HARQ-ACK Feedback for Multi-Cell Scheduling and CBG Retransmission

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Solution Overview

Problem

Existing wireless communication systems face inefficiencies in signal transmission, particularly in cellular networks, and lack effective methods for transmitting and receiving downlink control channels and handling code block group (CBG)-based transmissions in user equipment.

Innovation Solution

A method and apparatus for generating hybrid automatic repeat request acknowledgment (HARQ-ACK) bit sequences in user equipment, distinguishing between transport block (TB)-based and CBG-based transmissions, and optimizing HARQ-ACK bit sequences using downlink assignment indexes (DAI) to minimize overhead and enhance transmission efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If downlink control information is transmitted for each cell in carrier aggregation, then scheduling flexibility is improved, but control information overhead increases

Engineering Contradiction:

Improvescheduling flexibilityVSAvoidcontrol information overhead

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent merges the HARQ-ACK feedback for multiple cells into a single unified bit sequence transmitted through one uplink resource. Instead of transmitting separate control information for each cell, the system combines acknowledgments for all scheduled cells into one consolidated feedback message, reducing the total control information overhead while maintaining the ability to schedule multiple cells independently.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The downlink assignment index (DAI) mechanism serves multiple functions simultaneously: it tracks the number of scheduled cells, enables the UE to generate correctly sized HARQ-ACK sequences, and provides implicit signaling for resource allocation. This multi-functional approach allows the system to maintain scheduling flexibility across multiple cells without proportionally increasing control overhead.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If HARQ-ACK feedback is transmitted for every scheduled transport block, then transmission reliability is improved, but uplink resource consumption increases

Engineering Contradiction:

Improvetransmission reliabilityVSAvoiduplink resource consumption

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent dynamically adjusts the number of HARQ-ACK bits in the feedback sequence based on the actual number of scheduled cells and transport blocks. The DAI parameter enables the UE to determine the exact length of the HARQ-ACK sequence needed, transmitting only the necessary number of acknowledgment bits rather than a fixed maximum size, thereby reducing uplink resource consumption while maintaining complete feedback coverage for all scheduled transmissions.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If code block group-based transmission is implemented, then retransmission efficiency is improved, but processing complexity increases

Engineering Contradiction:

Improveretransmission efficiencyVSAvoidprocessing complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent segments the transport block into multiple code block groups (CBGs), each with its own HARQ-ACK feedback bit. This segmentation enables selective retransmission of only the failed CBGs rather than retransmitting the entire transport block, improving retransmission efficiency. The DAI mechanism automatically tracks which CBGs were scheduled, allowing the UE to generate appropriately sized feedback sequences without manual configuration.

Inventive Principle:

Principle #1Segmentation

4Productivity

If dynamic slot configuration is used to adapt to traffic patterns, then network efficiency is improved, but signaling overhead increases

Engineering Contradiction:

Improvenetwork efficiencyVSAvoidsignaling overhead

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The base station performs preliminary configuration of slot formats and traffic patterns through RRC signaling, establishing a framework for dynamic TDD operation. During actual operation, the DAI mechanism enables rapid adaptation to changing traffic conditions by simply adjusting the number of scheduled cells and transport blocks without requiring additional real-time signaling for each configuration change, thus maintaining network efficiency while minimizing ongoing signaling overhead.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12580687B2Method, apparatus, and system for transmitting or receiving data channel and control channel in wireless communication system

Publication Date: 2026.03.17 WILUS INSTITUTE OF STANDARDS & TECHNOLOGY INC

AI summary

Disclosed are a user equipment of a wireless communication system and a wireless communication method using the same. More specifically, disclosed are a user equipment including a processor configured to receive DCI through a PDCCH indicating PDSCH scheduling information of each cell in one or more cell(s), identify a transmission scheme in each cell based on a DCI format of the DCI, receive a PDSCH of each cell in the one or more cell(s) based on the scheduling information of the PDCCH, generate a hybrid automatic repeat request acknowledgment (HARQ-ACK) bit sequence for the one or more cell(s) based on the identified transmission scheme of each cell in response to receiving the PDSCH of each cell, and transmit the generated HARQ-ACK bit sequence and a wireless communication method using the same.