ACK/NACK Transmission in TDD Wireless Systems
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Solution Overview
Problem
In wireless communication systems based on Time Division Duplex (TDD), there is a need to efficiently transmit HARQ ACK/NACK signals across multiple serving cells while maintaining transmission reliability, as existing methods can lead to unnecessary retransmissions due to mismatched ACK/NACK bundling and insufficient control channel capacity.
Innovation Solution
A method and apparatus for transmitting 2-bit ACK/NACK signals in a TDD system, where a user equipment receives a semi-persistent scheduling downlink transport block without a corresponding PDCCH, determines the ACK/NACK, and modulates it using Quadrature Phase Shift Keying (QPSK) to transmit on an uplink control channel, utilizing a resource index derived from the detected PDCCH, thereby selecting an appropriate control channel based on the payload size and reducing unnecessary retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ACK/NACK bundling is used to reduce control channel overhead, then control channel capacity is improved, but transmission reliability deteriorates due to mismatched bundling with downlink subframes
Solution Approach 1:
The patent dynamically determines ACK/NACK bundling based on the actual number of detected downlink subframes. The bundling behavior changes adaptively: when all downlink subframes are detected, bundling is applied; when subframes are missed, bundling is adjusted or disabled. This dynamic adjustment resolves the contradiction by optimizing control channel capacity utilization while maintaining transmission reliability under varying detection conditions.
Solution Approach 2:
The patent changes the bundling parameter based on detection outcomes. When downlink subframes are missed, the system transitions from bundled ACK/NACK transmission to non-bundled transmission, effectively changing the transmission parameter to match the actual channel conditions and detection status, thereby preventing reliability degradation.
2Adaptability or versatility
If multiple control channels are introduced to support multiple serving cells, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent enables a single control channel to serve multiple functions: it can handle both bundled and non-bundled ACK/NACK transmissions, support multiple serving cells, and adapt to different detection scenarios. This multi-functionality reduces the need for separate specialized channels for each scenario, thereby maintaining adaptability while reducing overall system complexity.
3Speed
If ACK/NACK signals are transmitted without accurate subframe matching, then transmission speed is improved, but loss of information increases due to retransmission errors
Solution Approach 1:
The patent implements a feedback mechanism where the user equipment monitors downlink subframe detection status and adjusts ACK/NACK transmission accordingly. This feedback loop ensures that ACK/NACK signals are accurately matched to their corresponding downlink subframes, preventing information loss from retransmission errors while maintaining efficient transmission speed through adaptive rather than blanket retransmission.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the reliability of HARQ ACK/NACK transmission by accurately matching ACK/NACK signals with their corresponding downlink subframes, reducing errors and retransmissions, and optimizing the use of control channels across multiple serving cells.
Implementation Method 1
determines a 2 bit ACK/NACK for the SPS downlink transport block and the downlink transport block and a resource index from a plurality of resource indexes, modulating the 2 bit ACK/NACK to generate a modulation symbol
Data Source
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AI summary
Provided are a method and a device for ACK/NACK transmission in a TDD(Time Division Duplex)-based wireless communication system. The terminal receives a SPS downlink transmission block on a physical downlink shared channel (PDSCH) without a physical downlink control channel (PDCCH), and receives a downlink transmission block on the PDSCH that is indicated by the PDCCH having a downlink assignment index (DAI). The terminal transmits a 2-bit ACK/NACK regarding the SPS downlink transmission block and the downlink transmission block on an uplink control channel.