicity is maintained, but performance guarantee in dynamic interference scenarios is compromised
Solution Approach 1:
The patent performs CBR measurement in advance (in a time interval before PSFCH transmission) so that the measured value is available when needed for congestion control decisions. This preliminary action allows the system to guarantee PSFCH performance while avoiding the complexity of real-time measurement during transmission.
3Measurement precision
If measurement time window is extended to capture more interference data, then measurement accuracy improves, but latency increases
Solution Approach 1:
The patent defines a specific measurement time window that extends before the PSFCH transmission time by a certain offset. This partial measurement approach captures sufficient interference data for accurate CBR calculation without requiring an excessively long measurement period, thus balancing accuracy and latency requirements.
Data Source
AI summary
A method for performing wireless communication by a first apparatus and an apparatus for supporting same are provided. The method may comprise the steps of: receiving a physical sidelink control channel (PSCCH) from a second apparatus; receiving a physical sidelink shared channel (PSSCH) related to the PSCCH from the second apparatus; determining a physical sidelink feedback channel (PSFCH) resource related to the PSSCH, on the basis of a slot and sub-channel related to the PSSCH; and obtaining a channel busy ratio (CBR) value related to PSFCH transmission on the PSFCH resource. The CBR value may be obtained on the basis of (i) a first slot before a first offset from a slot that received the PSSCH related to the PSFCH resource, and (ii) measurement in a time section between the first slot and a second slot before a second offset.