HARQ-ACK Codebook Determination for Carrier Aggregation
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Solution Overview
Problem
In carrier aggregation (CA) for wireless communication, determining the size of the HARQ-ACK codebook for multiple downlink or uplink resources across multiple carriers in the carrier and time domains is challenging, leading to potential misunderstandings between base units and remote units during data transmission.
Innovation Solution
The solution involves dividing the dynamic HARQ-ACK codebook into two sub-codebooks, one for TB-based HARQ-ACK feedback and another for CBG-based HARQ-ACK feedback, with the latter appended to the former to form a single HARQ-ACK codebook, and using a last carrier indicator (LCI) in control signals to synchronize the codebook size, reducing signaling overhead and ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single dynamic HARQ-ACK codebook is used for multiple carriers in carrier aggregation, then the codebook can accommodate flexible scheduling across carriers, but the determination of codebook size becomes ambiguous leading to misunderstandings between base unit and remote unit
Solution Approach 1:
The patent divides the single dynamic HARQ-ACK codebook into two separate sub-codebooks: one for TB-based HARQ-ACK feedback and another for CBG-based HARQ-ACK feedback. Each sub-codebook is determined independently using separate codebook determination processes, which eliminates the ambiguity in codebook size determination while maintaining the ability to handle multiple carriers flexibly. The two sub-codebooks are then appended to form the complete HARQ-ACK codebook.
2Reliability
If separate codebook determination methods are used for TB-based and CBG-based HARQ-ACK feedback, then codebook size ambiguity is eliminated, but the signaling overhead and complexity increase
Solution Approach 1:
The patent merges the two separate codebook determination processes by appending the TB-based HARQ-ACK sub-codebook and the CBG-based HARQ-ACK sub-codebook to form a single unified HARQ-ACK codebook. This unified codebook structure simplifies the overall determination process while maintaining the reliability benefits of separate determination methods. The LCI indicator in the control signal coordinates the combined codebook construction at the remote unit.
3Reliability
If the HARQ-ACK codebook includes feedback for all carriers regardless of scheduling status, then complete feedback coverage is achieved, but the codebook size increases unnecessarily increasing signaling overhead
Solution Approach 1:
The patent applies local quality by making the HARQ-ACK feedback structure adaptive to the actual scheduling status of each carrier. The LCI (Last Carrier Indicator) in the control signal indicates whether a carrier is the last scheduled carrier, allowing the remote unit to determine the codebook size dynamically based on actual scheduling requirements. This ensures that the codebook includes feedback only for scheduled carriers, avoiding unnecessary overhead while maintaining complete coverage for all actively scheduled carriers.
Data Source
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AI summary
The present application is related to a method and apparatus for determining a hybrid automatic repeat request-acknowledge (HARQ-ACK) codebook for carrier aggregation (CA). A method for determining a HARQ-ACK codebook for CA includes receiving a first control signal on a carrier within a carrier group in a slot, wherein the first control signal includes an indicator for indicating whether the carrier is a last scheduled carrier of the carrier group for downlink transmissions. The method further includes transmitting a hybrid automatic repeat request acknowledgement (HARQ-ACK) codebook corresponding to the downlink transmissions in the slot for the carrier group, wherein, based on the first control signal, one or more HARQ-ACK bits for the last scheduled carrier are arranged at the end of the HARQ-ACK codebook. The present application reduces signaling overhead for a HARQ-ACK codebook and avoids misunderstanding between a base unit and a remote unit when determining the HARQ-ACK codebook for CA.