HARQ-ACK Codebook Compression for Low-Probability NACK Feedback
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Solution Overview
Problem
In 5G wireless communication networks, especially in 5G NR systems, the asymmetric probability of events such as NACK feedback compared to ACK feedback leads to inefficient payload size and processing overhead due to the rarity of NACK events, particularly in URLLC systems, where the probability of NACK is very low.
Innovation Solution
The implementation of a method to compress signaling bits for rare events, allowing multiple messages with a certain number of NACK occurrences to be compressed into a single message, reducing payload size and processing overhead by utilizing a compression technique based on the probability or number of occurrences of events, and enabling or disabling compression through DCI signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple NACK feedback messages are transmitted separately, then the reliability of error indication is maintained, but the payload size and processing overhead increase
Solution Approach 1:
The patent combines multiple NACK feedback messages into a single compressed message by encoding the positions of multiple NACKs using unary coding. Instead of transmitting separate messages for each NACK, the system merges them into one message that indicates multiple error positions, thereby reducing payload size while maintaining reliability of error indication.
Solution Approach 2:
The patent changes the encoding parameter from individual bit representation to unary coding representation. By changing how NACK positions are encoded (using unary coding where the position is represented by a sequence of bits indicating the index), the system achieves more efficient compression for low-probability events while preserving the ability to accurately convey error information.
2Quantity of substance
If compression is applied to NACK feedback messages, then the payload size is reduced, but the complexity of encoding and decoding increases
Solution Approach 1:
The patent segments the feedback message into different parts: ACK messages are handled separately from NACK messages. The NACK portion is further segmented by position, with each NACK position encoded independently using unary coding. This segmentation simplifies the overall encoding process by handling different message types with appropriate methods rather than applying complex compression to the entire message.
Solution Approach 2:
The patent uses a simple and lightweight unary coding scheme that is computationally inexpensive to implement. The encoding method uses basic bit operations to represent positions, avoiding the need for complex compression algorithms. This disposable-like simplicity in encoding makes the system easy to implement and decode while achieving effective compression for sparse NACK events.
3Productivity
If separate transmission of each feedback message is used, then the processing overhead is high, but the simplicity of implementation is maintained
Solution Approach 1:
The patent creates a universal feedback message format that can handle both ACK and NACK messages within a single transmission structure. The compressed message format is multi-functional, capable of representing zero or more NACK positions along with ACK information. This universal format improves processing efficiency by reducing the number of separate transmissions needed while maintaining implementation clarity through a standardized encoding approach.
Data Source
AI summary
Aspects relate to compression of messages in a wireless communication system. For messages, such as ACK/NACK feedback in a communication system, messages having an occurrence above or below a certain number of events (e.g., ACK/NACK events) or a probability of the occurrence may be compressed into a single message. By compressing the messages into a single message, the overhead used to transmit such messages may be reduced.