Sidelink Channel Occupancy Ratio Calculation for V2X Congestion Control
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Solution Overview
Problem
Existing methods for calculating the channel occupancy ratio (CR) in LTE-based V2X systems do not effectively consider new sidelink transmissions, leading to potential congestion issues due to the lack of integration of sidelink transmission measurements in the CR calculation.
Innovation Solution
A method and apparatus for calculating the CR by user equipment (UE) in a wireless communication system, which involves receiving a radio channel resource occupancy limit, calculating the CR over past multiple subframes, and transmitting data in sidelink only if the calculated CR is lower than the configured limit, thereby accounting for new sidelink transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing CR calculation methods are used without integrating sidelink transmission measurements, then the calculation process remains simple, but congestion control effectiveness deteriorates due to inaccurate CR measurement
Solution Approach 1:
The patent merges sidelink transmission measurements with the existing CR calculation process by integrating the sensing procedure and resource selection into the CR measurement framework. This combines previously separate functions into a unified CR calculation mechanism that accurately reflects actual channel occupancy including sidelink transmissions.
Solution Approach 2:
The patent implements preliminary sensing and resource selection procedures before actual data transmission. The UE performs sensing to identify available resources and selects resources based on predicted CR values, preparing the transmission decision in advance to ensure accurate CR measurement and effective congestion control.
2Measurement precision
If sidelink transmission measurements are integrated into CR calculation, then congestion control accuracy improves, but measurement and calculation time increases
Solution Approach 1:
The patent employs periodic sensing and measurement cycles where the UE periodically performs sensing procedures to update CR measurements. This periodic action allows the system to maintain accurate CR measurement without requiring continuous measurement, reducing overall time loss while preserving measurement precision.
Solution Approach 2:
The patent performs preliminary sensing and resource selection before actual data transmission occurs. By conducting these measurements and calculations in advance, the system reduces the time impact during actual transmission and achieves more accurate CR measurement without significant delay to data throughput.
3Object-affected harmful factors
If CR limit is enforced strictly, then channel congestion is reduced, but available transmission opportunities decrease
Solution Approach 1:
The patent implements dynamic CR limit adjustment where the CR limit is not fixed but adapts based on current channel conditions and measurement results. The system dynamically modifies transmission opportunities and resource allocation to maintain optimal congestion control while maximizing available transmission chances under varying network conditions.
Solution Approach 2:
The patent changes the CR parameter dynamically based on measured channel occupancy and congestion conditions. By adjusting the CR limit and related parameters in response to real-time measurements, the system balances congestion control effectiveness with transmission opportunity availability, preventing both excessive congestion and unnecessary transmission restrictions.
Data Source
AI summary
For congestion control is an important aspect for PC5-based vehicle-to-everything (V2X) communication, a channel occupancy ratio (CR) has been introduced. CR is defined as the total number of sub-channels used by a user equipment (UE) for its transmissions divided by the total number of configured sub-channels over a measurement period of 1000 ms. The present invention provides a method and apparatus for calculating a CR over past multiple N subframes up to a subframe at which data is to be transmitted in sidelink. Accordingly, new sidelink transmission (or retransmission) can be considered for CR measurement.