HARQ Feedback Codebook Compression for Nonuniform ACK/NACK
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Solution Overview
Problem
Current wireless communication systems lack efficient methods for encoding non-uniform message transmission, particularly for hybrid-automatic repeat request (HARQ) feedback messages with non-uniform probabilities of acknowledgment (ACK) and negative acknowledgment (NACK), leading to inefficiencies in resource utilization.
Innovation Solution
A method and apparatus for generating and selecting codewords based on a threshold, where a representative codeword in a codebook maps to multiple candidate codewords with low probability, and other codewords have a one-to-one mapping, allowing for efficient compression and transmission of non-uniform messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional uniform encoding methods are used for HARQ feedback, then the encoding process is simple, but resource utilization is inefficient due to non-uniform probability of ACK/NACK
Solution Approach 1:
The patent changes the encoding parameters by introducing a threshold parameter (e.g., threshold = 2) that determines when to use compressed representation. When the number of NACKs exceeds this threshold, the system switches to a compressed codebook representation, thereby adapting the encoding parameters to the actual distribution of feedback messages and improving resource utilization efficiency.
Solution Approach 2:
The patent implements a dynamic encoding strategy where the codebook selection changes based on the content of the feedback message. The system dynamically switches between a first codebook (for messages with fewer NACKs) and a second codebook (for messages with more NACKs), allowing the encoding process to adapt its complexity based on the actual feedback characteristics.
2Loss of information
If a larger codebook is used to represent all possible feedback messages, then all messages can be represented accurately, but transmission overhead increases
Solution Approach 1:
The patent segments the codebook into multiple subsets (first codebook and second codebook) based on the number of NACKs they contain. This segmentation allows the system to use a smaller, more efficient codebook for common cases (messages with fewer NACKs) while reserving a larger codebook only when necessary, thereby reducing overall transmission overhead while maintaining accurate representation capability.
Solution Approach 2:
The patent merges multiple possible feedback messages into a single representative message in the compressed codebook. For example, multiple messages with different NACK patterns are mapped to a single codebook entry, reducing the total number of entries needed and thereby reducing transmission overhead while preserving the essential information.
3Quantity of substance
If compression is applied to reduce codebook size, then transmission overhead is reduced, but decoding complexity increases
Solution Approach 1:
The patent uses feedback mechanisms where the receiver provides information about the actual feedback message content (e.g., the number of NACKs) to guide the encoder's selection of the appropriate codebook. This feedback allows the system to use simpler decoding processes by pre-determining which codebook should be used based on the feedback characteristics, thereby reducing decoding complexity despite the presence of compression.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. Techniques described herein provide for compression based encoding for nonuniform message transmission. In some examples, a user equipment (UE) may generate a first candidate codeword that is one of a first set of candidate codewords. The UE may select, based on the first candidate codeword, a first selected codeword from a second set of codewords in a codebook. The second set of codewords may include a representative codeword that maps to more than one of the first set of candidate codewords, and remaining codewords other than the representative codeword of the second set of codewords may be each mapped to a respective one of the first set of candidate codewords. The UE may transmit the first selected codeword.