Unequal HARQ Error Protection Using Tuned Decoding Thresholds
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Solution Overview
Problem
Existing techniques fail to achieve unequal error protection (UEP) for decoding hybrid automatic repeat request (HARQ) bits, particularly in multi-bit coded payloads, leading to unreliable network communication due to biased decoding of acknowledgement (ACK) and negative acknowledgement (NACK) bits.
Innovation Solution
A network node decodes HARQ bits using a decoding rule based on posterior probabilities and a threshold tuned to achieve UEP, ensuring different error rates for ACK and NACK bits, prioritizing correct decoding of NACKs over ACKs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional decoding methods are used for HARQ bits, then the decoding process is simple and fast, but unequal error protection cannot be achieved leading to biased decoding of ACK and NACK bits
Solution Approach 1:
The patent applies local quality by implementing different error protection levels for different types of HARQ bits. Specifically, NACK bits are protected with higher reliability requirements than ACK bits through tailored decoding rules and threshold adjustments. This allows the system to prioritize correct decoding of NACKs (which require retransmission) over ACKs (which indicate successful reception), thereby achieving unequal error protection within the same decoding framework.
Solution Approach 2:
The patent changes decoding parameters dynamically based on the bit type. By adjusting decision thresholds and posterior probability criteria specifically for NACK versus ACK bits, the system achieves differential error protection. The decoding rule modifies parameters such as threshold values and probability thresholds to ensure that NACK detection achieves lower error rates compared to ACK detection, thus resolving the contradiction between reliability and complexity.
2Reliability
If unequal error protection is implemented for HARQ bits, then network reliability improves, but decoding complexity increases due to tuned thresholds and posterior probabilities
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal decoding thresholds and decision rules for different HARQ bit types before actual decoding operations. The system prepares lookup tables or pre-computed parameter sets that encode the complex posterior probability calculations and threshold adjustments, allowing the decoder to apply these pre-prepared rules during runtime without performing complex real-time calculations, thus reducing operational complexity while maintaining reliability.
Solution Approach 2:
The patent introduces an intermediary layer between the received signal and the final decoding decision. This intermediary involves computing posterior probabilities as an intermediate step that bridges the raw signal and the final ACK/NACK determination. By using this intermediate probability calculation with tuned thresholds, the system achieves unequal error protection while managing complexity through a structured two-stage process: probability computation followed by threshold-based decision making.
3Productivity
If standard decoding thresholds are used, then decoding is computationally efficient, but error rates for ACK and NACK bits are equal leading to suboptimal performance
Solution Approach 1:
The patent applies dynamics by making the decoding thresholds adaptive rather than static. The system dynamically adjusts thresholds based on the detected bit type (ACK or NACK) and the computed posterior probabilities. This dynamic adjustment allows the decoder to optimize performance for each bit type individually, achieving different error rates for ACK and NACK detection while maintaining computational efficiency through conditional threshold selection rather than exhaustive optimization.
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a network node may receive, from a user equipment (UE), a codeword including a plurality of hybrid automatic repeat request (HARQ) bits. The network node may decode each of the plurality of HARQ bits of the codeword using a decoding rule that is based at least in part on posterior probabilities associated with the plurality of HARQ bits and a threshold tuned to achieve unequal error protection (UEP) for decoding acknowledgement (ACK) and negative acknowledgement (NACK) bits. Numerous other aspects are described.