NTN ACK/NACK Feedback Triggers for Long-RTT Link Adaptation
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Solution Overview
Problem
In non-terrestrial networks (NTN) like satellite communications, the long round-trip time (RTT) leads to inefficiencies in hybrid automatic repeat request (HARQ) processes, causing issues with link adaptation algorithms and scheduler performance due to delayed ACK/NACK feedback, which affects throughput and battery life.
Innovation Solution
Implementing a method where ACK/NACK feedback is minimized to save overhead and UE battery life, while still providing sufficient feedback for link adaptation, by configuring triggers for UE to report ACK/NACK based on packet counts, elapsed time, BLER, or network requests, even with HARQ retransmissions disabled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ACK/NACK feedback is transmitted frequently in NTN, then link adaptation accuracy is improved, but overhead and battery consumption increase
Solution Approach 1:
The patent implements periodic ACK/NACK feedback transmission at configured intervals rather than after every packet. The network configures the UE with a periodicity parameter, and the UE transmits ACK/NACK reports only at these periodic intervals, reducing transmission frequency while maintaining sufficient link adaptation information.
Solution Approach 2:
The patent transmits ACK/NACK feedback only when necessary conditions are met, such as when there is actual data to acknowledge or when link quality thresholds are exceeded. This partial action approach avoids redundant transmissions while ensuring critical feedback is provided for link adaptation.
2Productivity
If ACK/NACK feedback is transmitted after every packet in NTN, then throughput is improved through timely error correction, but overhead increases
Solution Approach 1:
The patent combines multiple ACK/NACK feedback instances into single periodic reports. Instead of transmitting separate ACK/NACK for each packet, the UE accumulates acknowledgment information and transmits it in consolidated periodic reports, reducing the quantity of feedback messages while maintaining error correction capability.
Solution Approach 2:
The patent implements periodic feedback transmission where the UE sends ACK/NACK reports at configured time intervals rather than continuously after each packet. This periodic approach reduces feedback overhead while maintaining sufficient information for the network to identify and retransmit erroneous packets.
3Reliability
If HARQ retransmissions are enabled in NTN, then reliability is improved, but the long RTT causes scheduler performance degradation
Solution Approach 1:
The patent segments the HARQ process into independent parallel instances, each handling specific data packets. The network configures multiple HARQ processes that can operate independently, allowing the scheduler to manage retransmissions without being blocked by long RTT delays, as other HARQ processes continue to function simultaneously.
Data Source
AI summary
Various techniques are provided for generating and communicating an acknowledgement/negative acknowledgement (ACK/NACK).