HARQ-ACK Codebook Size Indication for Wireless Feedback
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Solution Overview
Problem
In wireless communication systems, user equipment (UE) may fail to detect downlink messages, leading to inaccurate or incomplete hybrid automatic repeat request (HARQ) feedback, resulting in inefficient communications due to codebook size mismatches between the UE and the base station.
Innovation Solution
The UE transmits a HARQ-ACK codebook along with an indication of its size, using various methods such as a predefined field, channel coding, or reference signal patterns, to ensure the base station can identify any missed downlink transmissions and adjust feedback accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the UE transmits HARQ feedback without indicating codebook size, then the feedback transmission is simpler, but the base station cannot identify missed downlink transmissions leading to communication inefficiency
Solution Approach 1:
The patent introduces an intermediary mechanism (codebook size indication field or reference signal pattern) that mediates between the UE and base station. This intermediary carries size information without requiring complex changes to the existing HARQ feedback structure, enabling the base station to identify missed transmissions while keeping the feedback mechanism relatively simple.
Solution Approach 2:
The patent changes the parameter being transmitted by adding codebook size information. This can be done by adding a size indication field to the feedback message or by modulating reference signal patterns to encode size information. This parameter change enables the base station to detect mismatches and identify missed downlink transmissions.
2Reliability
If the UE transmits codebook size indication, then the base station can identify missed transmissions improving reliability, but the feedback transmission becomes more complex
Solution Approach 1:
The patent applies partial action by transmitting only the essential size indication information rather than complete codebook contents. The size indication can be achieved through compact fields or patterns that convey minimal necessary information (just the size) to enable reliability improvements without proportionally increasing complexity.
Solution Approach 2:
The patent makes existing feedback structures multi-functional by enabling them to carry both traditional HARQ acknowledgment information and codebook size indication. Reference signals and feedback fields serve dual purposes: maintaining their original acknowledgment function while simultaneously encoding size information, thereby improving reliability without adding separate dedicated mechanisms.
3Productivity
If the codebook size is dynamically adjusted based on detected transmissions, then the feedback is more efficient, but mismatches occur when transmissions are missed
Solution Approach 1:
The patent introduces a feedback loop where the base station receives both the HARQ feedback and the codebook size indication, compares the indicated size with the expected size based on transmitted downlink messages, and identifies mismatches. This feedback mechanism enables dynamic adjustment while detecting errors, allowing the system to maintain efficiency when matching occurs and improve reliability when mismatches are detected.
Solution Approach 2:
The patent applies preliminary action by having the UE indicate the codebook size in advance or concurrently with the HARQ feedback transmission. This preliminary size indication allows the base station to prepare for potential mismatches and identify missed transmissions before attempting to process the full feedback, enabling more efficient error detection and correction.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A size of a hybrid automatic repeat request (HARQ)-acknowledgment (ACK) codebook may be determined and indicated when the HARQ-ACK codebook is transmitted. For example, a user equipment (UE) may transmit a number of information bits within a HARQ-ACK codebook, and may further indicate a size of the HARQ-ACK codebook based on the number of information bits. The UE may transmit the indication of the size of the HARQ-ACK codebook on the same or different time/frequency resources as the HARQ-ACK codebook, using a particular field, using a different uplink channels, or the like. Additionally or alternatively, the UE may indicate the size of the HARQ-ACK codebook using a particular pattern or sequence of reference signals associated with the channel used to carry the HARQ-ACK codebook.