HARQ-ACK Payload Determination in TDD Carrier Aggregation

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Solution Overview

Problem

In Time Division Duplex (TDD) communication systems, User Equipment (UE) faces challenges in accurately transmitting HARQ-ACK information due to missed DL SAs, leading to unnecessary retransmissions, reduced throughput, and incorrect understanding of HARQ-ACK bits between the UE and the NodeB, especially with Carrier Aggregation (CA) and multiple DL cells, which affects HARQ-ACK reception reliability and power consumption.

Innovation Solution

A method for a UE to determine the HARQ-ACK payload and transmission power in a PUCCH by calculating the number of received and missed TBs across configured DL cells, using DL DAI IE values to infer missed PDSCHs, and adjusting the HARQ-ACK payload based on configured transmission modes, ensuring accurate HARQ-ACK information transmission and minimizing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the UE transmits HARQ-ACK information for all configured DL cells without considering missed DL SAs, then the NodeB can maintain a consistent understanding of HARQ-ACK bits, but the UE experiences unnecessary power consumption and reduced throughput due to unnecessary retransmissions

Engineering Contradiction:

ImproveHARQ-ACK reception reliabilityVSAvoidUE power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The UE performs preliminary detection of DL SAs and determines which PDSCHs were missed before generating HARQ-ACK information. By using the DL DAI IE values from detected DL SAs, the UE can infer missed PDSCHs and adjust the HARQ-ACK payload accordingly, preventing unnecessary retransmissions and reducing power consumption while maintaining reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses DL DAI IE values as feedback information embedded in DL SAs to enable the UE to detect missed PDSCHs. The DL DAI IE provides counting information that allows the UE to determine whether a DL SA or PDSCH was missed, enabling accurate HARQ-ACK payload determination without excessive power consumption

Inventive Principle:

Principle #23Feedback

2Use of energy by moving object

If the UE determines HARQ-ACK payload based on detected DL SAs only, then the UE can reduce power consumption, but the NodeB and UE may have different understanding of HARQ-ACK bits due to missed DL SAs

Engineering Contradiction:

ImproveUE power consumptionVSAvoidHARQ-ACK bit understanding accuracy

Core Design Contradiction:

Use of energy by moving objectVSLoss of information

Solution Approach 1:

The UE performs preliminary analysis of DL DAI IE values from detected DL SAs to infer which PDSCHs were missed. By calculating the expected DL SA count and comparing it with the actual detected DL SAs, the UE can determine the HARQ-ACK payload size that both the UE and NodeB will understand consistently, preventing information loss

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The DL DAI IE acts as an intermediary information element that bridges the gap between UE detection and NodeB transmission intent. It provides counting information that enables the UE to infer missed PDSCHs and adjust the HARQ-ACK payload to match the NodeB's understanding, ensuring consistent interpretation of HARQ-ACK bits

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the UE transmits maximum HARQ-ACK payload for all configured DL cells, then the HARQ-ACK reception reliability is improved, but the throughput is reduced due to unnecessary retransmissions triggered by NACKs

Engineering Contradiction:

ImproveHARQ-ACK reception reliabilityVSAvoidSystem throughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The UE performs preliminary detection and inference of missed PDSCHs using DL DAI IE values before generating HARQ-ACK information. This allows the UE to transmit an accurate HARQ-ACK payload size that reflects actual PDSCH reception status, avoiding unnecessary NACKs and retransmissions while maintaining reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically changes the HARQ-ACK payload size parameter based on the actual number of detected DL SAs and inferred missed PDSCHs. Instead of always transmitting the maximum payload, the UE adjusts the payload size to match the actual communication state, improving throughput while maintaining reliability through accurate ACK/NACK feedback

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3952195A1Generation of HARQ-ACK information and power control of HARQ-ACK signals in TDD systems with downlink of carrier aggregation

Publication Date: 2022.02.09 SAMSUNG ELECTRONICS CO LTD

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AI summary

Methods and apparatus are provided for a User Equipment (UE) configured to have multiple cells in a DownLink (DL) of a Time Division Duplex (TDD) communication system so as to determine a power of an acknowledgement signal that the UE transmits in a control channel and to determine a number of acknowledgement information bits that the UE multiplexes with data information bits in a data channel. A transmission power of the control signal is determined based on DL Assignment Index (DAI) Information Elements (IEs) in DL Scheduling Assignments (SAs) that the UE detects through multiple transmission time intervals and through the multiple configured DL cells. The number of acknowledgement information bits in the data channel is determined based on a DAI IE of an UpLink (UL) SA associated with the transmission of the data channel.