Sidelink Congestion Control via CBR Slot Segmentation
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Solution Overview
Problem
Existing congestion control techniques for sidelink communication in unlicensed spectrum are inadequate due to issues with channel busy ratio (CBR) measurements being affected by Wi-Fi activities, leading to ineffective channel occupancy assessment for vehicle-to-everything (V2X) systems.
Innovation Solution
The proposed method determines channel busy ratio (CBR) relevant slots by excluding resource occupancy by other radio access technologies (RATs) and uses these slots to calculate CBR, thereby deciding whether to transmit sidelink transmissions, ensuring that the total number of transmissions within a window does not exceed a predetermined limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CBR measurement includes all slots in measurement window, then measurement coverage is comprehensive, but measurement precision deteriorates due to Wi-Fi activities affecting the measurement
Solution Approach 1:
The measurement window is segmented into CBR relevant slots and non-CBR relevant slots based on whether sidelink transmissions are detected. This segmentation allows the system to exclude Wi-Fi affected slots from CBR measurement, thereby improving measurement precision while maintaining manageable complexity through systematic slot classification
Solution Approach 2:
The presence of sidelink transmissions acts as an intermediary indicator to identify CBR relevant slots. By using detected sidelink transmissions as a mediator to mark relevant slots, the system can distinguish between slots affected by sidelink communication and those affected by Wi-Fi, thus improving CBR measurement accuracy
2Reliability
If sidelink transmission limit is set low, then channel congestion is reduced, but communication productivity decreases
Solution Approach 1:
The transmission limit is made dynamic by adjusting it based on measured CBR values. When CBR is low (indicating light congestion), the transmission limit is increased to allow more transmissions and improve productivity. When CBR is high (indicating heavy congestion), the transmission limit is reduced to prevent excessive transmissions and maintain reliability. This dynamic adjustment resolves the contradiction between congestion control and throughput
Solution Approach 2:
The system implements feedback by continuously monitoring CBR measurements and adjusting transmission limits accordingly. The measured CBR provides feedback about channel conditions, which is then used to adaptively set the transmission limit, ensuring optimal balance between congestion control and communication productivity under varying channel conditions
Data Source
AI summary
In an aspect, the present disclosure includes a method and apparatus for sidelink communications for identifying at least one slot in a measurement window as a channel busy ratio (CBR) relevant slot, calculating a CBR based on at least a measurement in at least the CBR relevant slot, and transmitting, or refraining from transmitting, a sidelink transmission based at least on the CBR.