Multi-transmission NACK Feedback for Sidelink Reliability
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Solution Overview
Problem
In wireless communication systems, particularly in the 5G New Radio (NR) standard, the NACK-only feedback mode poses challenges as the target UE may not be able to correctly receive and send NACKs for multiple transmissions due to exceeding its feedback capability, leading to unsuccessful retransmissions when the originating UE assumes successful receipt.
Innovation Solution
Implementing a multi-transmission NACK feedback mechanism, where a target apparatus can send a single NACK feedback indicating multiple unreceived transmissions, reducing the resource intensity and enabling the originating apparatus to retransmit the not-successfully-received group of transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the target UE sends individual NACK feedback for each transmission, then the feedback accuracy is improved, but the feedback capability is exceeded and resource overhead increases
Solution Approach 1:
The patent combines multiple individual NACK feedbacks into a single multi-transmission NACK feedback. The target UE aggregates acknowledgment information for multiple transmissions and sends them together in one feedback message, thereby reducing feedback overhead while maintaining comprehensive feedback coverage for all transmissions.
Solution Approach 2:
The multi-transmission NACK feedback mechanism serves multiple functions simultaneously: it provides feedback for multiple transmissions in one message, identifies which specific transmissions failed, and enables the originating UE to perform selective retransmission. This multi-functional approach resolves the contradiction by making the feedback system more efficient without sacrificing accuracy.
2Reliability
If the target UE sends individual NACK feedback for each transmission, then the reliability of retransmission is improved, but the latency increases due to multiple feedback messages
Solution Approach 1:
By merging multiple NACK feedbacks into a single multi-transmission NACK message, the patent reduces the time required for feedback transmission. The originating UE receives all necessary retransmission information in one message rather than waiting for multiple sequential feedback messages, thereby reducing latency while maintaining retransmission reliability.
Solution Approach 2:
The multi-transmission NACK feedback performs preliminary identification of all failed transmissions in a single operation. This allows the originating UE to prepare and execute selective retransmission more efficiently, reducing the overall time required for the retransmission process while ensuring all necessary transmissions are reliably delivered.
3Loss of information
If the target UE sends individual NACK feedback for each transmission, then the completeness of feedback information is improved, but the spectral efficiency decreases
Solution Approach 1:
The patent merges multiple feedback information elements into a single compact multi-transmission NACK message. This consolidation maintains complete feedback information about all transmissions while using fewer radio resources, thereby improving spectral efficiency without sacrificing information completeness.
Solution Approach 2:
The patent changes the parameter structure of the feedback message from multiple individual NACKs to a single multi-transmission NACK with aggregated information. This parameter transformation allows the same amount of feedback information to be transmitted more efficiently, improving spectral efficiency while maintaining completeness.
Data Source
AI summary
Disclosed are techniques related to performing wireless sidelink communication. Originating (e.g., transmitting) and target (e.g., receiving) apparatuses may operate in a NACK-only mode. In this mode, the target apparatus only provides NACK feedbacks to transmissions that it did not receive. Lack of NACK feedback is interpreted by the originating apparatus that the transmissions were successfully received. However, the target apparatus maybe incapable of transmitting NACK for each of missed transmission. In NACK-only mode, the originating would not retransmit these missed transmissions. To address this issue, the target apparatus can transmit a multi-transmission NACK feedback to indicate that multiple transmissions were not successfully received. The multi-transmission NACK is a single feedback, and thus can enable a target apparatus with limited feedback capacity to indicate NACK for multiple transmissions.