ACK/NACK Feedback Based on RSRP Thresholds in V2X Groupcast
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Solution Overview
Problem
Current groupcast protocols in V2X communications lead to inefficient use of radio resources due to excessive ACK/NACK feedbacks, particularly in scenarios where only a subset of receivers fail to decode messages, resulting in unnecessary retransmissions and network congestion.
Innovation Solution
Implementing rules that determine when to send HARQ ACK/NACK feedback based on Reference Signal Received Power (RSRP) thresholds, distance criteria, or a combination of both, to reduce unnecessary feedback transmissions and optimize resource usage in V2X sidelink communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ACK/NACK feedback is sent for all groupcast messages, then reliability of message delivery is improved, but radio resource consumption increases and network congestion occurs
Solution Approach 1:
The patent applies local quality by making the feedback transmission behavior dependent on the specific local condition (RSRP measurement). Each receiving device independently evaluates its own RSRP measurement and decides whether to send feedback based on this local quality metric. This resolves the contradiction by allowing feedback only when locally needed (low RSRP indicating poor reception), rather than universally sending feedback which wastes resources.
2Reliability
If ACK/NACK feedback is sent by all receiving devices, then message delivery reliability is improved, but device complexity and processing overhead increase
Solution Approach 1:
The patent implements partial action by having only a subset of receiving devices send feedback instead of all devices. Specifically, only devices that measure RSRP below the threshold send ACK/NACK feedback, while devices with RSRP above the threshold remain silent. This partial feedback approach maintains reliability for devices that need it while reducing overall processing overhead and device complexity.
Data Source
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AI summary
A method is provided to operate a first wireless device associated with a group including the first wireless device and a second wireless device. A data packet is received from the second wireless device of the group. A reference signal received power RSRP is measured based on a reference signal received from the second wireless device of the group. It is then determined whether or not to transmit Acknowledgement/Negative ACK/NACK feedback for the data packet based on a comparison between the RSRP and an RSRP threshold. Related wireless devices, computer programs, and computer program products are also discussed.