HARQ Retransmission Skipping for LTE NR and NTN Power Saving
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Solution Overview
Problem
In wireless communication systems, when a User Equipment (UE) fails to decode a Physical Downlink Shared Channel (PDSCH) transmission and does not respond with an acknowledgement (ACK or NACK), the network continues futile retransmissions, wasting computation resources, especially in Non-terrestrial Networks (NTN) due to higher latency and current HARQ process implementations.
Innovation Solution
The network determines if a retransmission is likely to succeed based on channel quality index (CQI) and block error rate (BLER), and sends a new PDSCH transmission with updated Modulated Coding Scheme (MCS) and New Data Indicator (NDI) to avoid unnecessary retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network continues retransmissions when UE misses PDSCH, then reliability of data delivery is improved, but computation resources are wasted
Solution Approach 1:
The network uses HARQ feedback mechanisms to detect when UE has missed PDSCH transmissions. By monitoring for DTX conditions and using CQI/BLER feedback, the system can identify failed transmissions and adjust retransmission behavior accordingly, preventing wasteful continued retransmissions while maintaining reliable data delivery through targeted retransmission attempts.
Solution Approach 2:
The system dynamically changes transmission parameters including MCS (Modulation and Coding Scheme), NDI (New Data Indicator), and retransmission timing based on channel conditions and HARQ feedback. When DTX is detected or poor channel conditions are identified through CQI/BLER metrics, the network adjusts these parameters to optimize between reliable delivery and resource conservation.
2Reliability
If the network attempts retransmission after detecting DTX, then data delivery reliability is improved, but power consumption increases
Solution Approach 1:
Instead of always performing full retransmission procedures when DTX is detected, the network applies partial action by first evaluating channel conditions using CQI and BLER metrics. Only when conditions warrant does the network proceed with retransmission, otherwise it conserves power by avoiding unnecessary transmission attempts while still maintaining adequate reliability through selective retransmission.
3Productivity
If the network sends new PDSCH transmission with updated MCS and NDI, then resource utilization is improved, but complexity of transmission management increases
Solution Approach 1:
The system dynamically adjusts transmission parameters including MCS and NDI based on real-time channel conditions and HARQ feedback. The network transitions between different transmission modes (new transmission vs. retransmission) and adapts MCS levels according to channel quality, optimizing resource utilization while managing complexity through standardized dynamic adaptation procedures rather than complex custom management logic.
Data Source
AI summary
Methods and devices for saving power in a HARQ process are disclosed. The method includes a network transmitting a PDSCH transmission comprising first Downlink Control Information (DCI) and detecting a discontinuous transmission (DTX) in response to the PDSCH transmission. The network determines that a retransmission is unlikely to be successful, skips the retransmissions attempts, and transmits a new PDSCH transmission comprising second DCI.