IoT-NTN HARQ Feedback Disabling for GEO Delay Bottlenecks
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Solution Overview
Problem
HARQ stalling occurs in IoT-NTN networks due to long Round-Trip Delay (RTD) in GEO satellite systems, leading to degraded system throughput, and increasing the number of HARQ processes is impractical for IoT services.
Innovation Solution
Disabling HARQ-ACK feedback and configuring UE to omit HARQ-ACK transmission, with reduced UE processing delay, and using an NDI bit to signal HARQ-ACK feedback enable/disable, allowing faster NPDCCH monitoring and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of HARQ processes is increased to address HARQ stalling in GEO satellite systems, then the HARQ stalling problem is resolved, but the complexity of base station and UE increases significantly
Solution Approach 1:
The patent extracts the HARQ-ACK feedback mechanism from the traditional HARQ process and disables it entirely for NPUSCH format 2 transmissions. By removing the feedback requirement, the system no longer needs to manage multiple HARQ processes to handle retransmissions, thus resolving HARQ stalling without increasing device complexity. The base station schedules resources without waiting for ACK/NACK feedback, and the UE simply transmits uplink data or HARQ-ITS without expecting retransmission control.
Solution Approach 2:
Instead of using HARQ-ACK feedback to control retransmissions (traditional approach), the patent inverts the approach by disabling feedback entirely and using a single-shot transmission model. The NDI bit is repurposed to indicate whether the transmission contains new data or is a retransmission, eliminating the need for feedback-based flow control and reducing complexity while maintaining reliability.
2Productivity
If HARQ-ACK feedback is disabled to reduce processing delay, then system throughput is improved, but the ability to perform downlink budgeting based on feedback is lost
Solution Approach 1:
The patent introduces the NDI (New Data Indicator) bit as an intermediary mechanism to carry transmission status information without requiring full HARQ-ACK feedback. The NDI bit provides the base station with sufficient information to determine whether a transmission is new or a retransmission, enabling simplified downlink budgeting and resource allocation without the overhead and delay of traditional ACK/NACK feedback.
3Measurement precision
If NPDCCH transmission is delayed to allow UE processing, then UE decoding accuracy is maintained, but scheduling efficiency and system throughput are degraded
Solution Approach 1:
The patent applies preliminary action by pre-configuring UE processing capabilities and pre-scheduling resources without waiting for feedback. The base station sends NPDCCH transmissions with sufficient advance notice of resource allocations, and the UE is pre-configured to process transmissions within known time constraints. This eliminates the need for delayed scheduling decisions while maintaining decoding accuracy through proper resource allocation and processing time guarantees.
Data Source
AI summary
Described are implementations for HARQ-disabling in IoT-NTN deployment AND disabling HARQ-ACK feedback. Signaling mechanisms include configurations for HARQ process ID(s), NPDCCH monitoring, a New Data Indicator (NDI) bit in Downlink Control Information (DCI), and a HARQ-ACK feedback transmission in the uplink.