HARQ ACK/NACK Feedback via Code Block Groups
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Solution Overview
Problem
In wireless communication systems, particularly in 5G, there is a challenge in efficiently transmitting and receiving HARQ ACK/NACK signals, leading to unnecessary retransmission of entire transport blocks due to the lack of granular feedback on code block decoding success or failure.
Innovation Solution
The method involves transmitting and receiving HARQ ACK/NACK signals in units of code block groups, where an ACK is sent only when all code blocks in a group are successfully decoded, and an NACK is sent if any code block fails, allowing for targeted retransmission of specific code blocks rather than entire transport blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If HARQ ACK/NACK signals are transmitted in unit of entire transport block, then feedback overhead is reduced, but retransmission efficiency deteriorates due to unnecessary retransmission of successfully decoded code blocks
Solution Approach 1:
The transport block is segmented into multiple code block groups (CBGs), and ACK/NACK feedback is provided at the CBG level rather than at the entire transport block level. This segmentation allows selective retransmission of only those CBGs that failed decoding, improving retransmission efficiency while maintaining manageable feedback overhead through grouped structure.
Solution Approach 2:
Different feedback and retransmission treatment is applied to different code block groups based on their individual decoding status. Successfully decoded CBGs are not retransmitted, while failed CBGs are retransmitted selectively. This local differentiation optimizes overall system efficiency by avoiding unnecessary retransmissions of good data.
2Productivity
If HARQ ACK/NACK signals are transmitted in unit of code block groups, then retransmission efficiency is improved through selective retransmission, but device complexity increases due to finer granularity processing
Solution Approach 1:
The transport block is divided into multiple code block groups, creating a hierarchical structure that balances granularity and complexity. Each CBG can be independently processed and acknowledged, enabling selective retransmission while avoiding the need to process every individual code block separately, thus controlling device complexity.
Solution Approach 2:
Instead of processing and providing feedback for every single code block (excessive action), the system processes code blocks in groups (partial action). This approach provides sufficient granularity to enable selective retransmission of failed CBGs while reducing processing complexity compared to individual code block-level handling.
3Reliability
If entire transport block is retransmitted, then reliability is maintained through complete redundancy, but loss of time increases due to unnecessary retransmission of successfully decoded data
Solution Approach 1:
By segmenting the transport block into multiple CBGs and providing separate ACK/NACK feedback for each CBG, the system enables selective retransmission of only failed CBGs. This maintains reliability for successfully decoded CBGs (no retransmission needed) while reducing retransmission time for failed CBGs compared to retransmitting the entire transport block.
Solution Approach 2:
The system extracts and identifies specifically which code block groups failed decoding through CBG-level ACK/NACK feedback. Only these failed CBGs are extracted for retransmission, while successfully decoded CBGs are left out of the retransmission process, thereby reducing overall retransmission time while maintaining reliability.
Data Source
AI summary
A method for transmitting a hybrid automatic repeat and request (HARQ) ACK/NACK signal by a reception side in a wireless communication system may further comprise the steps of: receiving a transmission block including a plurality of code blocks from a transmission side; decoding the received transmission block; and transmitting an ACK/NACK for the transmission block in units of code block groups, wherein the code block group includes at least one code block.